Dynamic and structural studies on 1,2,3-trichloropropane in the solid phase

Abstract

35Cl nuclear quadrupole resonance (NQR) frequencies nu Q and spin-lattice relaxation times T1 were measured between 100 and 250 K in 1,2,3-trichloropropane (CH2ClCHClCH2Cl). Three narrow lines were detected in the stable solid phase, indicating that only one of the six possible conformers is present. Also, the three lines were assigned to the three chlorine atoms in the molecule from their distinct temperature behaviours. The dominant mechanism responsible for the relaxation above 200 K is proposed to be the reorientational motion of the CH2Cl end groups, and activation energies of 32.5 and 49.0 kJ mol-1 are determined for the two end groups. The 1H nuclear magnetic resonance lineshape f(H) shows a structure due to the dipolar interaction between the protons of the CH2Cl groups. From the analysis of f(H) a distance dHH=1.68 AA is obtained, which turns out to be quite close to that already determined in solid dichloroethane. Fast cooling of the sample from the liquid state produces very broad NQR signals. The results of differential thermal analysis seem to indicate the existence of a glassy state with a characteristic Tg=144 K.