NMR study of molecular motions in perisubstituted naphthalenes

Molecular motions in solid 8-substituted 1-methylnaphthalenes with the substituents H, CH3, Cl, and Br have been investigated by the temperature dependence of the 1H spin-lattice relaxation times and of the 1H second moments and high-resolution solid-state 13C NMR spectra with or without magic-angle sample spinning. The observed barriers to rotation of the perimethyl groups increase in the order of H (2.30 kcal/mol)≪CH3 (3.22)