NMERI 97/6/33010 

IDENTIFICATION AND PROOF TESTING OF NEW TOTAL FLOODING AGENTS: 

COMBUSTION SUPPRESSION CHEMISTRY AND CUP-BURNER TESTING 

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

Joseph L. Lifke, and Ted A. Moore 

Center for Global Environmental Technologies 

NEW MEXICO ENGINEERING RESEARCH INSTITUTE 

The University of New Mexico 

901 University Boulevard SE 

Albuquerque, New Mexico 87106-4339 

Final Report, February 1997 - February 1998 

May 1998 

Sponsored by: 

U. S. 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 

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Final Report, 3 Feb. 1997 - 2 Feb. 1998

4. TITLE AND SUBTITLE 

 Identification and Proof Testing of New Total Flooding 

Agents: Combustion Suppression Chemistry and CupBurner Testing 

5. FUNDING NUMBERS 

 

 C MDA972-97-M-0011

6. AUTHOR(S) 

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

Heinonen, Joseph L. Lifke, and Ted A. Moore

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 97/6/33010

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 

U.S. 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 U. S. at the end of 1993. To 

date, no environmentally acceptable halon substitute equivalent to the existing halons in toxicity, effectiveness, 

and dimensionality has been identified. The objectives of the overall effort is to reassess the higher volatility 

chemicals in the families of phosphorus nitrides, silanes, siloxanes, fluorinated amines and/or ethers, and other 

non-halocarbons which might be appropriate for Halon 1301 replacement applications. In an accompanying 

report (Tapscott, R. E., Heinonen, E. W., and Mather, J. D., Identification and Proof Testing of New Total 

Flooding Agents: Toxicity and Global Environmental Assessment, NMERI 97/29/33010, U. S.DoD Strategic 

Environmental Research and Development Program and the Defense Advance Research Projects Agency—

Arlington, VA, February 1998), the toxicities, Ozone Depletion Potentials,and Global Warming Potentials 

were examined. The present report examines the chemistry and flame extinguishment characteristics of the 

materials. A list of compounds for further study is presented.

14. SUBJECT TERMS 

 halon; fire extinguishment; cup burner; phosphorus; amines; silicon; ethers

15. NUMBER OF PAGES 

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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 U.S. Department of Defense, Strategic 

Environmental Research and Development Program, under Contract MDA972-97-M-0011, 

NMERI Number 8-33010. 

The Start Date was 3 February 1997, and the End Date was 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 97/6/33010 
iv

SUMMARY 

A. TASK OBJECTIVES 

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

families of phosphorus nitrides, silanes, siloxanes, fluorinated amines and/or ethers, and other 

nonhalocarbons, which might be appropriate for Halon 1301 replacement applications. 

B. TECHNICAL PROBLEMS 

Many of the compounds believed to contain favorable environmental, toxicological, and 

potentially acceptable performance characteristics are difficult to synthesize and are as a result 

not immediately available for testing. Potential sources and synthetic routes to some of these 

materials have, however, been determined. In many but not all cases, basic physical properties 

(boiling point and vapor pressure, for example), toxicities, and environmental values (ozone 

depletion potentials and global warming potentials) are likewise not available. On the other 

hand, relatively reliable estimates of the environmental properties have been determined and are 

presented in an accompanying report (Identification and Proof Testing of New Total Flooding 

Agents: Toxicity and Global Environmental Assessment, Interim Report, Tapscott, R. E., 

Heinonen, E. W., and Mather, J. D., NMERI 97/29/33010, U. S. DoD Strategic Environmental 

Research and Development Program and the Defense Advance Research Projects Agency, 

Arlington, VA, February 1998). 

C. GENERAL METHODOLOGY 

This project involves the four tasks described below: 

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

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

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

be estimated. Estimation techniques will include Quantitative Structure Activity 

Relationships (QSAR) for toxicity; estimated or known hydroxyl free radical rate 

constants with globally averaged atmospheric hydroxyl radical concentrations for 
v

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, quantities of synthesized compounds sufficient 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. 

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. 

D. TECHNICAL RESULTS 

New identified chemistry and extinguishment data to supplement information in past 

reports have been provided for phosphorus compounds, silicon compounds, amines, and 

fluoroethers. 

Syntheses were attempted on some compounds, and cup-burner testing was attempted on 

12 compounds. In several cases, however, compound volatility was too low to permit testing or, 

at least, to obtain reliable results. 

Nineteen (19) phosphorus compounds, silicon compounds, amines, and fluoroethers are 

recommended for further study. 

E. IMPORTANT FINDINGS AND CONCLUSIONS 

Of the families examined, phosphorus compounds provide the most promising candidates 

for continued work. Of particular importance is the relatively low n-heptane cup-burner 

extinguishment concentration of 2.4 vol.% found for tris(2,2,2-trifluoroethyl)phosphite 

(P(OCH2CF3)3). Phosphines provide good materials for mechanistic studies; however, 
vi

phosphines can be ruled out as candidates owing to their inherent low stability (many are 

flammable, sometimes spontaneously, even with fluorinated substituents) and high toxicities. 

Though it is possible to obtain fire extinguishment (sometimes, very good) with phosphazenes, 

these compounds have an inherently high molecular weight and, therefore, very low volatility. 

Of the phosphorus compounds, the esters of phosphorus-containing acids are the most promising 

candidates. 

The primary problems of phosphorus-containing esters are their often high boiling points 

and viscosities and the flammability of many of the materials. Fluorination would, of course, aid 

in all of these problems. The most promising compounds are phosphites with formulas such as 

P(ORf)3, where Rf is a fluorinated group, which should have as low a molecular weight and as 

high a fluorination as possible. Tris(trifluoromethyl)phosphite (P(OCF3)3), if it can be made, is 

an ideal compound for evaluation. Others of particular interest are phosphites containing mixed 

-CF3 and -C2F5 groups and tris(pentafluoroethyl)phosphite (P(OCF2CF3)3). The second most 

promising families are the phosphates with structures similar to those presented above for the 

phosphites, e.g., tris(trifluoromethyl)phosphate (O=P(OCF3)3) and tris(pentafluoroethyl) 

phosphate (O=P(OCF2CF3)3). Finally, phosphites and phosphates with a bromine-containing 

alkyl group, e.g., (bromodifluoromethyl)bis(trifluoromethyl)phosphite (P(OCF3)2(OCF2Br)) and 

(bromodifluoromethyl)bis(trifluoromethyl)phosphate (O=P(OCF3)2(OCF2Br)) require 

investigation. Such compounds are expected to exhibit fire suppression synergism between the 

bromine and phosphorus. 

A major problem is syntheses of phosphate and phosphite esters of the types proposed. 

Phosphites can be easily synthesized by reaction of PCl3 with ROH. These, in turn, can be 

oxidized to the phosphates. Unfortunately, alcohols that could be used to prepare esters 

containing fluorine bound to the carbon atom adjacent to oxygen are inherently unstable, 

breaking down by a 1,2-elimination of hydrogen fluoride (HF) to give carbonyl compounds. 

There may, however, be other means to prepare such esters. 

Silicon compounds appear to offer relatively little promise. Silicon offers little inherent 

fire suppression capability due to the silicon itself, and many of the most interesting compounds 

(e.g., those containing bromofluoroalkyl and/or fluoroalkyl groups) are difficult to synthesize. 
vii

Of particular concern is the instability of compounds containing -CF3 groups immediately 

adjacent to the silicon atom, and such compounds are not considered here. All of the most 

promising silicon compounds are likely to have a low volatility and a high viscosity. 

Amines, on the other hand, offer significant promise, particularly because a large amount 

of research is underway in Japan on the applications of fluoroalkyl amines as halon and CFC 

replacements. Compounds such as N(CF3)(CHF2)(CF2Br) could provide short atmospheric 

lifetimes and chemical suppression. 

A large amount of research is underway on fluoroethers as CFC replacements. The ether 

linkage provides a lower atmospheric lifetime only if it contains some hydrogen atoms. Work 

here and elsewhere indicates that in the absence of a bromine group, fluorinated ethers offer a 

fire suppression capability no higher than that of the hydrofluorocarbons and perfluorocarbons. 

Thus, there is little reason to pursue hydrofluoroethers or perfluoroethers further. Of interest, 

however, are hydrobromofluoroethers. 

F. SIGNIFICANT HARDWARE DEVELOPMENTS 

During this project, the NMERI Cup Burner (as reported in “An Update on NMERI CupBurner Test Results,” Moore, T. A., Weitz, C. A., and Tapscott, R. E., Proceedings, Halon 

Options Technical Working Conference, Albuquerque, NM, pp. 551-567, May 1996) was 

modified to use volume delivered by a syringe pump rather than weight to measure agent

delivery rates. The use of a syringe pump has been demonstrated to allow cup-burner testing of 

high boiling point and/or viscous materials, particularly those that are difficult to pass through 

valves and delivery lines. Because the syringe pump delivery method allows less holdup of 

agent in lines and requires less storage, this method allows testing of agents available only in 

limited amounts. Overall, however, the use of weight is still the most accurate and reliable 

method for testing. 

G. SPECIAL COMMENTS 

There are no special comments. 
viii

H. IMPLICATIONS FOR FURTHER RESEARCH 

Of the compounds examined in this project, future work should emphasize phosphites 

and, secondarily, amines. Of particular importance is the preparation, if possible, of P(OCF3)3. 
ix

TABLE OF CONTENTS 

Section Page

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

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

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

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

 II PHOSPHORUS COMPOUNDS....................................................................................5 

A. FIRE SUPPRESSION...........................................................................................5 

1. Flame Suppression Studies ..........................................................................5 

2. Flame Retardants .........................................................................................6 

3. Flame Inhibition Mechanisms .....................................................................8 

B. CHEMISTRY .....................................................................................................10 

1. Phosphonitriles...........................................................................................10 

2. Fluoroalkyl Phosphines..............................................................................12 

3. Amino Fluoroalkylphosphines...................................................................13 

4. Phosphorus(III) Acids and Esters ..............................................................14 

5. Phosphorus(V) Acids and Esters ...............................................................15 

6. Phosphoranes .............................................................................................15 

C. ACQUISITION AND TESTING .......................................................................16 

1. Tris(2,2,2-trifluoroethyl)phosphate ...........................................................16 

2. Dimethylmethylphosphonate .....................................................................18 

3. Trimethylphosphate ...................................................................................18 

4. Trimethylphosphite....................................................................................19 

5. (Bromodifluoromethyl)diethylphosphonate ..............................................19 

6. Hexamethylphosphoramide .......................................................................20 

7. Bis(2,2,2-trifluoroethyl)phosphite .............................................................20 

8. Tris(2,2,2-trifluoroethyl)phosphite ............................................................20 

 III SILICON......................................................................................................................22 

A. FIRE SUPPRESSION.........................................................................................22 

B. CHEMISTRY .....................................................................................................23 

1. Bromoalkylsilanes .....................................................................................23 

2. Fluoroalkoxysilanes ...................................................................................23 
x

TABLE OF CONTENTS (concluded) 

Section Page

C. ACQUISITION AND TESTING .......................................................................24 

1. Silicon Tetrachloride..................................................................................24 

2. Bromotrimethylsilane ................................................................................25 

3. Silicon Tetrabromide .................................................................................25 

 IV AMINES ......................................................................................................................26 

A. FIRE SUPPRESSION.........................................................................................26 

B. CHEMISTRY .....................................................................................................26 

C. ACQUISITION AND TESTING .......................................................................28 

1. Chemicals for Testing................................................................................28 

2. N,N-bis(trifluoromethyl)pentafluoroethanamine.......................................28 

3. N,N-bis(trifluoromethyl)trifluoromethanamine.........................................28 

 V FLUORINATED ETHERS .........................................................................................29 

A. FIRE SUPPRESSION.........................................................................................29 

B. CHEMISTRY .....................................................................................................29 

C. ACQUISITION AND TESTING .......................................................................29 

1. Chemicals for Testing................................................................................29 

2. 1-Methoxynonafluorobutane .....................................................................29 

3. Hydrofluoropolyether ................................................................................30 

 VI RESULTS AND CONCLUSIONS..............................................................................31 

A. MODIFIED NMERI CUP BURNER .................................................................31 

B. CUP-BURNER RESULTS.................................................................................31 

C. CONCLUSIONS.................................................................................................31 

 VII RECOMMENDATIONS.............................................................................................36 

REFERENCES .............................................................................................................................37 

APPENDICES A FLUORINATED AMINES FROM CCOD...............................................45 

 B FLUORINATED ETHERS FROM CCOD ...............................................47 
xi

LIST OF TABLES 

Table Page

1. COMPOUNDS FOR POSSIBLE SYNTHESIS IN RUSSIAN FACILITIES ....................4 

2. FLUOROALKYL PHOSPHINES.....................................................................................13 

3. AMINO FLUOROALKYLPHOSPHINES .......................................................................14 

4. PHOSPHORUS-CONTAINING COMPOUNDS SELECTED FOR TESTING..............17 

5. TETRA(FLUOROALKOXY)SILANES...........................................................................24 

6. SILICON-CONTAINING COMPOUNDS SELECTED FOR TESTING........................25 

7. BROMOALKYLAMINES. ...............................................................................................27 

8. NITROGEN-CONTAINING COMPOUNDS SELECTED FOR TESTING. ..................28 

9. FLUORINATED ETHERS SELECTED FOR TESTING. ...............................................29 

10. CUP-BURNER TEST RESULTS. ....................................................................................32 

11. FINAL LIST OF RECOMMENDED COMPOUNDS......................................................35 
xii

LIST OF ABBREVIATIONS 

BCC Business Communications Company 

CCOD CGET Chemical Options Database 

CGET Center for Global Environmental Technologies 

COTR Contracting Officer’s Technical Representative 

DMMP dimethyl methylphosphonate 

GC gas chromatography 

GC/MS gas chromatography/mass spectrometry 

GWP Global Warming Potential 

HFPE hydrofluoropolyether 

HMPA hexamethylphosphoramide 

MSDS Material Safety Data Sheet 

NIRI National Industrial Research Institute 

NMERI New Mexico Engineering Research Institute 

ISO International Standards Organization 

ODP Ozone Depletion Potential 

QSAR Quantitative Structure-Activity Relationship 

RT retention time 

USIC United States Industry Coalition, Inc. 

LIST OF UNITS AND SYMBOLS 

cp centipoise 

g/s grams/second 

vol% percent by gas volume 
1

SECTION I 

INTRODUCTION 

A. OBJECTIVE 

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

phosphorus nitrides, silanes, siloxanes, fluorinated amines and/or ethers, and other nonhalocarbons, which that might be appropriate for Halon 1301 replacement applications. 

B. SCOPE 

The overall project consists of four requirements: 

1. From literature citations and previously determined principles, estimate the 

toxicity, Ozone Depletion Potential (ODP), and Global Warming Potential (GWP) of the 

chemicals of interest. This phase of the project was completed earlier and results were presented 

in an interim report (Reference 1). 

2. Select specific compounds for study 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. Be 

prepared to provide sufficient quantities of these chemicals 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 

and manufacturability, (3) ODP and GWP, and (4) fire suppression and inertion effectiveness. 
2

C. APPROACH 

The following tasks were accomplished in this phase of the work: 

1. Specific compounds were selected for study based on the information obtained in 

Task 1. Attempts were made to synthesize some compounds not readily available. 

2. Cup-burner flame extinguishment evaluations were performed using the New 

Mexico Engineering Research Institute (NMERI) Cup Burner and n-heptane fuel. As normally 

configured, the NMERI Cup Burner apparatus monitors weight to determine the agent delivery 

rate (Reference 2); however, owing to the high boiling point of many of the materials examined 

here, a need to limit agent holdup in lines, and concerns about agent viscosity, a second version 

of the NMERI Cup Burner, which employs a syringe pump and monitors flow, was developed. 

The modification incorporates a syringe pump to inject the liquid directly into the heated 

chamber, rather than using overpressure to drive the agent into the chamber. Three advantages 

with such an apparatus are (1) decreased risk of accidental release due to a leaking line or hose 

break, (2) lower compound requirement, and (3) decreased possibility of agent retention in lines. 

The last two advantages result from the absence of lines leading to the needle passing into the 

mixing chamber. 

In this revised procedure, a 5-mL syringe is filled with the test compound and connected 

to the cup burner, and the flow rate is increased until extinguishment is attained. The syringe is 

then refilled with the test compound, weighed, and placed back into the syringe pump. After 

discharge for one minute at the syringe-pump setting for extinguishment, the syringe is 

reweighed, and the flow rates in mass per unit time can be obtained. 

Calibration of the syringe pump delivery with perfluorohexane (C6F14) gave 

extinguishing concentrations of 4.25, 4.58, 4.93, and 4.74 vol.% (average 4.625 vol.%), similar 

to the extinguishment concentration of 4.42 vol.% (Reference 2) determined in the same cup 

burner using the unmodified method. 

The two different cup burner apparatuses are referred to in this report as the Standard 

NMERI Cup Burner and the Modified NMERI Cup Burner. 
3

3. The information obtained in the above tasks were assessed to develop a list of 

19 optimal candidate Halon 1301 replacement agents. The criteria for this list are based 

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

(4) fire suppression and inertion effectiveness. 

During this program, scientists in Russia were found to be a potential source for many 

compounds of interest. The Applied Chemistry Division of the Russian Scientific Center in 

St. Petersburg was identified as a particularly promising source for low-cost materials. The list 

of compounds (Table 1) submitted to this organization for consideration for synthesis received a 

favorable response; however, it was determined, as the work progressed, that many of the 

compounds requested had undesirable properties (e.g., P(CF3)3 is pyrophoric). It was, therefore, 

decided to postpone ordering compounds until the requirements were better defined (possibly in 

a future project). 
4

TABLE 1. COMPOUNDS FOR POSSIBLE SYNTHESIS IN RUSSIAN FACILITIES. 

Formula Name 

Bromofluoroamines 

(CBrF2)(CHF2)2N (bromodifluoromethyl)bis(difluoromethyl)amine 

(CBrF2)(CF3)(CH3)N methyl(bromodifluoromethyl)(trifluoromethyl)amine 

(CF3)2(CH2CBrF2)N bis(trifluoromethyl)(2-bromo-2,2-

difluoroethyl)amine 

(CBrF2)(CF3)2N bis(trifluoromethyl)(bromodifluoromethyl)amine 

Silicon Compounds 

Si(CF3)4 tetrakis(trifluoromethyl)silane 

Si(CF3)3(CF2Br) (bromodifluoromethyl)tris(trifluoromethyl)silane 

Si(CF2CF3)4 tetrakis(pentafluoroethyl)silane 

Si(CF2CF3)3(CF2CF2Br) (2-bromo-1,1,2,2-

tetrafluoroethyl)tris(pentafluoroethyl)silane 

(CF3CF2)3Si-O-Si(CF2CF3)3 hexakis(pentafluoroethyl)disiloxane 

(CF3CF2)3Si-OSi(CF2CF3)2(CF2CF2Br) (2-bromo-1,1,2,2-tetrafluoroethyl)-

pentakis(pentafluoroethyl)disiloxane 

Phosphorus Compounds 

P(CF3)3 tris(trifluoromethyl)phosphine 

P(CF3)2(CF2Br) (bromodifluoromethyl)tris(trifluoromethyl)phosphin

e 

N3P3(CF3)6 hexakis(trifluoromethyl)cyclotriphosphazene 

N3P3(OCH2CF3)6 hexakis(2,2,2-trifluoroethoxy)cyclotriphosphazene 

(CF3)2NP(CF3)2 perfluoro-(dimethylamino)dimethylphosphine 

((CF3)2N)2P(CF3) perfluoro-bis(dimethylamino)methylphosphine 

((CF3)2N)3P perfluoro-tris(dimethylamino)phosphine 
5

SECTION II 

PHOSPHORUS COMPOUNDS 

A review of the chemistry and fire suppression properties of phosphorus compounds has 

been presented in Reference 3. Except as otherwise stated, all of the information presented here 

is newly acquired or is an expansion of information contained in that source. 

A. FIRE SUPPRESSION 

Liquid fire suppressants with halocarbons containing both phosphates and phosphites 

have been claimed as fire extinguishants (Reference 4). The mixtures are claimed to give 

significantly increased fire suppression for Class B fires compared to conventional 

monoammonium phosphate and halons, and for Class A fires compared to Halon 1211. 

Reference 3 cites a number of additional papers on fire suppression by phosphorus compounds. 

1. Flame Suppression Studies 

A relatively large amount of work has been performed on flame suppression by 

phosphorus containing compounds (Reference 3). Despite the fact that much of this work was 

performed on phosphorus halides such as phosphorus(V) oxychloride (POCl3) and phosphorus 

trichloride (PCl3), there is little doubt that phosphorus itself contributes significantly to 

extinguishment. Thus, for example, POCl3 is about 10 times more effective than an equivalent 

amount of chlorine (Reference 5). Moreover, trimethyl phosphate ((O=P(OCH3)3) shows a more 

pronounced effect on flame velocity than Cl2 and Br2 (Reference 6). Phosphate esters are of 

particular interest as fire suppressants since they are difficult to ignite and will self-extinguish 

(Reference 7). 

An opposed-jet burner apparatus has been used to study the effectiveness of 

dimethyl methylphosphonate (DMMP, O=P(CH3)(OCH3)2) (Reference 8). Global extinction 

strain rates show that introduction of DMMP with an oxidizer gives significant inhibition of nonpremixed methane-air flames. DMMP is approximately 40 times more effective than nitrogen on 

a molar basis, and about 4 times more effective than Halon 1301. The extinction strain rate 

decreases linearly with the mole fraction of DMMP for loadings up to 1500 ppm. Studies on flat 

H2/O2/Ar flames by molecular beam mass spectrometry indicate that DMMP acts as a flame 
6

promoter (Reference 9). It is proposed that the DMMP catalyzes the recombination of •OH and 

•H free radicals. 

Owing to the spectral richness associated with phosphorus in flames (e.g., 

Reference 10), a large amount of spectroscopic work has been accomplished on phosphorus in 

combustion processes. A quantitative study of the emission spectra of counterflow diffusion 

flames of ethylene, methane, or hydrogen burning with air has been made for addition of the 

inhibitors methyl bromide (CH3Br), bromine (Br2), carbon tetrachloride (CCl4), chlorine (Cl2), or 

phosphorus oxychloride (O=PCl3) to either the air or fuel supply (Reference 11). Specific 

effects occur for various fuels and inhibitors, but in general, •OH and HCO• emission decreases, 

C2 increases, and CH varies little with increasing inhibitor concentration. Of particular interest 

is that phosphorus oxychloride gives the greatest reduction in •OH and also gives the largest 

inhibiting action of the agents tested for methane and ethene fuels. It is proposed that the 

inhibitors remove •OH radicals and, secondarily, promote formation of carbon particulate, which 

increases radiation losses and cools the flame. It is proposed that the extinguishment action of 

POCl3 is due to the chlorine and that its high efficiency is due to ready formation of HCl in the 

flame. 

2. Flame Retardants 

A search of the Chemical Abstracts Database for the key words “flame,” “fire,” 

and “flammable” coupled with “phosphonitriles” and related terms yielded 366 references, 

nearly all of which were for fire retardants for polymers. Recently identified reviews of cycloand polyphosphazenes as fire retardants and as fire resistant materials are contained in 

References 12 and 13. 

A number of interesting and potentially important papers were presented at the 

Business Communications Company (BCC) Conference on Flame Retardancy, in Stamford, CT, 

2-4 June 1997. Phosphorus compounds appear to act as flame retardants by both condensedphase and gas-phase mechanisms, depending on the compound and polymer (Reference 14). 

The mechanisms, however, are still widely debated. 

Phosphorus and bromine behave as synergistic flame retardants, and the greatest 

synergism appears to be when the two elements are combined in the same molecule 
7

(References 15 and 16). It has been proposed that in polyesters, compounds containing both 

phosphorus and bromine act in two separate roles as flame retardants (Reference 17). The work 

cited indicates that the phosphorus induces formation of aromatic residues and char, which 

reduce the transport of gases to the flame. The bromine is believed to reduce the overall 

oxidation rate, reducing the heat transported back to the solid. The preparation of halogenated 

triaryl phosphines as flame retardants has been reported (Reference 18). An example is shown in 

Reactions 1 and 2 for tris(parachlorophenyl)phosphine (solid, melting point 106 °C). A number 

of phosphonium salts were prepared as shown in Reaction 3, where R1, R2, and R3 are various 

alkyl and aryl groups. All of these materials are, of course, solids. 

Cl Br N atmosphere

Mg Et O anhydrous

2

⎯ → ⎯⎯⎯⎯⎯⎯⎯⎯ ,( ) 2 ⎯ Cl MgBr (1) 

Cl MgBr + PCl3 → P

3

Cl (2) 

BrH2C CH2Br

CH2

Br

 + P(R1R2R3)3 → 3BrCH2

PR1R2R3

+

CH2PR1R2R3

+

+

R1R2R3PCH2

 (3) 

Resorcinol bis(diphenyl phosphate) (I, n = 1 to 8), a polymeric material 

containing no halogen, has been reported to act as a flame retardant additive (Reference 19). 

The material, which is made from phosphorus oxychloride, resorcinol, and phenol, is a colorless 

to light yellow liquid with a viscosity of 600 cp at room temperature and 100 cp at 55 °C. 

n

P P

O O

O O

PhO

PhO OPh

OPh

(I) 

Phosphorus-containing groups have been incorporated directly onto polymeric 

molecules rather than using phosphorus additives to provide flame retardancy. Fire resistant 
8

organosilicon polymers have been prepared by incorporation of phosphazenes (Reference 20). 

Resins containing melamine combined with triethyl phosphate and dimethyl methylphosphonate 

have been reported as flame retardants (Reference 21). A number of compounds containing 

vinyl groups attached to phosphorus have been prepared to permit copolymer formation (e.g., II 

and III, Reference 22). It is believed that when incorporated directly into a polymer, these 

materials provide flame retardancy primarily by char formation. 

O O

P

O

O O

P

O

(II) (III) 

3. Flame Inhibition Mechanisms 

Among the most important free-radical recombinations in both extinguishment by 

chemically active agents and combustion are combination of hydrogen atoms to form diatomic 

hydrogen and recombination of hydroxyl free radical with hydrogen atoms to form water. In the 

absence of catalysis, these reactions require the presence of a third body (M) to carry off excess 

energy (Reactions 4 and 5). 

•H + •H + M → H2 + M* (4) 

•H + •OH + M → H2O + M* (5) 

Catalytic cycles have been proposed to accelerate Reactions 4 and 5 by 

phosphorus-containing compounds. Hastie and Bonnell (Reference 23) have proposed three 

cycles (Reactions 6 through 8; 9 and 10; and 11 and 12) for recombination of hydrogen atoms 

to form diatomic hydrogen. 

•H + •PO2 + M → HOPO + M* (6) 

•H + HOPO → •PO + H2O (7) 

 H2O + •PO → •PO2 + H2 (8) 
9

•H + •PO + M → HPO + M* (9) 

•H + HPO → •PO + H2 (10) 

•H + •PO2 + M → HOPO + M* (11) 

•H + HOPO → •PO2 + H2 (12) 

Twarowski has observed large increases in the relaxation rate of •OH to 

equilibrium concentrations following H2O photolysis (References 24 through 26). Mixtures of 

phosphine (PH3), oxygen, hydrogen, and argon were ignited in a stirred-flow reactor, and the 

products were passed into a chamber where the H2O product was photolyzed. From the data 

generated and reaction modeling with sensitivity analysis, three cycles were proposed as the 

predominant pathways for recombination of •H and •OH radicals to form H2O. The first cycle 

involves three steps (Reactions 13 to 15), one of which (Reaction 14) involves no phosphorus 

containing species. •PO2 is consumed in a ternary reaction step (Reaction 13) and then 

regenerated (Reaction 15). In the second proposed reaction cycle, •PO2 is consumed in a ternary 

reaction step (Reaction 16). This is followed by a two-body reaction completing the •H + •OH 

recombination and regenerating •PO2 (Reaction 17). In the third cycle (Reactions 18 and 19), 

•PO is the catalytic species. Consideration of the sensitivity analysis results, species abundance, 

and rates indicates that the first catalytic cycle is the most important and that the third cycle is 

the least important. The ternary step in the second and third cycles involves reactions with •OH 

(Reactions 16 and 18), which are suggested to be slower than the ternary reaction with •H in 

Reaction 13. Moreover, the low abundance of •PO compared to •PO2, makes the third cycle 

even less favorable. 

•H + •PO2 + M → HOPO + M* (13) 

•OH + H2 → H2O + •H (14) 

•H + HOPO → H2 + •PO2 (15) 

•OH + •PO2 + M → HOPO2 + M* (16) 

•H + HOPO2 → H2O + •PO2 (17) 

•OH + •PO + M→ HOPO + M* (18) 

•H + HOPO → H2O + •PO (19) 
10

An alternative cycle, in which Reactions 14 and 15 are replaced by Reaction 20 is 

possible; however, Reaction 20 does not appear to be as rapid as the first two under the 

experimental conditions used in the studies cited above (References 24 through 26). 

HOPO + •OH → •PO2 + H2O (20) 

Further calculations and modeling by Twarowski indicate that due to the highly 

coupled reaction system, the accelerated formation of H2O from •H and •OH appears to be 

highly dependent on H2 formation by the cycle of Reactions 11 and 12 (Reference 27). 

Molecular beam mass spectrometry of the combustion of trimethylphosphate 

(TMP, O=P(OCH3)3) has indicated the processes shown in Reactions 21 and 22, both of which 

would allow elimination of hydrogen atoms (Reference 28). 

O=P(OCH3)3 + •H → O=P(OH)(OCH3)2 + •CH3 (21) 

O=P(OCH3)3 + •H → O=PH(OCH3)2 + •OCH3 (22) 

B. CHEMISTRY 

Phosphorus chemistry has been the subject of a number of relatively recent reviews (e.g., 

the papers in Reference 29); however, most of this work has been on nonvolatile or flammable 

chemicals. Again, Reference 3 provides a good overview of phosphorus chemistry as it applies 

to chemicals of interest as fire suppressants. Only updated information or newly identified 

references are presented here. 

1. Phosphonitriles 

Among the phosphorus compounds, phosphonitriles have been of primary interest 

as halon replacement candidates in the past; however, there are relatively few that have 

sufficiently high volatility to allow use. There may, however, be some interest in using these 

materials in carriers for some applications. 

The linear phosphonitriles, for which preparations have been reported 

(Reference 30), are considerably more reactive than the cyclic compounds, particularly toward 

hydrolysis (Reference 31). This makes them somewhat less attractive than the cyclic materials 
11

for study as halon replacements. The reactivity of the 3-membered ring system P3N3Cl6 toward 

chloride exchange is lower than that of the four-membered and larger cyclics (Reference 32). 

Of particular interest are the fluorinated phosphonitriles. Fluorination normally 

occurs as geminal substitution; however, procedures for making nongeminal derivatives have 

been reported (Reference 33). Although a number of chloro- and fluoro-substituted 

bis(dimethylamino)cyclotriphosphonitriles have been reported (Reference 34), most of these are 

solids. Compound IV is, however, a liquid. 

N

P

N

P

N

P

Cl

F F

N(CH3)2

Cl

(CH3)2N

(IV) 

Bromine-containing phosphonitriles are of some interest due to the potential for 

fire extinguishment contribution by bromine and for possible synergism between bromine and 

phosphorus. The fully brominated compounds are solids or oils (Reference 35) and are, 

therefore, unlikely to be appropriate for investigation as fire extinguishants, though they may 

have other uses (e.g., flame retardants). Crown ether complexes have been used to prepare the 

highly colored solid compound NP2Br9 from KBr and hexachlorocyclotriphosphonitrile 

(P3N3Cl6) (Reference 36). This compound can then be heated to form the more stable NP2Br7. 

Structures are given for neither of these materials. The preparation of mixed fluorine- and 

bromine-substituted phosphonitriles have been prepared by reaction of silver fluoride with 

P3N3Br6 (Reference 37); however, the properties are not given. 

Mixed methyl- and fluorine-substituted phosphonitriles have been prepared by 

reaction of octafluorocyclotetraphosphonitrile with methyl lithium (References 38 and 39). The 

compounds are high boiling liquids and solids. Derivatives with tert-butyl and n-butyl 
12

substituents (References 40 and 41) and with 1- and 2-propenyl substituents (Reference 42) have 

also been reported. 

2. Fluoroalkyl Phosphines 

In Reference 3, we noted that at high temperatures and pressures, phosphorus 

reacts with a number of fluoroalkyl iodides (RI) to give compounds having the structure PRI2, 

PR2I, and PR3; however, we did not cite the references nor did we go into this any further other 

than to make a mixture of the iodo and diiodo compounds with fluoropropyl groups. The 

presence of fluorine in the alkyl groups of these materials greatly decreases their basicity 

(Reference 43) and could, by analogy with the amines, decrease toxicity. Owing to the 

simplicity of these materials and, in particular, the interest in the perfluorinated 

trialkylphosphines, these compounds were examined further under this project. 

The simplest member of the perfluorinated trialkyl is tris(trifluoromethyl)-

phosphine ((CF3)3P), which has been prepared as a mixture with trifluoromethyldiiodophosphine 

((CF3)PI2) and bis(trifluoromethyl)iodophosphine ((CF3)2PI) by reaction of phosphorus with 

trifluoroiodomethane (CF3I) (Reference 44) and also by reaction of tris(diethylamino)phosphine 

(P(N(C2H5)2)3) with trifluoromethyl bromide (CBrF3, Halon 1301) and triphenylphosphite 

(O=P(OC6H5)3) in tris(dimethylamino)phosphine oxide (OP(N(CH3)2)3, hexamethylphosphoramide, HMPA) (Reference 45). Unfortunately this material (like some of its complexes, 

Reference 46) is spontaneously flammable (Table 2). The iodide derivatives are exceedingly 

useful precursors for a number of compounds of interest here; however, even with optimized 

procedures (Reference 47), the syntheses are difficult, and the reactants and products are hard to 

handle. Reaction of (CF3)2PI with mercury gives the flammable compound tetrakis(trifluoromethyl)diphosphine ((CF3)2PP(CF3)2) (Reference 44) and the tetrameric and pentameric cyclic 

compounds (CF3P)4 and (CF3P)5 (Reference 48) (Table 2). The compounds (CF3)PF2 and 

(CF3)2PF are also known (Reference 49). 
13

TABLE 2. FLUOROALKYL PHOSPHINES. 

Compound Boiling point, °C Properties Reference 

(CF3)3P 17 Spontaneously flammable 44 

(CF3P)4 Not available Solid, melting point 66.4 °C 48 

(CF3P)5 190 Not available 48 

(CF3)2PP(CF3)2 83-84 Flammable 44 

(C2F5)3P 70 Not available 43 

The higher molecular weight perfluoroalkyl derivatives are likely to be more 

stable than the methyl compounds. Tris(pentafluoroethyl)phosphine ((C2F5)3P), a liquid boiling 

at 70 °C, has been prepared by reaction of phosphorus trichloride (PCl3) with ethyl lithium 

(C2F5Li), which can be prepared by reaction of chloropentafluoroethane (C2F5Cl) with n-butyl 

lithium (C4F9Li) (Reference 43). The procedure, however, has not been published. It has proven 

impossible to prepare the tris(heptafluoropropyl)phosphine ((C3F7)3P), apparently due to steric 

hindrance (Reference 50). 

A large number of trifluoromethyl-substituted diphosphorus compounds having 

the general formula (CF3)2PRP(CF3)2, where “R” represents a branched or linear hydrocarbon or 

fluorocarbon chain, have been synthesized as bidentate ligands starting with (CF3)2PP(CF3)2

(Reference 51 and 52). It has been stated that these compounds are difficult to prepare owing to 

difficulty in synthesis of the diphosphine precursor (Reference 43). These materials, though 

liquid, have relatively high boiling points. A similar compound has also been prepared: 

(C2F5)2PCH2CH2P(C2F5)2, boiling point 105 °C at 80 torr (Reference 53). The primary interest 

in these compounds is as bidentate ligands (Reference 54). 

3. Amino Fluoroalkylphosphines 

Aminobis(trifluoromethyl)phosphines ((CF3)2PNR2, R= -H, -CH3) have been 

prepared by reaction of chlorobis(trifluoromethyl)phosphine ((CF3)2PCl) with the appropriate 

amine (Reference 55). Though these materials are relatively stable liquids (Table 3), they are 

readily oxidized in air (and the simplest amino compound is spontaneously flammable). 
14

Moreover, the (CF3)2PCl starting material is spontaneously flammable. Amines containing two 

and three bis(trifluorophosphine) groups (Reference 56) and compounds of the type 

[(CF3)2N]nP(CF3)3-n, n=1-3 (the latter discussed further in Reference 3) have also been prepared 

(Table 3). The starting materials, however, are also spontaneously flammable—(CF3)2PCl or 

tris(trifluoromethyl)phosphine ((CF3)3P). Aminobis(heptafluoropropyl)phosphine 

((C3F7)2PNH2), a high boiling liquid (Table 3), has been prepared by reaction of (C3F7)2PCl with 

anhydrous ammonia (Reference 50). As is typical for all of these reactions, the starting material 

was prepared by reaction of heptafluoropropyl iodide with phosphorus at high temperature and 

pressure followed by replacement of the iodide with chloride using silver chloride. 

TABLE 3. AMINO FLUOROALKYLPHOSPHINES. 

Compound Boiling point, °Ca

 Properties Reference 

(CF3)2PNH2 67.1 Spontaneously flammable 55 

(CF3)2PNH(CH3) 72.3 Not available 55 

(CF3)2PN(CH3)2 83.2 Not available 55 

((CF3)2P)2NH Not available Vapor pressure 46.7 torr at 23.9 °C 56 

((CF3)2P)2NCH3 Not available Vapor pressure 17.3 torr at 25.0 °C 56 

((CF3)2P)3N Not available Solid, melting point 36.5-36.8 °C 56 

(CF3)2NP(CF3)2 51 Stable at room temperature 57 

((CF3)2N)2P(CF3) 92.5 Stable at room temperature 57 

((CF3)2N)3P 135 Stable at room temperature 57 

(C2F7)2PNH2 143 Not available 50 

a

One atmosphere (nominal) pressure. 

4. Phosphorus(III) Acids and Esters 

The phosphorus(III) acids of interest are the trioxy acid, which can be formulated 

as the hypothetical phosphorous acid (P(OH)3) but actually exists as phosphonic 

(“ortho-phosphorous”) acid (O=PH(OH)2); the dioxy acid phosphinic (“hypophosphorous”) acid 

(O=PH2(OH)); and the monooxy phosphinous acid (O=PH3). A major problem exists when 

discussing the esters of these acids, since more than one form is often possible, and the actual 

structure may be unknown (Reference 3). The tri-, di-, and mono-esters of phosphorous acid are 
15

the phosphites P(OR)3, P(OH)(OR)2,and P(OH)2(OR), which often rearrange to the phosphonate 

structures, of which there are five possibilities: O=PR(OR)2, O=PH(OR)2, O=PR(OH)(OR), 

O=PH(OH)(OR), and O=PR(OH)2. These latter five structures are formally derivatives of 

phosphonic acid. The esters of phosphinic acid (the phosphinites) are O=PH2(OR), 

O=PHR(OR), and O=PR2(OR). Phosphites (P(OR)3) are rather easily prepared by reaction of 

PCl3 in anhydrous ether with an alcohol in the presence of the base pyridine (Equation 23). 

Appropriate conditions will also give the phosphonates O=PH(OR)2 and O=PH2(OR) or the 

phosphites P(OH)2(OR) and P(OH)(OR)2. 

PCl3 + 3ROH → P(OR)3 + 3HCl (23) 

Tris(hexafluoroisopropyl)phosphite (P(OCH(CF3)2)3) has been prepared and used 

as a ligand in a metal catalyst (Reference 58). The phosphinous acid (CF3)2POH has been 

prepared in a rather complex series of steps with (CF3)2POP(CF3)2 as the immediate precursor 

(Reference 59). Esters are known, and, unlike the nonfluorinated compounds, are stable toward 

PR2(OR) → O=PR3 rearrangement (Reference 60). The heptafluoropropyl phosphonous acid 

((C3F7)P(OH)2 or O=PH(C3F7)(OH)) has been reported (Reference 50). Routes to other 

perfluoroalkylphosphonic and perfluoroalkylphosphinic acids (O=PR2(OH) and O=PR(OH)2, 

R = -CF3, -C2F5, -n-C3F7, -n-C4F9) have been described (References 50 and 61). Like many of 

the fluoroalkyl phosphorus compounds involving direct carbon-phosphorus bonds, the first steps 

involve the difficult syntheses of R2PI and RPI2. Syntheses of a number of fluoroalkyl acid 

phosphates and precursor phosphorus compounds have also been reported (Reference 62). 

5. Phosphorus(V) Acids and Esters 

The parent acid is orthophosphoric acid (O=P(OH)3), with condensed structures 

containing one or more P-O-P groups known. The esters of phosphoric acid are the triester 

O=P(OR)3 and the acid phosphates O=P(OH)2(OR), and O=P(OH)(OR)2. With four oxygen 

atoms, the multiple structures found for the phosphorus(III) esters do not occur. 

6. Phosphoranes 

A number of fluorophosphoranes (pentacoordinate phosphorus(V) compounds), 

including some amino-substituted products have been described (References 63 and 64). 
16

Although all of these contain phosphorus-fluorine bonds (making them unlikely candidates as 

halon replacements), the boiling points are in acceptable ranges for a number of compounds. 

Unfortunately, none of the alkyl derivatives in the sources cited is fluorinated. 

C. ACQUISITION AND TESTING 

Consideration of the information presented above indicated that phosphonitriles were not 

ideal for testing owing to their low volatility and that phosphines were likely to be too toxic to 

consider, except possibly for mechanistic studies. Table 4 presents phosphorus-containing 

compounds selected for testing. 

1. Tris(2,2,2-trifluoroethyl)phosphate 

Synthesis of tris(2,2,2-trifluoroethyl)phosphate (O=P(OCH2CF3)3) was attempted 

by reaction of phosphorus(V) oxychloride (O=PCl3) with 2,2,2-trifluoroethanol (CF3CH2OH) in 

pyridine (Reaction 24). This synthesis is similar to that used to prepare the monoester, 

(2,2,2-trifluoroethyl)phosphate (O=P(OCH2CF3)3) (Reference 65). 

O=PCl3 + 3CF3CH2OH pyridine ⎯ → ⎯⎯⎯ O=P(OCH2CF3)3 + 3HCl (24) 

The pyridine acts as an hydrogen acceptor giving the insoluble hydrochloride salt 

as a byproduct. Pyridine (0.42 mL, 0.0052 mole) and 2,2,2-trifluoroethanol (0.52 mL, 0.0072 
17

TABLE 4. PHOSPHORUS-CONTAINING COMPOUNDS SELECTED FOR TESTING. 

Compound Formula Boiling point, 

°C (torr) 

Flash point, 

°C 

Tris(2,2,2-trifluoroethyl)phosphate O=P(OCH2CF3)3 Not available Not available 

Dimethylmethylphosphonate O=P(CH3)(OCH3)2 a181 a68 

Trimethylphosphate O=P(OCH3)3 197 None 

Trimethylphosphite P(OCH3)3 111-112 27 

(Bromodifluoromethyl) 

diethylphosphonate 

O=P(CBrF2)(C2H5)2

b

99-102 (16) 

c

220 (760) 

Not available 

Hexamethylphosphoramide O=P[N(CH3)2]3 230-232 (740) Not available 

Bis(2,2,2-trifluoroethyl)phosphite O=PH(OCH2CF3)2 a

43-44 (2) 

c

190 (760) 

a

76 

Tris(2,2,2-trifluoroethyl)phosphite P(OCH2CF3)3 a130-131 (743) a>110 

a

Reference 66. 

b

Reference 67. 

c

Estimated using pressure-temperature nomograph. 

mole) were introduced by syringe into a 250-mL round-bottom flask and mixed by gentle 

swirling of the stoppered flask. To this mixture, 0.1 mL (0.0011 mole) of phosphorus(V) 

oxychloride was added by syringe. Instantaneous fuming and a slight warming of the flask was 

observed with an almost immediate precipitation of clear crystalline material. The flask and its 

liquid contents were swirled frequently to ensure mixing and reaction, and the mixture was 

allowed to sit for 48 hours. Direct injection gas chromatography (GC) employing a 30M 

capillary column and isothermal (34 °C) conditions of the reaction product showed two major 

peaks with retention times of 5.49 and 12.02 min. A minor peak representing only 3 percent of 

the total combined integrated GC peak areas was observed at 1.10 min. 

GC/MS analysis showed four peaks eluting at retention times (RT) of 1.34 min 

(2.9 percent), 1.48 min (12.6 percent), 3.99 min (58.9 percent), and 7.52 min (25.5 percent), 

where values in parentheses are the percentages of the total peak areas. Software-based peak 

identifications were performed for each GC peak employing a cut off of 90 percent for 

acceptance of the quality of fit of observed ion abundance peak pattern comparisons to library 

data. The software-based assignments were RT 1.34, unknown; RT 1.48, 2,2,2-trifluoroethanol; 

RT 3.99, pyridine; and RT 7.52, unknown. The RT 7.52 peak had major ion peaks at 324, 325, 
18

and 275 amu consistent with the loss of HF, F and CF3, respectively from O=P(OCH2CF3)3. The 

mass peak at 245 amu could result from additional loss of H2CO (formaldehyde) from the 

275-amu ion or loss of OCH2CF3 ion from the parent molecule (more likely). Although no 

parent mass peak (344 amu) was observed, it is likely that the RT 7.52 GC peak was 

O=P(OCH2CF3)3. 

Insufficient product was obtained during this synthesis to perform cup-burner 

testing. However, it is planned that larger scale syntheses will be carried out in the future. 

Commercial sources were used for the remaining compounds in this section. 

2. Dimethylmethylphosphonate 

Testing of dimethylmethylphosphonate (O=P(CH3)(OCH3)2) was attempted using 

the Standard NMERI Cup Burner. Due to its low volatility (boiling point 181 °C), the material 

was difficult to volatilize without excessive heating in the heated cup-burner mixing chamber. 

This excessive heat apparently caused some decomposition since a black, tarry substance was 

obtained. A single test that appeared to have the least difficulties gave an extinguishing 

concentration of 5 vol.%. Since some condensation on the glass beads above the mixing 

chamber and decomposition may have occurred, this value should be considered a maximum 

because not all of the compound was available to extinguish the fire. 

3. Trimethylphosphate 

Trimethylphosphate (O=P(OCH3)3) was tested using the Modified NMERI Cup 

Burner. Due to its high boiling point (197 °C), this compound was extremely difficult to test. 

The first run gave an extinguishment concentration of 6.60 vol.%; however, this value may be 

slightly high since it was observed that a small amount of the compound did not volatilize in the 

mixing chamber (which was maintained at 145 °C) at the point of extinguishment. With a higher 

mixing chamber temperature (328 °C), an extinguishment concentration of 6.85 vol.% was 

obtained. Again, some of the compound in the mixing chamber did not volatilize. At an even 

higher mixing chamber temperature (344 °C), a lower cup-burner value of 5.3 vol.% was 

obtained; however, this value is suspect since the chimney temperature was sufficiently high 

(156 °C) that the n-heptane in the fuel cup boiled and was difficult to control. 
19

4. Trimethylphosphite 

Trimethylphosphite (O=P(OCH3)3), with a boiling point of 111-112 °C, provided 

few operational problems with the Modified NMERI Cup Burner. The compound was, however, 

sufficiently flammable that it ignited at the glass beads. Moreover, complete extinguishment of 

the n-heptane flame was not achieved. Cup-burner testing of this compound was, therefore, 

suspended. In separate testing, the compound ignited with difficulty with a butane ignitor and 

continued to burn once the flame was removed. 

5. (Bromodifluoromethyl)diethylphosphonate 

(Bromodifluoromethyl)diethylphosphonate (O=P(CBrF2)(C2H5)2) was tested 

using the Modified NMERI Cup Burner. Since only a small amount of material was available, 

the first test was used to determine an upper bound for the extinguishing concentration with as 

little compound as possible. From the results (i.e., ready extinguishment, difficult/near 

extinguishment, no extinguishment) of a fixed and relatively high flow rate, it was hoped to 

estimate the flow rate for subsequent tests. During the first test, the flame extinguished readily at 

a concentration of 4.73 vol.%. The second test employed a much lower flow rate (approximately 

one-third that of the first test). Even though the temperature of the heated chamber at the base of 

the cup burner was 250 °C, it appeared that the compound did not volatilize completely. The 

flame continued to show some extinguishment from the compound after the syringe pump was 

turned off, which indicates that the compound in the mixing chamber continued to volatilize 

even after the agent supply was stopped. The temperature of the heated chamber was therefore 

increased to 300 °C. 

During the next test, the compound appeared to volatilize well, and the flame was 

close to extinguishment; however, the n-heptane became sufficiently hot that boiling was 

observed. At this point, the agent concentration was 1.43 vol.%. Thus, the extinguishment 

concentration was estimated to be between 1.43 and 4.73 vol.%. A test with an increased flow 

rate and a slightly lower chamber temperature (270 °C) resulted in an extinguishment 

concentration of 3.29 vol.%. Although some condensation on the glass beads was observed, it 

was not considered significant. Thus, the cup-burner extinguishment concentration is higher 

than 1.43 vol.% (since extinguishment did not occur at that concentration although there was 
20

good volatilization) and lower than 3.29 vol% (since extinguishment was obtained at that 

concentra-tion without complete volatilization). 

6. Hexamethylphosphoramide 

Testing of hexamethylphosphoramide (O=P[N(CH3)2]3) was extremely difficult 

due to its high boiling point and low vapor pressure. Using the highest possible heating chamber 

temperatures, a maximum concentration of 8.70 vol.% could be obtained, which neither 

extinguished the flame nor reduced its size. 

7. Bis(2,2,2-trifluoroethyl)phosphite 

Bis(2,2,2-trifluoroethyl)phosphite was tested using the Modified NMERI Cup 

Burner. Inadequate vaporization was observed even for heating chamber temperatures of 

200 °C. The compound continued to boil in the bottom of the mixing chamber for 3.5 min after 

the syringe pump was turned off. Moreover, condensation on the glass beads above the mixing 

chamber was obvious. This is not surprising since the boiling point of this compound is 43 °C at 

2 torr (estimated to be 190 °C at 760 torr by a pressure/temperature nomograph). Thus, testing 

was discontinued. 

8. Tris(2,2,2-trifluoroethyl)phosphite 

Tris(2,2,2-trifluoroethyl)phosphite was tested using the Modified NMERI Cup 

Burner, house air, and a heating chamber temperature of 120 °C. Tests were reproducible, with 

extinguishment concentrations of 2.18, 2.61, and 2.59 vol.% (average 2.43 ± 0.17 vol.%). 

In a second series, tests were run using the Standard NMERI Cup Burner 

apparatus and bottled breathing air (medical quality) with a heating chamber temperature of 

200 °C. Extinguishing concentrations of 1.22, 1.27, 1.43, 1.47, 1.57, 1.52, 1.57, 1.33, 1.33, and 

1.47 vol.% (average 1.41 ± 0.11 vol.%) were obtained. 

The very large difference may have been due to inadequate volatilization in the 

heated mixing chamber in the first series; however, in that series, the compound appeared to 

vaporize completely in the mixing chamber without condensation on the beads in the cup burner. 

It also may have resulted from the use of different air sources. To check the latter, the n-heptane 

extinguishment concentration of HFC-125 (CHF2CH3) was determined with the Standard 
21

NMERI Cup Burner using both bottled breathing air and house air. The measured 

concentrations were 7.44, 7.49, 7.74, 7.85, and 7.81 vol.% (average 7.66 ± 0.16 vol.%) with the 

bottled air and 8.43, 8.52, 8.33, 8.38, and 8.38 vol.% (average 8.41 ± 0.06 vol.%) with the house 

air. Further investigation indicates that the oxygen content of the bottled air was low. Only the 

results of the house air determination are therefore used in this report. 
22

SECTION III 

SILICON 

A review of the chemistry and fire suppression properties of silicon compounds has been 

presented in Reference 68. Except as otherwise stated, all of the information presented here is 

newly acquired or is an expansion of information contained in that source. Of particular interest 

as fires suppressants are silicon-containing compounds with fluorinated alkyl groups. Fluoroorganosilicon polymers have been of some commercial interest (Reference 69). 

A. FIRE SUPPRESSION 

Many organosilicon materials are relatively stable, inert, have a low toxicity, and have 

lower atmospheric lifetimes than do closely related carbon compounds. This allows the 

incorporation of bromine in silanes and siloxanes without having unacceptably large ODPs. 

While silicon compounds without bromine do not appear to have significant fire suppression 

capabilities, the addition of bromine could provide a compound with good fire suppression 

capability while maintaining good environmental characteristics. 

Overall, there is little evidence that silicon, itself, plays a significant role in flame 

extinguishment, even though one could propose combustion free radical recombination cycles 

such as those in Reactions 25 and 26, similar to those proposed for other metals (Reference 5). It 

is difficult to determine why such cycles are favorable in some cases and not in others. 

SiO• + •H + X → SiOH + X* (25) 

SiOH + •H → H2 + SiO• (26) 

The combustion and explosive properties of dichlorosilane (SiH2Cl2) have been 

thoroughly studied (Reference 70). Polyorganosiloxanes and inorganic silicates have been 

examined as potential flame retardants (Reference 71). The major mode of reaction is apparently 

formation of protective surface coatings during a fire. The flammability of silicone polymers has 

been reduced through addition of fluorine, bromine, and CCl3 groups (Reference 72). 
23

Claims have been made that liquid fire extinguishing compositions containing 

haloalkanes and cyclic polysiloxanes increase penetration and throw distance (Reference 73); 

however, there is no claim that the silicon-containing compounds actually increase the intrinsic 

fire suppression capability. 

B. CHEMISTRY 

Silicon chemistry has been the subject of a number of relatively recent reviews (e.g., the 

papers in Reference 74); however, the number of nonflammable silicon compounds that can be 

considered for use in this project is small. 

1. Bromoalkylsilanes 

A series of bromoalkylsilanes has been prepared in a two-step synthesis from a 

halomethane and a bis(trimethylsilyl)amide (Reference 75). The preparation is shown in 

Reactions 27 and 28, where “M” is sodium or potassium and “R” is a nonfluorinated 

(compounds containing fluorine on a carbon atom adjacent to silicon are usually unstable) 

haloalkyl group. 

(M+ [(CH3)3Si]2N-) + RH → [(CH3)3Si]2NH + (M+ R-) (27) 

(M+ R-) + (CH3)3SiCl → (CH3)3SiR + MCl (28) 

The reaction of trialkylchlorosilane (SiClR3) with chlorotrifluoroethene 

(CClF=CF2) allows the synthesis of a number of trifluorovinylsilanes (CF2=CFSiR3) 

(Reference 76). Bromination or hydrobromination of the double bond may permit the formation 

of the compounds CBrF2CBrFSiR3, CBrF2CHFSiR3, and CHF2CBrFSiR3. 

2. Fluoroalkoxysilanes 

A series of tetrafluoroalkoxysilanes (Si(OR)4) has been prepared by reaction of 

the appropriate fluorinated alcohol with silicon tetrafluoride (SiF4) (Reference 77). All of the 
24

TABLE 5. TETRA(FLUOROALKOXY)SILANES. 

Name Formula Boiling 

point, °C 

(torr) 

Liquid 

density 

g/mL 

(°C) 

Liquid 

viscosity, 

20°C, cp

tetrakis(2,2,2-

trifluoroethoxy)silane 

Si(OCH2CF3)4 155.5 - 157 

(743) 

1.5107 

(20) 

2.2089 

tetrakis(2,2,3,3-

tetrafluoropropoxy)silane 

Si(OCH2CF2CHF2)4 117 - 118

(4) 

1.5927 

(20) 

18.92 

tetrakis(2,2,3,3,4,4,4-

heptafluorobutoxy)silane 

Si(OCH2(CF2)2CF3)4 96 - 97 

(4) 

1.5740 

(71.1) 

7.613 

tetrakis(2,2,3,3,4,4,5,5-

octafluoropentoxy)silane 

Si(OCH2(CF2)3CHF2)4 156 - 159

(2.5) 

1.8150 

(20) 

42.75 

tetrakis(2,2,3,3,4,4,5,5,6,6,7,7-

dodecafluoropentoxy)silane 

Si(OCH2(CF2)5CHF2)4 201 - 204

(3) 

1.7181 

(71.1) 

108.8 

tetrakis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,

9,9-hexadecafluorononoxy)silane 

Si(OCH2(CF2)7CHF2)4 a235 - 240

(2.5) 

Not 

reported 

Not 

reported 

a

With decomposition. 

compounds are liquids at room temperature with very low melting points (less than -68 °C 

except for Si(OCH2CF3)4); however, the boiling points and viscosities are high (Table 5). One 

major problem with such alkoxy compounds is that they hydrolyze readily and then polymerize. 

C. ACQUISITION AND TESTING 

Due to the complexity of the syntheses, no attempt was made to prepare 

fluoroalkyl-containing silicon compounds during the present project. Table 6 contains those 

silicon compounds selected for testing to obtain at least some baseline data. 

1. Silicon Tetrachloride 

Silicon tetrachloride (SiCl4) has a relatively low boiling point; however, this 

compound caused problems with the Standard NMERI Cup Burner. During the first test, the 

metering valve on the cup-burner apparatus became increasingly difficult to adjust and finally 

froze. Upon disassembly, the valve and line leading to the valve were found to be clogged with 

particulate matter. It is likely that silicon dioxide was formed by hydrolysis. No further testing 
25

TABLE 6. SILICON-CONTAINING COMPOUNDS SELECTED FOR TESTING. 

Compound Formula Boiling point, 

°C (torr) 

Flash point, 

°C 

Reference 

Silicon tetrachloride SiCl4 57.6 None 66 

Bromotrimethylsilane SiBr(CH3)3 79 32 66 

Silicon tetrabromide SiBr4 153 None 66 

was attempted; however, with care, it is likely that the Modified NMERI Cup Burner could be 

used for this or similar compounds in the future. 

2. Bromotrimethylsilane 

Bromotrimethylsilane (SiBr(CH3)3) was tested using the Modified NMERI Cup 

Burner. With a boiling point of 79 °C, this compound is relatively easily volatilized; however, 

the material is flammable. Two tests gave cup-burner extinguishment concentrations of 2.28 

vol.%. As the flow rate of the compound was increased, there appeared to be some effect on the 

flame, although no distinct lifting of the flame off of the fuel cup was observed. The flame 

wandered around, occasionally falling down the side of the cup. When the flow rate reached 

0.043 g/s, the flame behaved erratically and traveled to the bottom of the chimney (to the glass 

beads). The flame in the fuel cup was extinguished, but the compound continued to burn on the 

surface of the glass beads. A small amount of the compound was found to sustain a flame. 

3. Silicon Tetrabromide 

As expected, silicon tetrabromide (SiBr4) was more effective than the other 

silicon compounds tested. The first test with the Modified NMERI Cup Burner gave an 

extinguishment concentration of 2.04 vol.%. During subsequent testing, however, serious 

problems with clogging of the syringe pump were encountered. Cleaning the syringe completely 

and repeating the test resulted in the same problem. This problem casts doubt on the 

extinguishment value of 2.04 vol.% obtained in the first test. If the syringe was sticking, the 

measured flow rate would be less than the actual flow rate, because the syringe pump is allowed 

to slip for safety. This would result in a low cup-burner value. 
26

SECTION IV 

AMINES 

A relatively short discussion of the chemistry and fire suppression properties of amine 

compounds has been presented in Reference 78. Except as otherwise stated, all information 

presented here is newly acquired or is an expansion of information contained in that source. 

A. FIRE SUPPRESSION 

Fluorinated derivatives of carboxylic acid hydrazides having the general formula 

RC(O)N(CF2X)NHCF2X, where R is a hydrocarbon and X is fluorine, perfluoroalkyl, or 

ω-hydroperfluoroalkyl, are reported to be nonflammable and, in some cases, to act as fire 

extinguishants (Reference 79). The compounds can be prepared by reaction of an aldehyde with 

a polyfluoroazoalkane (Reaction 29). One example of a fire extinguishing compound of this 

type is N,N’-bis(perfluoropropyl)-N-butyrohydrazide (V). 

RC(O)H + CF2XN=NCF2X → RC(O)N(CF2X)NHCF2X (29) 

CH3CH2CH2 NH CF

CF3

CF3

O

C N

CF

CF3 CF3

(V) 

B. CHEMISTRY 

Appendix A contains a list of all fluorinated amines contained in the CGET Chemical 

Options Database (CCOD) with the ID number for each. The following chemical information is 

additional to that found in Reference 78. 
27

N-Bromobistrifluoromethylamine ((CF3)2NBr) adds to the unsaturated compounds 

tetrafluoroethene (CF2=CF2), trifluoroethene (CHF=CF2), 1,1-difluoroethene (CH2=CF2), 

cis-1,2-difluoroethene (CHF=CHF), ethene (CH2=CH2), hexafluoropropene (CF2=CFCF3), 

chlorotrifluoroethene (CClF=CF2), and 1,2-dichlorodifluoroethene (CClF=CClF) under mild 

conditions, to give the 1:1 adducts in high yield. The (CF3)2N attaches only to the CH2 group of 

1,1-difluoroethene, whereas trifluoroethene gives the isomers (CF3)2NCHFCF2Br (78%) and 

(CF3)2NCF2CHFBr (22%). Hexafluorocyclobutene and octafluorobut-2-ene require more drastic 

conditions, and give the olefin dibromide and tetrakistrifluoromethylhydrazine rather than 

addition of the N-bromo-compound (Reference 80). The properties of the compounds of interest 

are shown in Table 7. 

TABLE 7. BROMOALKYLAMINES. 

Compound Boiling point, 1 atmosphere, °C 

(CF3)2NCH2CH2Br a85.6 

(CF3)2NCH2CBrF2 79.9 

(CF3)2NCHFCHBrF 76.4 

(CF3)2NCHFCBrF2 62.4 

(CF3)2NCF2CHBrF 74.0 

(CF3)2NCF2CBrF2 60.9 

(CF3)2NCF2CBrClF 93.5 

(CF3)2NCFClCBrClF 125.6 

(CF3)2NCF2CBrFCF3 82.2 

a

Also reported as 141 °C (Reference 81). 

Reaction of N-bromobistrifluoromethylamine ((CF3)2NBr) with ethyne (CH≡CH) 

gives (CF3)2NCH=CHBr, which a boiling point of 68.8 °C (Reference 81). This compound is of 

high interest in this project since the atmospheric lifetime should be quite short. 
28

C. ACQUISITION AND TESTING 

1. Chemicals for Testing 

Table 8 is a list of nitrogen-containing compounds selected for testing. 

TABLE 8. NITROGEN-CONTAINING COMPOUNDS SELECTED FOR TESTING. 

Compound Formula Boiling point,°C Reference 

N,N-bis(trifluoromethyl) 

pentafluoroethanamine 

N(CF3)2(C2F5) a20 to 22 82 

N,N-bis(trifluoromethyl) 

trifluoromethanamine 

N(CF3)3 a-10 82 

2. N,N-bis(trifluoromethyl)pentafluoroethanamine 

N,N-bis(trifluoromethyl)pentafluoroethanamine ((pentafluoroethyl)bis(dimethyl)-

amine, N(CF3)2(C2F5)) was obtained from Dr. Takashi Abe, National Industrial Research 

Institute (NIRI), Japan. Three tests were run with the Standard NMERI Cup Burner with house 

air and a gas delivery (measured with a bubble meter) to give extinguishment concentrations of 

3.7, 3.8, and 3.8 vol.% (average 3.77±0.04 vol.%). 

3. N,N-bis(trifluoromethyl)trifluoromethanamine 

Synthesis of N,N-bis(trifluoromethyl)trifluoromethanamine 

(tris(trifluoromethyl)amine, N(CF3)3) was attempted using the procedure shown in Reaction 30. 

The two gases were mixed in a round bottom flask under room-temperature conditions, with both 

photolysis (UV) and heating. In all cases, the combination of the two gases resulted in formation 

of condensation on the flask walls. With photolysis, free iodine appeared to be generated as the 

vessel developed a light purple color. GC analysis indicated the formation of new peaks; all GC 

peaks eluted very early. No further work was done to prepare this material. 

NH3 + 3CF3I → N(CF3)3 + 3HI (30) 
29

SECTION V 

FLUORINATED ETHERS 

A. FIRE SUPPRESSION 

Hydrofluoropolyethers (HFPE) are being introduced into the market, and there is some 

evidence for relatively good fire suppression performance (Reference 83). There is, however, 

little evidence that ethers provide any special mode of action in fire suppression. 

B. CHEMISTRY 

A list of fluorinated ethers contained in the CGET Chemical Options Database with the 

ID numbers and boiling points is contained in Appendix B. 

C. ACQUISITION AND TESTING 

1. Chemicals for Testing 

Table 8 is a list of fluorinated ethers selected for testing. 

TABLE 9. FLUORINATED ETHERS SELECTED FOR TESTING. 

Compound Formula Boiling point, 

°C 

1-methoxynonafluorobutane 

(Halocarbon No. HFE-E449s1) 

CF3CF2CF2CF2-O-CH3 a60 

hydrofluoropolyether HF2CO(CF2O)n-

(CF2CF2O)mCF2H 

b

100 

a

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

Solvent Alternatives,” Precision Cleaning '95, Rosemont, IL, 15-17 May 1995. 

b

Reference 84. 

2. 1-Methoxynonafluorobutane 

1-Methoxynonafluorobutane was obtained from 3M Company. Standard NMERI 

cup-burner testing gave an extinguishment concentration of 6.1 vol.%. 
30

3. Hydrofluoropolyether 

A mixture of hydrofluoropolyethers was obtained as an experimental product 

from Ausimont S.p.A. in Milano, Italy. Testing with the Standard NMERI Cup Burner gave an 

average extinguishment concentration of 5.1 vol.%. 
31

SECTION VI 

RESULTS AND CONCLUSIONS 

A. MODIFIED NMERI CUP BURNER 

During this project, the NMERI Cup Burner (Reference 2) was modified to use volume 

delivered by a syringe pump rather than weight to measure agent delivery rates. The use of a 

syringe pump has been demonstrated to allow cup-burner testing of high boiling point and/or 

viscous materials, particularly those that are difficult to pass through valves and delivery lines. 

Because the syringe pump delivery method allows less holdup of agent in lines and requires less 

storage, this method allows testing of agents available only in limited amounts. Overall, 

however, the use of weight is still the most accurate and reliable method for testing. 

B. CUP-BURNER RESULTS 

Table 10 gives the results of the cup burner testing. In a number of cases, the volatility 

(or flammability) was too high to give reliable results. 

C. CONCLUSIONS 

Of the families examined, phosphorus compounds provide the most promising candidates 

for continued work. Phosphines provide good materials for mechanistic studies; however, 

phosphines can be ruled out as candidates owing to their inherent low stability (many are 

flammable, sometimes spontaneously, even with fluorinated substituents) and high toxicities. 

Though it is possible to obtain fire extinguishment (sometimes, very good) with phosphazenes, 

these compounds have an inherently high molecular weight and, therefore, very low volatility. 

Of the phosphorus compounds, the esters of phosphorus-containing acids are the most promising 

candidates. 
32

TABLE 10. CUP-BURNER TEST RESULTS. 

Compound Formula Ext. conc., 

vol% 

Comments 

Tris(2,2,2-trifluoroethyl)phosphate O=P(OCH2CF3)3 --- synthesis 

incomplete 

Dimethylmethylphosphonate O=P(CH3)(OCH3)2 5 single value with 

decomposition 

Trimethylphosphate O=P(OCH3)3 5.3-6.8 suspect value 

Trimethylphosphite P(OCH3)3 --- flammability 

prevented testing 

(Bromodifluoromethyl) 

diethylphosphonate 

O=P(CBrF2)(C2H5)2 <3.3 upper limit 

Hexamethylphosphoramide O=P[N(CH3)2]3 >8.7 no extinguishment 

Bis(2,2,2-trifluoroethyl)phosphite O=PH(OCH2CF3)2 --- volatility too low 

for test 

Tris(2,2,2-trifluoroethyl)phosphite P(OCH2CF3)3 2.43 --- 

Silicon tetrachloride SiCl4 --- reaction with 

apparatus prevented 

testing 

Bromotrimethylsilane SiBr(CH3)3 2.28 --- 

Silicon tetrabromide SiBr4 2.04 suspect value 

N,N-bis(trifluoromethyl)-

pentafluoroethanamine 

N(CF3)2(C2F5) 3.77 --- 

N,N-bis(trifluoromethyl)-

trifluoromethanamine 

N(CF3)3 --- synthesis 

incomplete 

1-Methoxynonafluorobutane CF3CF2CF2CF2-OCH36.1 --- 

Hydrofluoropolyether HF2CO(CF2O)n-

(CF2CF2O)mCF2H 

5.1 --- 
33

The primary problems of phosphorus-containing esters is their often high boiling points 

and viscosities and the flammability of many of the materials. Fluorination would, of course, aid 

in all of these problems. Thus, tris(2,2,2-trifluoroethyl)phosphite (P(OCH2CF3)3) provides very 

good extinguishment. All other things being equal, compounds with phosphite structures are 

preferred over phosphonates or phosphates to increase the volatility. For example, bis(2,2,2-

trifluoroethyl)phosphite (O=PH(OCH2CF3)2), which actually has a phosphonate structure, has 

too low a volatility for a standard cup-burner test. Nevertheless, phosphates and phosphonates 

should not be dismissed. The most promising compounds would, therefore, be phosphites with 

formulas such as P(ORf)3, where Rf is a fluorinated group, which should have as low a molecular 

weight and as high a fluorination as possible. First, tris(2,2,2-trifluoroethyl)phosphite 

(P(OCH2CF3)3) should be examined further. This compound has a relatively low cup-burner 

extinguishment concentration, although the boiling point is high. Tris(trifluoromethyl)phosphite 

(P(OCF3)3), if it can be made, is an ideal compound for evaluation. Others of particular interest 

are tris(pentafluoroethyl)phosphite (P(OCF2CF3)3) and phosphites containing mixed -CF3 and 

-C2F5 groups. The second most promising families are the phosphates with structures similar to 

those presented above for the phosphites, e.g., tris(trifluoromethyl)phosphate (O=P(OCF3)3) and 

tris(pentafluoroethyl)phosphate (O=P(OCF2CF3)3). Finally, phosphites and phosphates with a 

bromine-containing alkyl group, e.g., (bromodifluoromethyl)bis(trifluoromethyl)phosphite 

(P(OCF3)2(OCF2Br)) and (bromodifluoromethyl)bis(trifluoromethyl)phosphate 

(O=P(OCF3)2(OCF2Br)) require investigation. Such compounds are expected to exhibit fire 

suppression synergism between the bromine and phosphorus. The list of promising phosphorus 

compounds is shown in Table 11. 

A major problem is performing syntheses of the phosphate and phosphite esters of the 

types proposed. Phosphites can be easily synthesized by reaction of PCl3 with ROH. These, in 

turn, can be oxidized to the phosphates. Unfortunately, alcohols that could be used to prepare 

esters containing fluorine bound to the carbon atom adjacent to oxygen are inherently unstable, 

breaking down by a 1,2-elimination of hydrogen fluoride (HF) to give carbonyl compounds. 

There may, however, be other ways to prepare such esters. One possibility is shown in Reaction 

31 for tris(trifluoromethyl)phosphite. 

P(OH)3 + 3CF3I → P(OCF3)3 + 3HI (31) 
34

Silicon compounds appear to offer relatively little promise. Silicon offers few inherent 

fire suppression capabilities due to the silicon itself, and many of the most interesting 

compounds (e.g., those containing bromofluoroalkyl and/or fluoroalkyl groups) are difficult to 

synthesize. Of particular concern is the instability of compounds containing -CF3 groups 

immediately adjacent to the silicon atom, and such compounds are not considered here. Two 

silicon compounds do, however, offer promise at least for mechanistic studies if they can be 

prepared (Table 11). In these cases, -ORf and/or -OCF2Br groups are attached to the silicon 

atom. All of these are likely to have a low volatility and a high viscosity. 

Amines, on the other hand, offer significant promise, particularly because a large amount 

of research is underway in Japan on the applications of fluoroalkyl amines as halon and CFC 

replacements. Note, however, that much of this research appears to be headed in the wrong 

direction. Much of it is on perfluoroalkyl amines, which are likely to have long atmospheric 

lifetimes. Nevertheless, the work provides synthetic routes and property evaluations. 

Compounds such as N(CF3)(CHF2)(CF2Br) could provide short atmospheric lifetimes and 

chemical suppression. A list of promising amines is shown in Table 11. Note that the first two 

listed (one of which was tested under the present program) are likely to have long atmospheric 

lifetimes; however, this needs to be investigated further. 

A large amount of research is underway on fluoroethers as CFC replacements. The ether 

linkage provides a lower atmospheric lifetime only if it contains some hydrogen atoms. Work 

here and elsewhere indicates that in the absence of a bromine group, fluorinated ethers offer a 

fire suppression capability no higher than that of the hydrofluorocarbons and perfluorocarbons. 

Thus, there is little reason to pursue hydrofluoroethers or perfluoroethers further. Of interest, 

however, are hydrobromofluoroethers, and two such compounds are recommended in Table 11. 
35

TABLE 11. FINAL LIST OF RECOMMENDED COMPOUNDS. 

Formula Name 

Phosphorus Compounds 

P(OCH2CF3)3 tris(2,2,2-trifluoroethyl)phosphite 

P(OCF3)3 tris(trifluoromethyl)phosphite 

P(OCF2CF3)3 tris(pentafluoroethyl)phosphite 

P(OCF3)2(OCF2Br) (bromodifluoromethyl)bis(trifluoromethyl)phosphite 

O=P(OCF3)3 tris(trifluoromethyl)phosphate 

O=P(OCF2CF3)3 tris(pentafluoroethyl)phosphate 

O=P(OCF3)2(OCF2Br) (bromodifluoromethyl)bis(trifluoromethyl)phosphate 

Silicon Compounds 

Si(OCF3)4 tetrakis(trifluoromethyl)silicate 

Si(OCF3)3(OCF2Br) (bromodifluoromethyl)tris(trifluoromethyl)silicate 

Si(OCH2CF3)4 tetrakis(2,2,2-trifluoroethyl)silicate 

Si(OCF2Br)4 tetrakis(bromotrifluoromethyl)silicate 

Bromofluoroamines 

(CF3)3N tris(trifluoromethyl)amine 

(CF3)2(CF3CF2)N bis(trifluoromethyl)(pentafluoroethyl)amine 

(CBrF2)(CHF2)2N (bromodifluoromethyl)bis(difluoromethyl)amine 

(CBrF2)(CF3)(CH3)N methyl(bromodifluoromethyl)(trifluoromethyl)amine 

(CF3)2(CH2CBrF2)N bis(trifluoromethyl)(2-bromo-2,2-

difluoroethyl)amine 

(CBrF2)(CF3)2N bis(trifluoromethyl)(bromodifluoromethyl)amine 

 Fluoroethers 

CH3-O-CF2Br methoxybromodifluoromethane 

CF2H-O-CF2Br difluoromethoxybromodifluoromethane 
36

SECTION VII 

RECOMMENDATIONS 

Of the compounds examined in this project, future work should emphasize phosphites 

and, secondarily, amines. Of particular importance is the preparation, if possible, of P(OCF3)3. 

Dr. Jean'ne M. Shreeve at the University of Idaho could provide expertise in this area as well as 

in the preparation of other fluoroalkyl and bromofluoroalkyl compounds (both main group 

compounds and materials such as ethers), and the possibility of a collaborative arrangement will 

be examined. 

Contacts have been made with Russian scientists, and these appear to offer good sources 

at reasonable cost for a number of materials of interest in this project and in future projects on 

main group compounds. 
37

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44

APPENDIX A 

FLUORINATED AMINES FROM CCOD 

CCOD 

ID 

Formula Empirical 

formula 

Molecular mass, 

amu 

Boiling point, 

°C 

Nonbrominated Fluoroalkylamines 

922 N(CF3)3 C3F9N 221.03 -10 

918 N(CF3)2(CF2CF3) C4F11N 271.03 20.5 

1315 N(CF3)(CF2CF3)2 C5F13N 321.04 46 

991 N(CF2CF3)3 C6F15N 371.049 70.3 

1316 N(CF2CF3)2(CF2CF2CF3) C7F17N 421.06 93 

1317 N(CF2CF3)(CF2CF2CF3)2 C8F19N 471.06 114 

1318 N(CF2CF3)2(CF2CF2CF2CF3) C8F19N 471.06 115 

758 N(CF2CF2CF2CF3)3 C12F27N 671.10 174 

759 N(CF2CF2CF2CF2CF3)3 C15F33N 821.12 215 

920 N(CF3)2(CF=CF2) C4F9N 233.04 13.7 

1044 N(CF3)2(CHF2) C3HF8N 203.03 7.8 

921 N(CF3)2(CF2CHF2) C4HF10N 253.04 32 

1010 N(CF3)2(CH2CF3) C4H2F9N 235.05 38 

1006 N(CH3)(CF3)2 C3H3F6N 167.05 11.5 

1009 N(CF3)2(CH2CHF2) C4H3F8N 217.06 51.35 

1008 N(CF3)2(CH2CH3) C4H5F6N 181.08 33.29 

1319 N(CH3)2(CF3) C3H6F3N 113.08 20 

1320 N(CF3)(CH2CH3)2 C5H10F3N 141.14 71 

1321 -CH2CH2CH2CH2CH2N(CF3)- C6H10F3N 153.15 107 

1322 -CH2CH2CH2CH2CH2CH2N(CF3)- C7H12F3N 167.17 133 

1323 N(CH(CH3)2)2(CF3) C7H14F3N 169.19 109 
45

APPENDIX A 

FLUORINATED AMINES FROM CCOD (CONCLUDED) 

CCOD 

ID 

Formula Empirical 

formula 

Molecular mass, 

amu 

Boiling point, 

°C 

Brominated Fluoroalkylamines 

990 N(CBrF2)(CF3)2 C3BrF8N 281.93 40.6 

919 N(CF3)2(CF2CF2Br) C4BrF10N 331.94 60 

1203 N(CF3)2(CHFCF2Br) C4HBrF9N 313.95 62.4 

1204 N(CF3)2(CF2CHFBr) C4HBrF9N 313.95 74 

1249 N(CF3)2(CH=CHBr) C4H2BrF6N 257.96 68.8 

1200 N(CF3)2(CHFCHBrF) C4H2BrF8N 295.96 76.4 

1053 N(CF3)2(CH2CBrF2) C4H2BrF8N 295.96 79.9 

1202 N(CF3)2(CH2CH2Br) C4H4BrF6N 259.98 85.6 

1209 N(CF3)2(CF2CFBrCF3) C5BrF12N 381.95 82.2 

1207 N(CF3)2(CF2CFClBr) C4BrClF9N 348.39 93.5 

1208 N(CF3)2(CFClCFClBr) C4BrCl2F8N 364.85 125.6 
46

APPENDIX B 

FLUORINATED ETHERS FROM CCOD 

CCOD ID Molecular formula Empirical formula Boiling point, °C 

No Chlorine or Bromine Atoms 

886 CF3-O-CF3 C2F6O -59 

890 CHF2-O-CF3 C2HF5O -35 

892 cyclo-O-CF2CF2CF2- C3F6O -29.2 

891 CF3-O-CF2CF3 C3F8O -23.3 

 CH3OCH3 C2H6O -24.8 

887 CH3-O-CF3 C2H3F3O -24.2 

1223 cyclo-CF2-O-CF2-O-CF2- C3F6O2 -22.1 

1334 CH2F-O-CF3 C2H2F4O -20 

897 CF3-O-CF2-O-CF3 C3F8O2 -10.2 

1034 CF3CHF-O-CF3 C3HF7O -9.6 

1246 CHF2CF2-O-CF3 C3HF7O -4.2 

1248 CHF2-O-CF2CF3 C3HF7O 0 

691 CHF2-O-CHF2 C2H2F4O 2 

1259 cyclo-O-CF2CHFCF2- C3HF5O 3.4 

1314 CF3CF2-O-CF2CF3 C4F10O 5 

1005 CH3-O-CF2CF3 C3H3F5O 5.59 

1004 CF3CH2-O-CF3 C3H2F6O 5.69 

1240 CH3CH2-O-CF3 C3H5F3O 6 

1313 CF3-O-CF2CF2CF3 C4F10O 6.8 

 CH3-O-CH2CH3 C4H8O 7.4 

1344 CF3-O-CF2CF2-O-CF3 C4F10O2 16.7 

1227 CHF2CF2-O-CF2CF3 C4HF9O 22 

1011 CHF2-O-CHFCF3 C3H2F6O 23.31 

895 CHF2-O-CH2CF3 C3H3F5O 26.1 

894 CF3-O-CH(CF3)CH3 C4H4F6O 27 
47

APPENDIX B 

FLUORINATED ETHERS FROM CCOD (CONTINUED) 

CCOD ID Molecular formula Empirical formula Boiling point, °C 

No Chlorine or Bromine Atoms (continued) 

1014 CF3CH2-O-CF2CF3 C4H2F8O 27.76 

893 CHF2-O-CF2CHF2 C3H2F6O 28.5 

1013 CH3-O-CF(CF3)2 C4H3F7O 29.35 

809 CH3-O-CH2CF3 C3H5F3O 31.62 

1012 CH3-O-CF2CF2CF3 C4H3F7O 34.18 

 CH3CH2-O-CH2CH3 C4H10O 34.5 

1216 CHF2-O-CF2-O-CHF2 C3H2F6O2 35 

1345 CF3-O-CF2CF2CF2CF3 C5F12O 36 

1346 CF3-O-CF2CF(CF3)CF3 C5F12O 36 

1003 CH3-O-CF2CHF2 C3H4F4O 37.19 

1335 CF3CHF-O-CF2CF2CF3 C5HF11O 40.8 

1040 CHF2-O-CH(CF3)2 C4H2F8O 42.1 

1019 CHF2-O-CF2CH2F C3H3F5O 43.1 

593 CF3CH2-O-CH=CH2 C4H5F3O 43.7 

1341 CHF2-O-CF(CH3)CF3 C4H4F6O 45 

1023 CHF2-O-CH2CF2CF3 C4H3F7O 45.9 

1339 CH3-O-CH(CH3)CF3 C4H7F3O 47.8 

1340 CHF2-O-CH(CH3)CF3 C4H5F5O 48 

120 CF3CH2-O-CH2CH3 C4H7F3O 50.3 

1024 CH3-O-CH(CF3)2 C4H4F6O 51 

1243 CH2F-O-CF2CHF2 C3H3F5O 53 

1031 CF3CH2-O-CF2CHF2 C4H3F7O 56.2 

1217 CHF2-O-CF2CF2-O-CHF2 C4H2F8O2 58 

913 CF3CF2CF2CF2-O-CH3 C5H3F9O 60 

172 CHF2CH2-O-CH2CH3 C4H8F2O 65 
48

APPENDIX B 

FLUORINATED ETHERS FROM CCOD (CONTINUED) 

CCOD ID Molecular formula Empirical formula Boiling point, °C 

No Chlorine or Bromine Atoms (continued) 

1336 CH3-O-CH2CF2CHF2 C4H6F4O 66 

1218 CHF2-O-CF2-O-CF2-O-CHF2 C4H2F8O3 68 

1022 CHF2-O-CH2CF2CHF2 C4H4F6O 69 

914 CF3CF2CF2CF2-O-CH2CH3 C6H5F9O 73 

1338 CHF2-O-CHFCF2CHF2 C4H3F7O 74 

1219 CHF2-O-CF2-O-CF2CF2-O-CHF2 C5H2F10O3 85 

1220 CHF2-O-CF2CF2-O-CF2CF2-O-CHF2 C6H2F12O3 98 

1094 cyclo-O-CF(C4F9)CF2CF2CF2- C8F16O 103 

1221 CHF2-O-CF2-O-CF2-O-CF2CF2-OCHF2

C6H2F12O4 110 

1222 CHF2-O-CF2-O-CF2-O-CF2-OCF2CF2-O-CHF2C7H2F14O5 130 

Bromine-Containing 

1165 CH3-O-CF2CH2Br C3H5BrF2O a54.7 

1162 CH3-O-CF2CHBr2 C3H4Br2F2O b55.8 

1163 CH3CH2-O-CF2CHBr2 C4H6Br2F2O c

65 

1166 CH3CH2-O-CF2CH2Br C4H7BrF2O d

70 

1164 CH3CH2CH2-O-CF2CHBr2 C5H8Br2F2O e72.2 

1342 CHF2-O-CF2CHBrF C3H2BrF5O 73 

1160 CH3CH2CH2-O-CF2CHFBr C5H8BrF3O b75.2 

1170 CF3-O-CH2CH2Br C3H4BrF3O 78.5 

1343 CH3-O-CF(CF3)CBrF2 C4H3BrF6O 80 

497 CH3-O-CF2CHBrF C3H4BrF3O 88.8 

1148 CF3CBrFCH2-O-CH2-O-CH2CBrFCF3 C7H8Br2F8O2

f

92 

1158 CH3CH2-O-CF2CHFBr C4H6BrF3O 106 

1157 CHFBrCF2CH2-O-CH3 C4H6BrF3O 125 
49

APPENDIX B 

FLUORINATED ETHERS FROM CCOD (CONCLUDED) 

CCOD ID Molecular formula Empirical formula Boiling point, °C 

Bromine-Containing (concluded) 

1168 CF3CHBrCH2-O-CH2CHBrCF3 C6H6Br2F6O 167 

1125 CBrF2CF2CH2CH2CH2CH2-O-CH2CH3 C8H13BrF4O 185.7 

1169 CF3CHBrCH2-O-CH2-O-CH2CHBrCF3 C7H8Br2F6O2 195 

Chlorine-Containing 

1049 CHF2-O-CHClCF3 C3H2ClF5O 48.5 

1048 CHF2-O-CF2CHClF C3H2ClF5O 56.5 

1176 CF3-O-CBrClCHBr-O-CF3 C4HBr2ClF6O2 94.5 

978 CH3-O-CF2CHCl2 C3H4Cl2F2O 105 

a

220 torr; b130 torr; c26 torr; d175 torr; e23 torr; f28 torr