Magnetic Resonance Studies of Anisotropic Molecular Rotation in Liquid Acetonitrile-d3

The magnetic relaxation times T₁ for ¹⁴N and ²D in liquid CD₃CN have been measured as functions of temperature and concentration of added ionic salts. With no model assumed for the reorientation process, the molecular rotation is demonstrated to be anisotropic. The further assumption of a rotational diffusion equation permits the determination of the rotational diffusion constants. At 25°C, D_⊥=1.35×10¹¹(sec)⁻¹, and D_∥=1.2×10¹²(sec)⁻¹. The rotational diffusion tensor remains anisotropic over a wide range of temperatures. The addition of the perchlorates of silver, lithium, or sodium to CD₃CN reduces $D_{\perp }$ for bound CD₃CN by a factor of 10, but leaves D_∥ unchanged.