Knowledge Bank

The conformation of the methyl group in $CH2=CClCH2D$ has been determined by a normal coordinate analysis of the vibrational spectra. The methyl group has been found to eclipse the double bond. A formulation of the Hamiltonian of general mass point systems undergoing large deformations is given and has been specified to the torsional vibrational problem of molecules with one degree of freedom of internal rotation. A numerical treatment has been applied to three isotopic species of 2-chloropropene. For the torsional barrier the value $882.3\pm 8.9cm-1$ has been obtained. In the case of the species with the monodeuterated methyl group a comparison of the calculated vibrational fundamentals with the corresponding values of the normal coordinate treatment shows a possible systematic error in the latter approach.