Organic thermochemistry at high ab initio levels. 1. A G2(MP2) and G2 study of cyclic saturated and unsaturated hydrocarbons (including aromatics)

With the purpose of exploring the reliability of the enthalpies of formatio n calculated using G2 methods, we have examined a series of saturated and u nsaturated alicyclic hydrocarbons varying the size and the number of formal double bonds in the molecule. Heats of formation have been calculated at t he G2(MP2) and G2 levels through both atomization reactions and bond separa tion isodesmic reactions, and comparison with experimental values has been made. A linear relationship between the differences between experimental an d calculated (from atomization reactions) heats of formation and the number of formal double bonds is obtained.