The Effects of Conformation and Crystalline Packing on the Solid State sup 13 C NMR Chemical Shifts Observed for Bisphenol A

In the reported crystal structure of bisphenol A (4,4'-dihydroxydiphenyl- dimethylmethane), three independent molecules with different conformations are found to make up the asymmetric unit of the crystalline unit cell. The high resolution, solid state sup 13 C NMR spectrum of crystalline bisphenol A reveals multiple resonances for all carbons except the tetra-substituted methane carbon. Analysis of the conformations of the three independent bisphenol. A molecules in the asymmetric unit and their packing arrangements within the unit cell and with the bisphenol A molecules of neighboring unit cells permits a rational, complete assignment of the observed spectrum. Interestingly, the close intermolecular packing of oxygen and carbon atoms with the observed carbons produces a deshielding of their resonances, while a shielding results for those carbons that are proximal as a consequence of their intramolecular conformational arrangements.