Crystallization of 4-pyrimidinone from CHCl3 produced colorless needles that were shown by X-ray crystallography to consist of cyclic hydrogen-bonded dimers 2 of the 4 (3 H)- pyrimidinone tautomer 1. Vapor-pressure osmometry established that a simple derivative, 5- (2-phenylethyl)-4 (3 H)-pyrimidinone (5), self-associates in solution with a value of K a (220±110 m-1 at 26° C in CH2Cl2) close to that measured for 2-pyridinone under similar ...
