CNDO/2 calculations on the relative basicities of alkyl benzenes

Abstract

CNDO/2 calculations were performed for toluene, ethyl benzene, iso-propyl benzene, t-butyl benzene, and neo-pentyl benzene, and the corresponding ortho, meta, and para protonated species. All rotational conformers against the benzene ring were examined and detailed energy differences and charge analyses are presented and discussed. The calculated energy differences suggest that for gas phase species the order of alkyl substituent rate enhancement for electrophilic aromatic reactions is t-Bu>i-Pr>Et>Me>H, thus the inductive order is found, rather than the hyperconjugative or Baker-Nathan order.