THERMAL STUDIES OF ISOXAZOLYL-NAPHTHOQUINONES BY SIMULTANEOUS DTA-TG-DTG .2. SOLID-STATE STUDIES ON A KETOENOL SYSTEM

The tautomeric binary system consisting of -dimethyl-5-isoxazolyl)-4-a mino-1,2-naphthoquinone (1), m.p. 156 degrees C, and 4-dimethyl-5-isox azolyl)-1,4-naphthoquinon-4-imine (2), m.p. 218 degrees C, was studied by DTA-TG-DTG and IR spectrometry. Crystals of 1, left in contact wit h their mother liquor during 4 months, exhibited thermal behaviour sim ilar to that of physical mixtures of 1 and 2, which reveal the presenc e of a eutectic at about 146 degrees C. The effects of light, heat and humidity on the stabilities of 1 and 2 were also studied. Heat (up to 110 degrees C) did not induce any change observable by DTA-TG-DTG in either 1 or 2. Moisture and daylight affected only 1. Upon melting, in terconversion of the isomers was not observed.