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| Vinyl acetate |
.pdf+-+SumatraPDF_2012-12-13_01-29-31.png) |
| Methyl benzoate |
.pdf+-+SumatraPDF_2012-12-13_01-29-11.png) |
| Methyl methacrylate |
.pdf+-+SumatraPDF_2012-12-13_01-29-38.png) |
| Methyl salicylate |
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| Ethly butyrate |
The C=O of an ester appears near 1750-1735 which can overlap with some ketone C=O stretches. One can usually eliminate ketones by considering the strong and broad C-O peak at 1300-1000. A ketones absorptions will have a weaker and narrower bands. Compare the ethyl butyrate ester above to the ketone below:
Esters can also conjugate on the side of the single-bonded oxygen:
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Apparently this form of conjugation interferes with resonance of the carbonyl group, hence increasing the arbsorption frequency of the C=O bond.
α-keto esters: One might expect two C=O peaks due to the two different carbonyls. In practice, it usually manifests as a shoulder on the main C=O peak or a single broadened band.
β-keto esters: These give a strong intensity doublet for the C=O stretches. Since they do not tautomerize to the same extent as β-diketones, one cannot generally observe the OH stretch from the enol form.
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