The tautomerism of heteroaromatic compounds with five-membered rings—I : 5-hydroxyisoxazoles-isoxazol-5-ones

Abstract

Infra-red and ultra-violet spectra show that 3,4-dimethyl-5-hydroxyisoxazole exists in aqueous and chloroform solution, and in the solid phase in the OH form; and that 3-phenyl-, 4-bromo-3-phenyl-, and 4-methyl-3-phenyl-isoxazol-5-ones exist as mixtures of the CH and NH forms in solution, the proportion of the NH form increasing with the polarity of the solvent. The basicities of isoxazole and some of its derivatives are recorded. Isoxazol-5-ones are acids of comparable strength with carboxylic acids.