ELECTRONIC EFFECT OF METHYL GROUP - PARTIAL RATE FACTORS FOR NITRATION OF XYLENES

The electronic effect of the Me group has been investigated using several different models within the PPP formalism. For Me substituted benzenes the optimum agreement between calculated and observed properties is obtained when both, inductive and hyperconjugative mesomeric effects of the substituent are included. The properties investigated are frequency shifts and changes in intensities of electronic transitions, changes in ionization potentials, changes in π charge distribution and positional and relative reactivities in electrophilic substitution. In the case of the latter the nitration (HNO3/HOAC media) of the xylenes has been investigated over a wide temperature range, and competitive nitrations at 25° with benzene have been carried out to give partial rate factors. © 1969.