Ortho Methyl Group Effects in Cumyl Systems

Article abstract of DOI:10.1021/jo00121a057

In an attempt to evaluate the steric effect of ortho methyl groups on the stability of the cumyl radical, 2,2',4,4',6,6'-hexamethylazocumene (6) was synthesized and its rate of decomposition was measured.The fact that 6 decomposes 40 times faster than azocumene is attributed to a ground state steric effect.Calculations on the mesitylcumyl radical 1 and cation 2 show both systems to be substantially nonplanar with dihedral angles of 48 deg and 35 deg, respectively.Calculated charge distributions for cation 2 corroborate previously obtained NMR results which showed substantial loss of charge delocalization.