SPECTRA AND STRUCTURE OF SMALL RING COMPOUNDS .65. CONFORMATIONAL STABILITY, BARRIERS TO INVERSION, AB-INITIO CALCULATIONS AND VIBRATIONAL ASSIGNMENT OF CHLOROCYCLOPENTANE

The infrared (3500-40 cm(-1)) and Raman (3400-20 cm(-1)) spectra of ga seous and solid chlorocyclopentane, c-C5H9Cl, have been recorded. Addi tionally, the Raman spectrum of the liquid has been obtained and quali tative depolarization values were measured. Experimental values for th e enthalpy difference between the two stable conformers, i.e. the axia l form with lower energy and more stable conformer and the equatorial form, have been determined for both the liquid (120 +/- 8 cm(-1); 343 +/- 23 cal mol(-1)) and gas (146 +/- 24 cm(-1); 417 +/- 69 cal mol(-1) ) from investigations of the Raman spectra at various temperatures. Vi brational assignments are given for both conformers which are supporte d by normal coordinate calculations. The conformational stability, ent halpy difference, structural parameters, and fundamental vibrational f requencies, which have been determined experimentally, are compared wi th those obtained from ab initio Hartree-Fock calculations employing b oth the RHF/3-21G and the RHF/6-31G* basis sets. Revised ro structura l parameters are given based on previously reported microwave rotation al constants. These results are compared with those obtained for some similar molecules.