PROTONATED CARBONYL GROUPS: V. Α-Pyridone SALTS

Abstract

Salts of 1-methyl-2-pyridone and 1-methyl-2-quinolone with strong acids have been prepared and their infrared spectra recorded between 4 000 and 650 cm−1. Protonation of the carbonyl group occurs giving rise to OH stretching, in-plane and out-of-plane bending vibrations which absorb in characteristic regions of the spectrum, namely 1 900 – 3 300 cm−1 (depending on the anion), ~ 1 250 cm−1, and ~ 800 cm−1 respectively, with appropriate shifts on deuteration. Other tentative assignments are made.

The structure of the cations from 2– and 4‐pyridones and related pyridines

“…The became controversial when Spinner originally concluded that protonation took place on the ring nitrogen atom leading to cations 3 and 4 (12). Spinner later revised these structures and agreed that they are correctly represented by 5 and 6, respectively (13,14,26,27). This project set o u t to compare the IR spectra of a number of salts of 2and 4-pyridones with those of closely related 2and 4-substituted pyridinium salts in order to obtain additional evidence for structures 5 and 6.…”