Proton Spin-Lattice Relaxation Studies of Intermolecular Interactions in the Mixtures of Chloroform and Proton-Acceptor Solvents

Proton spin-lattice relaxation measurements were carried out on chloroform in carbon tetrachloride, benzene, pyridine, acetone, and dimethylsulfoxide (DMSO) in order to investigate the effect of the intermolecular interaction on the spin-lattice relaxation time, T1 of chloroform. It was found that the order of the effects of solvents on T1 is as follows: DMSO>acetone, pyridine>benzene, carbon tetrachloride; this order corresponds to that of the association constant of chloroform with these solvents. The T1 values of benzene and acetone were also determined on chloroform-benzene and chloroform-acetone mixtures. On the basis of the results obtained on these solutions together with the results on the T1 of chloroform in various solvents, we estimated the lifetimes of the chloroform-benzene complex and of the chloroform-acetone hydrogen-bonding complex. We tried to keep the proton-density constant throughout the solutions, in order to avoid an ambiguity arising from its change, by adopting the corresponding deuterated compounds.