NATL INST. OF STAND & TECH MIST

PUBLICAHON|

NBSIR 74-551

An Appraisal of Methods for

Estimating Self-Reaction Hazards

W. Tsang and E. S. Domalski

Physical Chemistry Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

June 1974

Interim Report for Period January -June 1974

Prepared for Office of Hazardous Materials

sartment of Transportation

shington, D. C. 20024

NBSIR 74-551

AN APPRAISAL OF METHODS FOR

ESTIMATING SELF-REACTION HAZARDS

W. Tsang and E. S. Domalski

Physical Chemistry Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

June 1974

Interim Report for Period January- June 1974

Prepared for Office of Hazardous Materials

Department of Transportation

Washington, D.C. 20024

, 7 ,

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS. Richard W. Roberts. Director

Preface

The production of chemical compounds and their transportation

constitutes a vital segment of our nation's technological growth and

economic stability. Hazardous materials require appropriate labeling

and identification in connection with their handling and transport in

commerce and industry. The Hazardous Classification System proposed

by the Department of Transportation, Hazardous Materials Regulations

Board, describes various classifications for materials, however,

thermally unstable or self-reactive materials are indicated only as

a secondary descriptor. The possibility of identifying thermal

instability of chemical substances without recourse to experimental

studies is the basic purpose of this study. Our approach has been to

evaluate certain procedures which claim to be capable of estimating

hazard potential by a direct comparison with the results of explosive

sensitivity tests and the predictions from the hazard evaluation

schemes.

In particular, we have examined both the CHETAH program and Stull's

modification of the CRUISE programs for estimating the hazard potential

of chemical compounds. As presently constituted we believe tha-t these

schemes over-emphasize power as opposed to sensitivity . The latter is

a vastly more complex property in comparison with the former because it

involves a detailed knowledge of the rates and mechanism of the initial

decomposition or polymerization reaction. We suspect that no simple

computational scheme of the type under discussion here will be adequate

for the classification of all materials or serve as a substitute for

experimental results. Nevertheless these programs dp Introduce concepts

- 1 -
which when properly utilized are to some degree correlatable with

sensitivity test results. They represent important beginnings in the

efforts to rationalize a subject which until now must be considered more

of an art than science.

We wish to thank Dr. Eli Freedman (U.S. Army, Ballistics Research

Laboratories, Aberdeen Proving Ground, Aberdeen, MD) , Dr. Daniel R,

Stull (Dow Chemical Company, Midland, MI), and Ms. Eleonore G. Kayser

(Chemistry Research Department, Naval Ordnance Laboratory, White Oak,

MD) for their assistance and for many useful discussions on various

aspects of thermal instability appraisal.

- ii -
Table of Contents page

Preface

List of Tables

List of Figures ^

I. Introduction

II. Description of Methods 3

A. CHETAH Computer Pror,ram 3

B. CRUISE Computer Program 22

III. Comparison of Certain Parameters with 33

Sensitivity Test Results

A. Test Procedures 33

B. Test Results 38

C. Correlations 40

IV, Discussion 60

A. Heat of Reaction (Decomposition) 60

B. Activation Energy for Decomposition 72

C. Oxygen Balance 74

D. Polymerization Reactions 75

V, Conclusions and Recommendations 78

VI. References 81

VII. Appendix - Bond Dissociation Energies 85

- iii -
List of Tables page

Table 1. Decomposition Reactions Computer by the CHETAH Program 6

Table 2. Maximum Enthalpy of Decomposition 8

Table 3. AH (combust Ion) - AH(decompositlon) 11

Table 4. Oxygen Balance 14

Table 5. Modified Enthalpy of Decomposition Criterion 16

Table 6. Summary of CHETAH Hazard Criteria 19

Table 7. Ranking of RHI Values 26

Table 8. Maximum Decomposition Temperatures Calculated using the

CRUISE Program , 30

Table 9. Test Data and Possible Sensitivity Parameters for Various

Materials 42

Table 10. Comparison of Decomposition Reactions and their Enthalpies

at 25 °C 65

Table 11. Table of Bond Dissociation Energies 86

- Iv -
List of Figures page

Figure 1. Nomograph of Maximum Decomposition Temperature vs.

Activation Energy 23

Figure 2. Explosion Temperature vs. Heat of Reaction 51

Figure 3. Thermal Surge Test vs. Heat of Reaction 52

Figure 4. Impact Test vs. Heat of Reaction 53

Figure 5. Explosion Temperature vs. Oxygen Balance 54

Figure 6. Thermal Surge Test vs. Oxygen Balance 55

Figure 7, Impact Test vs. Oxygen Balance 56

Figure 8. Explosion Temperature vs. Activation Energy 57

Figure 9. Thermal Surge Test vs. Activation Energy 58

Figure 10. Impact Test vs. Activation Energy 59

- V -

I. Introduction

The Hazardous Materials Regulations Board of the Department of

Transportation (DOT) is presently considering the adoption of amendments to its existing regulations which would characterize more definitively thermally unstable materials and would give detailed instructions

for their handling and transport. Improved labeling and placarding

of hazardous materials are part of DOT's proposed Hazard Information

System (HI System) and will furnish appropriate identifiers to persons

who might possibly be confronted with an emergency hazard situation.

At present, "SELF REACTIVE" or "THERMALLY TJNSTABLE" is proposed as a

secondary or tertiary descriptor in the HI System after a primary

descriptor such as "FLAMMABLE LIQUID" or "OXIDIZER".

Until recently interest in the characterization of materials on the

basis of their self-reaction potential has been limited to those with

interest in explosives. Numerous investigations have produced ingenious

test methods which permit the ranking order of explosives with regard

to shock, impact or thermal sensitivity. In the past few years, spurred

by the continual introduction of new chemicals by industry (many of

which, although unsuitable for use as explosives, may behave as such

under appropriate conditions), attempts have been made to rank substances

with regard to susceptibility of self-reaction on the basis of various

molecular parameters. Two recent therrao chemical studies, one by Treweek,

- 1 -
Claydon, and Seaton [1] and the other by Stull [2,3] have attempted to

rank substances with respect to self-decomposition. Both studies

describe predictive schemes to estimate hazard potential and have been

adapted for machine calculation.

The present investigation represents an attempt at evaluating these

schemes. Our procedure will be first to outline the two pertinent

schemes and then to illustrate their operational procedure by referring

to specific compounds. The latter will permit some immediate conclusions

to be drawn with regard to the efficacy of these procedures. Following

this, we will proceed with an evaluation on a more formal plane. As

a result of identifying the important molecular parameters from the

earlier discussion that are supposed to be related to sensitivity, we

select from the literature sensitivity test results and then demonstrate

directly the degree of correlation or non-correlation for the two sets

of data. From these results we will select the molecular property or

properties of particular pertinence to material sensitivity and

attempt to provide a theoretical justification. At the same time

this will indicate the situations where the correlations cannot be

expected to apply; in particular with polymerization reactions.

Ultimately this will lead to our general tonclusions and recommendations

with regard to the proposed prediction schemes, test methods, and

future work.

Numbers in brackets indicate literature references at the end of

the paper,

- 2 -
II . Description of Methods

A. CHETAH Computer Program

A computer program called CHETAH ( Chemical Thermodynamics And

energy Hazard evaluation) has been developed bv the American Society

for Testing and Materials (ASTM) Committee E-27 to estimate thermodynamic properties of organic compounds between 300 and 1500 K solely

from a knowledge of molecular structure. The calculated thermodynamic

data are then used bv CHETAH to calculate four energy hazard criteria:

namely, (1) maximum enthalpy (heat) of decomposition , (2) the difference

between the heat of combustion and maximum heat of decomposition,

(3) oxygen balance, and (4) a modification of the maximum heat of

decomposition.

The program contains a data bank which consists of Benson's [4,5]

second-order group-contribution values for the enthalpy (heat) of

formation (AHf°) at 298 K, entropy (S°) at 298 K, and heat capacity

(Cp°) at 300, 400, 500, 600, 800, 1000, and 1500 K. For certain calculations, the method of group equations described by Janz [6] is used.

The data bank also contains thermodynamic information on a large

number of individual compounds. At present the sum total of groupcontribution values and data on individual compounds amounts to over

850 items. The CHETAH program can accommodate inorganic and organo-

* The terms "enthalpy" and "heat" are used interchangeably throughout

the text. Endothermic and exothermic reactions correspond to

positive and negative enthalpies, respectively.

- 3 -
metallic compounds, however, proper specification of their reaction

products will depend upon the contents of the data bank.

The four hazard criteria of the CHETAH program are discussed in

more detail below:

(1) Maximum Enthalpy of Decomposition

The first hazard criterion provides a calculation of the maximum

enthalpy of decomposition. Input data for a test run consist of

identifying the compound or the group-contributions which comprise the

compound and the location of the corresponding thermodynamic information within the data bank. Using these data, a linear programming

subroutine selects those decomposition products (also specifically

identified in the program data bank) which could be formed from the

reactant compound and balances the stoichiometry . The decomposition

process which gives a maximum (negative) enthalpy is then chosen. The

method is also applicable to reactant mixtures and provides the

corresponding maximum enthalpy of decomposition.

The basic approach in the CHETAH program for selecting decomposition

products in CHNO compounds is for the oxygen in the molecule to use

up the maximum number of hydrogens to form water, H^O. Excess oxygen

would form CO^ while excess hydrogen would combine with the carbon

and form CH^. Nitrogen present in the molecule would usually end up

as molecular nitrogen, N2 , in the products, however, an excess of hydrogen,

or hydrogen and oxygen could yield ammonia, NH^, or nitric acid, HNO^,

respectively.

- 4 -
For this criterion, the program lists the energy hazard potential

as low if the maximum heat of decomposition is more positive than -0.3

kcal/g, as medium if the maximum heat of decomposition is between -0.3

and -0.7 kcal/g, and as high if it is equal to or more negative than

-0.7 kcal/g. These values were established by ASTM Committee E-2 7 using

experimental results for 120 compounds, about half of which were found

to be shock sensitive and half of which were believed to be inert to

shock.

We have taken twenty-two compounds to illustrate the CHETAH

hazard criteria and have arranged them in approximate decreasing order

of explosive sensitivity. Given below in Table 1 are: the name of

the compound, and the corresponding formula weight, enthalpy of formation

at 25°C in kcal mol \, and reference to the cited value. In addition^

we have provided the decomposition reaction which yields the maximum

reaction enthalpy (heat) computed by the CHETAH program. Both

reactants and products are gaseous unless otherwise identified.

Formula weights were calculated from the 1971 table of atomic weights

[7 ] which showed: C = 12.011; H = 1.0079; N - 14.0067; .0 = 15.9994;

CI = 35.453; Br = 79.904; Pb = 207.2; Ag = 107.868; Hg - 200.59.

Table 2 lists the twenty-two selected compornds^ identifies

their calculated maximum enthalpy at 298 K, and gives their hazard

rating

- 5 -
Table 1. Decomposition reactions computed by the CHETAH program

1. mercury fulminate; 284.6242; AHf° =64 [9]

HgCONO^Cs) -> CO^ + Hg(s) + + C(s)

2. silver azide; 149.8881; AHf° = 73.8 [7]

AgN^Cs) Ag(s) + 1.5

3. lead azide; 291.2402; AHf° = 114.3 [9]

Pb(N^)2Cs) -> Pb(s) + 3

4. nitroglycerin; 227.0872; AHf* = -64.7 [8]

C^H^N^Og -> 3 CO^ + 2.4 H^O + 1.4 +0.2 HNO^

5. ethylenedinitramine; 150.0938; AHf° = 4.8 [10]

C^H^N.O, 0.5 C0_ + 3 H„0 + 2 N„ + 1.5 C(s)

2 6 4 4 I I 2

6. ethyl nitrate; 91.0664; AHf° = -36.80 [9]

C2H^ON02 0.25 CO^ + 2.50 H^O + 0.5 N2 + 1.75 C(s)

7. 2,4,6-trinitrotoluene; 227.133; AHf° = 12.3 [8]

C^H,N„0, -> 1.75 CO^ + 2.5 tLO + 1.5 N. + 5.25 C(s)

8. azoethane; 86.1364; 32.2 [5,16]

Vl0^2 ^'^ ^"4 -^'^ '^^^^ ^2

9. nitrome thane; 61.0402; AHf° = -17.86 [9]

CH^NO^ 0.25 + 1.5 H^O + 0.5 + 0.75 C(s)

10. diacetyl peroxide; 118.089; AHf° = -116.1 [3]

C,H,0, -> 0.5 CO^ + 3 H^O + 3.5 C(s)

4 6 4 2 2 11. peracetic acid; 76.0518; AHf° = -97.7 [3]

S^4°3 '^'^2 2 H^O + 1.5 C(s)

- 6 -
Table 1 - continued

12. ethylene oxide; 4A.053; AHf° = -12.58 [9]

C,H 0 -y H^O + 0.5 CH, + 1.5 C(s)

2 4 2 4

13. propargyl bromide; 118.9607; AHf° = 52.5 [10]

C^H^Br ^ 0.5 CH, + HBr + 2.5 C(s)

1 i 4

14. vinyl chloride; 62.4987; AHf° = 8.4 [9]

C^H^Cl ^ 0.5 CH, + HCl + 1.5 C(s)

2 J 4

15. ethylene; 28.0536; AHf° = 12.50 [9]

C^H^ - CH^ + C(s)

16. 1-octene; 112.2144; AHf° =-19.82 [11]

C H,, ^ 4 CH, +4 C(s)

o lb 4

17. acetic acid; 60.0524; AHf° = -103.93 [9]

^I'^lPl 2 H^O + 2 C(s)

18. ethyl acetate; 88.1060; AHf° = -106.34 [12]

^4^8°2 ^ 2 H^O + 3 C(s) + CH^

19. acetamide; 59.0676; -57.8 [5,16]

C^H_NO -> H^O + 0.75 CH, + 1.25 C(s) + 0.5

2 5 2 4 2 20. dimethyl ether; 46.0688; AHf° = -43.99 [9]

C^H.O ^ H^O + CH, + C(s) ZD Z 4

21. ethyl chloride; 64.5145; AHf° = -26.70 [9]

C^H^Cl HCl + C(s)

22. n-octane; 114.2302; AHf° = -49.82 [11]

CgH^g 4.5 CH^ + 3.5 C(s)

- 7 -
Table 2. Maximum Enthalpy of Decomposition

Formula name

HgCONOjCc) mercury fulminate

AgN (c) silver azide

Pb(Nj)2(c) lead azide

C3H3N3O, nitroglycerin

ethylenedinitramine

C2H5ONO2 ethyl nitrate

trinitrotoluene

'^4»10''2 azoethane

CH NO nitromethane

Wi diacetyl peroxide

peracetic acid

ethylene oxide

propargyl bromide

CjH.Cl vinyl chloride

ethylene

1-octene

W2 acetic acid

W2 ethyl acetate

C H NO acetamide

dimethyl ether

C2H3CI ethyl chloride

n-octane

maximum AH (decomposition) hazard

kcal mol ^ kcal g

^ rating

-158. -0.56 medium

-73.8 -0.49 medium

-114.3 -0. 39 meditim

-362.6 -1.60 high

-225.2 -1.50 high

-131.2 -1.44 high

-321.4 -1.41 high

-76.9 -0.89 high

-92.3 -1.51 high

-104.3 -0.88 high

-64.9 -0.85 high

-54.2 -1.23 high

-70.1 . -0.59 medium

-39.4 -0.63 medium

-30.4 -1.08 high

-51.7 -0.46 medium

-11.66 -0.19 low

-27.1 -0.31 medium

-13.4 -0.23 low

-31.7 -0.69 medium

-13.3 -0.21 low

-30.7 -0.27 low
Examination of Table 2 shows that (on the basis of intuition) valid predictions

of hazard rating are obtained for many compounds; nitroglycerin, trinitrotoluene, ethylenedinitramine , azoethane, nitromethane , and ethyl nitrate

are considered explosive and hazardous materials and are rated as high

hazards. We acknowledge the large difference in explosive sensitivity

between nitroglycerin and TNT, however, such selectivity is beyond the capability of this method. Others, such as n-octane, acetamide, acetic acid,

and ethyl chloride are rated as low hazard, as expected. Inconsistencies do

occur, however, since detonators like lead azide, silver azlde , and mercury

fulminate are classed as medium hazard and should really be high hazard

because they are the most sensitive explosives in the listing. Similarly,

compounds such as dimethyl ether and ethyl acetate are rated as medium

hazard and more realistically should be in the low hazard grouping.

Ethylene is classed as being of high hazard assuming it decomposes

into elemental graphite and methane, however, polymerization is a

more likely reaction pathway for this compound. As yet, the CHETAH

program has no facility for identifying or classifying compounds

which are hazardous on the basis of their tendency to polymerize.

The errors in hazard ratings which have been generated in this

hazard criterion are partly related to the maximization of the enthalpy

(heat) of decomposition. Although the maximization technique is

mathematically convenient, it departs significantly from the decomposition processes of the real world and the decomposition products

selected are not what one would always obtain. The decomposition

products obtained by CHETAH for the detonators are likely reaction

products, however, these errors suggest strongly that this criterion

does not clearly correlate with explosive sensitivity,

- 9 -
(2) Enthalpy Difference Criterion

The difference between the enthalpy of combustion and enthalpy

of decomposition at 25 constitutes the second hazard criterion, and

is based on the idea that a compound which contains within its own

structure sufficient oxygen to convert the compound to its normal

oxidation products, presents a greater energy hazard than one which

does not. The rating in this criterion is high if [AH (combustion) -

AH (decomposition) ] is less negative than -3.0 kcal/g, medium if between -3.0

and -5,0 kcal/g, and low if more negative than -5.0 kcal/g.

Table 3 below gives the results of calculation [AH (combustion) -

AH (decomposition) ] at 25°C for the twenty-two compounds and the corresponding hazard rating.

- 10 -
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- 11 -
Examination of the Ixazard ratings obtained for the second hazard

criterion in Table 3 shows that nitroglycerin holds true to form with

essentially a zero value for [AH(comb)-Z;Ji(decomp) ] indicating this

compound contains enough oxygen within its own molecular structure

to provide for its own decomposition, and hence merits a high hazard

rating. Similarly, the conventional explosive ccxnpounds (TNT,

ethyienedinitramine , diacetyl peroxide, etc.) are found to have a

high hazard rating. The detonators are classed as expected, very

close to nitroglycerin in actual value, and henceforth, are high

hazards. Both ethylene and ethylene oxide are rated as low hazard

here in contrast to the high hazard rating obtained with the first

hazard criterion. This low hazard rating for these compounds is not

realistic since both are reactive because of their tendency to polymerize. Azoethane is rated low by the second criterion, however, it

is known to decompose explosively. Propargyl bromide is rated as

being a high hazard in this criterion in contrast to a medium rating

with the maximum AH(decomposition) criterion. This compound has a

very positive enthalpy of formation in addition to being highly

unsaturated so that reaction by decomposition and pol5mier ization are

both likely.

(3) Oxygen Balance

The third criterion, or the oxygen balance, is the quantity

of oxygen required for the complete conversion of the elements present

in a compound to their corresponding normal combustion products. A

different mathematical expression is required for compounds with

- 12 -
elements comprising their stoichiome tries . Examples are given below:

C^H^ + (a + (b/4))02 aCO^ + (b/2)H20

oxygen balance = [-1600(2a + b/2)] /(formula wt.)

^pVc + (a + (b/4))02 -> aCO^ + (b/2)H20 + (c/2)N2

oxygen balance = [-1600(2a + (b/2)) ]/ (formula V7t.)

^A^d+ + ^b/-^) - (d/2))02 -> aCO^ + (b/2)H20

oxyge n balance = [-1600(2a + (b/2)-d ) ]/(formula wt.

)

C^H^N^O^ + (a + (b/4) - (d/2))0^ aCO^ + (b/2)H20 + (c/2)N2

oxygen balance = [-1600(2a + (b /2) -d) ]/(f ormula wt.)

C H, CI + (a + (b/4) - (e/4)0„

^

aCO. + (b/2) - (e/2) H_0 + eHCl

a D G II I oxygen balance = [-1600(2a + (b/2) - (e/2)) ]/(f ormula wt.)

C^H^Br^+ (a + (b/4) - (f/4))02 -> aCO^ + (b/2) - (f/2) H^O + fHBr

oxygen balance = [-1600(2a + (b/2) - (f /2) )]/ (formula wt.)

This criterion^ like the second criterion, is a measure of the amount

of oxygen bonded within ttie molecular structure which could convert

part or all of the molecule to its normal oxidation products. If the

oxygen balance is more positive than 240.0 or more negative than

-160.0, the energy hazard potential is rated as low. If the oxygen

balance is between +240.0 and +120.0 or -160.0 and -80.0, the energy

hazard potential is rated as medium. If the oxygen balance is

between -80.0 and +120.0, the energy hazard potential is rated as high.

Table 4 provides calculated values of the oxygen balance for the

twenty-two compounds and their corresponding hazard rating.

- 13 -
Table 4. Oxygen Balance

Formula name

HgCONC)^ (c) mercury fulminate

AgN^(c) silver azide

Pb (N^)2(c) lead azide

nitroglycerin

ethylenedini tramlne

C2H^ON02 ethyl nitrate

r H NT n L L in 1 L ru LO X ueiic

Vl0^2 azoethane

OUT "M/^ nitrome thane

Wu diacetyl peroxide

r* TJ peracetic acid

ethylene oxide

S"3^" propargyl bromide

C^H^Cl vxnyx cnxorxae ethylene

1-octene

S"4°2 acetic acid

^4"8°2 ethyl acetate

C^H^NO acetamide

dimethyl ether

C2H3CI ethyl chloride

^8^18 n-octane

oxygen hazard

balance rating

-16.9 high

-10.7 high

-5.5 high

3.5 high

-32.0 high

-61.5 high

-74.0 high

-241.5 low

-13.1 high

-94.9 medium

-63.1 high

-181.6 low

-94.1 medium

-128.0 medium

-342.2 low

-342.2 low

-79.9 high

-181.6 low

-149.0 medium

-208.4 low

-148.8 medium

-350.2 low

- 14 -
The hazard ratings from Table 4 shew both the explosives and detonation

receiving a rating of high. The oxygen balance criterion failed to

identify diace ty Iperoxide (medium)^ ethylene oxide (low)^ or propargyl

bromide (medium) as probably worthy of a high hazard rating. On the

other hand certain substances were suggested as being hazardous when

experience indicates otherwise. For example: acetic acid (high) and

ethyl chloride (medium) are more correctly identified as low hazard.

(4) Modified Enthalpy of Decomposition Criterion

The fourth criterion is described by the following equation:

y = (10) (Z«(decomp))^(W)/(n)

where AH(decomp) is the maximum enthalpy of decomposition in kcal g

^,

W is the formula weight of the compound undergoing decomposition^ and

n is the number of atoms which make up the latter compound. If y is

greater than 110.0, the energy hazard potential is rated as high. If

y is between 30.0 and 110.0, the energy hazard potential is rated as

medium. If y is below 30.0, the energy hazard potential is rated as low

Table 5 shows the y value and hazard rating for the twenty- two compounds

When a comparison is made between the hazard rating provided in Table 5

and the hazard rating from the enthalpy of decomposition given in

Table 2^ improvement is found for dimethyl ether, ethyl acetate, and

1-octene in going from medium to low. Similarly, mercury fulminate^

a detonator, is rated a high hazard in Table 5 by criterion (4),

however, the absolute value of y is nowhere near TNT or nitroglycerin.

Lead azide and silver azide are rated incorrectly as being only of

medium hazard. Comparison shows diace tyl peroxide, peracetic acid

and ethylene oxide as having a medium hazard rating (Table 5) from
Table 5. Modified Enthalpy of Decomposition Criterion

Formula name

HgCONO^Cc) mercury fulminate

AgN^(c) silver azide

lead azide

C3H3N3O5 nitroglycerin

e thylenedlni tramine

ethyl nitrate

trinitrotoluene

azoe thane

CH3NO2 nitromethane

diacetyl peroxide

peracetic acid

ethylene oxide

CjHjBr propargyl bromide

CjHjCl vinyl chloride

ethylene

V16 1-octene

Wi acetic acid

ethyl acetate

C^H^NO acetamide

w dimethyl ether

C^HjCl ethyl chloride

n-octane

y hazard

(y = 10 (AH ,JW/n)

d rating

125.2 high

90.7 medium

63.9 medium

291.7 high

211.1 high

171.7 high

215.0 high

42.6 medium

198.8 high

65.3 medium

61.1 medium

95.2 medium

59.1 medium

41.3 medium

54.5 high

9.9 low

2.7 low

6.0 low

3.5 low

24.4 low

3.6 low

3.2 low

- 16 -
criterion (4) whereas they were rated more correctly as high hazard

(Table 2) by criterion (1).

- 17 -
Overall^ the two ftindamental properties of importance in CHETAH

are (1) maximum enthalpy of decomposition (criterion 1 and 4) and (2)

oxygen balance (criterion 2 and 3). Validation of the program has

been provided by the ASTM Committee E-27 and shows that preliminary

correlations of the CHETAH hazard criteria with experimental shocksensitivity data on 218 organic compounds yield correct identification

of all of the shock-sensitive compounds (83), but incorrect identification of 16 (or about 12%) of the shock-sensitive compounds.

The sensitivity data were obtained from three types of experimental

test methods, namely, the impact test ( 120 kg-cm for liquids

and 500 kg-cm for solids)^ and detonation from the explosion of (#9)

blasting cap and (50 g)-pellet of tetryl.

We have provided a summary of the four hazard criteria for the

twenty-two compounds in Table 6. We note that only six (nitroglycerin,

ethy lenedinitramiue , ethyl nitrate, TNT, vinyl chloride, n-octane)

out of twenty- two compounds received the same hazard rating for

all four criteria while three compounds (azoethane, ethylene oxide,

acetic acid) received ratings of lew, medium, and high among the

four categories.

- 18 -
Table 6. Summary of CHETAH Hazard Criteria

Formula Name

Hg(0NC)2(c) mercury fulminate

AgN^(c) silver azide

Pb (N^)^(c) lead azide

C H N„0^

3 5 3 9

ni trogly cerin

C„H,N, 0,

2 6 4 4 ethylenedinitramine

C^H.ONO^

2 5 2 ethyl nitrate

7 5 3 6

2 ,4 ,6-trinitrotoluene

4 10 2 azoe thane

CH^NO_

3 2 nitromethane

2 4 3 peracetic acid

C.H.O,

4 6 4 diacetyl peroxide

C H,0

2 4 ethylene oxide

C H Br

3 3 propargyl bromide

C^H-Cl

2 3 vinyl chloride

C H,

2 4 e thylene

C-,H. , 8 16

1-octene

2 4 2 acetic acid

C, H„0_

4 8 2 ethyl acetate

ace t amide

dimethyl ether

C2H5C1 ethyl chloride

^8^18 n-octane

Hazard Rating*

(1) (2) (3) (4)

medium high high high

medium high high medium

medium high high medium

high high high high

high high high high

high high high high

high high high high

high low low medium

high high high high

high high high medium

high high medium medium

high lov; low medium

medium high medium medium

medium medium medium medium

high low low high

medium low low low

low medium high low

Ulc (i X UlU -Low J. UW X*J w low medium medium medium

medium low low low

low medium medium low

low low low low

(1) Maximum Enthalpy of Decomposition

(2) Enthalpy Difference Criterion

(3) Oxygen Balance

(4) Modified Maximum Enthalpy of Decomposition

- 19 -
The detonators, PbCN^)^, ^8^^, and HgCONC)^ are more correctly

identified by oxygen balance than by the maximum enthalpy of decomposition because their decomposition reactions do not conserve any

oxygen and with reasonably high formula weights yield values for

criteria 2 and 3 which are small enough to fall into the high hazard

range. Compounds with low formula weights and modest oxygen consumption, such as ethyl chloride, and acetic acid, will be classed

higher than they actually should be.

Strictly speaking, the maximum enthalpy of decomposition is a

measure of explosive power and need not always correspond with

explosive sensitivity. This has indeed been borne out by the

incorrect rating of criterion 1 (and for the most part with criterion

4) for the detonators. From the standpoint of overall screening

of substances, there are dangers in equating detonators with

substances such as dimethyl ether, ethyl acetate, and acetamide.

For many explosive substances, these criteria can provide an accurate

rating, however, for all other compounds large overestimates are

made to the extent that the overestimates intrude into the range of

values occupied by substances that are truly dangerous.

In an effort to improve the predictive capabilities of the CHETAH

program and better establish the separation between shock-sensitive

and shock-insensitive compounds a combination of the CHETAH hazard

criteria is recommended by ASTM Committee E-27 . Hence, an organic

compound is identified as shock sensitive 1ft (1) the heat of decomposition is calculated to be greater than -0.7 kcal g

^ or either

(2) criterion 2 or 3 (oxygen balance) classes the compound to have

- 20 -
medium or high hazard rating. According to this combination only

four compounds could be considered as shock insensitive, namely:

ethyl acetate, 1-octene, dimethyl ether, and n-octane. Included^

in the shock sensitive group, however, would be: acetic acid,

acetamide and ethyl chloride.

- 21 -
B. CRUISE Computer Program

The computational method used by D, R. Stull (Dow Chemical Co.,

Midland, Michigan) is a modification of a computer program reported by

D. R. Cruise for the calculation of chemical equilibria [13]. The data

base used by Stull consists of the JANAF Thermochemical Tables [8], which

contain mostly inorganic compounds, and similar tables compiled for the

text by Stull, Westrum, and Sinke [11] on the chemical thermodynamic

properties of over 900 organic compounds. The modified Cruise program

can accommodate up to eight chemical elements (this includes oxygen) in

any stoichiometry required by ten reactive species. Input data to the

program consist of specifying the s toichiometries of the reactants and

their enthalpies of formation at 298 K. As a result of examining the

chemical elements present in the reactant species, the program finds

a set of potential decomposition products. The program then calculates

the thermodynamically most stable products on the basis of their Gibbs

energies, balances the stoichiometry, computes the heat of decomposition

at 298 K, total number of moles of products, and the maximum temperature,

T , and the pressure. P., of the products. Both T, and P. are based on

d a d d

the assumption that 100 grams of reactant are contained in a gram:-molarvolume of 24.5 liters at 298 K and that the process takes place at

constant volume.

Dr. Stull has provided us with a copy of the back-up computer

calculations on some 80 organic compounds covered in his recent paper,

"Linking Thermodynamics and Kinetics to Predict Real Chemical Hazards"

[3]. Two computations were made through the CRUISE program for each

- 22 -
compound; one for the self-decomposition of the compound, the other for

the complete combustion of the compound in oxygen. We have presented

some of these data in Table 10 (see page 65).

Stull correlated the calculated for the 80 compounds with

literature data on activation energies, E , for these compounds. A scale

a with T, increasing upward from 0 to 3000 K was plotted on the left side of

a

a square while E was plotted on the right side with values from 0 to

100 kcal mol ^ increasing in the opposite direction (downward). The

Reaction Hazard Index Line (RHI) which connects T, = 0 with E = 0 is

d a divided into 10 units. Another line is drawn for a given compound from

its T to its corresponding E . A value for RHI is assigned at the

d a interception of the Reaction Hazard Index Line. The relationship

is shown below in figure 1.

Figure 1. Nomograph of maximum decomposition temperature vs. activation energy. Examples cited are nitroglycerin,

ethylene, and ethane.

- 23 -
For validation Stull [2] demonstrates a trend between the RHI values

and the reactivity rating values established for these compounds by the

National Fire Protection Association (NFPA)

A table of common hazard chemicals has been published by NFPA [15]

on almost a yearly basis since 1962. A detailed discussion of the

NFPA Hazard Identification System is provided in reference [15] describing

ratings for health, flammabili ty , and reactivity. Only the NFPA reactivity

ratings are pertinent to our discussion and are given below,

NFPA Reactivity Ratings

(4) Materials which in themselves are readily capable of detonation

or of explosive decomposition or explosive reaction at normal temperatures

and pressures. Includes materials which are sensitive to mechanical or

localized thermal shock. If a chemical with this hazard rating is in an

advanced or massive fire, the area should be evacuated.

(3) Materials which in themselves are capable of detonation or of

explosive decomposition or of explosive reaction but which require a

strong initiating source or which must be heated under confinement before

initiation. Includes materials which are sensitive to thermal or

mechanical shock at elevated temperatures and pressures or which react

explosively with water without requiring heat or confinement, Hre

fighting should be done from an explosion-resistant location.

- 24 -
(2) Materials which in themselves are normally unstable and readily

undergo violent chemical change but do not detonate. Includes materials

which can undergo chemical change with rapid release of energy at normal

temperatures and pressures or which can undergo violent chemical change

at elevated temperatures and pressures. Also includes those materials

which may react violently with water or which may form potentially

explosive mixtures with water. In advanced or massive fires, fire

fighting should be done from a protected location,

(1) Materials which in themselves are normally stable but which

may become unstable at elevated temperatures and pressures or which

may react with water with some release of energy but not violently.

Caution must be used in approaching the fire and applying water,

(0) Materials which are normally stable even under fire exposure

conditions and which are not reactive with water. Normal fire fighting

procedures may be used.

A reasonable trend has been shown to exist between the Reaction

Hazard Index and the ratings of these compounds by the National Fire

Protection Association (NFPA) . For illustration we have listed the 80

compounds examined by Stull [2] according to increasing RHI value in

Table 7. This arrangement gives a better idea of how the NFPA ratings

vary with Stull' s scheme. The value of T^ is, of course, calculated by

the CRUISE program while the activation energies (not shown in Table 7)

were extracted from the literature.

- 25 -
Table 7. Ranking of RHI Values

No. Formula Name

1. CH,

4

methane

2,

L D ethane

3. 4 10

n-butane

4. C _ Ht _ 5 122, 2-dime thylpropane

5.

2 40

acetic acid

6. C, H, „0

4 10 diethyl ether

7. C„H_

3 8

pro pa ne

8.

7 o toluene

9. 4 10

tert. -butyl alcohol

10. CH„C1

3

methyl chloride

11.

8 10 4-xylene

12.

6 12 cyclohexa ne

13

C „ 5 12 n-pentane

14C H ^5 12

2-tne t hy Ibu ta ne

15. propylene

16.

6 14 diisopropyl ether

17. C, H_0

4 8

2 -butanone

18. C„H,0

3 6 a ce t one

19.

7 14 me thy 1 c yc 1 ohe xa ne

20. C_ H,

8 10 ethylbenzene

21.

4- ^1 niU

2-me thylpropane

22. C H,.0

5 12

2 , 2-dimethy Ipropanol

23.

7 7

benzyl chloride

24. C, HgCl

4

n-butyl chloride

25.

3 5 propionitrile

26. C_H,C1 ethyl chloride

27. ^4»6 \

3-butadiene

28. C2H^Br ethyl bromide

29. n-propyl chloride

30. C^HgBr n-butyl bromide

- 26

(K) RHI NFPA

d rating

298 0.88 0

597 1.82 0

633 1.96 0

59 7 1.98 0

634 2.38 1 761 2.46 0

626 2.48 0

859 2.52 0

628 2.54 0

744 2.55 0

817 2.55 0

677 2 .60 0

645 2.60 0

626 2.62 0

866 2.70 1 712 2.72 1 755 2.72 0

744 2.75 0

660 2.75 0

830 2.75 0

611 2.76 0

725 2.87 0

831 2.89 1 701 9 Q 1 u 903 2.93 1 701 2.93 0

991 2.94 2 670 2.96 0

699 2.98 0

668 3.04 0
Table 7. Ranking of RHI Values (continued)

No. Formula Name T,(K) RHI

a

31. CH^NH^ methylamine 767 3.06

32. %\ cyclobutane 865 3. 16

33. '^8^12 vinyl cyclohexene 876 3. 18

34. 1-butene 825 3.18

35. eye lopropane 936 3.22

36. CHCl chloroform 683 3.26

37. ethylacetate 735 3.38

38. S«10°2 Isopropyl acetate 715 3.40

39. =6«1202 butyl acetate 715 3.41

40. 1 , 1-diehloroe thane 847 3.45

41. propiona Idehyde 819 3.52

42. propylene oxide 948 3.53

43. S"lO°3 diethyl carbonate 753 3.53

44. C^H NHj ethylamlne 740 3.62

45. S"6°2 dioxolane 911 3.64

46. S"l4°2 tert.-amyl acetate 705 3.68

47.

S"4'^^2

1^2-dichloroe tha ne 849 3.76

48. S«4° ace ta Idehyde 866 3.76

49. dime thy lamine 792 3.78

50. Wo ethylene oxide 1062 3.81

51. 1 , 1-dime thy Ihydraz ine 953 3.90

52. methylhydraz ine 1022 3.96

53. =4«8° vinylethyl ether 880 3.98

54. ^4''8° erotonyl alcohol 863 4.12

55. S»4 ethylene 1005 4.19

56. C,HjBr allyl bromide 988 4.20

57. S"7«°2 1-nitropropane 1046 4.22

58. ''2«4 hydrazine 1338 4.24

59. °8"l8°2 di-tert . -butyl peroxide 850 4.30

60. =4«6°2 acetic anhydride 793 4.34

- 27 -
Table 7. Ranking of RHI Values (continued)

No. Formula Name T^(K) RHI NFPA

d rating

61.

4 10 2 tert . -buty Ihydroperoxide 919 4 .48 4

62. Cj - ^ H. ^ 10 12

d icyc lope n tadiene -exo 990 4 .61 1

63.

2 5 2 nitr oe thane 1161 4 .62 3

64 . C H 0

4 10 2 diethyl peroxide 968 4 .64 4

65

CH 0

2 2 formic acid BOO 4 .66 0

66 ^2 4

1005 4 .71 2

u / . •^10^12 U J. L- y J- U pt. llLdU -Lt: lltr t; llvJU 990 4 9 3 1 68u o • run ^2^4"3 mC:1,CH^CL.J-V^ Cl JL Li 976 . 04 4

69

C H 0 ^5 10^ V1 nv 1 allvl pt hp r 959 5 . 11 2

70. C H 0 sppt'vl npTOxidp 983 5 . 26 4

71. C H 0

9 12 2 cume ne hydroperoxide 989 5 . 32 4

72

C H

4 6

1, 3— butad ie ne 991 5 .12 2

73. CH^NO^ nitr ome thane 2621 5 .97 4

74. ^12«16\°18

^ cellulose nitrate 2213 6 . 12 3

75. styrene" 993 6 .33 2 76. C^H^NO^ ethyl nitrate 2094 6 .36 4

77. SV3°9 nitroglycerin 2895 7 .05 4

78. S^2 acetylene 2898 7 .05 4

79. S«4 vinyl acetylene 2317 7 .33 3

(Only 79 compounds are present in this list due to a duplicate listing for

di-tert . -butyl peroxide in [2].)

* For the polymerization process.

- 28 -
In table 8 we list a series of explosives from reference [2,3] in

the order of decreasing adiabatic decomposition temperatures to see if

there is a corresponding trend with the reactivity of the compound.

Contrary to what is indicated RDX or HMX is not more sensitive than

nitroglycerin; nitromethane is not of the same sensitivity as ethylenedinitramine. For non-explosives [2,3] a sinilar listing appears in

in table 8 and covers the temperature range 850-950°K, Tert-butyl

hydroperoxide is not more stable than propylene oxide; di-tert-butyl

peroxide is not as stable as toluene. It appears that the use of a

maximum decomposition temperature is not a significant improvement over

the heat of decomposition criteria. Furthermore in the section on

Decomposition Reactions, it will be shown that for non-explosives the

products predicted by Stull do not correspond to the observations from

experiments, and the use of the Cruise program to calculate T

d

provides a parameter of correlating capacity no better than the heat

of decomposition.

The introduction by Stull of the activation energy for decomposition

is of key importance; for example, the hydroperoxides and peroxides are

unstable because of the weak 0-0 bond and thus have a low bond dissociation

energy for decomposition. In order to identify hazard with bond

dissociation energies, such values must ultimately refer to a process

that generates heat and Stull provides this linkage by correlating

the activation energy with the maximum decomposition temperature, T^.

Conflicts arise, however, with respect to the process identified with

the activation energy. To be more specific, consider the case of

- ?Q -
Table 8. Maximum Decomposition Te

CRUISE Program

Decomposition Temperature, °K

Explosives

2932

2921

2880

2865

2859

2806

2718

2698

2673

2621

256A

2542

Non-explosives

948

9 36

919

911

880

876

866

865

859

850

ratures Calculated using the

Compound

cyclonite - RDX

beta - HMX

glycol dinitrate

mannitol hexanitrate

nitroglycerine

dipentaerythritol hexanitrate

glycerol monolactate trinitrate

metriol trinitrate

tetryl

nitrome thane

polyvinyl nitrate

e thylenedini tramine

propylene oxide

cyclopropane

tert-butyl hydroperoxide

dioxalane

vinyl ethyl ether

vinyl ' cyclohexene

propylene

cyclobutane

toluene

dl-tert-butyl peroxide
tert-arnyl acetate: the reaction hazard index (RHT) according to

Stull is 3.68 which will place it in the vicinity of compounds such

as ethylene oxide (RHI = 3.81), dioxolane (RHI = 3.64), and

propylene oxide (RHI = 3.53). Comparing tert-amyl acetate to these

latter compounds is contrary to everyday experience in terms of their

expected self-reactivity. The RHI value for tert-amyl acetate was

calculated by Stull using an activation energy which corresponds with

the formation of acetic acid and the methyl butenes. This latter

reaction is endothermic and bears little resemblance to the decomposition process calculated by the CRUISE program.

- 31 -
Both the CHETAH and CRUISE programs have been examined by Davis

and Ake [14] in addition to the NASA Lewis equilibrium program and the

program TIGER developed by the Army Materiel Conmand Explosive

Research Program. In this study a group of 31 compounds was chosen

which included some common stable compounds in addition to some well

known explosive materials. Three sensitivity test methods were

applied to these compounds, namely, the standard drop-weight shock

test, the shock of a #9 blasting cap, and the shock of a 50 gram

pellet of tetryl. Each compound was classified as insensitive,

borderline, or sensitive. A ranking coefficient equation was

devised in which R = P + aT + 60, where R is the ranking coefficient,

P and T are the reaction pressure and temperature and Q is the energy

of reaction as computed by TIGER. Rankings were evaluated by

correlating the calculated ranking position of each compound with a

master ranking based on the test data.

The program TIGER provided the best ranking with the CRUISE

program next, followed by NASA-Lewis and CHETAH. No significance

should be attributed to the superior performance of the TIGER program

according to Davis and Ake [14] because of possible bias in the chosen

set of compounds. The basic powers of prediction of all the programs

studied appeared to be about the same.

- 32 -
Ill . Comparison of Certain Parameters with Sensitivity Test Results

A. Test Procedures

In this section several of the test methods which have been

used in the assessment of material sensitivity will be described. The

experimental results for a wide variety of compounds will be summarized.

We will then demonstrate the degree of correlation or non-correlation

betV7een the molecular parameters that are considered to be of importance

by the predictive schemes, namely: heat of reaction (decomposition),

oxygen balance and bond dissociation energy (or lowest bond energy

in a molecule) and the test data. It should be noted that in Stull's

scheme a key parameter is the activation energy for decomposition.

For reactions which proceed by cleavage (into two radicals) the bond

dissociation energy is an important if not the most important component

of the activation energy for decomposition. For the present we ignore

the possibility of decomposition proceeding without free radical

intermediates (purely molecular reaction). This is probably satisfactory for the compounds that will now be considered. Discussion

on systems for which such an assumption is invalid can be found in

a subsequent section.

- 33 -
Until very recently practically all work on the sensitivity of

materials with respect to self-reaction has been carried out by

investigators with interest in explosives. The importance of this

problem in such a context is obvious and has led to the development

of a wide variety of test methods and the collection of a large

quantity of data. In the absence of any other information it will be

necessary to assume that such tests and results, although limited to compounds of a specific type, have general applicability. This may not

cause serious problems for organic compounds since the only common

factor is an exothermic heat of decomposition and from a cursory

examination of the properties of explosives this heat range extends

the full gamut from a few tenths of a kcal/gram to 1.6 kcal/gram

for nitroglycerine [25]. In any case it is not unreasonable to ask

any predictive scheme to give the correct rankings with respect to

explosive sensitivity.

For the present purposes, the test methods which appear to be the

most appropriate are the following:

a) Explosion Temperature Test [25,26] . This is basically the method

developed originally by Henkin and McGill [27], It involves loosely

loading No. 8 blasting caps with a 10 to 20 mg sample of the explosive

and determining the temperature at which the sample explodes, ignites

or decomposes after a 5 second period of immersion in a Wood's metal

bath. The principal uncertainty in this test is whether temperature

equilibration is truly obtained. This will be dependent on the thermal

conductivity of the sample. Minor problems are in some cases the need

to exclude air and to avoid volatilization.

- 34 -
b. Impact Test [25,26] . This is the simplest and most widely used

method for assessing material sensitivity. The basic operation is the

dropping of a weight from a given height upon a small sample (tens of

milligrams). The impact test value is the minimum height (on a statistical

basis) which will result in explosion. The interpretation of such

data is, however, more difficult. Of particular importance is the

physical state of the substance (liquid or solid). In the case of a

solid the mesh size of the material must be considered. Also of

importance is the receptacle holding the test sample. The absolute

values of weight and height are probably less meaningful than the

relative ranking of various substances. The actual physical process

involves the delivery of a pressure pulse of several hundred to

thousands of atmospheres, the generation of small hot spots and

ultimately explosion. The overall process takes place in the order

of 100 ysec. Note that the explosion appears to be thermal in original.

The main difference between this and the explosion temperature test

could be that the energy per unit time delivered to the material and

the ignition temperature are much higher in these experiments.

Bowden and Yoffe [28] have carried out extensive and elegant

studies on initiation by impact.

c. Thermal Surge Test [29] . This test method has been developed at

the Naval Ordnance Laboratory by Wenograd [29] in 1961, It is not

widely used but due to recent work sponsored by the Department of

Transportation at the Naval Ordnance Laboratory (NOL) [30] quantitative

- 35 -
results are available on materials generally considered non-explosive

(but which may nevertheless be dangerous) using this technique. The

operation of this test involves the loading of a test sample into

hypodermic needle tubing, the discharge of a capacitor across the tubing,

the determination of the reaction temperature from measurements on

the electrical resistivities of the tubing anc^ finally, the determination

of the delay time preceding the rupturing of the tubing. For purposes

of ranking the temperature which yields a delay time of 250 ysec is

used. In many ways this test may be considered the high temperature

analog of the explosion temperature test. The temperatures and time

scales are, however, much more akin to what is found in the impact

tests. Wenograd [29] has demonstrated a very satisfactory correspondence

between the results of Impact and thermal surge tests. Note that this

test can only be carried out with liquids that do not interact with

the stainless-steel tubing. It is of course necessary to melt any solids

previous to insertion into the hypodermic tubing, since the bursting

pressure of the hypodermic tubing must be quite. It may be that

the test results are truly representative of explosive sensitivity

(as opposed to explosive power) only for strong explosives.

In making the selection of test methods we have emphasized

sensitivity in contrast to explosive power. The former is intimately

connected with the initiation process while the latter is concerned

with the initial and final states (more related to thermodynamics),

Obviously a true hazard index for self-reaction should take both factors

into account. However, in the context of fire and transportation

situations even a minor explosion may lead to catastrophic consequences,

- 36 -
One is thus erring on the side of safety when the contribution from

sensitivity is considered to be paramount. This appears to be in line

with present day regulatory practice. Earlier, it has been noted that

the heats of decomposition of high explosives (a measure of explosive

power) cover a wide range. Nevertheless, the regulations lump all

high explosives into one group and do not take the extent of this range

into consideration enough. Finally, it should be noted that although

all test methods mentioned here are supposed to measure sensitivity,

a perfect one to one correspondence of the results of the different

tests should not be expected. The basic difference is the rate at

which energy is being fed into the system. Physically this means that

the initial temperature is highest in the impact and thermal surge

tests, and lowest for the explosion temperature test. This drastic

difference in initial temperature may well have serious effects

with regard to the mechanism of decomposition and be reflected in

sensitivity determinations. From a practical point of view the

results of the explosion temperature test are probably most appropriate

under fire conditions while the impact test will be applicable in

highway and rail collision accidents.

Overall, it is clear that there is no unique test which will

permit the categorization of a material with regard to its hazard

potential from self-reaction. As suggested earlier there is a need

for exact definitions. Furthermore the tests themselves are susceptible

to variations in physical state, trace impurities, material handling

and the apparatus itself. Thus at best the results can only be

interpreted as a probability that under conditions fairly close to

those generated in the test apparatus a given substance will be more

- 37 -
or less sensitive than another substance. This will become more clear

in the subsequent discussion,

B. Test Results

The r*^s"1 ^c; of t-^Rt'? on a vn'rio variety substances are sunnarize

in table 9. Also included are values for the heats of reaction, the

oxygen balance and the dissociation energy for the weakest bond in the

compound of interest. In the subsequent discussion we will first

comment on the test data and then discuss the three molecular parameters

which are presumed by the estimation schemes to be of importance with

respect to material sensitivity.

There are two entries for the impact tests. One set is derived

from the Bureau of Mines apparatus [26] and the other from the Picatinny

Arsenal apparatus [26]. They have been included because they are <l

readily available and demonstrate very well the dependence of the ^

results on the nature of the instrument and the handling of the material.

The chief difference between the two tests are that in the latter

apparatus the sample is held in a small steel die cup and the impulse

is transmitted by a vented steel plug. In the Bureau of Mines apparatus

the sample is held between two flat steel plates. This also means

that for liquid samples the test is carried out with the material

dissolved in filter paper. This is considerably different than tests

on the pure sample. There are also two sets of results for the thermal

ii

ij surge test. One is from Wenograd's original paper and appear to yield

results considerably higher than the subsequent X'/ork. The reason for

this is unclear. With regard to the explosion temperature test, the

tabulated data are in substantial agreement with the original work
of Henkin and McGill [271. This is not really surprising, since the basic

experiment may be regarded as a primitive form of differential thermal

analysis. One cannot but suspect that in view of the remarkable

advances in instrumentation In this field in recent years, the explosion

temperature test can be upgraded considerably.

With respect to the parameters used in the estimation schemes,

the oxygen balance is a defined quantity (see above) depending only

on the elementary composition of the compound in question. The heat

of decomposition in these schemes is estimated. For known explosives

the estimates of product distribution and enthalpies of reactions

are not seriously in error. This can be seen in table 10. The situation

for non-explosives is much less favorable. Further comparisons will

be reserved for a subsequent section. For the present purposes the

experimental numbers will be used. The bond dissociation energies

are traceable for the most part from careful kinetic experiments on

related molecules and from the use of the fact that within the present

context they may be considered a local property. In other words, similar

type bonds will have the same energy regardless of the molecular

environments. Thus for the aromatic nitro compounds the bond energy

is taken to be AH,(C^H^) + AH^(NO„) - AH^(C,H^NO^) = 71 kcal/mol, t65 I Z t 0 5 Z On this basis each of the groups A, organic nitrates; B, aromatic

nitro compounds, etc. in table g have a characteristic bond energy.

This is the reason for the ordering of compounds in table 9 . It is

suspected that the present approach will bring about an uncertainty

of 3-4 kcals/mol.

- 39 -
C. Correlations

Before proceeding with quantitative comparisons some general

observations are worthwhile. First of all, the experimental test

methods show that detonators are among the most sensitive of explosives.

Furthermore the least sensitive explosives are the aromatic nitro

compounds while the nitroamines appear to be slightly less sensitive than

the organic nitrates. All of this is in accord with general experience

and is indicative of the appropriateness of the test methods.

Direct comparisons between the results of the three test methods

and the three parameters used in the predictive schemes can be seen in

figures 2 thru 10. For purposes of identification the points in

the figures are given the letters and numbers assigned to the

particular compound in table 9. It is clear that there is no

quantitative one-to-one correlation between the three molecular parameters

in question and the test data. Qualitatively there does appear to

be some correlations between bond energy and the sensitivity tests.

To a much lesser degree this may also be true for oxygen balance .

On the other hand, it is not possible to consider the heat of reaction

(decomposition) as an important sensitivity parameter. Indeed,

a closer examination of the data shows that the use of the heat of

reaction as a sensitivity criterion leads to rather striking conclusions.

For example, the heats of decomposition of detonators such as lead azide

ML, lead 2 ,4-dinitroresorcinate (LDNR) LI, lead styphnate Kl, mercuryfulminate Jl, silver azide II, tetracene HI, and diazodinitrophenol

Fl, are: .37 kcal/g, .27 kcal/g, .46 kcal/g, .43 kcal/g, .45 kcal/g, .66

kcal/g, and .82 kcal/g, respectively. An ordinary high explosive

- 40 -
such as TNT B6 has a heat of decomposition of 1.08 kcal/g. Similarly

the heat of decomposition of tetryl C5 (a nitramine) is less than that

for nitromethane Dl but the former is vastly more sensitive both from

test data and everyday experience. The lack of relationship between

sensitivity and heat of reaction is well known to those with interest

in explosives. For example, according to Price [38], "Ease of initiation

is associated with the thermodynamic functions of activation and hence

the chemical kinetics of decomposition. The kinetics are unrelated

to the energy released by the decomposition..," If one apply the

same sort of individual comparisons to the oxygen balance criteria

similar discrepancies occur, although to a somewhat lesser extent.

For example, one still has nitromethane Dl being more sensitive than

tetryl C5, tetracene HI, and diazo dinitrophenol Fl , In comparison

the bond energy criterion does not appear to violate any of the

generally held ideas about sensitivity of explosives. This may

partly be due to the fact that the inorganic detonators have been

excluded from the plots since the bond energies are not well established.

But is should be noted that the organic detonators do fall into line.

The above consideration suggests that the bond dissociation energy

is the only parameter studied which appears to have a definitive relationship

with material sensitivity. Estimation schemes \-7hich use as important

parameters heats of reaction or oxygen balance or activation energy

for decomposition in a manner which includes reactions other than

those which involve bond-cleavage may thus lead to serious errors

with regard to the identification of reaction hazard.

- 41 -
Table 9. Test Data and Possible Sensitivity Parameters for Various Materials

COMPOUNDS

IMPACT SENSITTVITT

BOM cm/kg/mg (a) PA cm/kg/mg

(b)

RO-NO, (f) (39 kcal/mol)

1) 1 ,2 ,4 ,-Butanetriol Trinitrate (BTTTO (liq) 5 8 1

1 20 (I) 2.5 |2 |liq

2) Diethylene Glycol Dinitrate (DEGN) (liq) 100+ 2 |20 (I) 23 |2

1 |liq

3) Dipentaery thritol Hexanitrate (DPEHN) 14 ! 2 |20 10 1 2 1 10

vJiyi^tiLOJ. i 11 w XcH_LclLc ILXllJ-LLdL-C \^vj]_,li>iy ^J_XU/ z.9 1 ?n

j 5) Glycol Dmitrate (GDN) (liq) 56 2 1 20 / n \ (fj

6

)

Mannitol Hexanitrate (nitromannite) 11 2 |20 10 1

|ll

7) Metriol Trinitrate (MTN) (liq) 4 2 20 / n \ (£)

8) Nitrocellulose 12.67; N 8 2 20 7.5|2 |5

9) Nitrocellulose 13.5% N 9 2 20 7.5I2 |5

1\j0I

IN 1 L ro Cc 11 UJ Ubc 14, mA is Q0 z zuoc\ ^ 7.5|2 |5

11) Nitroglycerine (liq) 15 2 20 (I) 2.5 |2 |liq

12) Nitroisobutylglycerol (NIBTN) (liq) 25 2 20 (£)

13) Pentaerythritol Tetranitrate (PETN) 17 2 20 15|2 16

14) Polyvinylnitrate (PVN) 10|2 20

15) Triethylene Glycol Dinitrate (TEGN) (liq) 100+ 2 20 (I) IO8I2 liq

16) Tripentaery thritol Octanitrate (TPEON) 23|2 24

17) 1-Mono glyce r ine

18) 2-Mono glycerine

19) 1, 3-Dinitroglycerine

- 42 -
Zxolosion Temp. Thermal Surge Test Oxygen Balance Heat of Reaction

°C °C -kcal/

g

2 30 374 -17.0 1.46

237 374^^> -41 .84

255 -26

223 -30

257

319(c)

0 1.76

175 7.1 1.34-1.52

2 35 3 / 5 -35

170 -35 .85

-29 .97

-24 1.06

222 35 1.6

185 0

430*'^' -10 1.39

265 .9

9 9 H JZ -89 .36

225 -35

541<=) -5 3

544^=' -53

370^"=' -18

- 43 -
Table 9. (continued)

COMPOUNDS

BOM cm/kg/mg

IMPACT SENSITIVITY

(a) PA in /kg/mg^^^

20) 1 ,2-Dinitroglycerine

21) Ethylnitrate

22) n-Propylnitrate

B. R(})-N02 (g) (71 kcal/mol)

1) 2 ,4-Dinitrotoluene (DNT)

2) 2,4,672' ,4' ,6'-Hexanitro-oxanilide (HNO)

3) Picric Acid

4) Tetranitrocarbazole

5) 2,4,2' ,4'-Tetranitro-oxanilide (TNO)

6) Trinitrotoluene (TNT)

7) Picramide (TNA)

8) Trinitrobenzene

9) Trinitroanisole

10) Nitrobenzene

11) 2 ,4-Dinitrophenol

12) m-Dinitrobenzene

85 |2 |20

IOO+I2 |20

95-IOO+I2 I20

- 44 -
Explosion Temp. Thermal Surge Test Oxygen Balance Heat of Reaction

°C °C -kcal/g

^rr (C) -18

, , c (c) 415 -6 2

550 -99

310 -114

384 -53

320 717^^^ -46 1.0

4 70 -85

392 -84

475 745^^\l040^'^^ -74 1.1

-56 .56

848^"\l060^^^ -32

681^^^ -60

-161

791^"^ -78

-95

- 45 -
Table 9. (continued)

COMPOUNDS

BOM cm/kg/mg

IMPACT SENSITIVITY

(a) PA cn;/kg/mg

(b)

C. R^R^N-NO^ (h) ( 45 kcal/mol)

1) Cyclonite (RDX) 82] 2 20 20 2 18

2) Ethylene Dinitramine (EDNA) 48 2 20 35

1

2 17

3) beta HMX '

' 32 2 20 23 2 23

4) Nitroguanidine 47| 2 20 66] 2 7

5) Tetryl 26 2 20 20 2 18

D. R-NO^ (i) (59 kcal/mol)

1) Nitromethane (liq) 100+1 2 20 50| 2 liq

E. RC(N02)2 (j) (45 kcal/mol)

1) 2,2, 2-Trinitroethyl-A ,4 ,4-Trinitrobutyrate

2) 2 ,2-Dinitropropyl-4 ,4 ,4-Trinitrobutyrate

F. R^R2C=N2 (k) ( 36 kcal/mol)

1) Diazodinitrophenol 25 2 20 10 I 2 I , 18| 1 lb 1 15

G. Ri^^2*^"^2 ^ kcal/mol)

1) Trinitrotriazidobenzene

H. R^R2C-N-N=N- (m) (35 kcaVmol)

1) Tetracene (liq) 712120 5 |2|liq, 20|8 oz|liq

- 46 -
Explosion Temp. Thermal Surge Test

°C

Oxygen Balance Heat of Reaction

—k ral /

p

260 -22 1.28

189 -32 1.28

327 -22 1.36

275 -31 .72

257 880^"*^ -47 1.10

430 682^^) -39 1.22^"^

225

300

500^^)

830^^^

-42

-29

195 -61 .82

150 -29

- 47 -
Table 9. (continued)

COMPOUNDS

I. 1) Silver Azide (n) (30-40 kcaymol)

J. Hg(CN0)2

1) Mercury Fulminate

K. 1) Lead Styphnate

L. 1) Lead 2 ,4-Dinitroresorcinate (LDNR)

M. 1) Lead Azide

IMPACT SENSITIVITY

BOM cm/kg/mg^^^ PA cm/kg/mg^^^

6I2I2O 7.5|2|8

5|2!20, 35|l kg|20 5 |2|?, lOjl lb | 30

17|2 I20 7.5 |2 I?, 7.5 |8oz|22

30 |l kg|20 7.5 |2 |30

IOI2I2O 45|2|l8

N. R^R2C(N02)2 (o) (49 kcal/mol)

1) Bis(2 ,2-dinitropropyl)Fumarate (DNPF) 1004-|2|20 45|2|l8

2) Bis (2 ,2-dlnitropropyl)Succinate (DNPS)

3) Bis (2, 2-dinitropropyl) Formal

4) Bis (2 , 2-dinitropropyl) Acetal

0. 1) hydrazine (p) (65 kcal/mol)

P. 1) 1,1 dimethylhydrazine (q) (-^0 kcajymol)

0. 1) Tetranitrome thane (r) (41 kcal/mol)

- 48 -
Explosion Temp. Thermal Surge Test Oxygen Balance Heat of Reaction

°C °C -kcal/g

290 -5 .45

210 -17 .43

276 -19 .46

265 -32 .27

340 -5.5 .77

250 -59 .77

-63

541*^'^'^ -52

545^^-^ -59

9^2^c) -100

832^^^ -169

709^"^

- 49 -
Bureau of Mines Test, in height (cm), wt (kg), sample size (mg)

.

Liquid samples are in filter paper. Ref. [26],

Picatinny Arsenal Test, in height (in), wt (kg), sample size (mg)

.

Liquid samples are in die cup. Ref. [26].

Ref. [30].

Ref. [29].

Ref. [24].

f) From data on ethyl nitrate decomp., Ref. [16], pg. 471.

g) From Hf(C6H5) + Hf(N02) - Hf(C5H5N02) =80 [ 31 ] + 8 [14] -

17 [32] = 71 kcal/raol.

Estimated also see Ref. [33] and Ref. [34], pg. 178.

Ref. [16], pg. 473.

j) Estimated from RiR2C(N03)2 (49 kcal/mol) and C(N02)4 (41 kcal/mol)

.

k) From data on deazomethane and considering possible resonance

effects. Ref. [16], pg. 483.

From data on ethyl az de and considering possible resonance

effects. Ref. [16], pg. 483.

m) From data on tetraethyltetrazine. Ref. [16], pg. 460.

Ref. [35].

Ref. [36],

p. Ref. [37].

q) Estimated, see Ref. [16, 35].

Ref. [16], pg. 477.

- 50 -
Data points from Table 9.

o

5

o

a

o

•H

4-1 U

td

M-lO

CD<U EE

<a

u

Io

•H

(0O

s41U

PC4

Explosion Tb^erature - 51 -
Data points from Table 9.

o

o00 o

ovO o

o

Thermal Surge Test Temp °C (250 ySEC delay before explosion)
Data points from Table 9.

ID

Impact Test

Ln (height^ cm) - 53 -
Data points from Table 9.

- 54 - Explosion Temperature °C
Data points from Table 9.

Thermal Surge Results, Temp °C (250 vsec delay before expudsion)
Data points from Tabic 9.

I—

I

<

rpq

PQ

CMm

CNl

CM

<:

u

ft,

in

1—

(

<i1

r-i <

<

on

<

oc

I

—

o

I

O

<

CO

LU

<

i_J

- 56 -

Impact Test

\ji (height, cm) -G.932
m CM

fa (O m CO

H

Bo

u

c

O

CM

COo

m

sr «

t

c

in

LU l5

g

CM

<<: <:

< <

Tt

v£) 00

<ti <d

o

ou-1 c

o

o

o

o

oCM

Explosion Temperature °C - 57 -
Data points from Table 9,

o

m 00 "-Li.*- ^ a\

PQ r-r**"rH mm m

m m

- 58 - THERf^L Surge Result Temp °C (250 delay before explosion)
Data points from Table 9,

in

CO CQ PQ p3 pq CO

O

<

o

in

>-

U2

ino

<:

<

00< 0^ O

Impact Test

Ln (height, cm) -0.932
IV. Discussion

The data presented in the earlier sections provide the raw material

for consideration of the sensitivity problem from a more generalized

point of view. Our approach will be to take each of the designated

molecular parameters, heat of reaction, activation energy for decomposition, and oxygen balance and consider how they may be related to

material sensitivity on a theoretical basis. Finally we will

consider the situation with respect to polymerization processes.

A. Heat of Reaction (Decomposition)

In the earlier discussion, we have demonstrated that for

explosives the heat of reaction (decomposition) and sensitivity are

at best only Indirectly related. However, from a general standpoint,

it is possible that the heat of decomposition can be a valuable

criterion because if self-reaction is endo thermic , then in practically

all cases, no possible danger from self-decomposition should be

expected. The questions remains: can the available estimation

schemes provide reasonable heats of decomposition, i.e., heat of

decomposition which will approach physical reality?

We have compiled a table (Table 10) of decomposition reactions of

substances for the purpose of comparison with decomposition reactions

and enthalpies derived from the estimation schemes we had mentioned

earlier. The arrangement of reactions in the table begins with the

decomposition of stable compounds and then progresses to Increasingly

more hazardous materials. The decomposition reactions and their

enthalpies at 298 K were obtained from observed experimental studies

and are numbered throughout table 10. Accompanying the decomposition

reactions and enthalpy are: the reference from which the reaction was

obtained, the name of the compound, formula weight, and enthalpy of

- 60 -
formation of the reactant at 298 K and the reference from which the

latter was taken.

The decomposition reactions and enthalpies derived from estimation

schemes are listed in table 10 according to assigned letters. We have

listed the results of the CHETAH program calculation of the reaction

and maximum enthalpy of decomposition under a). We shall briefly repeat

the basic rationale of the CHETAH program with respect to decomposition

products: the oxygen present is allowed to exhaust the hydrogens

forming water with any remaining oxygen to form CO^. Un reacted carbon

atoms and nitrogen atoms yield C (graphite) and gaseous as decomposition products. In the event of an excess of hydrogen atoms (as

with hydrocarbon molecules) CH^ or NH^ are formed. We have entered the

data obtained from Dr. Stull under b) derived from calculations of the

CRUISE program for a given substance. In b), a set of possible products

are defined from the stoichiometry and the relative concentrations of

the products are determined on the basis of equilibrium considerations.

Examination of table lo shows that both the CHETAH and CRUTRF

programs yield heats of decomposition which are exothermic while most

experimentally observed results for these processes indicate that they

are endothermic. As a general trend the CRUISE program calculates a

heat of decomposition which is always less negative than that obtained

from the CHETAH program. We do not mean to suggest that this observation

is always appropriate.

- 61 -
As would be expected, both the experimental and calculated

heats of decomposition of nitromethane and 2 ,A ,6-trinitro toluene

are exothermic (negative). A compound having such a

large predicted heat of decomposition should be suspected as

being hazardous. The fact that the observed decomposition products

and those predicted by the CRUISE and CHETAH program are basically the

same, and that although not always in close agreement, both experimental

and predicted decomposition heats are very negative, suggests that these

programs are more generally accurate when applied to explosives than

when predicting heat values for thermally stable materials. The

empirical rules have not come into play with nitromethane or TNT

because no serious projection of hydrocarbon fragments was required

to specify decomposition products.

In other words, the CRUISE and CHETAH programs grossly overestimate

the heats of reaction of "safe" compounds. It is seen that the predicted

decomposition heats for some of these compounds are well in the range

of explosives. The reader will recall that for explosives these

programs yield heats of reaction which are fairly close to the experimental numbers. The overall effect is to compress and show the range

of possible heats of reaction. There is no chance of using these

schemes as a means of ruling a substance "safe" purely on the basis

that its heat of decomposition is endothermic or sufficiently less

exothermic than explosives. This is due to that fact that neither

the maximization of the heat of decomposition (CHETAH) nor minimization

of the Gibbs energies of the products (CRUISE), although computationally

convenient, provides the appropriate basis for selecting the proper

- 62 -
decomposition products and, hence, an accurate ranking of substances

from very hazardous to very stable Is not deduced. At best, the

maximization over-emphasizes explosive power, and this we have found

does not always correspond to explosive sensitivity.

There are several approaches toward arriving at more accurate

heats of decomposition. First of all one can make use of the large

volume of data on decomposition processes. From the product analysis

it is easy to deduce whether the reaction is endothermlc or exothermic.

Furthermore in the case of molecular reactions (as opposed to chain

decompositions), the fact that a molecule with a particular grouping decomposes

in some fashion implies that analogous molecules will decompose in

a similar manner. For example, the fact that ethyl acetate decomposes

to ethylene and acetic acid suggests that alkyl esters will decompose

to the olefin and acid with similar rates. Hien, from standard heats

one can determine the enthalpy of reaction. A particularly helpful

- 63 -
compendium is the review by Benson and O'Neal [16]; an older text by

Hurd [17] is also of use. l^^len no data are available one must rely

on chemical intuition.

Alternatively, we have attempted to set up rules which for

bond-breaking reactions at least are kinetically more realistic.

Referring to Table 10 again these possibilities include:

under entry c), if the reactant contains a carbonyl group or an ether

linkage, C-O-C, we assumed carbon monoxide, CO, to be a decomposition

product. A carboxyl group, -C00-, will give CO^ for a product. If the

reactant contains the groups, -C-O-H, -NO^ , -ONO^, the H^O can be assumed

to be a decomposition product. Under entry d) we have limited the formation

of CH^ as a decomposition product to only those situations in which the

structure of the reactant contained methyl groups; otherwise the formation

of decomposition products is similar to those selected in c). The

provisions of entry e) are identical to those of entry d) except that

the presence of methyl groups in the reactant structure results in the

formation of gaseous ethane, C„H, , as a decomposition product. In entry

L b

f ), the presence of CH^ or CH fragments in the reactant structure

results in the formation of ethylene, ^2^4' °^ ^2^4 graphite as

reaction products, respectively; otherwise product formation is similar

to those identified in entry e) . The provisions of entry g) are the

same as those for entry f) except that methyl groups in the reactant

appear as CH in the products instead of C^H . The presence of a

4 2 6

halogen atom in a reactant compound yields the corresponding hydrogen

halide as a decompositon product.

- 64 -
Table 10, Comparison of Decomposition Reactions and their Enthalpies at 25°C

Table Format

(1) Name of compound; formula weight; enthalpy of formation at 25 °C

[enthalpy reference]. Observed decomposition reaction, [reaction

reference], enthalpy in kcal mol

(a) Decomposition reaction calculated by CHETAH program; enthalpy.

(b) Decomposition reaction calculated by CRUISE program; enthalpy.

(c) If reactant has a carbonyl group, or a C-O-C bond, assume

carbon monoxide, CO, as a decomposition product. If reactant

contains C-O-H bond, then H^O can be assumed as a decomposition

product; enthalpy.

(d) Formation of CH^ as a decomposition product takes place only if

CH^ groups are part of the molecular structure. The remaining

carbon and hydrogen form solid graphite and gas; enthalpy.

(e) Same as (d) except that C„H instead of CH, is formed from lb H CH^ groups; enthalpy.

(f) Same as (e) except that the remaining CH^ fragments combine to

form ^-2^1^ and the CH fragments combine to form C^H^ and graphite;

enthalpy,

(g) Same as (d) except that the remaining CH^ fragments combine to

form ^2^1^ SiXid the CH fragments combine to form C^H^ and graphite;

enthalpy,

- 65 -
butane; 58.1230; AHf° = -30.15 [11]

44%

40%

5%

4%

1) C.H, „ -> CH, + CH CH=CH^

4 10 4 2

> + 22.3

a)

4 10

2.5 CH. + 1.5 C(s)

4 ^

^ -14.6

b) ^4^10 2.3067 CH, + 0.3865 H^ + 1.6933 C(s)

4 2 -11.1

c)

d) ^4^0 2 CH^ + 2 C(s) + H^ -5.6

e) ^4^10 C2Hg + 2 C(s) + 2 H^ +9.9

f) VlO ^2^6 ^2^4 +22.4

g) *^4"l0

2 CH, + 0.5 C^H, + C(s)

4 z 4

+0.6

isobutane; 58.1230; AHf° = -32.15 [11]

2) C.H,^ .62iC,H^ + .04 CH. + .31 C„H, + .02 C_H,

4 10 48 38 36 26

+ .41 CH, [19] +28.5

a) ^4^10 2.5 CH, + 1,5 C(s)

4

-12.6

b) ^4^10 -V 2.3557 CH, + 0.2885 H^ + 1.6443 C(s)

4 Z -10.0

c)

d) ^4^10

-> 2.5 CH, + 1.5 C(s)

4

-12.6

e) ^4^10 -> 1.5 C^H. + C(s) + 0.5 H2 6 z +1.4

f) ^4^10 -> +24.4

g) ^4^10 -y 2 CH, + 0.5 C^H,

4 2 4

+2.6

- 66 -
neopentane; 72.1498; AHf° = -40.27 [12]

3) C^n^^ -V (CH^)2C=CH2 + CH^ [20] +18.3

a) S"l2 3 CH^ + 2 C(s) -13.4

b) S"l2

-> 2.8573 CH, + 2.1427 C(s) + 0.2854

4 2 -11.5

c)

d) S«12

-> 3 CH, + 2 C(s) -13.4

e) ^5^12 2 C„H, + C(s)

/ b

-0.2

f) S"l2 2 C^Hg + C(s) -0.2

g) S"l2 2 CH^ + C^H^ +17.0

acetone; 58.0798; AHf° = -51.90 [12]

4) CH^COCH -> CH2=C=0 + CH^ [17] +22.4

a) CH^COCH^ -»2'3 + CH^ + 2 C(s) -23.8

b) CH^COCH^ -> 0.9030 + 0.7149 CH, + 0.6671 H^O

+ 2.0992 C(s) + 0.0388 CO + 0.1470 CO2 -14.2

c) CH^COCH^ -> CO + 1.5 CH^ + 0.5 C(s) -1.4

d) CH^COCH^ CO + 1.5 CH^ + 0.5 C(s) -1.4

e) CH^COCH^ -> CO + S«6 +5.2

f) CH^COCH^ -y CO + +5.2

g) CH^COCH^ -y CO + CH, + 0.5 C^H,

4 2 4 + 13.8 .

- 67 -
n-butyl acetate; 116.1596; AHf° = -116.10 [12]

5) CH»COOC, H- -V CH.COOH + 1-C,H^ [16] +12.3

a) CH^COOC^Hg t 2 H^O + 2 CH^ + 4 CCs) -34.7

b) CH_COOC,H- ^ 1.4667 H^O + 1.7219 CH, + 4 C(s)

3 4 9 I 4

- + 1.0896 + 0.2552 CO^ + 0.0229 CO -23.5

c) CH„COOC,H- CO. + 3 CH, + 2 C(s/

3 4 9 2 4

-34.5

d) CH COOC H -> CO + 2 CH + 3 C(s) + 2 H -16.6

e) CH-COOC.H- -> CO^ + C_H. + 3 C(s) + 3 H^

3 4 9 / 2 6 2 -1.0

f) CH„COOC,H„ -> CO^ + C^H^ + 1.5 C^H,

3 49 Z 26 24 +20.6

g) CH^COOC,H^ -> CO^ + 2 CH, + C^H, + C(s)

3 4 9 Z 4 2 4

-1.2

35.1 [12]

+13.1

a) C4H9CI -> HCl + 2 CH, + 2 C(s)

4 -22.6

b) C^HgCl ^ HCl + 1.6065 CH, + 0.7870 H^ +

4 2 2.3935 C(s) -15.6

c)

d) C.H^Cl

4 9 ^ HCl + CH, + 3 C(s) + 2 H4 2 -4.8

e) C^HgCl HCl + 0.5 C-H. + 3 C(s) + 2.5 H^

2 6 z + 3.0

f) C4H9C1 HCl + 0.5 C^H, + 1.25 C„H, + 0.5 C(s)

2 6 2 4 +18.5

g) C4H9C1 -> HCl + CH, + 0.5 C^H, + C(s)

4 2 4

+1.4

- 68 -

n-butyl chloride; 92.5681; AHf" = -

6) C,H^C1 ^ 1-C,H„ + HCl [16]

4 9 4 8
di-tert. butyl peroxide; 146.229; AHf° = -83.4 [12]

CgH^gO^ ^ 2 CH^COCH^ + C^H^ [16] -4 3.5

a) C^H^-O^ -> 2 H-0 + 3.5 CH, + 4.5 C(s) -96.7

o io 2. L 4 b) CgH^gO^ -> 1.2127 H^O + 1.6525 CH^ + 5.8065 C(s)

+ 4.4824 + 0.2462 CO^ + 0.2948 CO -49.1

c) C^H.-O- ^ 2 CO + 4.5 CH, + 1.5 C(s) -51.4

o xo z 4

d) C_H-_0- ^ 2 CO + 4.5 CH, + 1.5 C(s) -51.4

O lo L H e) CgH^gO^ 2 CO + 3 C^H^ -31.2

f) CgH^gO^ -V 2 CO + 3 C^H^ -31.2

g) CgH^gO^ ^ 2 CO + 3 CH^ + 1.5 C^H^ -6.2

nitrome thane; 61.0402; AHf° = -17.86 [9]

CH^NO^ ^ 0.882 H^O + 0.55 CO + 0.095 C(s) + 0.394

+ 0.261 CO^ + 0.294 H^ + 0.118 NH^ + 0.083 CH, +

2 2 3 4 0.008 HCN + 0.001 C„H, [23] -74.9

a) CH^NO^ 1.5 H^O + 0.25 CO^ + 0.75 C(s) -92.4

b) CH^NO^ -> 0.8148 H^O + 0.8355 CO + 0.4994 +

0.6472 H2 + 0.1644 CO^ + 0.0584 H + 0.0005 0^ +

0.0175 OH + 0.0012 NO + 0.001 0 -63.5

c) CH^N02 1.5 H^O + 0.5 CO + 0.5 N2 -82.0

d) —

e) —

f) —

g) -

- 69 -
2,4,6-trinltrotoluene; 227.133; AHf° = 12.3 [12]

9) 25 CO^ + 1.98 CO + 3.65 C(s) + 1.32

+ 1.60 H^O + 0.46 + 0.162 NH. + 0.099 CH, + 0.02 HCN

2 3 4 + 0.004 C^H.

2 6

[23] -248.3

a) ^ 1.75 CO^ + 2.5 H^O + 1.5 N2 +

D • Zj L. ^^S )

b) ^ 0.9613 C(s) + 1.4806 + 0.0002 H^O + 0.0001 CO^ + 5.9996 CO + 2.4760 + 0.0078 H + 0.0387 HCN + 0.0002 CH,

4

-374.5

c) -> 2.5 H^O + 1.75 CO + 0.875 CO^ +

1.5 N2 + 4.375 C(s) -285.3

d)

e)

f)

g)

- 70 -

i
For the first three compounds in Table 10, butene, isobutane, and

neopentane, the experimentally observed heats of decomposition are

endothermic, however, both the CRUISE and CHETAH programs calculate

exothermic values. Accommodation for the formation of C„H, and C^H, lb 2 4 as decomposition products in empirical rules e), f), and g) allows

for reasonable prediction of the endothermicity for butane and isobutane

by rule f) and for neopentane by rule g) (between 1 and 4 kcal mol ''").

Endothermic heats of decomposition are observed for acetone,

n-butyl acetate, and n-butyl chloride. These decompositions, however,

are molecular elimination reactions, and without a knowledge of the

actual mechanism prediction of the decomposition products is nearly

impossible. Hence, the agreement between the heats of decomposition

allowed by the empirical rules and the experimental values is not as

good (between 5 and 9 kcal mol . The calculated decomposition heats

for these compounds as obtained by the CRUISE and CHETAH programs still

yield exothermic values. Thus although our empirical rules do result

in some improvement, the products of decomposition processes are

frequently so specific that we do not believe it is possible to set

up an algorithm for the computation of realistic heats of decomposition

without recourse to a chemical knowledge on the specific mechanism

of decomposition.

- 71 -
B, Activation Energy for Decompositon

Of all the molecular properties that have been considered as

a sensitivity parameter, the activation energy for decomposition (as

defined here) appears to display the most clearcut relationship with

the sensitivity test data. This is in apparent accord with what may

be derived from thermal ignition theory. The fundamental relationship

is [25, 28]:

pc(|f) = AV^T + pQ(^)

where T = temperature ( °K) ; c = specific heat (cal/g °K) ; p = density

3 (g/cm ); X = temperature independent thermal conductivity (cal/cm-

°K-sec) ; Q = heat of reaction (cal/g); and e = fractional amount of

explosive reacted. The physical picture is that of a block of matter

reacting exothermally (third term of above reaction represents heat

generation) and thus subject to self-heating (first term) while at

the same time heat is lost through conduction (second term). For

the present purposes it is of interest to consider the special case

where the rate of heat generation is much greater than that of the

heat loss or where one can assume adiabatic self-heating. Then, since

^ = a - e) Z exp(- E/RT)

at

where Z = a constant pre-exponential factor and E = activation energy

for decomposition.

- 72 -
It is possible to define an induction time:

2

t = ^^^o exp(E/RT ),

that is, starting at a temperature T^, then Is the time necessary

prior to a point where the system temperature "taken off". To

some degree it can be regarded as a sensitivity parameter. Obviously

the longer the induction time, the less sensitive a material since

there will be a longer interval for the heat to leak out of the system.

Indeed under such an eventuality the above relationship will not

be strictly applicable and the resulting induction time will be an

underestimate.

For a complete discussion of these relations the reader is

referred to standard texts [25, 28].

- 72a -

In the case of bond-breaking reactions, the activation energy E

has been identified as equivalent to the bond dissociation energy.

This means that the bond dissociation process is the rate determining

step and the exothermicity is generated by subsequent fast reactions.

Although this involves some approximation, nevertheless the observed

correlation suggest that this picture retains some connection with

reality. Note that in the formulation given above the key quantity

is really the rate constant. The fact that the activation energy is

highlighted means that the pre-exponential factor Z does not fluctuate

widely for the compounds that have been considered. This is in accord

with modem day kinetic results which suggests that these numbers are

in the range of 10^^ — "^'^ sec ^ [16]. In the temperature range of

interest this is equivalent to an uncertainty in the activation energy

by 2 to 3 kcal mol ^ and is insignificant within the present context.

The exponential dependence on the activation energy compared with the

linear dependence on heat generation provides a satisfactory explanation for the absence of a clear-cut correlation with the heat of

reaction. Nevertheless it must be emphasized that the heat of decomposition is a necessary parameter. In the case where it is endothermic

obviously there is no possibility of explosion. This is the reason for

the prolonged earlier discussion on methods of estimating decomposition

heats. In the cases where it is small the heat conduction effects

cannot be neglected.

- 73 -
C, Oxygen Balance

The above discussion suggests that the observed correlation

between sensitivity and oxygen balance may be accidental, since in

the original paper on the oxygen balance concept Lothrop and

Handrick [39] demonstrate a correlation between the heat of

reaction and oxygen balance for nitrates, nitramines, aliphatic

nitro, aromatic nitro compounds, and their hybrids. Alternatively

this suggests that the present comparison between oxygen balance

and heat of reaction should be made in the absence of the inorganic

detonators. When one does this for the heats of reaction it is

possible to discuss the same sort of vague correlation as has been

observed for the oxygen balance. This indicates that the data may

have to be treated with more respect. The following represents a

possible explanation. For the CHNO compounds considered by Lothrop

and Handrick [39] the oxygen balance can be considered to be a

measure of the excess hydrocarbons present. It is well known that

the thermally stable products of hydrocarbon decomposition at the

temperature range of interest are the unsaturated compounds. These

are generally quite effective as inhibitors in chain decomposition.

Obviously as the quantity increases decomposition rates will be slowed

leading to a decrease in sensitivity. This is of course superimposed

upon the main parameter which is the bond dissociation energy.

- 74 -
D. Polymerization Reaction

The above Hlscnsslon has to r.r-\rh Hftcomposit-f on reactions. An

alternative source of self-reaction hazard comes from polymerization.

Unf orttmately both of the schemes that have been considered here

ignore this possibility. Furthermore unlike the situation with

disintegration where the existing data on explosives furnish a firm

tie point, there does not appear any quantitative data on monomer

sensitivity. In any case the lack of a general theory of thermal

polymerization leaves one without any framework for extrapolation.

Note that unlike the sitixation with explosives, very few polymer

chemists are interested in thermal polymerization since catalytic

processes are generally more efficient and in any case the products

from an uncontrolled polymerization are not usable. At the present

time the only method of deriving a hazard rating will be to use the

semi-quantitative ideas of polymer chemists as to what special molecular

groupings are conductive to polymerization. Work and progress [40,41]

along this line due to its obvious importance has been impressive

and extensive. The main problem is that of quantitation, that is,

while it may be possible to say that one monomer is more polymerizable

than another it may be considerably more difficult to assign a numerical

value to such conclusions.

It may soon be possible to make ratings on the basis of

thermodynamic considerations. The specific variable of interest is

the ceiling temperature T, or the enthalpy of polymerization divided

by the entropy of pol3mierization. Above this temperature

- 75 -
polymerization will not occur. Obviously, a stibstance that is shipped

above its ceiling temperature represents no hazard at all. Alternatively

if a substance is shipped as a liquid and the ceiling temperature is

below the boiling point, then It should be a lesser hazard than if

the converse is true. All of this presupposes a considerable degree

of knowledge of the polymers in question, and this is currently

unavailable. Benson's group additivity scheme [16] as embodied in the

work of Treweek and coworkers [1] can calculate the required numbers.

It is not expected to be accurate since it neglects 1-3, 1-4, etc.

interactions, i.e., interactions beyond nearest next-neighbor interactions,

and these are precisely the interactions which permit the differentiation

of polymerizab ility among ironomers. The scheme of Zwolinski and

Somayajula [A2] is more promising and has been applied with success to

the polymerization of alkanes. If the data g-^e sufficient to permit

them to be extended to CHONS systems, this will be of great importance

on the present context.

Overall, the need remains for test results. Some thermal surge

experiments have been carried out at the Naval Ordnance Laboratory [30]

on various monomers, however, this test may not be suitable for

polymerization reactions. Explosion temperature as well as DSC and

DTA results may be more meaningful. Note that in order to place all

materials on the same hazard scale, they must obviously be subject

to the same test procedure.

- 76 -
The above comments should not lead one to the conclusion that

the predicative schemes are neutral with regard to polymerization.

Actually, due to the particular manner of selecting products, the

rank ordering that is calculated on the basis of maximum heat of

decomposition measures the relative degree of strain in a molecule.

Since one way such strain is relieved is by polymerization, monomers

may score relatively high as potential hazard. However, many strained

molecules do not polymerize and as for disintegration

the schemes maximizes hazard to such an extent that all distinctions

are lost.

- 77 -
V. Conclusions and Recommendations

Our general conclusions are as follows:

1. CHETAH , Hazard prediction is based on the heat of decomposition

and oxygen balance. Both parameters overemphasize explosive

power as opposed to explosive sensitivity and, in general,

the hazard criteria label many compounds as hazardous when in

reality they are not.

2. CHETAH . Maximization of the heat of decomposition is primarily

a computational convenience. Although this feature appears in tune

with non-explosive materials, significant differences arise

between calculation and reality when decomposition products

are selected.

3. CRUISE ; The activation energy for decomposition, when properly

used, is an important parameter for material sensitivity. The

maximum decomposition temperature is at best a measure of explosive

power and has very little to do with sensitivity. It is a

parameter very similar to the maximum heat of decomposition.

4. CRUISE . Decomposition products (as specified by Stull) and

the product distributions as calculated by the program are

significantly different from those determined experimentally

from pyrolysis or thermal decomposition studies for nonexplosive compounds. Here also, minimization of the Gibbs

energies of the products ignores the mechanism of decomposition

(bond scission, molecular elimination, polymerization, etc.).

- 78 -
5. CHETAH and CRUISE . Neither scheme is applicable to selfreaction hazards arising from polymerization.

6. Test Methods . Explosive sensitivity correlates poorly with

the heat of decomposition. There may be some correlations with

oxygen balance and a somewhat closer relationship to the

bond dissociation energy . In the case of bond-breaking processes

the bond dissociation energy appears to have a definitive

relationship to material sensitivity, and in this context the

bond dissociation energy and activation energy are equivalent.

7. Test Methods . Explosion temperature test data are more applicable

to fire hazard situations while impact test data relate to

hazards in handling and transport.

We recommend that:

1. There is a paramount need for sensitivity test data, particularly

on monomers, borderline hazardous compounds, and new substances

considered hazardous. Success for future correlations with

thermochemical and kinetic parameters will depend on these data.

2. At present, regulations specifying the handling and transport

of commodities should follow the concept of self-reactivity based

on functional group (nitro, peroxide, azide, nitramine, etc.) [A3].

This makes use of the fact that bond dissociation energies

are to some degree a localized property. We do not feel the

predictive schemes as they now exist justify any high degree of

confidence. Certainly experimental test data should be preferred

to predictive schemes to evaluate reaction hazard.

- 79 -
Accurate predictive schemes must be based on a detailed unde

standing of the mechanism of self-reaction. Although more

complex and more difficult to work with, separate schemes

for polymerization, bond cleavage, and molecular elimination

reaction could result in a better identification of hazard

potential. This area should be explored.

i

- 80 -
VI. References

[I] Treweek, D. N. , Claydon, C. R. , and Seaton, W. H. , Chem. Eng.

Prog., Loss Prevention, 21-27 (1973).

[2] Stull, D. R. , Chem. Eng. Prog., Loss Prevention^, 16-24 (1970).

[3] Stull, D. R. , Chem. Eng. Prog., Loss Prevention bl-ll (1973);

J. Chem. Ed. 51^, A21 - A25 (1974).

[4] Eigenmann, H. K. , Golden, D. M. , and Benson, S, W. , J. Phys.

Chem. 77, 1687-1691 (1973).

[5] Benson, S. W. , Cruickshank , F. R. , Golden, D. M. , Haugen, G. R.

,

O'Neal, H. E., Rodgers, A. S. , Shaw, R. , and Walsh, R. , Chem.

Rev. 69, 179-324 (1969).

[6] Janz, G. J,, "Estimation of Thermodynamic Properties of Organic

Compounds", Revised Edition, Academic Press, Inc., New York, NY, 1967.

[7] Commission on Atomic Weights, lUPAC, Pure and Applied Chem. 30 ,

637-649 (1972); "Atomic Weights of the Elements 1971".

[8] Stull, D. R. and Prophet, H. , JANAF Thermo chemical Tables Second

Edition, NSRDS-NBS-37 , June 1971 (U.S. Government Printing

Office, Washington, DC 20402).

[9] Wagman, D. D. , Evans, W. H. , Parker, V. B. , Halow, I., Bailey, S. M.

,

and Schumm, R. H. , NBS Technical Note 270-3, January 1968.

[10] Estimated using group-contribution values in references [4] and

[5] when possible. Take N - (H)(C)(N02) = +9.0 kcal mol""^.

[II] Stull, D. R. , Westrum, E. F. , Jr., and Sinke, G. , "Thermodynamics

of Organic Compounds" (J. Wiley and Sons, Inc., New York, 1969).

[12] Cox, J. D. and Pilcher, G. , "Thermochemistry of Organic and

Organometallic CompoTjnds", (Academic Press, Inc., Publishers,

New York and London, 1970).

[13] Cruise, D. R. , J. Phys. Chem. 68, 3797-3802 (1964).
[14] Davis, E. J, and Ake, J, A., Chpm. '^ng. Progess Loss Prevention

7_, 28-34 (1973).

[15] "Hazardous Chemicals Data" 1973, NFPA No. 49, (National Fire

Protection Association, 470 Atlantic Avenue, Boston, MA 02210).

[16] Benson, S. W. and O'Neal, H. E. , "Kinetic Data on Gas Phase

Unimolecular Reactions", NSRDS-NBS-21 , U.S. Government Printing

Office, 1970.

[17] Hurd, C. D. , The Pyrolysis of Carbon Compounds ACS Monograph

Series #50, (1929).

[18] Crynes, B. L. and Albright, L. F. , Ind. and Eng. Chem. Process

Design and Development 8^, 25-31 (1969).

[19] Buehens, A, G. and Froment, G. F. , Ind. Eng. Chem. Process

and Design Dev. 10, 309-315 (1971).

[20] Baronnet, F. , Dzierzynski, M. , and Come, G. M. , Martin, R.

,

and Niclause, M. , Int. J. Chem. Kinetics 2> 197-213 (1971).

[21] Joshi, R. M. and Zwolinski, B. , in Vinyl Polymerization, G. Ham,

editor, (Marcel .Dekker , New York, 1967, pg, 445).

[22] Benson, S. W. , "Foundations of Chemical Kinetics" (McGraw

Hill, New York, 1960, pg. 379).

[23] Ornellas, D. L., J. Phys. Chem. 72., 2390-2394 (1968).

[24] Ornellas, D. L. , Carpenter, J. H. , and Gunn, S. R. , Rev.

Sci. Instruments 37, 907-912 (1966).

- 82 -
[25] Headquarters, U.S. Army Materiel Command, Engineering Design

Handbook, Principles of Explosive Behavior AMCP 706-180, April 1972.

[26] Headquarters, U.S. Army Materiel Command, Engineering Design

Handbook, Explosives Series Properties of Explosives of Military

Interest AMCP 706-171, January 1971.

[27] Henkin, H. and McGill, R. , Ind. Eng. Chem. 44, 1391-1395 (1952).

[28] Bowden, P. H. and Yoffe, A., Fast Reactions in Solids (Buttersworth Publishers London, 1958).

[29] Wenograd, J., Trans. Faraday Soc, 5_7, 1612-1620 (1961).

[30] Kayser, E. , Final Report to Dept. of Transportation TES-20-74-1

(NOLTR 74-44) February 1974.

[31] Golden, D. and Benson, S. W. , Chem. Rev. 69^, 125-134 (1969).

[32] Shaw, R. , J. Phys. Chem. 75, 4047-4049 (1971).

[33] Voskoboynikov, I. M. , Bogomolov, V. M. , and Apin, A. Ya.

,

Fiz. Goreniya Vzryva, 5_> -^71 (1969); Technical Translations

FSTC-HT-2 3-9 75-71,

[34] Cook, M. A., The Science of High Explosives (Reinhold Publishing

Corp. , New York, 1958)

.

[35] Bartlett, B. E. , Tompkins, F. C. , and Young, D. A., Proc.

Royal Soc, 246, 206-216 (1958).

[36] Shaw, R. , Int'l. J. Chem. Kinetics, 5_, 261-269 (1973).

[37] Tsang, W. , Interim Report on the Thermodynamics of Chemical

Species Important in Aerospace Technology, National Bureau of

Standards Report 10904.

[38] Price, D. , Chem. Rev., 52, 801-825 (1959).

[39] Lothrop, W. C. , and Handrick, C. R., Chem. Rev. 44_, 419-445 (1949).

[40] Dainton, F. S. and Ivin. K. J., Quarterly Rev. 12, 61-92 (1958).
[41] Ivin, K. J., Angew. Chem. Int'l. Edition 12, 487-49A (1973).

[42] Joshi, R. M. , Zwolinski, B, J., and Hayes, C. W. , Macromolecules

,

1, 30-36 (1968).

[43] Pletz, v., J. Gen. Chem. (USSR) 5_, 173 (1935); quoted in [39].

[44] Egger, K. W. and Cocks, A. T. , Helv. Chim. Acta 56^, 1516-1536

(1973).

- 84 -
VIII. Appendix - Bond Dissociation Energies

In a recent paper, Egger and Cocks [14] have critically evaluated

the literature data on heteropolar and homopolar two-center bond

dissociation energies in organic compounds in the gas phase and the

corresponding heats of formation of radicals and ions. We have

extracted the tabular data on homopolar two-center bond dissociation

energies and provide these data in Table 11. This information is useful

in estimating the weakest bond in a molecule and thus gives some

insight toward the mechanism of decomposition and, at times, product

formation. The vertical axis (extreme left) provides the formula and/or

name of the radical, R, along with its heat of formation at 25 °C,

while the horizontal axis (top) gives similar data for the other

reactant, X, Bond dissociation energies are tabulated for the general

dissociation reaction in the gas phase:

RX ^ R + X

Generally speaking, the lower the value shown in the table, the lower

the bond dissociation energy and the greater the tendency toward

decomposition.

For details as to the source or magnitude of the values tabulated,

the reference by Egger and Cocks [44] should be consulted.

- 85 -
Table 11. Bond Dissociation Energies

un. TM3 P H

S"5

n —P H -f — P H t-— P H r

-JS9^ . X1 9 S 7 90z u ft . 0 17 8 xoIRQ. 7

r 9 1 1 OA 9 1 OA Q ft Qft 7O Q '^ Q 9 7 Z Xjj • 0

hydrogen

JHtA 1 n/. XUH Pft 00 9 . Z

ftA OH ft . 0

ftt; 9 oD . Z

9.1, oH 9 . Zftl Ox ft

. 0 1XUOnfl R. 0

methyl

r H — 9 S 7 !7 0 ftA ft ftl OX ft . 0 ftl ox ft . 0 ftn OU . AH 77 Q XU107 1 / . X

2 5 eChyl

^ nVi—P\j^n.j~ V _ 9n ft Qft 7 0

fti^ 0 9 J . Z

ft! ox . A0 ftl '^ 0 X , Dftn OU A. H 77 ^ 1 n7 '\ XU / • J n-propyl

1 7 ft "J ftA OH 9 • <! ftO OU . AH ftO OU . AH 7ft / 0 9 , Z 7A 9 XUO 1 nft 1

. X i-propyl

Q9 ft! (J X . 80 711,1 7 7 7 7 S 7A/ H . Z9 68 8 X108W 0 . 4H t-butyl

L3H5- 0 X . J xuu 1 nn 7 • / ftQ A ftA 00 9 • Z 00 • J

8"^ OJ . AH 89OZ 7 . / xxu 110 . Q7 cyclopropyl

51.2 96.5 85.8 82.5 82.5 81.6 79 107.2

cyclobutyl

C^H — cyclopentyl

9 A QA ft ft'^ 0 J. ft0 OU • Jftfi OU s . D 7Q ft 77 xu^ 1 OS . z9

^6^11 X J . y y J . J

ftA OH « Q7ftn OU . AD OU • 7 RnOU • AH 77/ / . 80 XUO 1 Oft cyclohexyl

C7H13- Q 0 1^ yz . J

Q 1 ^ ox , J7 Q 1

/ 0 . Z

7 Q 0 /o. Z 77 0

/ / . 3

7 /. 7 /4 . / luZ .y cycloheptyl

p— p_ DO . H XUo 1 nft Q 7 0/. yn . J QAyM- . 3

0"^ y ft ^ . 0 on7U . AH xxo 118 . 7/ vinyl

PC5H5- , u_ 77 7 11,1 xxu QQ 7 y D . JOft ft yo . 0Q/. y't . J on ft xz1 9 Q J . y phenyl

C=C-C- 41.4 88.6 75.6 72.4 72.2 71.5 68.3 97.7 1 allyl

cc-c- 30.4 82.5 71.0 67.9 67.2 65.8 64.4 9 3.5 1 butenyl

C5H7- 38.4 82.3 71.6 67.8 67.2 65.6 61.6 93.5 i cyclopentenyl

86 -
Li Ti Url OCH3

3 2 29.0 26.7 25.5 9.0 3.4 47.2 45.2 38.2 21.6 7.9

103.1 87.4 71.3 119 105 110 103 95 49 79

83.6 69.8 56.1 91.1 81.4 86.7 83.6 77.9 40 60

80.8 67.6 53.2 90.9 80.8 84.3 82.3 76.3 38 58

80.1 68.0 53.4 91.0 81.0 84.8 82. 3 76.4 38 59

80.4 68 53.1 91.9 81.4 85 83 77.1 37 59

80.2 66.1 50.4 91.2 80.6 83.6 80.8 74.9 36 58

85.4 73.7 58.6 97.5 87.8 91.2 88.7 82.8 42.7 67.3

81.7 69.9 54.9 93.7 84 87.4 84.9 79 38.9 63.6

79.7 67.9 52.9 91.3 82 85.4 82.9 77 36.2 61.5

82 68.7 51.6 91.3 82.8 86.2 83.7 77.8 37 62.4

77.4 65.6 50.6 89.4 79.7 83.1 80.6 74.7 37 59.2

88.8 76.4 63 100.4 88.2

94.5 79.2 64.4 109.7 98.4 104.1

71.2 57.2 44.1 80 70.3 75.2 72.7 66.8 28 49.4

67,8 55.4 40.5 79.3 68.8 72.4 70.4 64.5 24 46

67.8 55.4 40.5 79.3 68.8 72.4 70.4 64.5 23.6 48.9

- 87 -
AH°(X) H ^2^5 n-C^H^ ^ S^7

4- n u T-1 r

AH°(R) 52.1 34 25.7 20.8 17.8 7.5 18.9

C=C-Cpropargyl

86.2 93.9 81.1 77.5 77.4 76.3 73.4 103.2

c=c

pentadienyl

48.3 75.2 64.2 60.4 60.4 58.2 54.2 86.1

trans

pentadienyl

48,3 82.3 69.5 65.9 65.8 64.7 61.8 91.6

C5H5-

cyclopentadlenyl

55 75.2 64.2 60.4 60.4 58.2 54.2 86.1

C6«7-

2 ,5-cyclohexadienyl

44 69.8 59 55.2 55.2 53 49 80.9

C6H7-

2 , A-cyclohexadienyl

44 70.1 59.3 55.5 55.5 53.3 49.3 81.2

C7H7-

cycloheptatrienyl

65 73.2 61.2 57.9 57.9 57 54.4 81.9

C6H5CH2-

benzyl

44.9 85 71.8 68.7 69 67.8 65 96.3

CH3C6H4CH2-

4-me thylbenzyl

37 84.8 71.8 68.4 68.4 67.6 65 95.1

CH^C^H^ CH2~

3-methylbenzyl

37 85 71.4 68.5 68.4 67.6 65 95.1

i

- 88 -
CI Br I OH OCH^ NHCH^ N(CH3)2 NO

29 26.7 25.5 9.0 3.4 47.2 45.2 38.2 21.6 7.9

* 76.7 63.9 49.3 86.9 76.9 80.7 78.2 72.3 33.9 54.9

, 60.4 48 33.1 71.9 61.4 65 63 57.1 17 39

65.1 52.3 37.7 75.3 65.3 69.1 66.6 60. 7

60.4 48.0 33.1 71.9 61.4 65 63 57.1

55.2 42.8 27.9 66.7 56.2 59.8 57.8 51.9 12.4 37.8

55.5 43.1 28.2 67 56.5 60.1 58.1 . 52.2

56.4 44.6 29.6 68.4 58.7 62.1 59.6 53.7 16 38.2

69.4 54.7 40 77.9 66.9 71.9 25 45.9

69 56.5 40 76.3 66.6 71.9 25 45.9

- 69 56.5 40 76.3 66.6 71.9 25 45.9

- 89 -
AH?(X)

r H CH„J 2 5 n-C-H_

3 7 3 7 t-C,H4 9

AH°(R) 52.1 34 25.7 20.8 17.8 7.5

0=C1 H9.5 87.5 83.2 80.7 79.2 79.6 75.2

0=C- -5.8 86 80.1 76.9 76.9 74.8 71

1c ,

benzoyl

26 1 86 9 an fi 77 a 77 S 77 '\ 7"^ 6

o=c-ct -5.5 98.5 85.5 82.1 82.2 80.9 78.3

1 C

HO-C- -4.6 95.6 85.6 82.3 82 81 76.3

c -2 7.1 90.1 81.6 77.7

1 HO-C1 c

o=c- -52.7 90 84.6 81.4 80.5 80.8 77.3

OH

0=C- -40.4 95.3 91.5 88.2 88.2 89.6 89.9

icH3

o=c-o1 -45 110.4 86.9 87 87 87.9 87.1

c

C.H^Ophenoxy

9.9 85 61.2 61.9 62.1 62.8 62.1

CH 0-

methoxy

3.4 103.6 81.4 80.8 81 81.4 80.6

C-O-C- -2.8 93. 3 82.9 79.7 80. 3 79. 3 76.7 ,

- 90 -

1

J
F CI Br I OH OCH^

3

NH

2 NHCH^ NO N0„

2 18.9 29 26.7 25.5 9.0 3.4 47.2 45.2 21.6 7.9

122 84 69 52 109.1 96.1 101.2 98.8

• 119.5 81.6 66.5 49.8 106.5 95.5 99.2 96.8

115 80.5 64.4 49.1 105.2 95.1 94.8 92.4

102 77 64.2 50.2 89.9 80.2

101 82.2 69.7 55.1 97.9 88.2

ou 0 / J J

Q c; OJ

42.8 38.5

25 17.7 38.5 39.1 23.7 21.2

44 36.9 56.8 57.4 42 .9 40.4

106 79.9 67.4 52 95.6 83.9

- 91 -
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- 92 -
U.S. DEPT. OF COMM.

RIRI 1 nn R A PM 1 f DATA

SHEET

1. iniHI.K A I'lON OK Kl I'OKT NO. NBSIR 74-551

2. ( Kiv 't Ac ces.s ion MNo.

3. Kei ipiont's At ccs.sion No.

4. n i AND .sDin i ri.i';

An Appraisal of Methods for Estimating

Self-Reaction Hazards

5. Puhl ii al ion Date June 1974

6. I\ rforniing ( )r);aii i /at ion ( ode

7. AO THOKfS)

W. Tsang and E. S. Domalskl

8. 1 r for iTi 1 [1 Or^a 11 . cpor t No

9. FI-:KI-0KMINC, OIU.ANIZA I KIN NAM1-: AND AOIIRI-.SS NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Froic-it /Task/Work Unit No. 3160415

1 1 . ( .oniraei / drant No.

12. Sponsoring Organ i>;at ion Name and < omphr.- .Address (Street, City, Stale, ZIP)

Office of Hazardous Materials

Department of Transportation

2100 Second Street, S.W.

Washington, DC 20024

13. 1 ype of Report Period

( overed ^ Final

1-1-74 thru 6-30-74

14. Sponsoring Agency (.ode

15. SUPPLKMENTARY NOThS

16. ABSTRACT (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

The ability to identify and specify the thermal Instability of chemical

substances has been appraised as a result of examining certain test

methods used to measure explosive sensitivity, and certain computer programs

designed to estimate reaction hazards from a t he rmo chemical approach.

The bond dissociation energy emerges as the parameter giving the best

correlation with material sensitivity. The computer programs overemphasize explosive power as opposed to explosive sensitivity and label

many compounds hazardous when they are not. At present, regulations

specifying the handling and transport of commodities should follow

the concept of self-reactivity based upon functional groups.

17. KhY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

Activation energy; bond dissociation energy; computer programs; explosive

sensitivity tests; heat of decomposition; oxygen balance.

18. AVAILAHILITY |X ' Unlimited

For Official Distribution. Do Not Rel'-asc to NTIS

[ ] Order From Sup. of Doc, U.S. Government Printing Office Washington, D.C:. 20 102, SD Cat. No. CM

Order from National Technical Information Service (N TIS)

Sprin^',1 leld, Virginia 22 I'll

19. SECURITY CLASS

(THIS REPORT)

unc:l assified

20. SEC URI I Y CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

99

22. Price

USCOMM-DC 29042-P7-

I *4