Molecular Interactions and Mechanisms in the 1 H NMR Relaxation of Residual CHCl 3 in Deuterochloroform Solution of a Two-Chain Ionic Surfactant

1 H NMR spin–lattice ( T 1 ) and spin–spin ( T 2 ) relaxation times have been measured for the residual CHCl 3 component of deuterochloroform (99.8 atom% D) in neat solvent samples and in a series of isotropic solutions of the ionic surfactant n -octylammonium- n -octadecanoate and also in degassed/dried and aerated solvent systems at 298 K. Analysis of the proton relaxation times as composite values from various relaxation mechanisms suggests that the spin–lattice process is predominantly via spin–rotation while spin–spin relaxation principally involves 1 H–Cl scalar coupling. Rotational correlation times from relaxation rates via the dipolar and spin–rotation mechanisms reveal similar fast picosecond molecular rotation of chloroform in the different samples. The presence of surfactant in the solution appreciably affects the 1 H NMR spin–lattice relaxation time of CHCl 3 and the chemical shift, which is concentration dependent owing to weak intermolecular interactions. Effects of sample condition and solvent degassing, drying, and aeration treatments on the NMR relaxation times and line shape properties of the residual CHCl 3 isotopomers are also examined.