| Abstract
| - The principal values of the 13C chemical-shift tensor (CST) for biphenyl have been determined with theFIREMAT experiment. The internal dihedral angle between the benzene rings in biphenyl is estimated to fallbetween 10 and 20° on the basis of quantum mechanical calculations of the CST principal values. A compositemodel of motion in the system, with contributions both from internal jumping between enantiomeric structuresand from overall molecular librations, yields the smallest variance between predicted and measured valuesfor an internal twist angle of 15° between the rings and a mean libration angle of ±12° from the most favoredmolecular orientation. The composite model is clearly preferred to a motionless model (with >98% probability)and is also preferred over either of the isolated contributing dynamics, i.e., only libration or only internaljumping.
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