AB-INITIO CALCULATION STUDY ON CONFORMATION AND VIBRATIONAL FREQUENCIES OF 3-METHYL-3-PENTEN-2-ONE

Geometries of nine conformers of 3-methyl-3-penten-2-one have been opt imized by ab initio method using both of STO-3G and 3-21G basis sets. The stabilities of different conformers are compared, and the properti es and barriers of internal rotations are discussed. Calculated result s show that (i) there are three possible stabler conformers; (ii) both of (trans, s-trans) and (trans, s-cis) conformers can simultaneously exist and can be tranformed into each other; (iii) calculated vibratio nal frequencies are in good agreement with experimental spectra.