| Abstract: | Conformational energies, computed with a forcefield including coulombic interactions and a simple accounting for the effects of solvent, of meso and racemic 2,4-diphenylpentane as model substances of polystyrene have been computed as functions of the skeletal torsion angles and the phenyl torsion angles. The relatively high energies of the ḡ conformations rendered these states negligible and no minimum was found in the meso-tt domain. Three minima for the meso diad (gt, tg, gg) and four minima for the racemo diad (tt, tg, gt, gg) are relevant. A two-state rotational isomeric state model is applicable with states at φt = 5°C and φg = 110° for both meso and racemo diads. Statistical weight matrices have been derived and values predicted for the characteristic ratio, the fractions of 2,4-diphenylpentane and 2,4,6-triphenylheptane at stereo-chemical equilibrium and the vicinal NMR coupling constants are found to be consistent with experimental results. |
