Libration of phenyl groups detected by VT-SSNMR: Comparison with X-ray crystallography.

Abstract

The X-ray crystal structure of 2-benzyl-1H-benzimidazole, 2BnBzIm, was determined at 293K showing no dynamic phenomena (disorder) of any class. On the other hand, some 13 C NMR signals were absent in the CPMAS spectrum (100MHz, 300K). We decided to carry out variable-temperature SSNMR and discovered that the missing signals are ortho and meta carbons of the phenyl ring of the benzyl group. Line-shape analysis and the Eyring equation were used to determine the barrier, which was compared with the calculated DFT for the gas phase that it is much lower.