13C CP/MAS NMR study of a phenyl group rotation in the solid state using T1ρ, lineshape and 2D EXSY measurements

Abstract

AbstractA combination of solid‐state 13C CP/MAS NMR methods was used to study the rates of rotation of the phenyl group in 3,5‐dimethyl‐1‐phenylhex‐1‐yn‐3‐ol. The methods used were T1ρ measurements, lineshape analysis and 2D exchange spectroscopy over the temperature range 219–284 K. The rates of rotation obtained from the lineshape and 2D EXSY methods give an energy of activation of 58.6 ± 3.0 kJ mol−1. In good agreement with this, the T1ρ measurements give an activation energy for the rotation of 58.7 ± 3.6 kJ mol−1. The two sets of data are shown to be compatible, within experimental error, with a calculated value for the dipolar carbon–hydrogen interaction (B) from an assumed molecular geometry.