Conformations of a phenyl group, and its effect on the barrier to rotation in substituted ethanes

Abstract

Barriers to rotation about the central butane bond of 2,2-dimethyl-3-phenylbutanes are unexpectedly low. This is discussed in terms of the conformation about the phenyl–C_α and C_α–C_β bonds. The low barrier may be due to a ground state interaction between an ortho-hydrogen and the 1-methyl group of the butane. Other evidence of this interaction is adduced.