Chapter 20: Carboxylic Acid Derivatives
Spectroscopic analyzis of Esters
IR -
presence of C=O, and two C-O bands (Csp
2
-O and Csp
3
-O bonds)
Absorbance (cm
-1
)
Interpretation
1735
C=O stretch
1300-1000
two bands for C-O stretch
1
H NMR
- deshielded proton of
H
-C-O is often recognisable, and
H
-C-C=O.
Resonance (ppm)
Interpretation
3.5-4.5
H
-COC
2-2.5
H
-C-C=O
13
C 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
p®p
*
(<200
nm) n
®p
*
(~207 nm)
p
electron from
p
of C=O
n
electron from O lone pair
p
*
antibonding C=O
Mass Spectrometry
Prominent peak corresponds to formation of acyl cations (acylium ions)
