Rotational Motion of a Solute Molecule in a Highly Viscous Liquid Studied by13C NMR: 1,3-Dibromoadamantane in Polymeric Chlorotrifluoroethene
✍ Scribed by S.F. Lienin; R. Brüschweiler; R.R. Ernst
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 199 KB
- Volume
- 131
- Category
- Article
- ISSN
- 1090-7807
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✦ Synopsis
The viscosity-dependent retarding effect of a polymeric solvent The rotational tumbling with the correlation time t c acts as on the rotation of small solute molecules is investigated by 13 C a multiplicative ''masking'' process of the intramolecular NMR relaxation measurements. It is found that the relaxation mobility with correlation time t i that is of primary interest. data of 1,3-dibromoadamantane in highly viscous polymeric chlo-As a result, t i can be determined with reasonable accuracy rotrifluoroethene can be explained neither by isotropic nor by realonly in the interval 0.1t c õ t i õ 10t c (8). This is a severe istic anisotropic tumbling in a single environment. The experimenpractical restriction in motional studies. tal data are rationalized in terms of fast exchange between at least It would be highly desirable to shift the ''observation wintwo environments with correlation times differing by up to two dow'' for t i by a change of t c . Within the framework of orders of magnitude. The study shows that a uniform retardation classical hydrodynamic theory, the rotational correlation time of molecular tumbling by a polymeric solvent, desirable for shifting for an interaction tensor of rank 2 in a spherical molecule obeys the NMR observation window in studies of intramolecular mobility, is not always feasible. ᭧ 1998 Academic Press the Stokes-Einstein-Debye (SED) relationship (1, 9)