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Unusual conformational preferences of 1,3-dimethyl-3-isopropoxy-3-silapiperidine

  • The conformational analysis of the first representative of the Si-alkoxy substituted six-membered Si,N-heterocycles, 1,3-dimethyl-3-isopropoxy-3-silapiperidine, was performed by low-temperature 1H and 13C NMR spectroscopy and DFT theoretical calculations. In contrast to the expectations from the conformational energies of methyl and alkoxy substituents, the Meaxi-PrOeq conformer was found to predominate in the conformational equilibrium in the ratio Meaxi-PrOeq : Meeqi-PrOax of ca. 2 : 1 as from the 1H and 13C NMR study. The thermodynamic parameters obtained by the complete line shape analysis showed that the main contribution to the barrier to ring inversion originates from the entropy term of the free energy of activation.

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Metadaten
Author:Svetlana V. Kirpichenko, Bagrat A. Shainyan, Erich Kleinpeter
DOI:https://doi.org/10.1002/poc.3028
ISSN:0894-3230 (print)
Parent Title (English):Journal of physical organic chemistry
Publisher:Wiley-Blackwell
Place of publication:Hoboken
Document Type:Article
Language:English
Year of first Publication:2012
Year of Completion:2012
Release Date:2017/03/26
Tag:DFT theoretical calculations; barrier to ring inversion; conformational equilibrium; dynamic NMR; silapiperidines
Volume:25
Issue:12
Pagenumber:7
First Page:1321
Last Page:1327
Funder:Russian Foundation for Basic Research; Deutsche Forschungsgemeinschaft [11-03-91334]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Peer Review:Referiert