PCILO AND AM1 CALCULATIONS OF VINYL-SUBSTITUTED COMPOUNDS

The molecular structure and conformational energies of methyl acrylate , methyl methacrylate, vinyl acetate, methyl propionate, methyl 2-meth ylpropionate and styrene have been investigated using PCILO (perturbat ive configuration interaction with localized orbitals) and AM1 (Austin model 1) semiempirical methods with total optimization of geometry. T he minimum-energy conformations obtained with both methods have been c ompared. The heats of formation calculated with the AM1 method are in excellent agreement with experimental values. The rotational barriers were also calculated and there are similarities in shape between the v arious compounds that do not involve an ester oxygen.