"Thermal studies of isoxazolylnaphthoquinones using simultaneous TG-DTG-DTA. 2. Solid state studies on a keto-enol system

NR SPERANDEO

JOURNAL OF THERMAL ANALYSIS

Springer

Año: 1997 vol. 48 p. 267 - 267

0368-4466

he tautomeric binary system consisting of N-(3,4-dimethyl-5-isoxazolyl)-4-amino-1,2-naphthoquinone (1),m.p. 156?C, and 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinon-4-imine (2),m.p. 218?C, was studied by DTA-TG-DTG and IR spectrometry. Crystals of 1, left in contact with their mother liquor during 4 months, exhibited thermal behaviour similar to that of physical mixtures of 1 and 2, which reveal the presence of a eutectic at about 146?C.The effects of light, heat and humidity on the stabilities of 1 and 2 were also studied. Heat (up to 110?C) did not induce any change observable by DTA-TG-DTG in either 1 or 2. Moisture and daylight affected only 1. Upon melting, interconversion of the isomers was not observed.