PHASE-TRANSITIONS AND BR-81 NQR OF TRIBROMOACETAMIDE

Thermal analyses revealed that Phase III of tribromoacetamide (TBAA) was transformed to Phase II at about 377 K and Phase II to Phase I at about 385 K. Phase II was superheated and Phase I was supercooled easily down to the 77-300 K region. Phase III of TBAA and Phase III of trichloroacetamide (TCAA) were proved to be isomorphous, but the nature of the phase transitions in TBAA was considerably different from that in TCAA. For Phase III and supercooled Phase I of TBAA, strong six and nine line Br-81 NQR spectra were detected at 77 K, respectively. Thermal motions of CBr3 groups in Phases I and III are discussed on the basis of the temperature dependence of the Br-81 NQR spectra.