Thermochemical Principles

In this text. Shields and Seybold carefully review the thermochemical principles involved in the measurement and prediction of acid dissociation constants. They further provide an extraordinarily useful comparison of several theoretical models that have been proposed, whether for more specific or more general applications, examining their relative utilities and ranges of applicability. Importantly, the authors tightly couple their analysis to the rich physical organic chemistry associated with all of the various functional groups that may serve as conjugate acids or bases, and they do so not only for the case of aqueous solution, but also for non-aqueous solvents. They wrap up with some welcome discussion of temperature effects, isotope effects, and other phenomena that can extend the utility of acid dissociation constants as reporters of electronic structure and reactivity. 

Pyrotechnics is based on the estabflshed principles of thermochemistry and the more general science of thermodynamics. There has been Httle work done on the kinetics of pyrotechnic reactions, largely due to the numerous chemical and nonchemical factors that affect the bum rate of a pyrotechnic mixture. Information on the fundamentals of pyrotechnics have been pubflshed in Russian (1) and English (2—6). Thermochemical data that ate useful in determining the energy outputs anticipated from pyrotechnic mixtures are contained in general chemical handbooks and more specialized pubHcations (7-9). 

A modified definition of resonance energy has been introduced by Dewar (66T(S8)75, 69JA6321) in which the reference point is the corresponding open-chain polyene. In principle this overcomes the difficulties inherent in comparing observed stability with that of an idealized molecule with pure single and double bonds, as thermochemical data for the reference acyclic polyenes are capable of direct experimental determination. In practice, as the required data were not available, recourse was made to theoretical calculations using a semiempirical SCF-MO method. The pertinent Dewar Resonance Energies are listed in Table 30. 

The quantitative computations were conducted using equilibrium thenuodynamic model. The proposed model for thermochemical processes divides layer of the sample into contacting and non-contacting zones with the material of the atomizer. The correlation of all initial components in thermodynamic system has been validated. Principles of results comparison with numerous experimental data to confirm the correctness of proposed mechanism have been validated as well. 

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