Transcript ppt

15.14 Spectroscoic Analysis of Alcohols and Thiols:
Infrared (IR): Characteristic O–H stretching absorption at
3300 to 3600 cm 1
Sharp absorption near 3600 cm-1 except if H-bonded:
then broad absorption 3300 to 3400 cm 1 range
Strong C–O stretching absorption near 1050 cm 1
%T
O
H
O-H
C-O
74
cm-1
1H
NMR: protons attached to the carbon bearing the hydroxyl
group are deshielded by the electron-withdrawing nature
of the oxygen,  3.3 to 4.7
H3C
H3C C
H
H H
C C OH
H H
= 3.65,
t, 2H
= 1.5,
q, 2H
= 0.9,
d, 3H
= 1.7,
= 2.25, m, 1H
br s, 1H
61.2
22.6
41.7 24.7
CDCl3
O-H
C-O
75
Usually no spin-spin coupling between the O–H proton and
neighboring protons on carbon due to exchange reaction
H A
C O H
C O H
H
H
+
H A
The chemical shift of the -OH proton occurs over a large
range (2.0 - 5.5 ppm). It chemical shift is dependent
upon the sample concentration and temperature. This
proton is often observed as a broad singlet (br s).
Exchangable protons are often not to be observed at all.
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13C
NMR: The oxygen of an alcohol will deshield the carbon
it is attached to. The chemical shift range is 50-80 ppm
 14
 19
 35
 62
CH3 — CH2 — CH2 — CH2 — OH
HO
OH
H
OH
145.2
H
H C C C H
H H H
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15.48 (fig 15.8, p. 658)
13C:
13C:
138.6
129.4
128.4
126.3
68.8
45.8
22.7
145.2
128.8
127.8
126.5
76.3
32.3
10.6
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