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" and ...