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.