Substantial formation of hydrates and hemiacetals from pyridinium ketones

Article abstract of DOI:10.1016/j.tetlet.2009.09.054

Pyridinium ketones have been found to exist as hydrates and hemiacetals in considerable amount in aqueous and alcoholic solutions, respectively. The relative position of the pyridinium positive charge has a large effect on the equilibrium constants. The polar substituent constants, σ,* of the pyridinium group substituted at different positions can be estimated from the hydration constants.