Orientational Ordering of Partially Deuterated Methyl Groups in Solid 2,6-Dichlorotoluene as Studied by Vibrational Spectroscopy

Infrared spectroscopic measurements were made between 6 K and 100 K in the range from 400 cm-1 to 4000 cm-1 for 2,6-dichlorotoluene and its methyl-deuterated analogs. For the —CH2D compound, four peaks associated with stretching modes of —CH2D were detected in the range of 2100 cm-1 to 2250 cm-1. Two peaks at 2140 cm-1 and 2190 cm-1 became weaker with decreasing temperature, while the other two peaks around 2210 cm-1 became stronger. The temperature dependence of those intensities was explained successfully by the three-level energy scheme obtained from the Schottky heat capacity.

(H. Suzuki & A. Inaba)

	Fig. 1. Infrared absorption spectra obtained at 6 K for 2,6–dichlorotoluene and its methyl–deuterated analogs.
	Fig. 2 Temperature evolution of the IR spectra obtained for C6H3Cl2—CH2D.
	Fig. 3. Temperature dependence of the scaled intensity of four peaks obtained for C6H3Cl2—CH2D (see Fig. 2), which is consistent with the occupancy for the three-level energy scheme obtained from the Schottky heat capacity (solid curves).