AN NMR-STUDY ON MOLECULAR MOTIONS OF ALPHA,2,6-TRICHLOROTOLUENE IN SOLUTION-STATE

Dynamics of CH2Cl group in alpha,2,6-trichlorotoluene dissolved in CDC l3 was studied by observing various relaxation modes for C-13 under pr oton undecoupled condition. Partially relaxed C-13 spectra were obtain ed at 34-degrees-C as a function of evolution time after applying vari ous designed pulse sequences to this AX2 spin system. It was found tha t nonlinear regression analysis of the relaxation data for these magne tization modes could provide the information about dipolar and spin-ro tational auto-correlation and cross-correlation spectral densities for fluctuation of the C-13-H-1 internuclear vector inCH2Cl group. The re sults show that the effect of cross-correlation is comparable in magni tude to that of auto-correlation and the relaxation in this spin syste m is dominated by dipolar mechanism rather than spin-rotational one. F rom the resulting spectral density data we could calculate the bond an gle angle HCH (105.1-degrees) and elements of the rotational diffusion tensor for CH2Cl group.