TEMPERATURE-DEPENDENCE OF THE PHASE-TRANSITIONS OF BENZALDAZINE AND ITS O-NITRO, M-NITRO, AND P-NITRO DERIVATIVES

The dielectric constants of benzaldazine (BA) and its nitro derivative s have been measured at different frequencies up to 200 kHz. The measu rements were carried out at temperatures up to and near the melting po int of each sample. Two phase transitions were obtained during measure ments at 310 and 480 K. Inversion -NN- rotation and inversion -CN- rot ation mechanisms may be responsible for these transitions. The effect of interaction between the strongly polar -NO2 group of o-, m- or p-ni trobenzaldazine and the central aldimino (-CH=N-) groups on the dielec tric constant is discussed. The electric dipole moments of the samples were calculated at the peak positions, and are discussed.