The structure of protonated amides and ureas and their thio analogues

Abstract

The electronic absorption spectra were studied of protonated thioamides and thio-ureas, as well as the infra-red spectra of alkylated acetamide, thioacetamide, urea and thiourea and their hydrochlorides. All results consistently show that the proton is normally attached to the oxygen (or sulphur) atom. Earlier data pointing to the existence of the ammonium structure are reinterpreted. The resonance within these molecules appears to be the decisive factor in determining the site of protonation.