Knowledge Bank

The potential energy surface for the double rotation of the methyl group in acetone was determined theoretically with fully relaxed geometry in the RHF and RHF+MP2 approxiamations and 6 -31 G (p, d) basis. The energy values were fitted to a symmetry adapted double Fourier expansion in seven terms. The rotational solutions were developed on the basis of the symmetry eigenvectors of the nonrigid group $G36$, which Factorize the Hamiltonian matrix into 16 boxes. From the eigenvalues and eigenfunctions the far infrared spectrum was deduced. The intensities were obtained from the from the calculated electric dipole moments. The intensity distributions appear to reproduce the observed patterns in the fundamental and first sequence series of bands.