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Acidity constants of benzimidazolium ketone and pyridinium aldehyde hydrates

1990; Wiley; Volume: 27; Issue: 4 Linguagem: Inglês

10.1002/jhet.5570270431

1943-5193

Terence C. Owen,

Synthesis of Organic Compounds

Abstract Acidity constants (p K a) of the hydroxyl groups of the quaternary heterocyclonium carbinols 2‐hydroxy‐methyl‐1‐methylpyridinium and 2‐(1‐hydroxyethyl)‐1,3‐dimethylbenzimidazolium ions are 11.5 ± 0.5. Acidity constants of the corresponding gem diols, the hydrates of 2‐formyl‐1‐methyl‐pyridinium and 2‐acetyl‐1,3‐dimethylbenzimidazolium ions hence are estimated to be 9 ± 0.5. Accordingly, acidity constants of the hydroxyl groups of pyridine aldehyde salt hydrates are 12–13, not 4–5 as previously reported; and conversely, acidity constants of the pyridinium groups are 4–5, not 12–13.