THE VIBRATIONAL-SPECTRUM, BARRIER TO INTERNAL-ROTATION, AND ABINITIO CALCULATIONS OF 2-CHLOROPROPANE

The Raman spectra (3200-50 cm-1) of gaseous, liquid, and solid 2-chloropropane-d3 (isopropyl-d3 chloride), CH3(CD3)-CHCl, and the infrared spectra (3200-50 cm-1) of the gas and solid have been recorded. The torsional transitions observed in the far infrared spectrum of the gaseous sample recorded at a resolution of 0.10 cm-1 between 265 and 135 cm-1 were analyzed in terms of the semirigid rotor model. An effective barrier of 1378 +/- 4 cm-1 (3.94 +/- 0.01 kcal/mol), cosine-cosine coupling term of 166 +/- 10 cm-1 (0.47 +/- 0.03 kcal/mol), and sine-sine coupling term of -173 +/- 1 cm-1 (-0.49 +/- 0.01 kcal/mol) were determined by fitting ten observed frequencies arising from the CH3 and CD3 torsions. The assignment of the 27 fundamentals is given and discussed. A complete equilibrium geometry, barrier to internal rotation, and vibrational frequencies have been determined by ab initio Hartree-Fock gradient calculations employing either 3-21G* or 6-31G* basis sets for both the d0 and d3 species. These calculated results are compared to the experimental values as well as to the corresponding quantities for some similar molecules.