The methyl-t3C and the 14N longitudinal relaxation times in acetonitrile, dissolved in a thermotropic liquid crystal are analyzed with a slowly relaxing local structure modeL This model gives rise to a frequency dependent relaxation mechanism which explains the relatively short 14N relaxation time compared to the methyl-13C relaxation time. 1. Illtrodllction In a previous paper [I], the results were given of an NMR relaxation study of acetonitrile dissolved in a nematic liquid crystal (Merck's Licrystalv). The longitudinal relaxation time of the methyl-% was measured by an inversion-recovery pulse sequence under proton decoupling. The 14N TI was abstracted from the proton decoupled cyan~-~~C line, which is substantially broadened due to the scalar relaxation mechanism_ In order to abstract the correlation times for rotational diffusion perpendicular to, and around the symmetry axis, from the measured relaxation times, the equations derived by Woessner [2,3] for NMR relaxation in the case of anisotropic rotational diffusion were modified in a simple manner, to allow for preferential orientation. In view of the relatively small degree of ordering (S,, = O-l), it was assumed that the classical model of rotational diffusion for an isotropic liquid was also valid for a small molecule as acetonitrile in a nematic liquid. Using a value of 3.6 MHz for the quadrupole coupling constant e2qQ/h of 14N as measured in a lyotropic liquid crystal [4], the methyl-r3C T1 and the cyano-14bl T1 appeared to be %ncompatible. Real values of r1 and r,r could only be obtained by increasing the 14N quadrclpole coupling constant by an undue amount (a factor of two at least). No such-discrepancies were found in relaxation time measurements on acetonitrile in normal liquids [3,5-71s