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Chapter 20: Carboxylic
Acid Derivatives |
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Spectroscopic Analysis
of Esters
- IR - presence of
C=O, and two C-O bands (Csp2-O and Csp3-O bonds)
Absorbance (cm-1)
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Interpretation
|
1735
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C=O stretch
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1300-1000
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two bands for C-O stretch
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- 1H
NMR - deshielded proton of H-C-O is often recognisable, and H-C-C=O.
Resonance (ppm)
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Interpretation
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3.5-4.5
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H-COC
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2-2.5
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H-C-C=O
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- 13C
NMR
C=O typically 160-180 ppm (deshielding due to O)
- minimal intensity, characteristic
of C's with no attached H's
- UV-VIS
two absorption maxima π→ π* (<200 nm) n→ π*
(~207 nm)
- π electron from π of
C=O
- n electron from O lone
pair
- π* antibonding
C=O