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

초록

Dynamics of CH2Cl group in alpha,2,6-trichlorotoluene dissolved in CDCl3 was studied by observing various relaxation modes for C-13 under proton undecoupled condition. Partially relaxed C-13 spectra were obtained at 34-degrees-C as a function of evolution time after applying various designed pulse sequences to this AX2 spin system. It was found that nonlinear regression analysis of the relaxation data for these magnetization modes could provide the information about dipolar and spin-rotational auto-correlation and cross-correlation spectral densities for fluctuation of the C-13-H-1 internuclear vector inCH2Cl group. The results show that the effect of cross-correlation is comparable in magnitude to that of auto-correlation and the relaxation in this spin system is dominated by dipolar mechanism rather than spin-rotational one. From the resulting spectral density data we could calculate the bond angle angle HCH (105.1-degrees) and elements of the rotational diffusion tensor for CH2Cl group.

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