A quantum‐chemical study of the preferred conformations of the model compounds of polypropylene

The total energies of some model compounds for polypropylene (PP) were calculated quantum‐chemically with the CNDO/2 method, taking into account their stereochemical configurations and preferred conformations. The statistical weights, τ and ω, are estimated using 2‐methylbutane and pentane, respectively and are compared with those obtained with semiempirical potential functions, in order to obtain informations on the conformation and configuration of PP. Moreover, it is pointed out that the shape of the potential curves nearby the energy‐minimum state is considerably different among the preferred conformations in some model compounds, such as dimer, trimer, and tetramer and this result demonstrates that one should be cautious with the application of the rotational isomeric state model to PP and its model compounds.