The Infrared Spectra of N-Acyltrialkylammonium Halides, in Relation to Those of Amide Salts

N-Acyltrialkylammonium halides have been prepared from the trialkylamine and acid halides. The ionic solids so produced can be easily handled in inert atmospheres but are easily attacked by moisture. Their infrared spectra have strong carbonyl bands near 1800 cm −1 , showing that the R 3 N + group, when attached to an acyl group, has strong electron-with-drawing characteristics, to a rather greater extent than the halogens in acid halides.Structurally, the N-acyltrialkylammonium halides would be similar to protonated (or alkylated) amides, if such protonation (or alkylation) occurred at the nitrogen atom. Since all amide salts examined hitherto have carbonyl frequencies over 100 cm −1 lower than 1800 cm −1 it is concluded that this work offers further evidence that protonation in amides occurs at the oxygen atom.