ISSN:
0749-1581
Keywords:
17O NMR
;
Substituted benzoquinones
;
α,β-Unsaturated cyclic ketones
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The 17O NMR chemical shift data for a series of substituted benzoquinones and α,β-unsaturated cyclic ketones in acetonitrile at 75°C are reported. In general, for the unsymmetrically substituted quinones two signals were observed, the assignments of which were made by 17O enrichment and exchange experiments. For the benzoquinones, the effect of α-methyl substitution (shielding) was greater on the signal for the 1-carbonyl group than on that for the 4-carbonyl group. α-tert-Butyl substitution resulted in deshielding of the proximate carbonyl group compared with that in the methyl analog. For the five- and six-membered ring enones the shielding effect of β-substituents was interpreted as electronic in origin. The large shielding effects observed for α-substitution in the quinone and enone systems appeared to be the result of a combination of electronic and attractive van der Waals effects.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260280405
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