Carbon acidity of the α-pyridinium carbon of a pyridoxamine analog

Organic & Biomolecular Chemistry Pub Date: 2005-04-26 DOI: 10.1039/B504399A

Abstract

We report second-order rate constants of kDO = 120 dm3 mol?1 s?1 and kB = 6.4 × 10?4 dm3 mol?1 s?1 for exchange for deuterium of the first α-methylene proton of the 4-(aminomethyl)pyridine dication in D2O at 25 °C and I = 1.0 (KCl). These data are consistent with a carbon acid pKa between 17 and 19 for ionization of this simple carbon acid and they show that the effect of an α-pyridinium substituent on carbon acidity is similar to that of an α-ester substituent.

Graphical abstract: Carbon acidity of the α-pyridinium carbon of a pyridoxamine analog
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