Conformational analysis of some alkyl groups on benzene: PMR spectra of 4‐alkyl‐2‐nitroacetanilides

The PMR spectra of 2‐nitroacetanilide and often 4‐alkyl substituted derivatives have been measured. Two about equally stable conformers have been detected for the derivatives with the groups ‐CHPr i Bu t , ‐CHBu t 2 , and ‐C(OH)Bu t 2 . The conformational isomerism is caused by a hindered rotation about the bond between the alkyl groups and the benzene ring; rotational barriers have been determined of approximately 12, 22, and 21 kcal/mole, respectively. The preferred conformations and the rotational barriers are discussed for the alkyl groups ‐CH 2 Bu t , ‐CHMeBu t , and ‐CHPr i 2 .