G(2) AB-INITIO CALCULATIONS OF ENTHALPIES OF HYDROGENATION, ISOMERIZATION, AND FORMATION OF C-3 CYCLIC AND ACYCLIC KETONES AND ALCOHOLS

We report the ab initio G2 enthalpies of hydrogenation and isomerizati on (Delta(hyd)H and Delta(isom)H) in the gaseous state, at 298 K, of 8 C-3 cyclic and acyclic ketones and alcohols, including cyclopropenone , cyclopropenol, and allyl alcohol. Delta(hyd)H(298) and Delta(isom)H( 298) are found from the differences in total energy (E-0) of the parti cipants in the hydrogenation and isomerization reactions. Combination of calculated Delta(hyd)H(298) and Delta(isom)H(298) with one experime ntal enthalpy of formation (Delta(f)H(298)) in the set yields Delta(f) H(298) of all the rest. Results lead to an estimate of 20.5 kcal mol-l for the resonance energy of cyclopropenone.