Effect of Pressure on the Anisotropic Reorientation of Acetonitrile-d3 in the Liquid State

The deuteron and nitrogen spin–lattice relaxation times of acetonitrile‐d₃ have been measured as a function of pressure up to 2 kbar at 23°C using the NMR pulse method. Since the quadrupole coupling constants for nitrogen and deuterons in acetonitrile‐d₃ are known, the experimental $T_1$ data were interpretable in terms of the rotational diffusion constants for motion perpendicular and parallel to the symmetry axis, $\mathrm{D\perp }$ and $D_{\Vert }$ , respectively. In agreement with our previous results the calculated activation volumes show that ${\mathrm{\Delta V}}^{‡}\mathrm{(D\perp )}$ is much larger than ${\mathrm{\Delta V}}^{‡}{\mathrm{(D}}_{\Vert })$ .