Theoretical study of carbocation derivatives of ethylene glycol vinyl glycidyl ether via the semiempirical Parametric Method 3

The study aims to assess how the structure of carbocations, including solvated carbocations – derivatives of ethylene glycol vinyl glycidyl ether (Vinylox) – affects their enthalpy of formation, geometry, and frontier orbital energies via a semiempirical quantum chemical method (Parametric Method 3). In this work, the enthalpy of Vinylox formation was calculated, as well as the energies of frontier (highest occupied and lowest unoccupied) molecular orbitals of carbocations formed during the heterolytic cleavage of vinyl oxide and epoxy groups. The calculations were performed with full geometry optimization. The characteristics of nine model structures (the subject matter of the study) that could potentially participate in cationic macromolecular chain growth processes were determined. It was found how the intramolecular and intermolecular anomeric ("through space") effects, involving the interaction of simple ether and epoxy oxygens with carbocation centers, affect the enthalpy of formation and frontier orbital energies. In all cases, the spatial geometry of structures with intramolecular anomeric interactions is bent. The geometry of the epoxy carbocation is linear due to the absence of such interactions. These interactions were found to significantly reduce both the enthalpy of carbocation formation and the energy of the highest occupied molecular orbitals. It is possible that such anomeric interactions are of donor-acceptor type, involving the unshared electron pairs of oxygen and the vacant p orbitals of carbocation centers. It is assumed that these interactions also occur in weakly polar aprotic solvents (chlorohydrocarbons), as proven by the example of chloroform.