Evaluation of 1H nuclear magnetic resonance spin–lattice relaxation times facilitated by analogous 13C studies, illustrated by studies of 1,3,5-trimethylbenzene

Abstract

It is shown that in certain situations ¹³C n.m.r. spin–lattice relaxation time and n.O.e. studies may be used to separate ¹H relaxation times into intra- and inter-molecular components. The approach, which applies only when the carbon and hydrogen atoms are considered subject to the same overall molecular motion, does not depend on the theoretical evaluation of any parameters intrinsically involved in the characterization of the relaxation times. However, it is shown that simple geometrical calculations can facilitate the evaluation of equivalent rotational correlation times from both ¹³C and ¹H intramolecular relaxation rates and that the constituents of the latter can be readily isolated. The overall approach is illustrated by studies of the aryl carbon and hydrogen nuclei of 1,3,5-trimethylbenzene dissolved in carbon tetrachloride and in mixtures of cyclohexane and tetramethyl silane.