Substituent effects of pyrrolidino and piperidino groups in benzoic acids and nitrobenzenes

Abstract
Benzoic acids and nitrobenzenes, substituted in the para position with a pyrrolidino or a piperidino group are compared with dialkylaminobenzoic acids and dialkylaminonitrobenzenes.The acidities of the substituted benzoic acids, the polarographic halfwave potentials of the nitrobenzenes and the rate of reduction of the nitrobenzenes with disodium disulfide, give the following order of electron releasing effect of the substituents:piperidino < dimethylamino < pyrrolidino < diethylamino < di‐isopropylamino.No steric inhibition or promotion of resonance is found with the pyrrolidino group, but steric inhibition of resonance seems important in the piperidinobenzenes. The basicities of the dialkylaminobenzoic acids show a greatly different sequence which is attributed to the changing configuration around the basic site.