Chemistry Reference
In-Depth Information
1465 : 1377 cm
1
. In ESBO and DiOH-SBO, the 1377 cm
1
peak is almost half
the intensity of the 1465 cm
1
peak, while in Ace-SBO, due to the addition of
methyls (-COCH
3
) in the structure, the peak at 1377 cm
1
(CH
3
bending
vibration) almost doubled compared to the one at 1465 cm
1
(CH
2
bending
vibration). Also, the intensities of peaks such as 1743 cm
1
(ester carbonyl)
and 1160 cm
1
(C-O stretching of esters) relative to the 2926 cm
1
peak
increased in Ace-SBO compared to ESBO and DiOH-SBO. This is due to an
increase in ester functionalities in the structure. A similar trend was ob-
served in the spectra of But-SBO, Isobut-SBO and Hex-SBO confirming the
formation of the final diester products.
11.3.2.2 NMR Characterization of Diester Products
Figure 11.2 shows the
1
H-NMR spectra of ESBO, DiOH-SBO, Ace-SBO, But-
SBO, Isobut-SBO and Hex-SBO in CDCl
3
, while their quantitative
1
H-NMR
spectral data is shown in Table 11.2. It can be seen that peaks at 2.8-3.0 ppm
due to epoxy groups are not present, except for in ESBO. The peaks at
3.0-3.2 ppm in DiOH-SBO due to the protons of the hydroxyl in the -CHOH
group are also not present in the diester products. The presence of additional
peaks at 1.85-2.18 ppm in the
1
H-NMR spectra, due to the methyl protons of
the -COCH
3
group, and the corresponding methyl carbons at 21-22.6 ppm
and carbonyl carbons at 171 ppm in the
13
C-NMR spectra confirms the
1
H-NMR data of ESBO and dihydroxy and diester derivatives of SBO.
(Reproduced from ref. 47 with kind permission from Springer Science
and Business Media from Springer and the AOCS Press.)
Table 11.2
NMR range/
ppm
DiOH-
SBO
Ace-
SBO
Isobut-
SBO
But-
SBO
Hex-
SBO
Assignment
ESBO
5.2-5.4
CH backbone
þ
CH-O-R
a
1
1
1.7
1.7
1.7
1.9
CH-O-R
a
4.8-5.1
—
—
1.9
1.8
1.8
2.1
4.08-4.3
CH
2
backbone
4
5.4
4
4
4
4
3.47-4.05
-CHOH dihydroxy
—
6.1
1.4
1.4
1.3
1.5
3.0-3.47
-CHOH dihydroxy
—
7.7
—
—
—
—
2.83-3.2
CH epoxy
8.6
—
—
—
—
0.4
2.5-2.8
CH isobutyric
—
0.8
—
3.3
0.4
2.23-2.5
CH
2
a to CO
6.2
7.5
6.1
6.3
13.5
14.1
1.83-2.2
CH
3
acetyl
—
1.4
11.7
1.1
1.6
3.1
1.16-1.9
CH
2
other
73.2
73.3
62.4
61.7
70.1
83.4
1.1-1.2
CH
3
isobutyric
—
—
— 21.8
—
—
0.95-1.1
CH
3
butyric
0.8
0.6
—
—
10.5
—
0.72-0.95
CH
3
8.8
9.1
8.5
8.7
8.1
18.6
N Epoxy rings
b
4.3
0
0
0
0
0.2
N Substituents
c
—
—
3.9
3.6
3.5
3.2
a
R
¼
acetyl and other branching groups.
b
Number of epoxy rings (CH epoxy protons/2).
c
Number of substituents on SBO estimated as: for acetyl, CH
3
protons (1.83-2.25 ppm)/3; for
isobutyric CH
3
protons (1.1-1.2 ppm)/6; for butyric CH
3
protons (0.95-1.1 ppm)/3; for hexanoic
[CH
3
protons (0.72-1.02 ppm)
9]/3.
