8. Thermochemistry of amines, nitroso, nitro compounds and related species 377
79.Strictly speaking, the reaction should read R C NO C M RNO C M, but the third body M does not affect our analysis. We note R/NO reactions in either direction are not expected to have an enthalpy of activation save that of the reaction enthalpy. This situation is thus unlike the reaction (RNO)2 2RNO whether or not the third body M is present.
80.A. A. Boyd, B. Noziere` and R. Desclaux, J. Phys. Chem., 99, 10815 (1995).
81.We are surprised that there are no enthalpies of formation available for either allylamine or 3- nitropropene. As such, we ignore the datum for 3-nitrosopropene. We also ignore the datum for nitrosoethane because we prefer the more recent one for ˛-nitrosotoluene as the archetype of an NO affixed to a primary carbon.
82.‘Thermochemically’ is the operative word here. After all, NO can formally delocalize and thus
stabilize both negative and positive charges as illustrated by the acidity of oximes; cf. the wellestablished existence of (R2CNO) and the Nef reaction, cf. the putative existence of (R2CNO)C .
83.Recall the following ‘thermochemical mimicry’ analysis from S. W. Slayden, J. F. Liebman and W. G. Mallard, in Supplement D2, The Chemistry of Organic Halides, Pseudohalides and Azides
(Eds. S. Patai and Z. Rappoport), Wiley, Chichester, 1995. The difference of the enthalpies of formation of RBr and RNH2 is largely independent of the alkyl group R but the difference for
bromobenzene and aniline shows the latter species enjoys ca 30 kJ mol 1 of stabilization relative to the former. By contrast, the difference of the enthalpies of formation of RCl and RNO2 is largely independent of the alkyl group R and the difference for chlorobenzene and nitrobenzene shows no particular stabilization or destabilization of the latter species relative to the former. Accordingly, aniline is more stabilized than nitrobenzene by ca 30 kJ mol 1.
84.The data for some of the more unusual isomers are from W. E. Garner and C. L. Abernethy, Proc. Royal Soc. London, 99A, 213 (1921). While these numbers have less reliability than those determined later, nonetheless these values are useful for comparison with each other and within sets of isomers.
85.We avoid here the comparison of the electronegativities of nitrogens as found in nitrobenzene and aniline. Questions of group electronegativities, hybridization and partial charges are usually interesting, but they are usually subtle and seemingly largely unresolved.
86.A. Greenberg and T. A. Stevenson, Molecular Structure and Energetics: Studies of Organic Molecules (Eds. J. F. Liebman and A. Greenberg), VCH, Deerfield Beach, 1986. See also the discussion in J. F. Liebman and R. M. Pollack, in The Chemistry of Enones, Part 1 (Eds. S. Patai and Z. Rappoport), Wiley, New York, 1989 wherein the resonance energy of crotonaldehyde was shown to be less than that of piperylene while the rotational barriers are in the reverse order.
87.From Stull, Westrum and Sinke we find the barrier to rotation of the nitro group in nitrobenzene
is 25.1 kJ mol 1, to be compared with the rotational barrier of the amino group in aniline of
14.2 kJ mol 1.
88.The ordering of the two values is hard to rationalize because there are two opposing influences. Because of its shape, p-dinitrobenzene may be expected to ‘pack’ better than the m-isomer, thereby increasing its relative enthalpy of fusion. However, the latter has a nonzero dipole moment while the former does not. Intermolecular, electrostatic attraction is expected to be stronger for the crystalline meta compound.
89.Z. A. Akopyan, Yu. T. Struchkov and V. G. Dashevskii, Zh. Strukt. Khim., 7, 408 (1966).
90. Two enthalpy-of-formation |
values were found for HNB |
(55) |
[C. L. Coon |
(Lawrence |
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Livermore National Laboratory), personal communication to M. S. C. (1985); Y. N. Matiushin, |
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V. V. Odintsov and V. I. Pepekin, High Explosive Database |
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Part C, Semenov Institute of |
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Chemical Physics, Moscow |
(1994)] but neither reference is |
readily |
useful for |
learning the |
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details on procedures used to keep the compound from decomposing during analysis. The kinetic instability of HNB has prevented its use as a production explosive although it is very powerful. The synthesis of HNB was challenging, and had the stability properties been calculated before it was made, the resources could have been used to make a more useful compound. The results from the study of HNB did help improve understanding of stability calculations. These methods include deriving densities96 and enthalpies of formation, two properties of explosives that determine their performance, and hence are useful as guides to the synthesis of new compounds.
91.This observation was made by Coon, in Reference 90. To the best of our knowledge, there are no experimental data for the enthalpy-of-formation difference of simple nitroarenes and aryl nitrites
such as PhNO2 and PhONO. Given earlier enunciated complications regarding measurements of alkyl nitrites, we are not surprised by this gap in our knowledge.
378Joel F. Liebman, Mary Stinecipher Campbell and Suzanne W. Slayden
92.J. F. Liebman, in Molecular Structure and Energetics: Studies of Organic Molecules (Eds.
J. F. Liebman and A. Greenberg), VCH, Deerfield Beach, 1986.
93.Picric acid was one of the first explosives to have been prepared (in 1758, by nitrating wool). It was also used as a dye because of its bright yellow color.
94.Encyclopedia of Explosives and Related Items, PATR 2700 [Picatinny Arsenal, Dover, NJ (1960 1978)].
95.D. Ornellas, J. Phys. Chem., 72, 2390 (1968). Strictly speaking, the code used in this paper was the RUBY code, H. B. Levine and R. E. Sharples, Report UCRL-6185, Lawrence Radiation Laboratory, Livermore, CA, 1962 using the BKW equation of state from C. L. Mader, Report LA-2900, Los Alamos Scientific Laboratory (1963). (See also C. L. Mader, Numerical Modeling of Detonation, University of California Press, 1979)
96.Tiger code reference: M. Cowperthwaite and W. H. Zwisler, TIGER Computer Documentation, SRI Publication No. Z106 (January 1973).
97.The enthalpies of formation of CO and CO2 are 110.53 and 393.51 kJ mol 1, respectively,
corresponding to an endothermicity of ca 85 kJ (mol CO) 1 produced in the formal reaction CO2(g) C C(s) ! 2CO.
98.A. Finch, P. J. Gardner, A. J. Head and H. S. Majdi, J. Chem. Thermodyn., 23, 1169 (1991).
99.K. -Y. Lee and M. M. Stinecipher, Propellants, Explosives, and Pyrotechnics, 14, 241 (1989).
Handrick (Reference 2b) spoke of a ‘salt link’ or correction of ca 67 kJ mol 1 associated with the formation of a salt from the reaction of an acid and base. From the enthalpy of formation of ethylenediamine from Pedley and of the ethylenediammonium salt of 3-nitro-1,2,4-triazol-5-one from the current reference, and the suggested ‘salt link’ (ð2), the enthalpy of formation of 3- nitro-1,2,4-triazol-5-one is predicted to be 135 kJ mol 1. This is in wonderful agreement with that reported in Reference 103.
100.K. -Y. Lee, C. B. Storm, M. A. Hiskey and M. D. Coburn, J. Energ. Mater., 9, 415 (1991).
101.K. -Y. Lee, M. D. Coburn and M. A. Hiskey, Los Alamos National Laboratory Technical Report, LA-12582-MS (June 1993).
102.K. -Y. Lee and M. D. Coburn, J. Energ. Mater., 1, 109 (1983).
103.R. Robertson, J. Chem. Soc., 119, 1 (1921).
104.P. M. Dobratz and P. C. Crawford, LLNL Explosives Handbook, UCRL-52997 Change 2 (January 1985).
105.R. N. Rogers, Thermochim. Acta, 11, 131 (1975).