The 13C NMR spectra of 23 di‐ and tri‐substitutedderivatives of esters, thioesters and amides of benzoic acids have been calculated and fully assigned. The Ai empirical parameters of the (alkoxy)(dialkoxycar‐bonyl) methylamino, (alkoxy)(alkoxycar‐bonyl)(cyano)methylamino, (alkylamino) (dialkoxycarbonyl) methylamino and (alkylthio) (dialkoxycarbonyl) methylamino groups have been calculated for use