Comprehensive Ureyhyphen;Bradley Force Field for Molecules with Geminal Methyl Groups. I. Acetone

摘要

The coupling of motion between methyl groups ingemhyphen;dimethyl molecules is studied by performing a normal coordinate analysis of acetone and acetonehyphen;d6. A Ureyhyphen;Bradley force field (UBFF) is employed, and the usefulness of fourhyphen;atom (cis) and fivehyphen;atom (supercis) configurations is investigated. Improvement over previous analyses of acetone is found when the inhyphen;planeCsngbnd;Hbending and nonbonded force constants are adjusted separately from the otherCsngbnd;Hterms, and when certaincisconfigurations are included. Possible physical significance is discussed for the negative value of thecisHsngbnd;Ononbonded force constant obtained; attraction between the inhyphen;plane hydrogens and the carbonyl oxygen is indicated.