Application of Quantum Chemical Calculations to the Identification of Positional Isomers of Polysubstituted Alkylbenzenes

The problem of assignment of positional isomers of alkylbenzenes to chromatographic peaks is addressed. Probable structures are attributed based on the correlation of stabilities of the isomers, which are expressed as the total molecular energies calculated by the MINDO/3 semiempirical quantum chemical method, and the proportions of the isomers in the reaction mixture. Multicomponent alkylbenzene mixtures were prepared and separated by capillary gas chromatography, and the identity of the isomers was confirmed by the gas chromatography-mass spectrometry combination.