1, 2, 4-Triazoles. III. The Tautomerism of 3-Phenyl-1, 2, 4-triazolin-5-one, 3-Phenyl-1, 2, 4-triazoline-5-thione and Their N-Methyl Derivatives

On the basis of ultraviolet (UV) and infrared (IR) evidence, 3-phenyl-1, 2, 4-triazolin-5-one and its N-methyl derivatives were all shown to exist as the oxo forms, except the 2-methyl derivative which existed as the hydroxy form. Similarly, UV data showed the predominance of the thione forms of 3-phenyl-1, 2, 4-triazoline-5-thione and its N-methyl derivatives. The syntheses of the N-methyl derivatives of the triazolines used in the present study were described.