NMERI 97/29/33010 

IDENTIFICATION AND PROOF TESTING OF NEW TOTAL FLOODING AGENTS: 

TOXICITY AND GLOBAL ENVIRONMENTAL ASSESSMENT 

Robert E. Tapscott, Everett W. Heinonen, and J. Douglas Mather 

Center for Global Environmental Technologies 

NEW MEXICO ENGINEERING RESEARCH INSTITUTE 

The University of New Mexico 

901 University Boulevard SE 

Albuquerque, New Mexico 87106-4339 

Interim Report, February 1997 - August 1997 

February 1998 

Sponsored by: 

The Department of Defense 

Strategic Environmental Research and Development Program 

The views and conclusions contained in this document are those of the authors and should not be 

interpreted as representing the official policies, either expressed or implied of the Strategic 

Environmental Research and Development Program or any other part of the U. S. Government. 
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 

 27 Feb 1998 

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Interim Report, 3 Feb 97 - 31 Aug 97

4. TITLE AND SUBTITLE 

 Identification and Proof Testing of New Total Flooding 

Agents: Toxicity and Global Environmental Assessment 

5. FUNDING NUMBERS 

 

 C MDA972-97-M-0011

6. AUTHOR(S) 

 Robert E. Tapscott, Everett W. Heinonen, and J. Douglas 

Mather 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

 New Mexico Engineering Research Institute 

The University of New Mexico 

Albuquerque, New Mexico 87106-4339

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

 NMERI 97/29/33010

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The Department Of Defense 

Strategic Environmental Research and Development 

Program

10. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

11 SUPPLEMENTARY NOTES 

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE 

13. ABSTRACT (Maximum 200 words)

Under the Montreal Protocol, an international treaty, the production of the fire and explosion protection 

agent Halon 1301 (bromotrifluoromethane, BFC-13B1, CBrF3) was phased out in the United States at the end 

of 1993. No environmentally acceptable halon substitute that is equivalent to the existing halons in toxicity, 

effectiveness, and dimensionality has been identified. The objective of the overall effort is to reassess the 

higher volatility chemicals in the families of phosphorus compounds (with particular attention paid to 

phosphorus nitrides), silicon compounds (in particular, silanes and siloxanes), fluorinated amines and ethers, 

and other nonhalocarbons that might be appropriate for Halon 1301 replacement applications. The toxicities, 

atmospheric lifetimes, ozone depletion potentials (ODP), and global warming potentials (GWP) have been 

assessed for compounds in these families, and the results are presented in this report. Compound procurement, 

combustion suppression, and laboratory studies are the subject of another report.

14. SUBJECT TERMS 

 ozone depletion potential; ODP; global warming potential; GWP; toxicity;

15. NUMBER OF PAGES 

 amines; phosphorus nitrides; silanes; siloxanes; ethers; fire extinguishment

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iii

PREFACE 

This report was prepared by the Center for Global Environmental Technologies (CGET) 

Division, New Mexico Engineering Research Institute (NMERI), The University of New 

Mexico, Albuquerque, New Mexico, for the Department of Defense, Strategic Environmental 

Research and Development Program (SERDP), under Contract MDA972-97-M-0011, NMERI 

Number 8-33010. 

The Start Date was 3 February 1997, and the End Date is 2 February 1998. The 

Technical Program Manager is Dr. Richard G. Gann, National Institute of Standards and 

Technology; the Contracting Officer’s Technical Representative (COTR) is Dr. Andrzej W. 

Miziolek, Army Research Laboratory, and the NMERI Principal Investigator is Dr. Robert E. 

Tapscott. 

NMERI 97/29/33010 
iv
v

SUMMARY 

A. TASK OBJECTIVES 

The objective of the overall effort is to assess the higher volatility chemicals in the 

families of phosphorus compounds (with particular attention paid to phosphorus nitrides), silicon 

compounds (in particular, silanes and siloxanes), fluorinated amines and ethers, and other 

nonhalocarbons that might be appropriate for Halon 1301 replacement applications. The present 

report on work performed from February 1997 through August 1997 covers the overall 

assessment of toxicological and environmental characteristics. Compound procurement, 

combustion suppression, and laboratory studies are the subject of another report. 

B. GENERAL METHODOLOGY 

This project involves four tasks. 

1. The toxicities, Ozone Depletion Potentials (ODP), and Global Warming 

Potentials (GWP) of phosphorus nitrides, silanes, siloxanes, fluorinated amines and ethers, and 

other nonhalocarbons that might be appropriate for Halon 1301 applications will be reviewed 

and/or estimated. Estimation techniques will include Quantitative Structure Activity 

Relationships for toxicity; estimated or known hydroxyl free radical rate constants with globally 

averaged atmospheric hydroxyl radical concentrations for lifetimes; estimation methods for 

conversion of lifetimes to ODP and GWP based on data fitting to known values; and estimation 

of physical removal and photolytic removal based on chemical and physical properties. 

2. Specific compounds will be selected for study based on the information obtained 

in Task 1. Compounds not readily available will be synthesized. To the extent practical, 

sufficient quantities of synthesized compounds to permit other researchers to examine the 

materials will be prepared. 

3. Cup-burner flame extinguishment evaluations will be performed using the New 

Mexico Engineering Research Institute (NMERI) Standard Cup Burner. Some determinations 

may also be performed using the International Standards Organization (ISO) cup burner. As 
vi

resources allow, sufficient quantities of the chemicals tested under this program will be provided 

to other laboratories for testing using opposed-flame burners or similar apparatuses. 

4. The information obtained in the above tasks will be assessed to develop a list of 

optimal candidate Halon 1301 replacement agents. The criteria for this list will be based 

primarily on (1) predicted toxicity, (2) synthesis and manufacturability, (3) ODP and GWP, and 

(4) fire suppression and inertion effectiveness. 

This report covers only the first task. 

C. TECHNICAL RESULTS 

A large amount of global environmental data, that has, as far as is known, been compiled 

elsewhere was obtained. In particular, considerable information is available on ethers related to 

compounds of interest to fire extinguishment. Little environmental data were, however, 

available for relevant compounds in the other families examined. 

Although the toxicity data are available for phosphorus compounds, most of the 

information is on compounds of little interest as fire extinguishants or as parent compounds for 

fire extinguishants. 

A general procedure for environmental screening of compounds was developed. 

D. IMPORTANT FINDINGS AND CONCLUSIONS 

It is highly unlikely that phosphorus compounds will create any global environmental 

problems. Atmospheric lifetimes are expected to be sufficiently short that global warming and 

ozone depletion (even with bromine substitution) would be negligible. 

The large variability in toxicity of phosphorus compounds and the possibility of 

cholinesterase inhibition causes toxicity concerns with these compounds. It appears that 

toxicity tends to decrease as the oxidation state of the phosphorus decreases (i.e., phosphines are 

generally the most toxic and phosphates are the least toxic). Phosphonitriles appear to have 

relatively low toxicities, but mutagenicity may be of concern. Compounds with P-halogen bonds 

are probably unacceptable as halon substitutes. 
vii

Silicon compounds are expected to have few, if any, global atmospheric impacts. This 

may be the case even when bromine is present. There is, however, a real need for studies of the 

photochemistry of bromine-containing silicon compounds. 

Little toxicity data are available on silicon compounds of interest as halon substitutes. 

On the other hand, many silicon compounds, particularly esters and siloxanes, are expected to 

have low toxicity. As in the case of phosphorus, compounds containing Si-halogen bonds are 

probably unacceptable as halon substitutes. 

Totally fluorinated amines could cause atmospheric lifetime and global warming 

problems. On the other hand, amines with partial fluorination are likely to have relatively short 

atmospheric lifetimes. It is difficult, however, to determine whether the lifetime would be 

sufficiently short to allow bromine substitution. 

Simple alkyl-substituted amines range from nontoxic in the case of totally fluorinated 

compounds to highly toxic for nonfluorinated materials. A major question is how the toxicity 

varies with partial fluorine substitution. 

The ether linkage enhances reactivity toward hydroxyl free radicals and, therefore, leads 

to lower atmospheric lifetimes. On the other hand, this is somewhat offset by fluorine 

substitution. It is possible that bromine substitution would be allowable; however, ethers are not 

as easily removed from the atmosphere as are amines, for example, and bromine substitution 

may lead to unacceptable ozone depletion potentials. 

The toxicity of ethers is relatively low compared to other materials evaluated in this 

report. Furthermore, the ether linkage has a relatively low biological and chemical reactivity. 

E. SIGNIFICANT HARDWARE DEVELOPMENTS 

No hardware has been developed as part of this project. 

F. SPECIAL COMMENTS 

There are no special comments for this stage of the project. 
viii

G. IMPLICATIONS FOR FURTHER RESEARCH 

A number of areas have been identified in this study for future research. Information is 

needed on photolysis of bromine-containing silicon compounds and on rate constants for 

reaction of bromine-containing amines with hydroxyl free radicals. A general study of the 

variation in toxicity as fluorination increases in trialkylamines is also needed. 
ix

TABLE OF CONTENTS 

Section Page

 I INTRODUCTION .........................................................................................................1 

A. OBJECTIVE .........................................................................................................1 

B. SCOPE ..................................................................................................................1 

C. APPROACH .........................................................................................................2 

 II GLOBAL ENVIRONMENTAL CHARACTERISTICS ..............................................3 

1. ODP and GWP.............................................................................................3 

2. Stratospheric Ozone Depletion ....................................................................3 

3. Atmospheric Lifetime ..................................................................................4 

4. Decision Tree...............................................................................................7 

 III PHOSPHORUS COMPOUNDS..................................................................................10 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP...............................................10 

1. Stratospheric Ozone Depletion ..................................................................10 

2. Reactions with Tropospheric •OH .............................................................13 

3. Reactions with Tropospheric O3 ................................................................14 

4. Other Tropospheric Removal Mechanisms ...............................................14 

5. Lifetimes and GWPs ..................................................................................15 

6. Conclusions................................................................................................15 

B. TOXICITY..........................................................................................................15 

1. Hexakis(2,2,2-trifluoroethoxy)cyclotriphosphazene toxicity....................15 

2. Phosphonitrilic Chloride Compounds (Chlorophosphazene) ....................16 

3. Other Phosphorus Compounds ..................................................................17 

4. Conclusions................................................................................................21 

 IV SILICON COMPOUNDS............................................................................................30 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP...............................................30 
x

TABLE OF CONTENTS (continued) 

Section Page

1. Stratospheric Ozone Depletion ..................................................................30 

2. Reactions with Tropospheric •OH .............................................................31 

3. Reactions with Tropospheric O3 ................................................................32 

4. Other Tropospheric Removal Processes ....................................................32 

5. Lifetimes and GWPs ..................................................................................33 

6. Conclusions................................................................................................33 

B. TOXICITY..........................................................................................................33 

1. Newly Acquired Information.....................................................................33 

2. Conclusions................................................................................................34 

 V FLUORINATED AMINES .........................................................................................35 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP...............................................35 

1. Stratospheric Ozone Depletion ..................................................................35 

2. Reactions with Tropospheric •OH .............................................................36 

3. Reactions with Tropospheric O3 ................................................................37 

4. Lifetimes and GWPs ..................................................................................38 

5. Conclusions................................................................................................39 

B. TOXICITY..........................................................................................................39 

1. Hydrofluoroamines ....................................................................................39 

2. Other Fluorine-Containing Nitrogen Compounds .....................................40 

3. Conclusions................................................................................................42 

 VI FLUORINATED ETHERS .........................................................................................43 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP...............................................43 

1. Reactions with Tropospheric •OH .............................................................43 

2. Reactions with Tropospheric O3 ................................................................43 

3. Lifetimes and GWPs ..................................................................................43 

4. Hydrofluoroethers......................................................................................50 
xi

TABLE OF CONTENTS (continued) 

Section Page

5. Conclusions................................................................................................51 

B. TOXICITY..........................................................................................................51 

 VII RESULTS AND CONCLUSIONS..............................................................................52 

A. PHOSPHORUS COMPOUNDS.........................................................................52 

B. SILICON COMPOUNDS...................................................................................52 

C. FLUORINATED AMINES ................................................................................52 

D. FLUORINATED ETHERS ................................................................................53 

REFERENCES ..............................................................................................................................55 
xii

LIST OF FIGURES 

Figure Page

1 Abbreviated Decision Tree......................................................................................8 

2 Decision Tree for Global Environmental Impact Screening. ..................................9 
xiii

LIST OF TABLES 

Table Page

1 ESTIMATED AND REPORTED ODPs FOR SELECTED 

HALOCARBONS. ..................................................................................................5 

2 RATE CONSTANTS •OH REACTIONS WITH PHOSPHORUS 

COMPOUNDS. .....................................................................................................13 

3 RESULTS OF TOXICITY STUDIES FOR CHLOROPHOSPHAZENES..........18 

4 TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS. ..........................................................................21 

5 •OH RATE CONSTANTS FOR SILICON COMPOUNDS.................................31 

6 •OH RATE CONSTANTS FOR NITROGEN-CONTAINING 

COMPOUNDS. .....................................................................................................37 

7 RATE CONSTANTS FOR REACTIONS OF O3 WITH AMINES .....................38 

8 ACUTE INHALATION TOXICITY OF HYDROFLUOROAMINES................40 

9 TOXICITY, SAFETY INFORMATION FOR SELECTED N, F 

COMPOUNDS. .....................................................................................................41 

10 RATE CONSTANTS FOR HYDROFLUOROETHER REACTIONS 

WITH •OH.............................................................................................................44 

11 ATMOSPHERIC LIFETIMES FOR FLUORINE-CONTAINING 

ETHERS. ...............................................................................................................46 
xiv

LIST OF ABBREVIATIONS 

BCC Business Communications Company 

CAS Chemical Abstracts Service (American Chemical Society) 

CFC chlorofluorocarbon 

CGET Center for Global Environmental Technologies 

COTR Contracting Officer’s Technical Representative 

DMMP dimethyl methylphosphonate 

DNA deoxyribonucleic acid 

EPA U. S. Environmental Protection Agency 

GWP global warming potential 

HFA hydrofluoroamine 

HCFC hydrochlorofluorocarbon 

HFC hydrofluorocarbon 

HFE hydrofluoroether 

HFPE hydrofluoropolyether 

HOMO highest occupied molecular orbital 

HR SAX Hazard Rating 

NIRI National Industrial Research Institute 

NMERI New Mexico Engineering Research Institute 

ISO International Standards Organization 

ODP ozone depletion potential 

QSAR Quantitative Structure-Activity Relationship 

RTECS Registry of Toxic Effects of Chemical Substances 

TMP trimethylphosphate 

USIC United States Industry Coalition, Inc. 
xv

LIST OF UNITS AND SYMBOLS 

cp centipoise 

cm centimeter 

D molecular diffusivity of a gas in water 

g gram 

GWPmax maximum allowable GWP 

hr hour 

hν photon 

K degree Kelvin 

k reaction rate constant 

kg kilogram 

khyd rate constant for hydrolysis 

kother second-order rate constant for reaction with species other than O3 and •OH 

kOH second-order rate constant for reaction with •OH 

kO3 second-order rate constant for reaction O3

k1 first-order reaction rate constant 

k2 second-order reaction rate constant 

kJ kilojoule 

L liter 

LCLO lowest concentration causing death 

LC50 concentration required to cause death in 50 percent of an animal test population 

LDLO lowest dose causing death 

LD50 dose required to cause death in 50 percent of an animal test population 

m meter 

mg milligram 

mL milliliter 

ODPmax maximum allowable ODP 

Pmax maximum allowable vapor pressure in screening 

Pvap vapor pressure 

ppb parts per billion 

ppm parts per million 
xvi

LIST OF UNITS AND SYMBOLS (concluded) 

s second 

thyd atmospheric lifetime due to hydrolysis 

tmax maximum allowable tropospheric lifetime 

tother tropospheric lifetime due to reactions other than with tropospheric ozone and •OH 

tOH tropospheric lifetime due to reaction with •OH 

tO3 tropospheric lifetime due to reaction with tropospheric ozone 

tphot tropospheric lifetime due to photolysis 

tphys tropospheric lifetime due to physical removal 

t1/e e-folding atmospheric lifetime 

α solubility coefficient 

β Henry’s law constant in moles/m3-atm 

ΔHf enthalpy of formation 

ΔHr enthalpy of reaction 

ΔGf free energy of formation 

ΔGt free energy of reaction 

σIR(λ) IR absorption cross section as a function of wavelength λ

σmid absorption cross section at the tropospheric window midpoint for solar radiation 

σmax maximum allowable value for absorption cross section at window midpoint 

μg microgram 

• denotes odd-electron species or free radical (e.g., •OH and •O) 
1

SECTION I 

INTRODUCTION 

A. OBJECTIVE 

The objective of this effort is to assess the higher volatility chemicals in the families of 

phosphorus compounds (with particular attention paid to phosphorus nitrides), silicon 

compounds (in particular, silanes and siloxanes), fluorinated amines and ethers, and other 

nonhalocarbons that might be appropriate for Halon 1301 replacement applications. Compound 

procurement, combustion suppression, and laboratory studies are a subject of another report 

(Reference 1). 

B. SCOPE 

The overall project consists of four requirements. 

1. From literature citations and previously determined principles, assess and/or 

estimate the toxicity, atmospheric lifetime, Ozone Depletion Potential (ODP), and Global 

Warming Potential (GWP) of chemicals in the phosphorus nitrides, silanes, siloxanes, 

fluorinated amines and/or ethers, and other nonhalocarbon families that show potential for 

replacement for Halon 1301 replacement. 

2. Select specific compounds for study. Obtain or synthesize the compounds, and, 

for those compounds that are not readily available, prepare sufficient quantities to permit other 

researchers to examine the materials. 

3. Perform cup-burner flame extinguishment evaluations of selected compounds. To 

the extent practical, synthesize (or recommend sources for, in case of compounds commercially 

available) sufficient quantities of these chemicals to send to other laboratories for testing using 

opposed-flame burners or similar apparatuses. 

4. Using the information obtained in the above tasks, develop a list of optimal 

candidate Halon 1301 replacement agents based primarily on (1) predicted toxicity, (2) synthesis 
2

and manufacturability, (3) atmospheric lifetime, ODP, and GWP, and (4) fire suppression and 

inertion effectiveness. 

The present report covers only the first task listed. 

C. APPROACH 

In the first part of this program, the toxicities, ODPs, and GWPs of phosphorus nitrides, 

silanes, siloxanes, fluorinated amines and ethers, and other nonhalocarbons that might be 

appropriate for Halon 1301 applications have been reviewed and estimated. Sources of toxicity 

and safety data include Sax and Lewis (Reference 2) and the Registry of Toxic Effects of 

Chemical Substances (RTECS) (Reference 3). 
3

SECTION II 

GLOBAL ENVIRONMENTAL CHARACTERISTICS 

Global environmental impacts of greatest concern here are atmospheric—stratospheric 

ozone depletion and climate change (in particular, global warming). To a large extent, global 

atmospheric environmental concerns are closely related to the atmospheric lifetime, which is 

determined by tropospheric removal processes. Reference 4 gives an overview of global 

environmental problems and presents a detailed discussion of ODP, GWP, the various 

tropospheric removal mechanisms, and approximation methods. A brief summary with 

significant new material and expansions is presented here. 

1. ODP and GWP 

The ability of a chemical to effect stratospheric ozone depletion is measured by 

its ODP; the impact of a chemical on global warming is determined by its GWP. The ODP and 

GWP give, respectively, the ozone depletion and global warming due to release of a unit mass of 

material relative to that produced by a reference chemical. The reference chemical for ODP is 

usually the chlorofluorocarbon (CFC) CFC-11 (trichlorofluoromethane, CCl3F), and the 

reference chemical for GWP is usually carbon dioxide (CO2), though CFC-11 is sometimes used 

for GWP also. Both ODP and GWP are calculated from appropriate rate constant data using 

multidimensional atmospheric models. GWP values depend on the time period (the “time 

horizon,” typically, 100 or 500 years) used in the calculation, and the time horizon used should 

be noted when reporting GWPs. 

2. Stratospheric Ozone Depletion 

A method for estimating ODPs for non-bromine-containing one- and two-carbon 

halocarbons has been proposed (Reference 5). The method relates the ODP to two factors, one a 

reactivity factor related to the number of chlorine atoms in the molecule and the other a survival 

factor giving the fraction of molecules reaching the stratosphere (and, therefore, related to the 

atmospheric lifetime). The proposed relationship is shown in Equation 1, where n is the number 

of chlorine atoms, t is the atmospheric lifetime, and c1, c2, and c3 are parameters to be fit. Here, 

nc2 is the reactivity factor, e−( /) c t 3 is the survival factor, and c1 is a normalizing constant. This 
4

equation gives values that are relatively close to the rigorously calculated ODPs used in fitting 

the parameters. Since the values for the rigorously calculated ODPs and atmospheric lifetimes 

used in the parameter fitting have changed since the equation was originally proposed, the 

reported parameters will not be given in the present report. 

ODP = cn e c ct

1 2 3 −( /) [1] 

In its present form, Equation 1 is not applicable to bromine-containing 

compounds. It has, however, been reported that the ODPs for bromine-containing compounds 

can be estimated from Equation 2 (Reference 6). Here, P is the photolysis factor, which is set 

equal to 1.0 if there are no special structural features that make the molecule subject to 

tropospheric photolysis. Otherwise, P = 0.180 for a bromine geminal to a chlorine (e.g., 

Br-C-Cl), P = 0.015 for geminal bromine atoms (Br-C-Br), or 0.370 for vicinal bromine atoms 

(Br-C-C-Br). A is the normalizing constant (0.446), B is 0.740, C is 32.000, and D is 1.120. 

The hydrogen factor E is 1.000 if there are no hydrogen atoms; otherwise it is 0.0625. #C, #Br, 

and #Cl are the numbers of carbon, bromine, and chlorine atoms, respectively. 

ODP = AEP[(#Cl)B + C(#Br)]D(#C-1) [2] 

Use of Equation 2 gives, at best, rough approximations, even if the equation is 

restricted to simple saturated halocarbons (Table 1). The trends, however, are preserved. It may 

be that a better fit of parameters could be obtained with a larger set of more recent data as a 

basis. 

3. Atmospheric Lifetime 

To a great extent, ODPs and GWPs are determined by tropospheric lifetimes. 

Regardless of the chemical, the ODP and GWP will be negligible given a sufficiently short 

tropospheric lifetime. Thus, tropospheric removal is one area of primary concern when 

evaluating global environmental impacts. Tropospheric removal reactions are either bimolecular 

or unimolecular. Bimolecular reactions involve reaction with atmospheric species such as 

hydroxyl free radicals (•OH), tropospheric ozone (O3), oxygen atoms (•O in 3

P, 1D electronic 

states), etc. Formally unimolecular reactions include photolysis, thermal dissociation, and 
5

TABLE 1. ESTIMATED AND REPORTED ODPs FOR SELECTED HALOCARBONS. 

Compound Formula Calculated ODP 

(relative to CFC-11)

Reported ODP 

(relative to CFC-11)

Reference 

Halon 1301 CBrF3 14.3 12 7 

Halon 1211 CBrClF2 2.6 5.1 7 

Halon 2402 CBrF2CBrF2 17.4 6.6 a 

HBFC-22B1 CHBrF2 0.89 0.74 8 

HBC-30B2 CH2Br2 0.03 0.17 9 

HBC-40B1 CH3Br 0.89 0.64 7 

HCFC-123 CHCl2CF3 0.050 0.014 7 

a

Connell, P. S., and Wuebbles, D. J., “Ozone Depletion Potential, Halons, and Halon Alternatives,” 

NMERI Halon Alternatives Program Review, Albuquerque, NM, 23-24 Jan 1991. 

heterogeneous absorption (aqueous or particulate aerosols). The rate of disappearance of a 

species C due to a bimolecular reaction with an atmospheric species A can be expressed as 

shown in Equation 3,* where [C] and [A] are the concentrations of species C and A, and k2 is a 

second-order reaction rate constant. Similarly, the rate of removal through unimolecular 

reactions is expressed by a first-order differential equation with the first-order reaction rate 

constant k1 as shown in Equation 4. Typical units for k2 and k1 are, respectively, cm3/molecule-s 

and seconds-1 with concentrations in molecules/cm3. The rate constants k1 and k2 are constant 

only under a given set of conditions. For example, for photolysis, k1 depends on the radiation 

flux and wavelength; for reaction with atmospheric particulate, k1 depends on the concentration 

(and composition and other characteristics) of particulate. 

d C

dt

k CA [ ] = − [ ][ ] 2 [3] 

d C

dt

k C [ ] = − [ ] 1 [4] 

Careful consideration shows that all reactions can actually be considered 

“bimolecular” in form since the concentration of particulate, for example, is incorporated into k1
6

for particulate removal, and the “concentration” (actually, the flux) of photons is incorporated 

into k1 for photolysis. Even thermal decomposition involves collisions with other molecules to 

transfer kinetic energy to the species undergoing decomposition (which is the reason that the 

term “formally unimolecular” is used above). 

The concentration of a species undergoing reaction, as shown in Equation 3 or 

Equation 4, decays exponentially as given by Equation 5. Here [C]o is the initial concentration, 

[C]t is the concentration at any time t, and t1/e is the “e-folding” atmospheric lifetime, i.e., the 

time required for the concentration of an atmospheric species to decay to 1/e (approximately 

0.369) of its initial value. The e-folding lifetime is related to the reaction rate constant by or 

depending on whether the reaction is bimolecular (Equation 6) or unimolecular (Equation 7). 

[] [] / / C Cet tt o e = 1 [5] 

t1/e = 1/k2[A] [6] 

t1/e = 1/k1 [7] 

Using Equation 6, one can estimate the atmospheric lifetime due to various 

removal processes by using globally averaged values for concentrations of reactant species. In 

this report, a globally averaged tropospheric hydroxyl free radical concentration of 9.7 x 105

molecules/cm3

 (Reference 10) and a globally averaged tropospheric ozone concentration of 5.0 x 

1011 molecules/cm3

 (Reference 11) are used for such estimations. In the global averaging 

approximation, one should use reaction rate constants for a mean tropospheric temperature. A 

temperature of 277 K has been recommended (Reference 12); however, values around 298 K, 

which are more prevalent, are often used and are generally used in this report. 

In the global average approximation, atmospheric lifetime is directly proportional 

to the second-order rate constant (kOH) for reaction with •OH, when this is the primary 

tropospheric removal process. Thus, an alternative way to estimate the atmospheric lifetime for 

a compound B removed only by reaction with •OH is to use Equation 8 to relate the lifetime of B 

( t e

B

1/ ) to that ( t e

C

1/ ) of a second compound C (Reference 13). Here, kOH

B and kOHC are the 

 

*Throughout this report, equation numbers are placed in brackets and reaction numbers are 
7

second-order hydroxyl reaction rate constants for the two materials. Methyl chloroform 

(CH3CCl3) is usually the reference compound (C). This method is equivalent to using the 

globally averaged •OH concentration when this concentration has been determined from 

measurements of atmospheric removal of methyl chloroform, as in the case of the value used in 

this report (Reference 10). Note that with the appropriate rate constants, one could use an 

equation similar to Equation 8 when a removal mechanism other than reaction with a hydroxyl 

free radical predominates, as long as the removal mechanism for the compound of interest (B) is 

the same as that for the reference compound (C). 

t tk k e

B

e

C

OH

C

OH

B

1 1 / / = (/) [8] 

Attempts to use Quantitative Structure-Activity Relationship (QSAR) to predict 

kOH values have not been highly successful (Reference 14). A procedure based on the C-H bond 

energy (and, thus, related to the activation energy for hydrogen atom abstraction by •OH) 

reported in Reference 5 gives rather disappointing fits to rigorously calculated atmospheric 

lifetimes, though reparameterization with more recent data may help. Since many of the 

compounds of interest as halon replacements contain fluorine atoms, there is one trend of 

interest. Examination of rate constants for a variety of fluorinated compounds indicates that 

fluorine substitution activates hydrogen atoms on the same carbon atom toward •OH abstraction, 

but deactivates hydrogen atoms on carbon atoms immediately adjacent. For example, the 

reaction of •OH with CH3CH2F proceeds primarily (85 percent) with the hydrogen atoms on the 

CH2F group (Reference 15). 

Better results may be available through quantum mechanical calculations. There 

is strong evidence that kOH values vary linearly with the calculated values for the highest 

occupied molecular orbital (HOMO) in hydrofluorocarbons (Reference 16). 

4. Decision Tree 

From the information presented in Reference 4 and in the present report, a 

decision tree for compound acceptability can be developed. The overall procedure evaluates in 

turn (1) atmospheric release, (2) hydrolysis, (3) physical removal, (4) photolysis, (5) reaction 

 

placed in parentheses. 
8

with hydroxyl free radicals, (6) reaction with tropospheric ozone, (7) other reactions, 

(8) stratospheric ozone removal, and (9) global warming, allowing decision points at each stage. 

The overall methodology for the decision tree can be summarized as shown in Figure 1. 

Release/

Hydrolysis Lifetime ODP GWP Accept

Accept Reject Reject Reject

Figure 1. Abbreviated Decision Tree. 

A more detailed decision tree is shown in Figure 2. Here, tmax is the maximum 

allowable atmospheric lifetime and thyd, tphys, tphot, tOH, and tO3 are the tropospheric lifetimes due 

to hydrolysis, physical removal, photolysis, reaction with •OH, and reaction with tropospheric 

ozone. The maximum allowable atmospheric lifetime and other criteria, which may change as 

the regulatory environment changes, must be established. The first step is to determine whether 

the vapor pressure (Pvap) is sufficient (less than some maximum allowable value Pmax) to permit 

release. Hydrolysis is then accessed from khyd, the hydrolysis rate constant. Lifetimes for 

various physical removal processes can be estimated—for rainout using α, the solubility 

coefficient (Reference 17); for aerosol scavenging using Pvap, the vapor pressure (at 298 K) 

(Reference 17); and for absorption (solution) into oceans using β, the (ocean) water solubility of 

a gas in moles/m3

-atm (essentially, a Henry’s law constant), and D, the molecular diffusivity of a 

gas inwater in m2

/year. One can estimate the possibility for photolysis from σmid, the absorption 

cross section at the tropospheric window midpoint for solar radiation, and σmax, the maximum 

allowable value for this cross section. One must collect chemical information on the material of 

interest to determine whether reaction with •OH, O3, or other species is possible. If reactions are 

possible, the lifetimes (tOH, tO3, tother) due to such reactions can be estimated from kinetic rate 

constants (kOH, kO3, kother) using a global averaging approximation. The final step, if needed, is 

to estimate the ODP and GWP (from σIR(λ), the IR absorption cross section as a function of 

wavelength λ) and compare the numbers obtained with ODPmax, and GWPmax, the maximum 

allowable values for these variables. Estimation methods are available for ODP and GWP 

(above and Reference 4). 
9

Pvap Release

Pvap < Pmax?

No

Yes Accept

No

Yes

Photolysis Calculation

φ(λ),

σ(λ)

Physical Removal Calculation

α, Pvap,

β, D

Hydrolysis

Possible?

No

Yes

Hydrolysis Calculation

khyd

OH Reaction

Possible?

No

Yes

OH Reaction Calculation

kOH

Tropospheric

O3 Reaction

Possible?

No

Yes

O3 Reaction Calculation

kO3

Other Reactions

Possible?

No

Yes

Other Reaction Calculation

kOther

Reject

σmid

Information

Information

Information

GWP Calculation

O3 Depletion

Possible?

No

Yes

ODP Calculation

GWP < GWPmax

ODP<ODPmax

ODP >

ODPmax

Reject

Accept

GWP > GWPmax

Reject

σIR(λ)

thyd < tmax

thyd > tmax

tphys < tmax

tphys > tmax

tphot < tmax

tphot > tmax

σmid < σmax?

tOH < tmax

tOH > tmax

tO3 < tmax

tO3 > tmax

tother < tmax

tother > tmax

Figure 2. Decision Tree for Global Environmental Impact Screening. 
10

SECTION III 

PHOSPHORUS COMPOUNDS 

A detailed overview of phosphorus chemistry, particularly as it relates to compounds that 

might be useful in fire extinguishment, is presented in Reference 18 and is not repeated here 

except as noted. The conclusions are developed both from material presented here and from data 

presented in Reference 18. 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP 

Atmospheric reactions due to the presence of phosphorus have not been studied. It is 

expected, of course, that organic substituents will generally undergo the same type of reactions 

found in the absence of phosphorus though modifications in actual rate constants are likely. 

1. Stratospheric Ozone Depletion 

The effect of phosphorus on stratospheric ozone has not been reported. A general 

cycle that may enable ozone depletion by phosphorus is shown in Reactions 1 and 2. Note, 

however, that the large stability and expected reluctance to add additional oxygen atoms make 

•PO3 and higher oxides unlikely candidates for direct participation in ozone depletion. •NO3 is 

known to photolyze sufficiently rapidly that at least some possible reactions are believed to be 

insignificant in atmospheric chemistry (Reference 19), and the higher oxides of phosphorus are 

likely to photolyze even more rapidly. 

•POx + O3 → •POx+1 + O2 (1) 

•POx+1 + •O → POx + O2 (2) 

Nitrogen oxides are believed to deplete stratospheric ozone by the reactions 

shown in Reactions 3 through 5 (Reference 20). Here and elsewhere in this report, enthalpies of 

reaction (ΔHr) and free energies of reaction (ΔGr) are calculated from standard enthalpies of 

formation (ΔHf) and standard free energies of formation (ΔGf) at 298.15 K taken from 

Reference 21 unless otherwise indicated. By analogy, one might propose Reactions 6 and 7 for 

ozone depletion by phosphorus. Reaction 6 is highly exothermic and has been proposed as the 
11

cause for the chemiluminescence observed for the reaction of ozone with phosphine 

(Reference 22). Here, however, the relatively large O-PO bond dissociation enthalpy (calculated 

as 540 kcal/mol from the standard enthalpies) compared to the O-NO bond dissociation energy 

(306 kJ/mole) makes the second reaction in the cycle (Reaction 7) unfavorable at 298.15 K. The 

higher stability of phosphorus dioxide can be seen from the total enthalpy of 1129 kJ/mole for 

dissociation of PO2 into its constituent atoms compared with the calculated value of 938 kJ/mole 

for NO2. 

•NO + O3 → •NO2 + O2, ΔHr = -200 kJ/mole, ΔGr = -199 kJ/mole (3) 

•NO2 + •O → •NO + O2, ΔHr = -192 kJ/mole, ΔGr = -196 kJ/mole (4) 

Net: •O + O3 → 2O2, ΔHr = -392 kJ/mole, ΔGr = -395 kJ/mole (5) 

•PO + O3 → •PO2 + O2, ΔHr = -435 kJ/mole, ΔGr = -433 kJ/mole (6) 

•PO2 + •O → •PO + O2, ΔHr = 42 kJ/mole, ΔGr = 38 kJ/mole (7) 

An alternative mechanism is described in Reactions 8 and 9, where, the second 

reaction is again distinctly unfavorable. This cycle is similar to the chlorine ozone depletion 

cycle in Reactions 10 and 11. Here, again, the large phosphorus-oxygen bond strength is an 

obstacle. The bond strength in diatomic PO is 599.1 kJ/mole compared with 269 kJ/mole for 

•ClO (Reference 23). 

•P + O3 → •PO + O2, ΔHr = -483 kJ/mole, ΔGr = -490 kJ/mole (8) 

•PO + •O → •P + O2, ΔHr = 91 kJ/mole, ΔGr = 95 kJ/mole (9) 

•Cl + O3 → •ClO + O2, ΔHr = -163 kJ/mole, ΔGr = -171 kJ/mole (10) 

•ClO + •O → •Cl + O2, ΔHr = -229 kJ/mole, ΔGr = -224 kJ/mole (11) 

A number of other reactions are possible. Bromine and chlorine jointly provide a 

highly effective mechanism for stratospheric ozone depletion through a cycle of Reactions 5 and 

12 through 14 (Reference 24). Here, ΔHf and ΔGf for •BrO are taken from Reference 23. A 

similar cycle can be proposed for phosphorus by coupling Reactions 8, 12, and 15. The free 

energy change for Reaction 15, however, is very large, positive, and, therefore, unfavorable. 
12

•Br + O3 → •BrO + O2, ΔHr = -129 kJ/mole, ΔGr = -137 kJ/mole (12) 

•ClO + •BrO → •Cl + •Br + O2, ΔHr = 6 kJ/mole, ΔGr = -18 kJ/mole (13) 

Net: 2O3 → 3O2, ΔHr = -285 kJ/mole, ΔGr = -326 kJ/mole (14) 

•PO + •BrO → •P + •Br + O2, ΔHr = 326 kJ/mole, ΔGr = 301 kJ/mole (15) 

The analysis presented above provides a strong indication that any ozone 

depletion must involve reaction of O3 with •PO (e.g., Reactions 6 and 7). The phosphorusoxygen bond in this diatomic molecule is too strong to allow formation of significant 

concentrations of atomic phosphorus. As noted above, however, the second reaction in the cycle 

(Reaction 7) is unfavorable at 298.15 K. The minimum stratospheric temperature (at the 

tropopause) varies from approximately 193 K to 223 K depending on the latitude, and the 

maximum stratospheric temperature (at the mesopause) is approximately 285 K depending on 

the season and latitude (Reference 25). Data from the JANAF tables (Reference 21) indicate that 

the reaction becomes even less favorable (ΔHr and ΔGr both become more positive) as the 

temperature decreases from 298.15 K. A major question is how fast •PO is removed by reaction 

with O3 (Reaction 6) before it reacts with O2 (the reverse of Reaction 7). Ozone concentrations 

vary widely in the stratosphere; however, we can take the concentration of ozone in the 

stratosphere to be approximately 1010 to 1011 molecules/cm3

 (Reference 26) compared to a 

maximum of around 109

 molecules/cm3 for •O(3P) (Reference 27).* Thus, the mixing ratio (the 

ratio to air) for •O(3

P) is calculated as approximately 1 ppm in the stratosphere. This implies 

that Reaction 7 would lie far to the left and that the concentration of •PO would be small. 

Missing, of course, from this analysis is an assessment of kinetics for Reactions 6 

and 7. Also missing is any discussion of other reactions of •PO and •PO2, both of which are 

highly polar and are likely to be absorbed onto ice crystals. Despite the shortcomings of this 

analysis, it is obvious that stratospheric ozone depletion by phosphorus-containing compounds is 

very unlikely. 

 

*The concentration of oxygen atoms in other than the 3

P ground state would be even smaller. 
13

2. Reactions with Tropospheric •OH 

Relatively little data are available on atmospheric lifetimes for phosphorus 

compounds. Atkinson has reported the rate constants for several phosphorus compounds 

(Reference 15), and these are shown in Table 2 along with atmospheric lifetimes estimated from 

the globally averaged tropospheric •OH concentration. Very limited data indicate that the 

presence of a phosphorus atom increases •OH reactivity. Thus, for example, methane (CH4) has 

a rate constant of 0.0836 x 10-12 cm3

/molecule-s at 298 K (Reference 15), a value considerably 

smaller than that found for phosphine (PH3), even though methane has one more reactive site 

(i.e., one more hydrogen atom). The activation energy for hydrogen atom abstraction decreases 

(as expected) with decreasing dissociation energy of the M-H bond (References 28 and 29), and 

this undoubtedly explains the higher rate constant for PH3 (bond strengths: H-PH2, 351.0 kJ/mol; 

C-CH3, 438.9 kJ/mol) (Reference 23). It is difficult to compare compounds with and without 

phosphorus and containing hydrogen bonded only to carbon, since there are no isostructural 

TABLE 2. RATE CONSTANTS •OH REACTIONS WITH PHOSPHORUS COMPOUNDS. 

Compound k2 at 297 K, cm3

/molecule-s Estimated tropospheric 

lifetime, days 

PH3 13 ± 3 x 10-12 0.9 

(CH3O)3PO 7.37 ± 0.74 x 10-12 1.6 

(C2H5O)3PO 55.3 ± 3.5 x 10-12 0.2 

(CH3O)2P(O)SCH3 9.29 ± 0.68 x 10-12 1.3 

(CH3S)2P(O)OCH3 9.59 ± 0.75 x 10-12 1.2 

(CH3O)3PS 69.7 ± 3.9 x 10-12 0.2 

(CH3O)2P(S)SCH3 56.0 ± 1.8 x 10-12 0.2 

(CH3O)2P(O)N(CH3)2 31.9 ± 2.4 x 10-12 0.4 

(CH3O)2P(S)N(CH3)2 46.8 ± 1.4 x 10-12 0.3 

(CH3O)2P(S)NHCH3 233 ± 15 x 10-12 0.05 

(CH3O)2P(S)NH2 244 ± 9 x 10-12 0.05 

(CH3O)2P(S)Cl 59.0 ± 3.8 x 10-12 0.2 
14

compounds. The rate constant of 3.92 x 10-12 cm3/molecule-s at 298 K for 2,2-dimethoxypropane (C(CH3)2(OCH3)2) is smaller than that of trimethyl phosphate ((CH3O)3PO), which has 

three fewer hydrogen atoms. The rate constant of 11.7 x 10-12 cm3

/molecule-s at 298 K for 

2,2-diethoxypropane (C(CH3)2(OC2H5)2) is smaller than that of triethyl phosphate 

((C2H5O)3PO), which has nearly the same number of hydrogen atoms (Reference 15). Since the 

predominant mechanism for reaction with the compounds in Table 2 appears to be hydrogen 

atom abstraction (Reference 15), it may be that a decreased bond strength accounts for the 

possibly higher reactivity for phosphorus-containing compounds; however, bond strength data to 

confirm this are lacking. 

3. Reactions with Tropospheric O3

Phosphorus compounds studied to date are quite unreactive toward ozone. An 

upper limit of 6 x 10-20 cm3

/molecule-s has been determined for reaction of trimethyl phosphate 

((CH3O)P=O) with ozone at 296 K (Reference 30). Using a globally averaged tropospheric 

ozone concentration, one estimates from this value a minimum lifetime of 386 days for reaction 

of trimethyl phosphate with tropospheric ozone. Atkinson (Reference 31) has reported rate 

constants with upper limits on the order of 10-19 at 296 K to 298 K for gas-phase reactions of O3

with phosphorus-containing compounds, giving estimated minimum lifetimes of around 200 

days. In none of these cases was a reaction observed. 

4. Other Tropospheric Removal Mechanisms 

It is likely that many phosphorus compounds are sufficiently polar that rainout is 

an important tropospheric removal mechanism. Atmospheric hydrolysis is possible for 

phosphonitriles containing direct P-halogen bonds even when the halogen is fluorine, and this is 

likely to be an effective tropospheric removal mechanism for such compounds. Photolysis is 

more important for compounds containing phosphorus than for corresponding carbon 

compounds; however, insufficient data are available to determine whether photolysis provides 

effective atmospheric removal. 
15

5. Lifetimes and GWPs 

No rigorous calculations of atmospheric lifetimes or GWPs of phosphoruscontaining compounds have been reported. A 3-day lifetime has been estimated for trimethyl 

phosphate based on the rate constant for reaction with •OH (Reference 30). This value differs 

slightly from that given in Table 2 due to the use of a slightly different globally averaged •OH. 

6. Conclusions 

Phosphorus compounds are unlikely sources of stratospheric ozone depletion due 

to the presence of phosphorus only. When hydrogen atoms are present, limited data indicate 

effective removal by tropospheric •OH and short atmospheric lifetimes. Insufficient data are 

available to judge tropospheric removal and atmospheric lifetimes for phosphorus compounds 

containing no hydrogen; however, it is likely that rainout and/or hydrolysis will give short 

atmospheric lifetimes. In summary, there is no evidence to suggest that phosphorus compounds 

will have unacceptable global atmospheric environmental properties (e.g., unacceptable ODP, 

GWP, or lifetime). 

B. TOXICITY 

A review of the toxicity of phosphorus compounds is provided in Reference 18. Except 

where noted, the present report includes only toxicity data obtained since Volume III 

(Reference 18) was prepared. One concern is that a number of phosphorus compounds 

(particularly phosphite esters) are cholinesterase inhibitors. 

1. Hexakis(2,2,2-trifluoroethoxy)cyclotriphosphazene toxicity 

An acute oral toxicity assessment utilizing male and female Fischer 344 rats and 

genotoxicity testing utilizing the Ames assay has been performed on hexakis(2,2,2-

trifluoroethoxy)cyclotriphosphazene (P3N3(OCH2CF3)6) (Reference 32). No deaths or signs of 

toxic stress were observed in any of the rats orally dosed at the limit test value of 5 grams of 

P3N3(OCH2CF3)6 per kilogram body weight. Body weights of the male rats during the 

subsequent 14-day observation period appeared unaffected by treatment. In the Ames assay, 

P3N3(OCH2CF3)6 produced no mutagenicity (base-pair substitution or frameshift mutation) in the 
16

bacterial (Salmonella) system. In summary, P3N3(OCH2CF3)6 produced no toxicity via the oral 

route of administration and was determined not to be genotoxic. 

2. Phosphonitrilic Chloride Compounds (Chlorophosphazene) 

In 1979, Ethyl Corporation submitted to the U. S. Environmental Protection Agency 

(EPA) in vitro and in vivo studies on two similar phosphonitrilic chloride compounds, each with 

the same CAS (Chemical Abstracts Service) No. (25034-79-1): 

— A refined (PNCl2)n composed of 87.7 percent (PNCl2)3 and 12.5 percent (PNCl2)4, 

 identified as compound code 3899-A 

— A crude product, consisting of 69.0 percent (PNCl2)3, 12.8 percent (PNCl2)4, 5.1 

 percent (PNCl2)5, and 1.8 percent (PNCl2)6 (total of 88.7 percent), identified as 

 compound code 3899-B. 

Sixteen reports, each covering a separate toxicological test for each compound, were 

submitted as follows: 

a. In vitro mammalian cell transformation assay (Reference 33 for refined compound 

and Reference 34 for crude compound). 

b. In vitro mammalian cell transformation assay in the presence of exogenous metabolic 

activation assay (Reference 35 for refined compound and Reference 36 for crude compound). 

c. In vivo mammalian cell point mutation assay (Reference 37 for refined compound and 

Reference 38 for crude compound). 

d. In vitro mammalian cell point mutation assay in the presence of exogeneous 

metabolic activation assay (Reference 39 for refined compound and Reference 40 for crude 

compound). 

e. In vivo cytogenetic assay in rodents for mutagenicity (Reference 41 for refined 

compound and Reference 42 for crude compound). 

f. Salmonella/Microsomal assay for bacterial mutagenicity assay (Reference 43 for 

refined compound and Reference 44 for crude compound). 

g. Differential inhibition of repair deficient and repair competent strains of Escherichia 

Coli: DNA (deoxyribonucleic acid) repair assay (Reference 45 for refined compound and 

Reference 46 for crude compound). 
17

h. Dominant lethal assay in rodents for mutagenicity assay (Reference 47 for refined 

compound and Reference 48 for crude compound). 

Table 3 paraphrases the results of the eight toxicity tests for each compound. Due to the 

limited solubility of the test compounds in vehicles compatible with mammalian cell culture 

systems, it was difficult to establish the exact concentration of that chemical in solution for the in 

vitro tests, a problem noted in the reports cited. 

The fact that a positive effect was obtained in a number of in vitro tests indicates that the 

material may be a potential mutagen. Thus, this class of materials may be mutagenic. Note that 

compound 3899-B (the crude compound) generally appeared more toxic, especially in the 

following tests: in vitro mammalian cell transformation assay (both with and without exogenous 

metabolic activation); in vitro cytogenetic assay in rodents for mutagenicity; Salmonella/ 

Microsomal assay for bacterial mutagenicity; and the differential inhibition of repair deficient 

and repair competent strains of Escherichia Coli (E coli): DNA repair assay. This indicates that 

impurities and other chemicals may increase toxicity to an unacceptable level even if the pure 

compounds are not unacceptably toxic. 

3. Other Phosphorus Compounds 

In a study of a number of phosphorus compounds, no toxic signs were observed 

following fifteen 6-hour exposures of two male and two female rats to 200 ppm tributyl 

phosphite, P(OC4H9)3 (Reference 49). The blood, urine, and organs (upon autopsy) were 

normal. The same study showed that tris(hydroxymethyl)propane bicyclic phosphite (I) has an 

unexpectedly high toxicity and is stated to be “one of the most toxic compounds handled in this 

laboratory.” All rats died following a 1-hour exposure to 10 ppm. The marked action on the 

central nervous system is probably due to its sufficient stability to penetrate cell membranes as a 

non-ionized molecule, possibly with subsequent hydrolysis. Note, however, that its hydrolysis 

product, dihydroxybutylphosphonic acid, has a low oral and parental toxicity. 
18

TABLE 3. RESULTS OF TOXICITY STUDIES FOR CHLOROPHOSPHAZENES. 

3899-A 3899-B 

In Vitro Mammalian Cell Transformation Assay 

a. Although the cytotoxicity tests were not 

reproducible in showing the toxic effects of 

the test compound with target cells, a dose 

response effect was observed in each of the 

cytotoxicity studies. 

b. The test compound was incapable of 

inducing morphological transformants (Type 

III foci) in the BALB/3T3 clone A31 cell 

system. 

a. The cytotoxicity studies demonstrated a 

dose response effect. 

b. The test chemical was demonstrated to be 

positive in producing a Type III foci at 60 

μg/mL concentration. Relative to solvent 

(acetone), the number of morphologically 

transformed (Type III) foci present at this 

concentration was statistically significant 

(P<0.05). 

In vitro Mammalian Cell Transformation Assay in the Presence of Exogenous 

Metabolic Activation 

a. Cytotoxic effects of the test agent appeared 

to increase in the presence of an exogeneous 

source of metabolizing activity (S-9). 

b. The test chemical was effective in inducing 

morphological transformation (Type III foci) 

at the 30 μg/mL concentration. Relative to the 

negative control, the number of morphologically transformants per number of cells at risk 

at the 30 μg/mL concentration was not 

statistically significant (P>0.05). 

a. Cytotoxic effects of the test agent appeared 

to increase in the presence of an exogeneous 

source of metabolizing activity (S-9). 

b. The test chemical was effective in inducing 

morphological transformation (Type III foci) 

in the BALB/3T3 Clone A31 cell system at all 

concentrations employed. 

In Vitro Mammalian Cell Point Mutation Assay 

a. Although the cytotoxicity tests were not 

reproducible in showing the toxic effects of 

the test compound with target cells, a dose 

response effect was observed in each of the 

cytotoxicity studies. 

b. The test compound was incapable of 

inducing oubain-resistant colonies at all of the 

doses tested. 

a. The cytotoxicity tests demonstrated a dose 

response effect. 

b. The test chemical was incapable of 

inducing oubain-resistant colonies at all 

concentrations. 
19

TABLE 3. RESULTS OF TOXICITY STUDIES FOR CHLOROPHOSPHAZENES 

(continued). 

3899-A 3899-B 

In Vitro Mammalian Cell Point Mutation Assay in the Presence of Exogeneous 

Metabolic Activation 

a. Cytotoxic effects of the test agent appeared 

to increase in the presence of an exogenous 

source of metabolizing activity (S-9). 

b. The test chemical was ineffective in 

inducing ouabain-resistant colonies in the 

BALB/3T3 Clone A31 cell system at all 

concentrations employed. 

a. The cytotoxic effects of the test agent 

appeared to increase in the presence of an 

exogenous source of metabolizing activity 

(S-9). 

b. The test chemical was ineffective in 

inducing ouabain-resistant colonies at all 

concentrations employed. 

In Vitro Cytogenetic Assay in Rodents for Mutagenicity 

The test compound exhibited little or no 

clastogenic activity. No dose response was 

observed. Under the conditions of this test, 

the data suggest that the test compound 

exhibits little or no mutagenic activity. 

The test compound exhibited moderate 

clastogenic activity. A dose response was 

observed. Under the conditions of this test, 

the data suggest that the compound exhibits 

mutagenic activity. 

Salmonella/Microsomal Assay for Bacterial Mutagenicity 

a. The test agent did not induce a significant 

increase in the number of point mutations in 

Salmonella typhimurium strains in the 

absence of activating system for strains 

TA1535, TA1537, TA1358, TA100, and 

TA98. 

b. It did not induce a significant increase in 

the number of point mutations with the 

addition of an exogenous source of liver 

enzymes for metabolic activation in strains of 

TA1535, TA1537, TA1358, TA100, and 

TA98. 

a. The test agent did not induce a significant 

increase in the number of point mutations in 

Salmonella typhimurium strains in the 

absence of activating system for strains 

TA1535, TA1537, TA100, and TA98. 

b. It did induce a significant increase in the 

number of point mutations in the absence of 

the activating system for strain TA1538. 

c. It did not induce a significant increase in 

the number of point mutations with the 

addition of an exogenous source of liver 

enzymes for metabolic activation in strains of 

TA1535, TA1537, TA1358, TA100, and 

TA98. 
20

TABLE 3. RESULTS OF TOXICITY STUDIES FOR CHLOROPHOSPHAZENES 

(CONCLUDED). 

3899-A 3899-B 

Differential Inhibition of Repair Deficient and Repair Competent Strains of 

Escherichia Coli (E. coli): DNA Repair 

The test chemical did not produce a 

statistically significant difference in its ability 

to produce cell death between repair deficient 

(polA-

) and repair competent (polA+) strains 

in E. coli. 

The test chemical did produce a statistically 

significant difference at 2 μl per plate in its 

ability to produce cell death between repair 

deficient (polA-

) and repair competent (polA+) 

strains in E. coli. 

Dominant Lethal Assay in Rodents for Mutagenicity 

The tests compound appeared to exhibit 

minimal activity in total implantations, 

number of live implantations per pregnant 

female, and pre-implantation losses. No 

statistically significant dose response was 

observed. The data suggest that the 

compound exhibits little or no mutagenic 

activity in the dominant lethal test. 

The tests compound appeared to exhibit 

minimal activity in total implantations, 

number of live implantations per pregnant 

female, and pre-implantation losses. No 

statistically significant dose response was 

observed. The data suggest that the 

compound exhibits little or no mutagenic 

activity in the dominant lethal test. 

CH3CH2C P

CH2

CH2O

CH2

O

O

I 

Table 4 contains information on toxicity and safety of some phosphorus-containing 

compounds related to compounds of interest here (Reference 18). Furthermore, the table has 

been updated with the addition of compounds having mouse and rat inhalation (inh) data from 

Reference 2 and the RTECS numbers where available. 
21

4. Conclusions 

A large amount of toxicity data is available for phosphorus compounds. In part 

this is because a number of phosphorus compounds (particularly phosphite esters) are 

cholinesterase inhibitors. The toxicity of phosphorus compounds is highly variable. As noted, 

many phosphorus compounds are cholinesterase inhibitors and, in some cases, highly toxic. 

Thus, toxicity must be given careful consideration. There is limited information indicating that 

toxicity may increase from phosphates to phosphites to phosphines. Phosphonitriles appear to 

have relatively low toxicities, but some show indications of mutagenicity. The presence of 

P-halogen bonds can cause severe irritation and lung damage owing to hydrolysis with formation 

of phosphorus-containing and hydrohalic acids. For this reason, compounds containing direct 

bonds to phosphorus are poor candidates as halon substitutes. 

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS. 

Compound Formula CAS No. Observationsa

bis(trifluoromethyl)-

chlorophosphine 

PCl(CF3)2 650-52-2 [BLO280] Ignites 

spontaneously in air. HR = 3. 

dibutylphosphate O=P(OH)(OC4H9)2 107-66-4 {RTECS HS630000} 

[DEG600] LD50 (rat, oral) = 

3200 mg/kg. Moderately 

toxic by ingestion. HR = 2. 

dibutylphosphonate O=PH(OC4H9)2 1809-19-4 {RTECS HS6475000} 

[DEG800] LD50 (rat, oral) 

= 3200 mg/kg, LD50 (rabbit, 

skin) = 1990 mg/kg. 

Moderately toxic by ingestion, 

skin contact. Severe eye 

irritant. HR = 2. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 
22

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (continued). 

Compound Formula CAS No. Observationsa

diethylphosphonate O=PH(OC2H5)2 762-04-5 {RTECS TG7875000} 

[DJW400] LD50 (rat, oral) 

= 3900 mg/kg, LD50 (rabbit, 

skin) = 2165 mg/kg. 

Moderately toxic by ingestion, 

skin contact. HR = 2. 

diisopropyl 

methylphosphonate 

O=P(CH3)-

[OCH(CH3)2]2

1445-75-6 {RTECS SZ9090000} 

[DNQ875] LD50 (rat, oral) 

= 826 mg/kg, LD50 (mouse, 

oral) = 1041 mg/kg. 

Moderately toxic by ingestion, 

skin contact. HR = 2. 

diisopropylphosphonate O=PH[OCH(CH3)2]2 1809-20-7 {RTECS SZ7660000} 

[DNQ600] LD50 (rat, oral) 

= 3100 mg/kg, LD50 (rabbit, 

skin) = 5700 mg/kg. 

Moderately toxic by ingestion. 

Mildly toxic by skin contact. 

HR = 2. 

dimethyl(1,2-dibromo2,2-dichloroethyl) 

phosphate 

O=P(OCH3)2-

(OCHBrCBrCl2) 

300-76-5 {RTECS TB9540000} 

[DRJ600] LD50 (rat, inh) = 

7700 μg/kg, LD50 (mouse, 

inh) = 156 mg/kg, LD50 (rat, 

oral) = 250 mg/kg, LD50

(rabbit, skin) = 1100 mg/kg. 

Poison by ingestion, 

inhalation. Moderately toxic 

by skin contact. Skin irritant. 

Insecticide of the cholinesterase inhibitor type. 

HR = 3. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 
23

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (continued). 

Compound Formula CAS No. Observationsa

dimethyl(2,2-

dichloroethenyl)-

phosphate 

O=P(OCH3)2-

(CH=Cl2) 

62-73-7 {RTECS TC0350000} 

[DRK200] LC50 (rat, inh, 4 

hr) = 15 mg/m3

, LC50 (mouse, 

inh, 4 hr) = 13 mg/kg, LD50

(rat, oral) = 25 mg/kg, LD50

(rabbit, skin) = 107 mg/kg. 

Poison by ingestion, 

inhalation, skin contact, 

intraperitoneal, intravenous, 

subcutaneous. Experimental 

teratogen, suspected 

carcinogen Cholinesterase 

inhibitor. HR = 3. 

dimethylphosphonate O=PH(OCH3)2 868-85-9 {RTECS SZ7710000} 

[DSG600] LD50 (rat, oral) 

= 3050 mg/kg, LD50 (rabbit, 

skin) = 2400 mg/kg. 

Moderately toxic by ingestion, 

skin contact. Experimental 

carcinogen. Skin, eye irritant. 

HR = 3. 

hexaethyltetraphosphate OP(OC2H5)2-

[OP(O)(OC2H5)]2-

OP(O)(OC2H5)2

757-58-4 {RTECS XF1575000} 

[HCY000] LD50 (rat, oral) 

= 7 mg/kg, LD50 (mouse, oral) 

= 56 mg/kg, LDLO (rat, skin) 

= 15 mg/kg. Poison by 

ingestion, skin contact, 

intraperitoneal, subcutaneous, 

intravenous, intramuscular. 

HR = 3. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 

b

The most probable (phosphonate) structure is given for these compounds, which can also be 

assigned the phosphite structure (P(OR)3). Both forms may exist. 
24

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (continued). 

Compound Formula CAS No. Observationsa

tris(2-chloroethyl) 

phosphite 

O=P(OCH2CH2Cl)2-

(CH2CH2Cl) b

140-08-9 {RTECS KK2810000} 

[PHO000] LD50 (rat, oral) 

= 100 mg/kg, LD50 (rabbit, 

skin) = 810 mg/kg. Poison by 

ingestion, intraperitoneal. 

Moderately toxic by skin 

contact. Severe eye irritant. 

HR = 3. 

tris(2-fluoroethyl) 

phosphite 

O=P(OCH2CH2F)2-

(CH2CH2F) b

63980-61-0 {RTECS KL1925000} 

[PHO250] LCLO (rat, inh, 10 

min) = 500 mg/m3

, LCLO

(mouse, inh, 10 min) = 

1000 mg/m3

. Poison by 

inhalation. HR = 3. 

tetraethylpyrophosphate P(O)(OC2H5)2-

OP(O)(OC2H5)2

107-49-3 {RTECS UX6825000} 

[TCF250] LD50 (rat, oral) 

= 500 μg/kg, LD50 (mouse, 

oral) = 7 mg/kg, LD50 (rat, 

skin) = 2400 μg/kg. Poison 

by ingestion, skin contact, 

intraperitoneal, intramuscular, 

other. Cholinesterase 

inhibitor. HR = 3. 

triethylphosphate O=P(OC2H5)3 78-40-0 {RTECS TC7900000} 

[TJT750] LDLO (rat, oral) 

= 1600 mg/kg, LDLO (mouse, 

oral) = 1600 mg/kg. 

Moderately toxic by ingestion, 

intraperitoneal, and 

intravenous. Reproductive 

effects. Mutagenic data. 

Cholinesterase inhibitor. 

HR = 2. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 

b

The most probable (phosphonate) structure is given for these compounds, which can also be 

assigned the phosphite structure (P(OR)3). Both forms may exist. 
25

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (continued). 

Compound Formula CAS No. Observationsa

triethylphosphite O=P(C2H5)(OC2H5)2

b

 122-52-1 {RTECS TH1130000} 

[TJT800] LD50 (rat, oral) 

= 3200 mg/kg. Moderately 

toxic by ingestion. Skin, eye 

irritant. HR = 2. 

tris(1-bromo-3-

chloroisopropyl)-

phosphate 

O=P[OCBr-

(CH3)(CH2Cl)]3

7328-28-1 {RTECS TC8600000} 

[TNE500] Mutagenic data. 

HR = D (insufficient data). 

triisooctylphosphite O=P[(CH2)5CH-

(CH3)2]-

[O(CH2)5CH(CH3)2]2

b

25103-12-3 {RTECS TH1150000} 

[TKT000] LD50 (rat, oral) 

= 9200 mg/kg, LD50 (rabbit, 

skin) = 3970 mg/kg. 

Moderately toxic by skin 

contact. Mildly toxic by 

ingestion. Skin irritant. 

HR = 2. 

triisopropylphosphite O=P[CH(CH3)2]-

[OCH(CH3)2]2

b

116-17-0 {RTECS TH2800000} 

[TKT500] LD50 (rat, oral) 

= 167 mg/kg. Poison by 

ingestion. Moderately toxic 

by intraperitoneal. HR = 3. 

trimethylphosphite O=P(CH3)(OCH3)2

b

 121-45-9 {RTECS TH1400000} 

[TMD500] LD50 (rat, oral) 

= 1600 mg/kg, LDLO (rabbit, 

skin) = 2200 mg/kg. 

Moderately toxic by ingestion, 

skin contact. Experimental 

teratogen. Severe skin, eye 

irritant. HR = 2. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 

b

The most probable (phosphonate) structure is given for these compounds, which can also be 

assigned the phosphite structure (P(OR)3). Both forms may exist. 
26

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (continued). 

Compound Formula CAS No. Observationsa

triphenylphosphite O=P(C6H5)(OC6H5)2

b 101-02-0 {RTECS TH1575000} 

[TMU250] LD50 (rat, oral) 

= 1600 mg/kg, LD50 (mouse, 

oral) = 1333 mg/kg. Poison 

by intraperitoneal, 

subcutaneous. Moderately 

toxic by ingestion. Severe 

skin irritant. HR = 3. 

tris(2-bromoethyl) 

phosphate 

O=P(OCH2CH2Br)]3 27568-90-7 {RTECS TC8480000} 

[TNE600] LCLO (rat, inh) = 

260 mg/m3

. Poison by 

inhalation. Mutagenic data. 

HR = 3. 

tributylphosphine 

oxide 

O=P(C4H9)3 814-29-9 {RTECS SZ1575000} 

[TNE750] Poison by 

intravenous route. Eye 

irritant. HR = 3. 

tritolylphosphate 

(tricresylphosphate) 

O=P(OC6H5CH3)3 1330-78-5 {RTECS TD0175000} 

[TNP500] LD50 (rat, oral) 

= 5190 mg/kg, LD50 (mouse, 

oral) = 3900 mg/kg. Poison 

by ingestion. Moderately 

toxic by skin contact. Eye, 

skin irritant. HR = 3. 

tri-2-tolylphosphate 

(tri-o-cresylphosphate) 

O=P(OC6H5CH3)3 78-30-8 {RTECS TD0350000} 

[TNP750] LD50 (rat, oral) 

= 1160 mg/kg. Poison by 

ingestion, subcutaneous, 

intramuscular, intravenous, 

intraperitoneal. Moderately 

toxic by ingestion. HR = 3. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 
27

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (continued). 

Compound Formula CAS No. Observationsa

dimethylfluorophosphate C4H10FO3P 358-74-7 {RTECS TE5600000} 

[DJJ400] LC50 (rat, inh, 10 

min) = 7 g/m3

, LC50 (mouse, 

inh, 10 min) = 500 mg/m3

. 

Poison by inhalation, skin. 

HR = 3. 

dimethylfluorophosphate C2H6FO3P 5954-50-7 {RTECS TE6125000} 

[DSA800] LC50 (rat, inh, 1 

min) = 1800 mg/m3

, LC50

(mouse, inh, 10 min) = 290 

mg/m3

. Poison by inhalation, 

skin contact, intravenous. 

HR = 3. 

2-ethyl2(hydroxymethyl)-1,3-

propane-diol, cyclic 

phosphate (1:1) 

C6H11O4P 1005-83-2 {RTECS TX6475000} 

[ELJ500] LC50 (rat, inh, 1 hr) 

= 30 mg/m3

. Poison by 

ingestion, inhalation, skin 

contact, intraperitoneal and 

intravenous routes. HR = 3. 

ethyl isopropyl 

fluorophosphonate 

C5H12FOP none 

assigned 

{RTECS SZ8552000} 

[ELX100] LC50 (rat, inh, 10 

min) = 260 mg/m3

, LC50

(mouse, inh, 5 min) = 245 

mg/m3

. Poisonous by 

inhalation, skin contact, and 

subcutaneous routes. HR = 3.

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 
28

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (concluded). 

Compound Formula CAS No. Observationsa

hexamethyl 

phosphoramide 

C6H18N3OP 680-31-9 {RTECS TD0875000} 

[HEK000] TCLO (rat, inh, 52 

wk continuous) = 50 ppb, 

carcinogenic. An 

experimental carcinogen and 

tumorigen. Moderately 

poisonous by ingestion, skin 

contact, intraperitoneal, 

intravenous. Experimental 

reproductive effects. Human 

mutagenic data. HR = 3. 

diisopropyl 

fluorophosphate 

C6H14FO3P 55-91-4 {RTECS TE5075000} 

[IKS249] LC50 (rat, inh, 10 

min) = 360 mg/m3

, LC50

(mouse, inh, 10 min) = 600 

mg/m3

, TCLO (human, inh, 10 

min) = 8200 μg/m3

 (eye and 

CNS). A poison by ingestion, 

inhalation, skin contact, 

subcutaneous, intravenous, 

intraperitoneal, ocular, and 

intramuscular routes. 

Experimental reproductive 

effects. HR = 3. 

isopropyl methyl 

fluorophosphonate 

C4H10FO2P 107-44-8 {RTECS TA8400000} 

[IPX000] LD50 (rat, inh, 10 

min) = 150 mg/m3

, LD50

(mouse, inh, 30 min) = 5 

mg/m3

, TCLO (man, inh) = 90 

μg/m3

 (eyes), LC50 (human, 

inh) = 70 mg/m3

. Deadly 

human poison by skin contact 

and inhalation. HR = 3. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 
29

TABLE 4. TOXICITY AND SAFETY INFORMATION FOR SELECTED 

PHOSPHORUS COMPOUNDS (concluded). 

Compound Formula CAS No. Observationsa

mevinphos 

(2-carbomethoxy-1-

methylvinyl dimethyl 

phosphate) 

C7H13O6P 7786-34-7 {RTECS GQ5250000} 

[MQR750] LC50 (rat, inh, 1 

hr) = 14 ppm. Poison by 

ingestion, inh, skin contact, 

subcutaneous, intravenous, 

intraperitoneal. HR = 3. 

monocrotophos 

(3-hydroxy-N-methylcis-crotonamide, 

dimethyl phosphate) 

C7H14NO5P 6923-22-4 {RTECS TC4375000} 

[MRH209] LC50 (rat, inh, 4 

hr) = 63 mg/m3

. Poison by 

ingestion, inh, skin contact, 

intraperitoneal, subcutaneous, 

and intravenous routes. 

Mutagenetic data. HR = 3. 

phosphine H3P 7803-51-2 {RTECS SY7525000} 

[PGY000] LC50 (rat, inh, 4 hr) 

= 11 ppm, LCLO (mouse, inh, 

2 hr) = 380 mg/m3

, TCLO

(human, inh) = 1000 ppm. A 

poison by inhalation. A very 

toxic gas. HR = 3. 

1,1,1-trishydroxymethylpropane bicyclic 

phosphite 

C6H11O3P 824-11-3 {RTECS TY6650000} 

[TNI750] LCLO (rat, inh, 4 hr) 

= 10 ppm. A poison by 

ingestion, inhalation, skin 

contact, intraperitoneal, and 

intravenous routes. HR = 3. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 
30

SECTION IV 

SILICON COMPOUNDS 

A review of the chemistry of silicon compounds related to compounds of interest in the 

development of fire suppressants is found in Reference 50. Except where noted, the information 

in this section is not contained in the reference cited. The conclusions are developed both from 

material presented here and from data presented in Reference 50. 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP 

1. Stratospheric Ozone Depletion 

Silicon, and other metalloids and metals, are known to be deposited in the upper 

atmosphere by meteors; however, it is believed that only the more polar metal oxides (e.g., 

sodium oxide) are likely to have any direct homogeneous chemical effect on atmospheric 

chemistry since these compounds have weak metal-oxygen bonds and can regenerate free atoms 

through photolysis and reactions with •O and •OH (Reference 51). (On the other hand, it must 

be recognized that silicon-containing particulates could play a significant role in heterogeneous 

atmospheric chemistry [Reference 52]). The silicon-oxygen bond is quite strong compared with 

the sodium-oxygen bond in the simple diatomics (Si-O, 799.6 kJ/mole; Na-O, 256.1 kJ/mole) 

(Reference 23). Thus, reactions proposed for ozone depletion by sodium (Reactions 16 and 17) 

are unlikely for ozone depletion by silicon (Reference 53). Sodium atoms generated in the 

atmosphere may also enhance ozone depletion by chlorine (Reference 54), although it is not 

known whether similar enhancement by silicon takes place. Note, however, that since 

approximately 40 to 300 metric tonnes of metals are deposited daily by meteorites 

(Reference 55), and since silicon is one of the more abundant elements in meteorites 

(Reference 54), it is unlikely that anthropogenic silicon would produce a significant atmospheric 

effect in comparison to other sources. 

•Na + O3 → •NaO + O2 (16) 

•NaO + •O → •Na + O2 (17) 
31

2. Reactions with Tropospheric •OH 

Rate constants for reactions of some silicon compounds with •OH free radicals 

and estimated lifetimes based on those rate constants are presented in Table 5. 

TABLE 5. •OH RATE CONSTANTS FOR SILICON COMPOUNDS. 

Reactant kOH, cm3

/molecule-s Atmospheric lifetime, daysa

SiH4

b

 12.2 x 10-12 0.97 

Si(CH3)H3

b

 34.3 x 10-12 0.35 

Si(CH3)2H2

b

 44.8 x 10-12 0.27 

Si(CH3)3Hb

 26.7 x 10-12 0.45 

Si(CH3)4

b

 1.09 x 10-12 10.9 

SiH4

c d

12.4 ± 1.9 x 10-12 0.96 

Si(C2H5)4

c e

75 x 10-12 0.16 

Si(CH3)4

f d

1.00 ± 0.09 x 10-12 11.9 

(CH3)3SiOSi(CH3)3

f d

1.38 ± 0.09 x 10-12 8.6 

[(CH3)2SiO]3

f d

5.2 ± 1.1 x 10-13 22.9 

[(CH3)2SiO]4

f d

1.01 ± 0.20 x 10-12 11.9 

[(CH3)2SiO]5

f d

1.55 ± 0.30 x 10-12 7.7 

(CH3)3SiOSi(CH3)2OHf d

1.89 ± 0.36 x 10-12 6.3 

a

Lifetimes estimated using globally averaged •OH model. 

b

Personal communication from Dr. Paul Marshall, Department of Chemistry, University of 

North Texas, Denton, to Dr. Robert E. Tapscott, 27 May 1997. Values are at 295 K. 

c

Reference 15 

d

297 K 

e

793 K 

f

Reference 31 

Methane (CH4) has a rate constant of 0.0836 x 10-12 cm3

/molecule-s at 298 K 

(Reference 15), a value considerably smaller than that found for silane (SiH4). This is, however, 

undoubtedly due to the lower Si-H bond strength in SiH4 (bond strengths: H-SiH3, 

384.1 kJ/mole; C-CH3, 438.9 kJ/mole) (Reference 23). Of greater interest are rate constants for 
32

silicon-containing molecules with no Si-H bonds. 2,2-Dimethylpropane (C(CH3)4) has an •OH 

rate constant of 0.875 x 10-12 cm3

/molecule-s at 298 K, which is slightly smaller than that of 

tetramethylsilane (Si(CH3)4). Unfortunately, other data allowing a direct comparison between 

C-H bond rate constants for carbon and silicon compounds are unavailable. Thus, at this time, 

there appears to be no reason to assume that, in the absence of Si-H bonds, silicon compounds 

are inherently more reactive toward •OH than are carbon compounds. 

3. Reactions with Tropospheric O3

Maximum rate constants (no reaction observed) on the order of 10-21 have been 

determined for the reaction of O3 with silicon-containing compounds (Reference 31). These data 

give minimum estimated lifetimes of the order of 2500 days, showing that there would be little, 

if any, removal by tropospheric ozone. 

4. Other Tropospheric Removal Processes 

In general, silicon compounds are considerably more unstable toward hydrolysis 

than are carbon compounds, and this property may provide an effective removal route for many 

of these materials. The Si-halogen bond hydrolyzes readily; however, the rapidity of this 

hydrolysis (and the resulting formation of toxic products) eliminates the consideration of 

compounds containing halogens bonded directly to silicon as fire suppressants (other than for 

basic laboratory studies). Compounds containing Si-H bonds also hydrolyze relatively easily 

when the pH is greater than 7, but are relatively stable in acidic solution. The alkoxy-Si bond is 

subject to hydrolysis and cleavage can cause condensation to higher polymers. Note, however, 

that this is highly dependent on the absence of steric hindrance. Alkoxy-substituted silanes with 

larger alkoxy groups are much more stable toward hydrolysis (Reference 56). Silanes containing 

only carbon bonded to silicon are relatively hydrolytically stable. 

Silicon compounds are expected to be more susceptible to photolysis than are the 

corresponding carbon compounds. The laser-induced photodissociation of silanes is one method 

used for vapor deposition of silicon films in the production of microelectronics (Reference 57). 
33

5. Lifetimes and GWPs 

A few, scattered, and, in some cases, suspect lifetime and GWP data have been 

reported for silicon-containing compounds (Reference 50). Siloxanes have been reported to 

have atmospheric lifetimes of from 10 to 30 days.*

6. Conclusions 

Silicon compounds are unlikely sources of stratospheric ozone depletion due to 

the presence of silicon only. When hydrogen atoms are present, limited data indicate effective 

removal by tropospheric •OH and short atmospheric lifetimes. Insufficient data are available to 

judge tropospheric removal and atmospheric lifetimes for silicon compounds containing no 

hydrogen, with one exception. Silicon compounds containing direct Si-halogen bonds will 

hydrolyze rapidly and give short atmospheric lifetimes; however, such compounds are unsuitable 

for halon substitutes due to their expected high toxicity. Photolysis may be a potential route to 

atmospheric removal in some cases. Of particular interest is possible photolytic “synergism” 

when both silicon and bromine are present; however, no data exist to evaluate such “synergism.” 

Unfortunately, there are no atmospheric data for fully halogenated organosilicon compounds 

containing no Si-H or Si-halogen bonds (and, in particular, compounds containing primarily 

fluorine as the halogen). Such compounds are unlikely to be removed rapidly by hydrolysis, 

rainout, or other processes, with the possible exception of photolytic decomposition. In 

summary, although there is no evidence that silicon compounds will have unacceptable global 

atmospheric environmental properties (e.g., unacceptable ODP, GWP, or lifetime), this may not 

be true for fully halogenated silicon compounds containing no Si-H or Si-halogen bonds. 

B. TOXICITY 

1. Newly Acquired Information 

The toxicity of silicon compounds is discussed in Reference 50 and, for that 

reason, will not be given here in any detail. 
34

One paper not presented in Reference 50 reported that no toxic signs were found 

for four male rats to a single 6-hour exposure at 8000 ppm or to fifteen 6-hour exposures at 

1000 ppm for tetramethylsilane, Si(CH3)4 (Reference 49). In the same study, twenty 6-hour 

exposures of four female rats to diphenyldimethoxysilane, Si(C6H5)2(OCH3)2, at its saturation 

vapor pressure showed no adverse effects. 

A recent EPA final action on significant new uses lists potential toxicity hazards 

for a number of silicon compounds (Reference 58). The final rule states that alkoxysilanes can 

cause lung toxicity and severe irritation to skin, eyes, and mucous membranes. Of particular 

interest is the finding that “Based on analogy to alkoxysilanes and perfluoro compounds,” 

Si(OCH3)3(CH2CH2CF2CF2CF2CF2CF2CF2CF2CF3) may cause lung toxicity, irritation to 

mucous membranes, liver toxicity, blood toxicity, immunosuppression, and reproductive 

toxicity. In part, this finding may be due to the analogy between the fluoroalkyl chain and some 

HFCs; it may have little or nothing to do with the silicon atom. 

2. Conclusions 

A relatively small amount of toxicity data is available for silicon compounds of 

primary interest here (compounds containing halogenated alkyl groups and no direct Si-halogen 

bonds). In general, siloxanes have moderately low toxicities. Alkoxy-containing silicon 

compounds could cause irritation to skin, eyes, and mucous membranes. The presence of 

Si-halogen bonds is expected, in all cases, to cause severe toxicity problems due to hydrolysis 

with formation of hydrohalic acids. Such compounds are probably unacceptable as halon 

substitutes. 

 

*Swanson, S. P., Cull, R. A., Bryant, D., and Moore, J., “New Technologies and Cleaning 

Performance Based on Volatile Methyl Siloxanes,” International Conference on Ozone 

Protection Technologies, Washington, DC, 21-23 October 1996. 
35

SECTION V 

FLUORINATED AMINES 

Some information on amines of interest as fire suppressants is presented in Reference 4. 

Information reported in that source will not be presented here except as noted. The conclusions 

are developed both from material presented here and from data presented in Reference 4. 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP 

1. Stratospheric Ozone Depletion 

The fact that nitrogen oxides could be direct depleters of stratospheric ozone 

through Reactions 3 through 5 (Reference 59) was actually recognized earlier than that 

halocarbons posed an environmental threat. The first concerns were about direct injection of 

nitrogen oxides into the stratosphere by high-altitude aircraft (Reference 60). Nitrogen 

compounds, however, play other roles in atmospheric chemistry involving ozone depletion. The 

ozone chemical balance depends directly on the total amount of active nitrogen species 

(Reference 61). Nitric oxide (NO) releases chlorine from chlorine monoxide (Reaction 18) 

(Reference 62). Nitrogen oxides can also decrease stratospheric ozone depletion by the 

formation of the chlorine nitrate (ClONO2) reservoir (Reaction 19) (Reference 62) and by the 

removal of •OH (Reactions 20 through 22) (Reference 63). Hydroxyl free radicals convert HCl 

and HBr to free chlorine and bromine atoms, which are potent depleters of stratospheric ozone. 

Removal of nitric acid by condensation is believed to play a major role in the Antarctic ozone 

hole (Reference 63). 

•NO + •ClO→ Cl + •NO2, ΔHr = -37 kJ/mole, ΔGr = -28 kJ/mole (18) 

•NO2 + •ClO→ ClONO2 (19) 

•OH + HNO3 → H2O + •NO3 (20) 

•NO3 + hν → •NO2 + •O (21) 

•OH + •NO2 + M → HNO3 + M*, ΔHr = -206 kJ/mole, ΔGr = -159 kJ/mole (22) 
36

Since some highly fluorinated amines have long atmospheric lifetimes, it is 

possible that anthropogenic amines of interest in this research could deplete stratospheric ozone. 

2. Reactions with Tropospheric •OH 

A relatively large amount of data are available for reactions of atmospheric •OH 

radicals with nitrogen-containing compounds; however, little experimental data (as opposed to 

estimations) are available for compounds that might be useful as halon replacements, those 

containing fully or partially fluorinated alkyl groups (to improve toxicity and flammability 

characteristics). Amines containing no hydrogen atoms are expected to be inert to attack by 

•OH, which can be seen in the absence of reaction observed with N,Nbis(pentafluoroethyl)penta-fluoroethanamine (N(CF2CF3)3), for which an •OH rate constant k2 < 

6 x 10-16 cm3

/molecule-s has been reported (Reference 64). This rate constant corresponds to an 

estimated atmospheric lifetime of greater than 55 years, a lifetime that is likely to be 

considerably higher. 

A relatively large amount of data are available for hydrogen-containing, 

nonfluorinated amines. Nitroalkanes (RNO2) have been relatively well studied (Reference 65), 

but these have little resemblance to amines, which are the most promising of the nitrogencontaining halon replacements. As a result of concerns about health impacts, the atmospheric 

chemistry of N-nitrosodimethylamine ((CH3)2N-NO) and dimethylnitramine ((CH3)2N-NO2) has 

been examined (Reference 66). Table 6 presents rate constants for hydroxyl free radicals 

reactions with several nonfluorinated amines (Reference 15). Where several values are given, 

the first value cited at or near 298 K is used for consistency. Note that these values are 

calculated on or near the high pressure limit. Atmospheric lifetimes in Table 6, calculated from 

a globally tropospheric •OH concentration of 9.7 x 105

 molecules/cm3, are on the order of a few 

days or less. The reactions of all of the compounds in Table 6 probably involve hydrogen atom 

abstraction from the alkyl groups. Since all of these compounds are highly polar, rainout would 

also be an effective removal mechanism. 
37

TABLE 6. •OH RATE CONSTANTS FOR NITROGEN-CONTAINING COMPOUNDS. 

Compound kOH, cm3

/molecule-s Temperature, 

K 

Atmospheric 

lifetime, daysa

Methylamine 

NH2(CH3) 

22.0 ± 2.2 x 10-12 299 0.5 

Ethylamine 

NH2(CH2CH3) 

27.7 ± 2.8 x 10-12 299.6 0.4 

Dimethylamine 

NH(CH3)2

64.5 ± 6.6 x 10-12 298.5 0.2 

Trimethylamine 

N(CH3)3

60.9 ± 6.1 x 10-12 298.7 0.2 

Diethylhydroxylamine 

N(CH2CH3)2OH 

101 x 10-12 308 0.1 

2-(Dimethylamino)ethanol 

CH2(N(CH3)2)CH2OH 

47 ± 12 x 10-12 300 ± 2 0.3 

2-Amino-2-methyl-1-propanol 

CH3C(CH3)(NH3)CH2OH 

28 ± 5 x 10-12 300 ± 2 0.4 

N-Nitrosodimethylamine 

(CH3)2N-NO 

02.53 ± 0.21 x 10-12 298 ± 2 4.7 

Dimethylnitramine 

(CH3)2N-NO2

03.84 ± 0.15 x 10-12 298 ± 2 3.1 

a

Based only on reaction with •OH. 

3. Reactions with Tropospheric O3

Rate constants have been compiled for gas-phase reactions of O3 with a number 

of nitrogen-containing compounds (Reference 67), and the data for amines are shown in Table 7. 

It is obvious that the rate constants increase and lifetimes (estimated from the globally averaged 

tropospheric O3 concentration) decrease with increasing alkyl substitution. This is also the 

direction of increasing proton affinity (-ΔH for the reaction B + H+ → BH+, where B is a base) 

(Reference 68). 
38

TABLE 7. RATE CONSTANTS FOR REACTIONS OF O3 WITH AMINES 

Compound k2 at 296 K, 

cm3

/molecule-s 

Estimated tropospheric 

lifetime, days 

Proton affinity, 

kJ/mole 

NH2(CH3) 2.13 ± 0.29 x 10-20 1087 896 

NH2(CH2CH3) 2.76 ± 0.34 x 10-20 839 908 

NH(CH3)2 2.61 ± 0.30 x 10-18 008.9 923 

N(CH3)3 9.73 ± 1.02 x 10-18 002.4 938 

The reactions appear to proceed by addition of O3 to the nitrogen to give 

R3N+-O-O-O-, which then decomposes by uncertain mechanisms. Data for reactions involving 

halogen-substituted alkyl amines have not been reported; however, it is likely that the reaction 

rates will decrease with increasing halogen substitution, which makes the nitrogen atom less 

electron rich. 

Rate constants have also been reported for reaction of O3 with pyridines 

(approximately 5 x 10-20 to 50 x 10-20 cm3

/molecule-s) and for unsaturated nitriles (< 1 x 10-19 to 

1.38 x 10-19 cm3

/molecule-s for acrylonitrile (CH2=CHCN) and 3.52 x 10-19 for methacrylonitrile 

(CH2=C(CH3)CN)) (Reference 31). Ozone is known to react with alkene derivatives, and the 

results for the acrylonitriles probably have little to do with the presence of nitrogen. The 

pyridines, which are, at best, distantly related to the amines of interest have calculated lifetimes 

for reaction with tropospheric ozone of approximately 1 year or less. The maximum values of 

the rate constants for reaction of N-nitrosodimethylamine ((CH3)2N-NO) and dimethylnitramine 

((CH3)2N-NO2) with tropospheric ozone are 1 x 10-20 and 3 x 10-21 cm3

/molecule-s (calculated 

lifetimes of 6 and 21 years) and could be less than this (Reference 66). Photolysis is probably 

the primary removal mechanism for N-nitrosodimethylamine.

4. Lifetimes and GWPs 

Of particular interest are alkyl-substituted amines, with one or more alkyl groups 

containing bromine atoms. The primary problem is that fluorination is needed to decrease both 

the flammability and toxicity of amines. As fluorination increases, both the polarity and the 

amine flammability are expected to decrease (for different reasons). The polarity is directly 
39

related to toxicity, since highly polar amines are strong bases and therefore irritants. The 

polarity is, however, also directly related to the effectiveness of atmospheric removal. 

Nonfluorinated amines are expected to undergo significant rainout. 

Reported lifetimes and GWPs are reviewed for several fluoroalkyl amines in 

Reference 4; however, the values are highly suspect. For example, the lifetime of (CH3)2NC2F5

is reported as 250 years, while that of the much less hydrogen-rich compound (CF3)2NCF2CF2H 

is given as 2.10 years.* Moreover, the estimation or calculation methods for the lifetimes and 

GWPs have not been reported. Eliminating the highly questionable value of 250 years gives 

estimated lifetimes for hydrofluoroamines (HFAs) of around 0.3 to 3 years.* 

5. Conclusions 

While there is nothing inherent in nitrogen compounds that would lead to 

atmospheric lifetime or GWP problems, individual compounds may have significant effects. 

HFAs have estimated atmospheric lifetimes in the order of 0.3 to 3 years. Replacement of 

fluorine atoms with bromine atoms would tend to reduce these numbers by a factor of 10 in some 

compounds. Data indicate that for bromine-containing alkanes, each 10-year increase in the 

atmospheric lifetime increases the ODP by approximately a factor of 2 (Reference 4). Therefore, 

hydrofluorobromoamines should have low ODPs. Any impact from nitrogen on stratospheric 

ozone would be negligible compared to that from bromine. 

B. TOXICITY 

1. Hydrofluoroamines 

The acute inhalation toxicities of some HFAs are given in Table 8.* These have 

also been reviewed in Reference 4; however, here the LC50 values are also given as volume 

percent. Although these lower bounds do not cause any concern, measurements at higher 

 

*Misaki, S., and Sekiya, A., “Development of a New Refrigerant,” presented at the International 

Chemical Congress of Pacific Basin Societies, Honolulu, Hawaii, 17-22 December 1995. 
40

concentrations are needed. In addition to the compounds shown in Table 8, the LCLO for mouse 

inhalation has been reported as 0.0123 percent for 2,2,2-trifluoroethylamine ((CF3CH2)NH2) 

(Reference 2), a value that appears rather low; however, this compound contains hydrogen atoms 

directly bonded to the nitrogen. 

TABLE 8. ACUTE INHALATION TOXICITY OF HYDROFLUOROAMINES. 

Compound Subject LC50, mg/L 

Molecular 

weight 

LC50, % 

 (CF3)2NCH3 3-hr rat >20 113.99 >0.43 

 (CF3)2NCF2CF2H 3-hr rat >20 253.04 >0.19 

 (CF3)2NCFHCF3 3-hr rat >20 253.04 >0.19 

 (CF3)2NCH2CF3 3-hr rat >20 235.05 >0.21 

 (CF3)2NCH2CF2H 4-hr rat >20 217.06 >0.23 

 (CF3)2NCH2CH3 4-hr rat >20 181.08 >0.27 

2. Other Fluorine-Containing Nitrogen Compounds 

A review of Reference 2 identified inhalation toxicity data for over 120 

compounds containing both nitrogen and fluorine; however, inhalation data are available for 

only 6 compounds (Table 9). The remaining compounds either did not reference toxicity data or 

the data were for oral, intravenous, or some other exposure route. Nearly every compound in 

this limited set is given a SAX HR of 3, signifying the worst hazard level. Note, however, that 

none of these compounds is closely related to amines, and most contain groups known to lead to 

toxicity. Many N-nitroso compounds, such as the nitrosocarbamates, are carcinogens. 
41

TABLE 9. TOXICITY, SAFETY INFORMATION FOR SELECTED N, F COMPOUNDS. 

Compound Formula CAS No. Observationsa

fluoroacetanilide C8H8FNO 330-68-7 {RTECS AE2975000} 

[FFH000] LCLO (mouse, inh, 

10 min) = 480 mg/m3

. Poison 

by ingestion, intraperitoneal, 

and possible other routes. 

Moderately toxic by 

inhalation. HR = 3. 

$-fluoroethyl-N-($-

chloroethyl)-Nnitrosocarbamate 

C4H8ClFN2O3 63884-92-4 {RTECS EZ2275000} 

[FIH000] LCLO (guinea pig, 

inh, 10 min) = 300 mg/m3

. 

Poison by inhalation. HR = 3.

2-fluoroethyl-N-methylN-nitrosocarbamate C4H7FN2O3 63982-15-0 {RTECS FC6475000} 

[FIS000] LCLO (guinea pig, 

inh, 10 min) = 100 mg/m3

, 

LCLO (mouse, inh, 10 min) = 

500 mg/m3

. Poison by 

inhalation. HR = 3. 

3-nitrobenzotrifluoride C7H4F3NO2 98-46-4 {RTECS XT3500000} 

[NFJ500] LC50 (rat, inh) = 

870 mg/kg, LC50 (mouse, inh, 

2 hr) = 880 mg/m3

. 

Moderately toxic by 

ingestion, inhalation, and 

subcutaneous routes. HR = 3. 

(",","-trifluoro-mtolyl)isocyanate 

C8H4F3NO 329-01-1 {RTECS NR0200000} 

[TKJ250] LC50 (rat, inh) = 

3600 mg/m3

, LC50 (mouse, 

inh) = 3300 mg/m3

. 

Moderately toxic by 

ingestion, inhalation, 

intraperitoneal routes. HR = 

2. 

2,4,6-trifluoro-s-triazine C3F3N3 675-14-9 {RTECS XZ1750000} 

[TKK000] LC50 (rat, inh, 4 

hr) = 3.1 ppm. Poison by skin 

contact, inhalation. HR = 3. 

a

The SAX No. (Reference 2) is given in brackets followed by information from that reference; the 

RTECS No. (Reference 3) is given in braces. “HR” denotes the SAX Hazard Rating. 
42

3. Conclusions 

No generalities on the toxicity of nitrogen compounds can be made. Amines 

range in toxicity from poisons to only slightly toxic. In fact, fully fluorinated alkyl amines show 

no toxicity. Some amines are skin irritants while others are sensitizers (Reference 2). Although 

LC50 values have been determined for some hydrofluoroamines (HFA), the test levels are very 

low and measurements at higher concentrations are needed. One brominated compound 

((CH3)2NCF2CBrF2) has tested negative for genotoxicity and cytotoxicity (Reference 69). 
43

SECTION VI 

FLUORINATED ETHERS 

Some information on fluorinated ethers of interest as fire suppressants is derived from 

Reference 4. Information reported in that source will not be included here except as noted. A 

large amount of new material has been obtained. The conclusions are developed both from 

material presented here and from data in Reference 4. 

A. ATMOSPHERIC LIFETIME, ODP, AND GWP 

1. Reactions with Tropospheric •OH 

The presence of the oxygen ether linkage increases reactivity toward hydrogen 

abstraction, though fluorine substitution decreases the enhancement (Reference 14). 

Hydrofluorocarbons show an approximately linear correlation between kOH and the highestoccupied molecular orbital (HOMO) energies (Reference 16). Rate constants, many estimated, 

reported for reaction of hydrofluoroethers (HFE) with •OH are shown in Table 10. In the 

absence of a hydrogen atom, fluorinated ethers exhibit no reaction with •OH. 

2. Reactions with Tropospheric O3

Very little work has been done on reactions of ethers with ozone, primarily due to 

their low reactivity. The rate constants for reaction with furan (2.42 x 10-18 cm3

/molecule-s) and 

2,5-dihydrofuran (1.61 x 10-17 cm3

/molecule-s) are relatively large owing to the presence of a 

double bond (Reference 67). For saturated ethers, however, rate constants are expected to be 

extremely slow, ≤ 10-20 at room temperature (Reference 67). 

3. Lifetimes and GWPs 

The energy of the HOMO has been used to estimate atmospheric lifetimes for a 

number of HFEs (Reference 70). A list of atmospheric lifetimes reported for halogenated ethers, 

most of which are estimated, are shown in Table 11. 
44

TABLE 10. RATE CONSTANTS FOR HYDROFLUOROETHER REACTIONS WITH •OH. 

Halocarbon No. Formula kOH, cm3

/molecule-s Reference 

HFE-CE225ea -O-CF2CHFCF2- a2.51 x 10-15 14 

a

2.4 x 10-15 14 

HFE-E CH3-O-CF(CF3)2

a,b1.6 x 10-14 13 

HFE-E CH3-O-CH(CF3)2

a,b2.2 x 10-13 13 

HFE-E CHF2-O-CH(CF3)2

a,b1.8 x 10-14 13 

HFE-E CH2F-O-CH(CF3)2 7.3 x 10-14 71 

HFE-E125 CHF2-O-CF3 a3.38 x 10-15 14 

a

3.56 x 10-15 14 

c

4.2 x 10-16 72 

HFE-E134 CHF2-O-CHF2 a2.53 x 10-14 14 

a

2.41 x 10-14 14 

a,b3 x 10-15 13 

c

2.3 x 10-15 72 

HFE-E143a CH3-O-CF3 a2.14 x 10-14 14 

HFE-E227ca1 CHF2-O-CF2CF3

b,d1.95 x 10-15 16 

HFE-E227ca2 CHF2CF2-O-CF3

b,d4.5 x 10-15 16 

HFE-E227ea1 CF3CHF-O-CF3

a,b5.1 x 10-15 13 

b,d3.5 x 10-15 16 

HFE-E236ca1 CHF2-O-CF2CHF2

b,d1.15 x 10-14 16 

HFE-E236ca12 CHF2-O-CF2-O-CHF2 1.3 x 10-15 72 

HFE-E236ea1 CHF2-O-CHFCF3

a,b9.5 x 10-15 13 

b,d7 x 10-15 16 

HFE-E236ea2 CHF2CHF-O-CF3

b,d3 x 10-14 16 

HFE-E236mf1 CF3CH2-O-CF3

a,b1.5 x 10-14 13 

HFE-E245ca2 CHF2-O-CF2CH2F b,d7 x 10-15 16 

HFE-E245cb1 CH3-O-CF2CF3 c1.07 x 10-14 73 

a,b4.6 x 10-14 13 

b,d5.5 x 10-14 16 

HFE-E245cb2 CH3CF2-O-CF3

b,d1.5 x 10-15 16 

a

296K 

b

Estimated from HOMO energy. 

c

298K 

d

Average 
45

TABLE 10. RATE CONSTANTS FOR HYDROFLUOROETHER REACTIONS WITH 

•OH (concluded). 

Halocarbon No. Formula kOH, cm3

/molecule-s Reference 

HFE-E245fa1 CHF2-O-CH2CF3 a1.25 x 10-12 14 

a

1.2 x 10-14 14 

a,b3.3 x 10-14 13 

b,d5 x 10-14 16 

HFE-E245fa2 CF3-O-CH2CHF2

a,b2.5 x 10-14 13 

b,d3.5 x 10-14 17 

HFE-E254cb1 CH3-O-CF2CHF2

a,b6.5 x 10-14 13 

b,d1.5 x 10-13 17 

HFE-E254cb2 CH3CF2-O-CHF2

b,d7.5 x 10-15 16 

HFE-E254fa1 CHF2-O-CH2CHF2

b,d9 x 10-14 16 

HFE-E254fb1 CH2F-O-CH2CF3

b,d4 x 10-13 16 

HFE-E254fb2 CH2FCH2-O-CF3

b,d6.5 x 10-14 16 

HFE-E263fb1 CH3-O-CH2CF3 a6.24 x 10-13 14 

a,b5.3 x 10-13 13 

b,d2 x 10-12 16 

HFE-E263fb2 CH3CH2-O-CF3

b

2 x 10-13 16 

HFE-E329p2 CHF2CF2-O-CF2CF3

a,b8.2 x 10-15 13 

HFE-E338mf2 CF3CH2-O-CF2CF3

a,b1.3 x 10-14 13 

HFE-E347pf2 CF3CF2-O-CH2CHF2

a,b2 x 10-14 13 

HFE-E347s1 CH3-O-CF2CF2CF3 c1.14 x 10-14 73 

a,b4.4 x 10-14 13 

HFE-E356mec1 CH3-O-CF2CHFCF3

a,b5.9 x 10-14 13 

HFE-E356pcc1 CH3-O-CF2CF2CHF2

a,b6 x 10-14 13 

HFE-E356pfc1 CHF2-O-CH2CF2CHF2

a,b4.4 x 10-14 13 

HFE-E356pfc2 CHF2CH2-O-CF2CHF2

a,b2.8 x 10-14 13 

HFE-E365mc1 CH3-O-CH2CF2CF3

a,b4.9 x 10-13 13 

HFE-E374pcf2 CH3CH2-O-CF2CHF2

a,b1.3 x 10-13 13 

HFE-E4-3-

10pccc124 

CHF2-O-CF2-O-CF2CF2-

O-CHF2

c,d4 x 10-15 72 

a

296K 

b

Estimated from HOMO energy. 

c

298K 

d

Average 
46

TABLE 11. ATMOSPHERIC LIFETIMES FOR FLUORINE-CONTAINING ETHERS. 

Halocarbon No. Formula Atmospheric 

lifetime, years 

Reference

FE-CE216 -O-CF2CF2CF2- a>330 14 

HCFE-E235ca2 CHF2-O-CF2CHClF a6 71 

HCFE-E235da1 CHF2-O-CHClCF3 a

5 71 

HFE-CE225ea -O-CF2CHFCF2- b,c26 14 

HFE-E CHF2-O-CH(CF3)2 a

3.77 d

HFE-E CH3-O-CF(CF3)2 4.9 d

 b,c3.5 13 

 4.3 74 

HFE-E CH3-O-CH(CF3)2

b,c0.25 13 

HFE-E CH2F-O-CH(CF3)2 a

1.4 71 

 b,c3.1 13 

HFE-E HF2CO(CF2O)n(CF2CF2O)mCF2H e

8 f

HFE-E125 CHF2-O-CF3 82 75 

 19 14 

 b,c156 72 

HFE-E134 CHF2-O-CHF2 8 75 

 b,c2.6 14 

 b,c19 13 

 b,c35 72 

HFE-E143a CH3-O-CF3

b,c3 14 

HFE-E227ca1 CHF2-O-CF2CF3

b,e,f16.05 70 

 b,e,f33 16 a

Estimated 

b

For reaction with •OH only. 

c

Non-rigorous calculation. 

d

Misaki, S., and Sekiya, A., “Development of a New Refrigerant,” presented at the International Chemical 

Congress of Pacific Basin Societies, Honolulu, Hawaii, 17-22 December 1995. e

Average 

f

Estimated from HOMO energy. 

g

Calculated by N. R. Jensen et al., E. U. Joint Research Centre, Ispra, Italy; personal correspondence from M. 

Visca, Ausimont S.p.A., to Dr. Robert E. Tapscott, 11 November 1997. h

Grenfell, M. W., Klink, F. W., Owens, J. G., and Yanome, H., “New Fluorinated Solvent Alternatives,” 

presented at Precision Cleaning '95, Rosemont, Illinois, 15-17 May 1995. 
47

TABLE 11. ATMOSPHERIC LIFETIMES FOR FLUORINE-CONTAINING 

ETHERS (continued). 

Halocarbon No. Formula Atmospheric 

lifetime, years 

Reference

HFE-E227ca2 CHF2CF2-O-CF3

b,e,f12.1 70 

 b,e,f17.5 16 

HFE-E227ea1 CF3CHF-O-CF3

b,c11 13 

 20 74 

 b,e,f23.5 16 

 b,e,f14.9 70 

HFE-E236ca1 CHF2-O-CF2CHF2

b,e,f5.95 70 

 b,e,f8.5 16 

HFE-E236cb1 CH2F-O-CF2CF3

b,e,f5.9 70 

HFE-E236cb2 CH2FCF2-O-CF3

b,e,f6.7 70 

HFE-E236ea1 CHF2-O-CHFCF3 a

4.04 d

 b,e,f6.5 16 

 b,e,f7.5 70 

HFE-E236ea2 CHF2CHF-O-CF3

b,e,f5.1 70 

 b,e,f4.55 16 

HFE-E236mf1 CF3CH2-O-CF3

b,c3.7 13 

 b,e,f4.75 70 

HFE-E245ca1 CH2F-O-CF2CHF2

b,e,f3.5 70 

HFE-E245ca2 CHF2-O-CF2CH2F a

2.18 d

 b,e,f6.5 16 

 b,e,f4.4 70 a

Estimated 

b

For reaction with •OH only. 

c

Non-rigorous calculation. 

d

Misaki, S., and Sekiya, A., “Development of a New Refrigerant,” presented at the International Chemical 

Congress of Pacific Basin Societies, Honolulu, Hawaii, 17-22 December 1995. e

Average 

f

Estimated from HOMO energy. 

g

Calculated by N. R. Jensen et al., E. U. Joint Research Centre, Ispra, Italy; personal correspondence from M. 

Visca, Ausimont S.p.A., to Dr. Robert E. Tapscott, 11 November 1997. h

Grenfell, M. W., Klink, F. W., Owens, J. G., and Yanome, H., “New Fluorinated Solvent Alternatives,” 

presented at Precision Cleaning '95, Rosemont, Illinois, 15-17 May 1995. 
48

TABLE 11. ATMOSPHERIC LIFETIMES FOR FLUORINE-CONTAINING 

ETHERS (continued). 

Halocarbon No. Formula Atmospheric 

lifetime, years 

Reference

HFE-E245cb1 CH3-O-CF2CF3 6.5 73 

 b,c1.2 13 

 b,e,f0.85 16 

 b,e,f1.4 70 

HFE-E245cb2 CH3CF2-O-CF3

b,e,f11.2 70 

 b,e,f27.5 16 

HFE-E245ea1 CHF2-O-CHFCHF2

b,e,f2.75 70 

HFE-E245eb1 CH2F-O-CHFCF3

b,e,f2.2 70 

HFE-E245eb2 CH2FCHF-O-CF3

b,e,f3.35 70 

HFE-E245fa1 CHF2-O-CH2CF3

b,c5.2 14 

 b,c1.7 13 

 b,e,f1.15 16 

 a

4.71 d

 b,f1.9 70 

HFE-E245fa2 CF3-O-CH2CHF2 c

2.2 13 

 b,e,f1.45 16 

 b,e,f2.65 70 

HFE-E254ca1 CH2F-O-CF2CH2F b,e,f3.1 70 

HFE-E254cb1 CH3-O-CF2CHF2 a

0.47 d

 b,c0.85 13 

 b,e,f0.35 16 

 b,e,f0.95 70 a

Estimated 

b

For reaction with •OH only. 

c

Non-rigorous calculation. 

d

Misaki, S., and Sekiya, A., “Development of a New Refrigerant,” presented at the International Chemical 

Congress of Pacific Basin Societies, Honolulu, Hawaii, 17-22 December 1995. e

Average 

f

Estimated from HOMO energy. 

g

Calculated by N. R. Jensen et al., E. U. Joint Research Centre, Ispra, Italy; personal correspondence from M. 

Visca, Ausimont S.p.A., to Dr. Robert E. Tapscott, 11 November 1997. h

Grenfell, M. W., Klink, F. W., Owens, J. G., and Yanome, H., “New Fluorinated Solvent Alternatives,” 

presented at Precision Cleaning '95, Rosemont, Illinois, 15-17 May 1995. 
49

TABLE 11. ATMOSPHERIC LIFETIMES FOR FLUORINE-CONTAINING 

ETHERS (continued). 

Halocarbon No. Formula Atmospheric 

lifetime, years 

Reference

HFE-E254cb2 CH3CF2-O-CHF2

b,e,f3.85 70 

 b,e,f6 16 

HFE-E254ea1 CH2F-O-CHFCHF2

b,e,f1.3 70 

HFE-E254ea2 CH2FCHF-O-CHF2

b,e,f1.75 70 

HFE-E254eb1 CH3-O-CHFCF3

b,f0.5 70 

HFE-E254eb2 CH3CHF-O-CF3

b,e,f2.45 70 

HFE-E254fa1 CHF2-O-CH2CHF2

b,e,f1.05 70 

 b,e,f0.45 16 

HFE-E254fb1 CH2F-O-CH2CF3

b,f0.5 70 

 b,e,f0.15 16 

HFE-E254fb2 CH2FCH2-O-CF3

b,e,f1.6 70 

 b,e,f0.7 16 

HFE-E263fb1 CH3-O-CH2CF3

b,c0.1 14 

 b,f<0.1 16 

 b,c0.1 13 

HFE-E263fb2 CH3CH2-O-CF3

b,f0.3 16 

HFE-E329p2 CHF2CF2-O-CF2CF3

b,c6.8 13 

HFE-E338mf2 CF3CH2-O-CF2CF3

b,c4.3 13 

HFE-E347pf1 CHF2-O-CH2CF2CF3 a

1.62 d

HFE-E347pf2 CF3CF2-O-CH2CHF2

b,c2.8 13 

HFE-E347s1 CH3-O-CF2CF2CF3 6.4 73 

 b,c1.3 13 

 5.6 74 a

Estimated 

b

For reaction with •OH only. 

c

Non-rigorous calculation. 

d

Misaki, S., and Sekiya, A., “Development of a New Refrigerant,” presented at the International Chemical 

Congress of Pacific Basin Societies, Honolulu, Hawaii, 17-22 December 1995. e

Average 

f

Estimated from HOMO energy. 

g

Calculated by N. R. Jensen et al., E. U. Joint Research Centre, Ispra, Italy; personal correspondence from M. 

Visca, Ausimont S.p.A., to Dr. Robert E. Tapscott, 11 November 1997. h

Grenfell, M. W., Klink, F. W., Owens, J. G., and Yanome, H., “New Fluorinated Solvent Alternatives,” 

presented at Precision Cleaning '95, Rosemont, Illinois, 15-17 May 1995. 
50

TABLE 11. ATMOSPHERIC LIFETIMES FOR FLUORINE-CONTAINING 

ETHERS (concluded). 

Halocarbon No. Formula Atmospheric 

lifetime, years 

Reference

HFE-E356mcf2 CF3CH2-O-CF2CH2F a1.84 d

HFE-E356mec1 CH3-O-CF2CHFCF3

b,c0.94 13 

HFE-E356mff2 CF3CH2-O-CH2CF3 a

0.5 d

HFE-E356pcc1 CH3-O-CF2CF2CHF2

b,c0.93 13 

HFE-E356pfc1 CHF2-O-CH2CF2CHF2

b,c1.3 13 

HFE-E356pfc2 CHF2CH2-O-CF2CHF2

b,c2 13 

HFE-E365mc1 CH3-O-CH2CF2CF3

b,c0.11 13 

HFE-E365sf2 CH3CH2-O-CF2CF3 a

0.3 d

HFE-E374pcf2 CH3CH2-O-CF2CHF2

b,c0.43 13 

HFE-E4-3-10pccc124 CHF2-O-CF2-O-CF2CF2-O-CHF2

b,c7 72 

HFE-E449s1 CF3CF2CF2CF2-O-CH3 4.1 76 

HFE-E569sf2 CF3CF2CF2CF2-O-CH2CH3 1.2 h

a

Estimated 

b

For reaction with •OH only. 

c

Non-rigorous calculation. 

d

Misaki, S., and Sekiya, A., “Development of a New Refrigerant,” presented at the International Chemical 

Congress of Pacific Basin Societies, Honolulu, Hawaii, 17-22 December 1995. e

Average 

f

Estimated from HOMO energy. 

g

Calculated by N. R. Jensen et al., E. U. Joint Research Centre, Ispra, Italy; personal correspondence from M. 

Visca, Ausimont S.p.A., to Dr. Robert E. Tapscott, 11 November 1997. h

Grenfell, M. W., Klink, F. W., Owens, J. G., and Yanome, H., “New Fluorinated Solvent Alternatives,” 

presented at Precision Cleaning '95, Rosemont, Illinois, 15-17 May 1995. 

4. Hydrofluoroethers 

Hydrofluoropolyethers (HFPE) are starting to be commercialized, and the 

environmental characteristics appear relatively good (Reference 72). The degradation products 

resulting from the alkoxy radicals formed after initial hydrogen atom abstraction from 

hydrofluoropolyethers (HFPE) have been studied (Reference 77). Chlorine-atom initiated 

photooxidations of the HFPEs in air (HCF2OCF2OCF2OCF2H, HCF2OCF2CF2OCF2H and 

HCF2OCF2OCF2H) produced C(O)F2 as the only carbon-containing product, with observed 

average C(O)F2 molar formation yields of 4.73, 3.77, and 2.82, respectively. In the early stages 

of the reaction, the C(O)F2 molar formation yields are close to the number of carbon atoms in 
51

each parent HFPE. Based on current knowledge of degradation pathways of hydrofluorocarbons 

(HFC) and hydrochlorofluorocarbons (HCFC), it is expected that C(O)F2 will also be produced 

with near-unit yield per carbon atom from the above HFPEs in the troposphere, where loss 

processes would be initiated primarily by reaction with •OH radicals. 

5. Conclusions 

There is no indication that the ether linkage provides any significant contribution 

to rainout. The polarity is too small. Perfluorinated saturated ethers are expected to have 

atmospheric lifetimes similar to those of the perfluorinated alkanes, a property that makes their 

use as halon replacements questionable. The atmospheric lifetimes for partially fluorinated 

ethers are much shorter. Even in this case, however, the lifetimes appear to be sufficiently long 

that ODPs for bromine-substituted ethers would be unacceptable. 

B. TOXICITY 

The toxicity of ethers has been discussed in Reference 4. The low reactivity of 

the ether linkage causes ethers to be relatively biologically benign, though, of course, there are 

many exceptions; anesthesia is a problem in some cases. 
52

SECTION VII 

RESULTS AND CONCLUSIONS 

A. PHOSPHORUS COMPOUNDS 

It is highly unlikely that phosphorus compounds will create any global environmental 

problems. Atmospheric lifetimes are expected to be sufficiently short that global warming and 

ozone depletion (even with bromine substitution) would be negligible. 

The large variability in toxicity of phosphorus compounds and the possibility of 

cholinesterase inhibition causes toxicity concerns with these compounds. It appears that toxicity 

tends to decrease as the oxidation state of the phosphorus decreases (i.e., phosphines are 

generally the most toxic and phosphates are the least toxic). Phosphonitriles appear to have 

relatively low toxicities, but mutagenicity may be of concern. Compounds with P-halogen bonds 

are probably unacceptable as halon substitutes. 

B. SILICON COMPOUNDS 

Silicon compounds are expected to have few if any global atmospheric impacts. This 

may be the case even when bromine is present. There is, however, a real need for studies of the 

photochemistry of bromine-containing silicon compounds. 

Little toxicity data are available on silicon compounds of interest as halon substitutes. 

On the other hand, many silicon compounds, particularly esters and siloxanes, are expected to 

have low toxicity. As in the case of phosphorus, compounds containing Si-halogen bonds are 

probably unacceptable as halon substitutes. 

C. FLUORINATED AMINES 

Totally fluorinated amines could cause atmospheric lifetime and global warming 

problems. On the other hand, amines with partial fluorination are likely to have relatively short 

atmospheric lifetimes. It is difficult, however, to determine whether the lifetime would be 

sufficiently short to allow bromine substitution. 
(The reverse of this page is intentionally left blank.) 

53

Simple alkyl-substituted amines range from nontoxic in the case of totally fluorinated 

compounds to highly toxic for nonfluorinated materials. A major question is how the toxicity 

varies with partial fluorine substitution. 

D. FLUORINATED ETHERS 

The ether linkage enhances reactivity toward hydroxyl free radicals and, therefore, leads 

to lower atmospheric lifetimes. On the other hand, this is somewhat offset by fluorine 

substitution. It is possible that bromine substitution would be allowable; however, ethers are not 

as easily removed from the atmosphere as are amines, for example, and bromine substitution 

may lead to unacceptable ozone depletion potentials. 

The toxicity of ethers is relatively low compared to other materials evaluated in this 

report. The ether linkage has a relatively low biological and chemical reactivity. 
54
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