A C-13 SPIN-LATTICE RELAXATION STUDY OF THE EFFECT OF SUBSTITUENTS ONRIGID-BODY ROTATIONAL DIFFUSION IN METHYLENE-CHLORIDE SOLUTION AND INTHE SOLID-STATE

A C-13 spin-lattice relaxation study at 298 K of substituted adamantan es in the liquid state at constant (0.10 M) concentration in deuterate d methylene chloride and in the solid state has been conducted. The an isotropic rotational diffusion tensor elements have been determined fr om the C-13 T1 data. Nearly spherical adamantane undergoes isotropic r otational diffusion with R1 = R2 = R3 = 11.0 X 10(10) rad2/S, while 1- adamantanol and 1-adamantyl isocyanate undergo axially symmetric rotat ional diffusion with R1 = R2 = 4.3 X 10(10) rad2/s and R3 = 10.6 X 10( 10) rad2/s, and R1 = R2 = 3.1 X 10(10) rad2/s and R3 = 11.2 X 10(10) r ad2/s, respectively. 2-Adamantanone undergoes asymmetric rotational di ffusion with R1 = 1.0 X 10(10) rad2/s, R2 = 2.0 X 10(10) rad2/s, and R 3 = 24.0 X 10(10) rad2/S. In the solid state at 294 K, adamantane's ro tational diffusion is still isotropic, but is 10 times slower, and tha t of 1-aminoadamantane is axially symmetric with R1 = R2 = 0.59 X 10(1 0) rad2/s and R3 = 2.72 X 10(10) rad2/s. In all cases, the intramolecu lar heteronuclear dipolar interaction is the main relaxation mechanism for C-13.