Transmission of electronic effects of substituents in vinyl esters

To elucidate the transmission mechanism of electronic effects of substituents in vinyl esters on the optical parameters of the absorption bands in the IR spectra, a comparison was made of the frequencies of corresponding absorption bands in vinyl ethers, vinyl esters, alkyl esters of carboxylic acids, ketones, and acid anhydrides. Calculation of the - and -electron structure of the molecules by the Hückel and Del Re approximations was made. The results were compared with the spectral characteristics. The conclusion was reached that the ester oxygen atom in vinyl esters reduces interaction of the carbonyl and vinyl groups, although it is not removed completely. In vinyl esters of aromatic acids the effect of benzene ring substituents is displayed by a change of the -electron structure of the CH₂=CH-O-CO- fragment. In vinyl esters of aliphatic acids the electronic influence of radicals of the acid portion is transmitted by the ester oxygen, mainly inductively, which, in its turn, shows a change in the ability of this atom to conjugate with the vinyl group.The authors express their thanks to Yu. A. Kruglyak for allowing use of the programs for the computation and for helpful advice.