FURTHER-STUDIES OF INTRAMOLECULAR MOTIONS IN CRYSTALLINE AMMONIUM BROMIDES BY CP MAS NMR/

A series of nine compounds consisting of dimethyl, trimethyl and ethyl dimethyl ammonium bromides in which the other alkyl group contains a ( 2-phenyl)ethyl moiety were synthesised and studied by CP/MAS NMR, The results of dynamic NMR studies on the solids suggest that there is a d ramatically wide range of molecular motions occurring in this simple s eries of compounds, A combination of dynamic line shape analyses and T -1p measurements reveals the considerable extent of intramolecular gro up motions including rotations of trimethylammonium, ethyldimethylammo nium and phenyl groups, Rates of rotation and activation parameters fo r these molecular motions are derived where appropriate.