ENTHALPIES OF FORMATION FOR AROMATIC COMPOUNDS FROM G3B3(MP2) CALCULATIONS

摘要

Polycyclic aromatic hydrocarbons (PAH) are precursors for soot formation in the combustion of hydrocarbons fuels under fuel-rich conditions. Detailed chemical kinetic models have been developed to describe the growth of PAH's in order to predict sooting beha- vior. The relative stability of these molecules (and their derivatives and radicals) influence the rate of their formation and consumption, since many of the important reactions (such as addition/eliminations, isomerizations, cyclizations, and beta-scissions) involve chemically- activated steps. Thermochemical data for many PAH species used in these detailed chemical kinetic models are estimated using group additivity methods (thus, uncertain). In other cases, there are signifi- cant uncertainties (5-15 kJ mol~(-1) ) in the condensed phase enthalpies of formation and heats of sublimation used to derived gas phase enthalpies of formation for prototypical PAH's such as naphthacene, pyracyclene, and coronene. This study is directed at computing enthalpies of formation for PAH's where no experimental data are available, identifying species where experimental data may be in error, and developing methodologies for accurately predicting the stability of PAH's utilizing quantum chemical methods.