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

The X-ray crystal structure of 2-benzyl-1H-benzimidazole, 2BnBzIm, was determined at 293 K showing no dynamic phenomena (disorder) of any class. On the other hand, some C NMR signals were absent in the CPMAS spectrum (100 MHz, 300 K). 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.This work was supported by Ministerio de Economía, Industria y Competitividad of Spain (CTQ2014‐56833‐R and CTQ2015‐63997‐C2‐2‐P) and Comunidad Autónoma de Madrid (Project FOTOCARBON, ref. S2013/ MIT2841). Carla I. Nieto is indebted to UNED for a predoctoral contract “FPI Grupos de Investigación.”Peer Reviewe