MOLECULAR MECHANICS (MM3) STUDIES OF MONOCHLOROALKANES

Monochloroalkanes were studied using molecular mechanics and parameter s were developed and incorporated into MM3, The new force field reprod uces well molecular structures, conformational energy differences and vibrational frequencies, The compounds studied were methyl, ethyl, n-p ropyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, neopentyl, cyclopentyl and cyclohexyl chloride, 4-tert-butyl-1-chlorocyclohexane and 1-chloroadamantane, The overall rms error for the averaged C-C an d C-Cl bond lengths for the above set of compounds excluding sec butyl chloride, neopentyl chloride and 1-chloroadamantane is 0.004 Angstrom , and the rms error for the vibrational frequencies is 37 cm(-1). The moments of inertia (r(g)) are approximately 1% greater than the microw ave values (r(a)(0)), Thermodynamic quantities are also compared with those observed using various experimental methods.