Polymorphism of 1,2,3-Trichloropropane: NQR and DTA study of the ordered and desordered phases

N. VEGLIO; M. J. ZURIAGA; G. A. MONTI

JOURNAL OF PHYSICS CONDENSED MATTER

Año: 2004 vol. 16 p. 7873 - 7887

0953-8984

1,2,3-Trichloropropane was investigated by means of  Nuclear Quadrupole Resonance, and Differential Thermal Analysis. One amorphous state and two crystalline monotropic phases (form I and II) were found depending on the thermal history of the sample and only one is stable up to the melting point. The different phases were characterized by 35Cl NQR. It was conclude that form I is an ordered crystal with only one molecular conformation present in the unit cell while form II is a disordered state with at least two molecules present in the unit cell.              In the two crystalline phases, the presence of group reorientations (-CH2Cl) and molecule reorientations as a whole can be inferred from 35Cl spin-lattice relaxation times (T1 ) with activation energies of  33 kJ/mol and 42 kJ/mol,  respectively, in form I. In form II, these activation energies are in the range 20 kJ/mol to 29 kJ/mol indicating that this polymorph is less compact crystalline packed in comparison to form I.