Substituent effects on the N.M.R. spectra of carboxylic acid derivatives. III. Correlation of ¹³C N.M.R. spectra of para substituted acetanilides and 4'-nitrophenyl 4-substituted benzoates with infrared carbonyl stretching frequencies, ¹H N.M.R., rate and equilibrium data

Abstract

The ¹³C n.m.r. spectra of 17 monosubstituted benzenes, 14 para substituted acetanilides and ten 4'-nitrophenyl 4-substituted benzoates have been measured in (CD₃)₂SO and the chemical shifts have been compared with the infrared carbonyl stretching frequencies of the substrates (in CCl₄), the ¹H n.m.r. chemical shifts of protons close to the reactive site of protonation, rates of hydrolysis or aminolysis and literature values of the corresponding basicity constants and rate constants. The observed substituent chemical shifts are non-additive and this result has been discussed in terms of the electronic properties of -NHCOCH₃ and -COOC₆H₄NO₂. The ¹³C n.m.r. and the i.r. data have been treated by single parameter and dual substituent parameter linear free energy relationships and σ_R values of best fit have been identified. Relative resonance and inductive contributions have been discussed.