Capon, B., Rycroft, D. S., Watson, T. W. and Zucco, C. (1981) Simple enols. 1.1 The generation of vinyl alcohol in solution and its detection and characterization by NMR spectroscopy. Journal of the American Chemical Society, 103(7), pp. 1761-1765. (doi: 10.1021/ja00397a029)
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Abstract
Vinyl alcohol has been generated by hydrolysis of methoxy(vinyloxy)methyl chloroacetate and acetate (1 and 3), bis(vinyloxy)methyl dichloroacetate and trichloroacetate (7 and 6), dimethyl vinyl orthoformate (4), dimethyl vinyl orthoacetate (5), and ketene methyl vinyl acetal (8) in aqueous [2H3]acetonitrile or aqueous [2H7]dimethylformamide. It was characterized by 1H and 13C NMR spectroscopy and by conversion into acetaldehyde. On replacement of OH by OD the 13C NMR spectrum shows isotope shifts of −0.12 and −0.09 ppm for the α- and β-carbons under conditions where no such shifts were detectable for the corresponding carbons of ethyl vinyl ether. Vinyl alcohol with an OH group was generated under conditions of slow hydroxyl-proton exchange with 8 as the precursor in CD3COCD3 (99 v %)/H2O (1 v %) at −10 °C and the following coupling constants were evaluated: 3Jtrans = +14.0, 3Jcis = +6.3, 2Jgem = −0.8, 3J(HOCαH) = +9.8, 4J(HOCβHanti) = +0.4, |4J(HOCβHsyn)| < 0.2 Hz. Under the conditions used vinyl alcohol was converted into acetaldehyde ca 100 times faster than ethyl vinyl ether but could nevertheless be kept in solution for several hours below ca −10 °C. The postulated intermediate, methyl vinyl hemiorthoformate, could not be detected in the hydrolysis of 1, 3, and 4 nor could methyl vinyl hemiorthoacetate be detected in the hydrolysis of 5 and 8. However divinyl hemiorthoformate was easily detected in the hydrolysis of 6 and 7. It was concluded that this resulted from the weaker "push" of the vinyloxy group which remained attached to the pro-acyl carbon atom compared to a methoxyl group.
| Item Type: | Articles |
|---|---|
| Keywords: | NMR spectroscopy. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Rycroft, Dr David |
| Authors: | Capon, B., Rycroft, D. S., Watson, T. W., and Zucco, C. |
| Subjects: | Q Science > QD Chemistry |
| College/School: | College of Science and Engineering > School of Chemistry |
| Journal Name: | Journal of the American Chemical Society |
| Publisher: | American Chemical Society |
| ISSN: | 0002-7863 |
| ISSN (Online): | 1520-5126 |
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