In this paper, we have assembled the molecular constants needed for the computation of the thermodynamic functions and the standard heats of formation for most of the low molecularhyphen;weight CmHnspecies which may be present in equilibrium at very high temperatures under a variety of external conditions. In the literature, the essential data are recorded for only 34 of the 73 species considered, and for those which are listed thermodynamic functions are given for the lower third of the temperature range included in our computations.In order to arrive at an estimate for each of the 39 molecular fragments the following steps were used: (a) assign to each fragment a formal electronic configuration (this establishes the framework for the analogies to be sought and fixes its groundhyphen;state electronic degeneracy); (b) select several paths for dissociation which, when followed, generate the species under consideration in going from one molecule of known structure to another; and (c) estimate the bond dissociation energies from known simple dissociations, corrected for nonlocalized electron interactions. These corrections are relatively small and have been obtained by comparing similar reactions for known species. The success of this procedure is demonstrated by the good agreement found between a few predicted and experimental heats of formation. The selfhyphen;consistency of the method is proven by the close check between estimates made for the heats of formation for many species following independent paths.
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