THE MOLECULAR-CONFORMATION OF METHYL-METHACRYLATE - AN INFRARED AND AB-INITIO STUDY

An infrared study of methyl methacrylate trapped in low temperature ma trixes has been carried out. Ab initio SCF calculations of harmonic fr equencies at the fully optimized geometries of the planar cis and tran s rotamers have been performed at the Hartree-Fock 4-31G* and 6-31G** basis set levels, with inclusion of electron correlation by second or der perturbation theory (MP2). Scaled 4-31G* anharmonic frequencies h ave been used as an aid to the assignment of the experimental spectrum over the spectral region 4000-400 cm(-1). The computed spectrum is in excellent agreement with experiment, and confirms the co-existence of two planar rotamers (cis and trans) of nearly equal energy.