The properties of the 2-(1-methoxyethyl)-3,4-dimethylthiazolium cation (3) and seven related thiazolium cations have been investigated as models for the behavior of 2-(1-hydroxyethyl)thiamin (1). The equilibrium acidity (pKHA+) of 3 in Me2SO solution was found to be 14.1 ± 0.05, and evidence is presented to indicate that the value in aqueous solution is within ±1 unit of this value. These values are 3 units, or more, lower than previous estimates for the pKHA+ at C-2α of the thiazolium moiety in 1, which were based on kinetic measurements. Related thiazolium cations, where Me, RO, or Ph groups were introduced into the C-2 side chain, were found to have acidities in the 9-15 pKHA+ range.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry