ISSN:
0030-4921
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The 13C NMR spectra have been determined of: (i) aliphatic compounds having at one end a functionalized sulphur atom (—SH, —S-, —SMe, —S(O)Me, —SO2Me and —S+Me2) and (ii) saturated sulphur heterocycles variously substituted at the S-atom . The results are discussed in terms of the familiar deshielding effects for α- and β-carbons and shielding effects for γ-carbons, exerted by the sulphur atom itself and/or by the atoms or groups of which the sulphur function is made up. The γ-effect of the S-atom appears to be nearly independent of the nature of the S-function and of comparable magnitude to that of an aliphatic carbon (-2·5 + -3·0 ppm). Surprisingly, however, a S—CH3 group shields the carbon in γ position with respect to CH3 by an amount (-5·4 ppm) which is more than twice that (-2·5 ppm) exerted by the aliphatic γ-carbon on the S-CH3 carbon itself. As to the cyclic compounds, the shieldings of the α- and β-carbons can be rationalized in terms of the conformational orientation of the substituent at sulphur, and the equilibrium distribution of the conformers. The results confirm the great value of 13C NMR for configurational and conformational assignment of S-heterocycles.
Additional Material:
5 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1270080209
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