Carbon-13 NMR spin-lattice relaxation in dithiarsolanes. Correlation between molecular motions and structural properties
✍ Scribed by D. W. Aksnes; T. A. Holak
- Publisher
- John Wiley and Sons
- Year
- 1981
- Tongue
- English
- Weight
- 426 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Abstract
^13^C NMR spin‐lattice relaxation times (T~1~) and nuclear Overhauser enhancements (η) were measured for dithiarsolanes. The contributions of dipolar (T) and spin‐rotation (T) mechanisms were determined. The T~1~ data were analysed to obtain information on the relative order of magnitude of the internal motion rates. The calculations were based on the isotropic, with internal rotation about the AsPh bond, model of reorientation. In cis, trans‐2‐phenyl‐4‐methyl‐1,3,2‐dithiarsolane, the internal rotation of the phenyl ring is c. three times faster than overall molecular reorientation. The internal motion of the arsolane ring is slightly slower than the phenyl ring rotation. The rotation of the methyl groups in the compounds appears to be considerably hindered, with rotation energy barriers of c. 10 kJ mol^−1^. In contrast to the situation in the 4‐methyldithiarsolane, the internal motion of the arsolane ring is twice as fast as the internal rotation of the phenyl ring for the methyl‐unsubstituted analogue, 2‐phenyl‐1,3,2‐dithiarsolane.