ISSN:
1434-193X
Keywords:
Conformation analysis
;
NMR spectroscopy
;
MM calculations
;
NMR spectroscopy
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
---A dynamic process has been detected in the solution 13C-NMR spectra oftBu-Si(iPr)3 (4) in the temperature range -145 °C to -163 °C, the corresponding free energy of activation being 5.5 kcal mol-1. Molecular mechanics calculations have identified three types of conformations that are markedly more stable than all the others, but the one with the highest symmetry cannot be populated, as is evident from the appearance of the spectrum at low temperature. This spectrum can be interpreted in terms of restricted rotation of the tert-butyl group and of the isopropyl groups, leading to a structure centered around the (a,g,-g) conformation. In the case of the analogous (iPr)3SiCl derivative (5), this dynamic process was not observed in solution, but an appropriate spectrum for the same (a,g,-g) conformation was obtained by the solid-state CP-MAS NMR spectroscopy at -100 °C.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
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