C-13 SPIN-LATTICE RELAXATION IN BENZOPHENONE AND ITS ISOTOPOMERS

In order to analyze deuterium effects on C-13 spin-lattice relaxation time (T1) in benzophenone (BPN), five BPN isotopomers were prepared and their C-13 NMR spectra recorded. In BPN all the phenyl carbon atoms, except the quarternary one, are predominantly relaxed by the dipole-dipole mechanism due to C-H dipole-dipole relaxation. Other contributions to the total spin-lattice relaxation times of individual carbon atoms are discussed as well. Deuteration affects also the magnitude of spin-lattice relaxation times. An increase in T1 by cca. 550% at the ortho (C2) and para (C4) carbon atoms in perdeuterated BPN has been observed.