Epimerization of 2,4-diphenylpentane, an oligomer of polystyrene

Chemical shift nonequivalence in prochiral groups

“…Diastereotopic Groups A. Meso Compounds nous by 0.78 ppm in carbon tetrachloride.9 However the para isomer (17) possesses a molecular symmetry plane (orthogonal to the plane of the ring) which passes through the prochiral methylene carbon atom; hence the methylene hydrogens are enantlotopic and Isochronous In achiral solvents. The meta Isomer provides another example of accidental chemical shift equivalence as, like…”

Epimerization of 2,4,6,8-tetramethylnonane and 2,4,6,8,10-pentamethylundecane, low molecular weight model compounds of polypropylene

“…Though the epimerization of cyclic hydrocarbons has been extensively investigated in both liquid1™13 and gas phase,14™17 the present knowledge about the epimerization of acyclic hydrocarbons seems to be limited to that obtained from the investigation of 2,4-diphenylpentane and 2,4,6-triphenylheptane. 18,19 The epimerization of suitable low molecular weight compounds is of interest because the composition of the equilibrium mixture can be used, adopting appropriate models,18™22 to attempt the evaluation of conformational parameters which are applicable to the investigation of conformational equilibria in high molecular weight compounds.…”

Conformations of 2,4-Diphenylpentane: A Quantum Chemistry and Gas-Phase Molecular Dynamics Simulation Study

“…These compounds can be considered polystyrene dimers and trimers, respectively. Far-infrared and depolarized Rayleigh scattering methods have been applied in the study of phenyl ring motion in these compounds, while conformational populations have been investigated by NMR vicinal coupling measurements, − depolarized Rayleigh scattering (optical anisotropy), , far-infrared and Raman spectroscopy, ultrasonic relaxation measurements, , and epimerization reactions. , These compounds have also been the subject of both molecular mechanics − and limited ab initio electronic structure calculations . These studies seem to establish racemic tt (r- tt ) as the lowest energy conformer of DPP.…”