Concerning lone-pair stereospecificity of intramolecular OH hydrogen bonds to oxygen and sulfur in solution
作者:
Ted Schaefer,
David M. McKinnon,
Rudy Sebastian,
James Peeling,
Glenn H. Penner,
Richard P. Veregin,
期刊:
Canadian Journal of Chemistry
(NRC Available online 1987)
卷期:
Volume 65,
issue 5
页码: 908-914
ISSN:0008-4042
年代: 1987
DOI:10.1139/v87-153
出版商: NRC Research Press
数据来源: NRC
摘要:
The1H nuclear magnetic resonance spectra for CCl4solutions are analyzed for 2-(thioethyl)phenol, 2,3-dimethoxyphenol, and 8-hydroxythiochroman. The chemical shifts of the hydroxyl protons in these compounds, in 2,3-dihydroxyanisole, and 2-hydroxybenzyl methyl ether are discussed in terms of stereospecific intramolecular OH hydrogen bonds to lone-pair electrons on oxygen and sulfur. The O—H … O hydrogen bonds can be adequately discussed in terms of equivalent lone pairs on oxygen. There is very little difference between the hydrogen bond energies for 2,3-dihydroxyanisole and 2,3-dimethoxyphenol. In the latter the central hydrogen bonded methoxy group lies nearly perpendicular to the ring plane. The O—H … S hydrogen bonds are best described in terms of nonequivalent, 3sand 3p, lone pairs on sulfur. It is estimated that an O—H … H 3shydrogen bond is at least 8 kJ/mol weaker than an O—H … 3phydrogen bond. The former is predominant in the thiochroman derivative and the latter in the thioethylphenol, in which the thioethyl group prefers a plane perpendicular to the benzene ring. The long-range benzylic coupling constants in the thiochroman derivative indicate inversion of the saturated ring between distorted half-chair conformations. The boat conformation can be ruled out.
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