The conformational problem of biphenyl in solution as investigated by the liquid crystal nuclear magnetic resonance spectrum of 3,3′,5,5′-tetrachlorobiphenyl

Abstract

The interpretation of the ¹H n.m.r. spectrum of a meta-substituted biphenyl (3,3′,5,5′-tetrachlorobiphenyl) dissolved in the nematic phase of a liquid crystalline solvent showed unambiguously that in solution it has neither a planar structure nor free rotation but exists in a twisted conformation. A fairly accurate measurement of the twisting angle could also be obtained (34° 20′), the experimental error being similar to that reported in the electron diffraction studies of the vapour phase. The effects of the substituents and of the nematic solvent upon the conformation are discussed and the conclusion is reached that they are rather small and acting in opposite directions. Biphenyl is thus expected to have a similar dihedral angle in solution.