S. Swarnalatha, G. Sekaran / Journal of Molecular Structure 840 (2007) 90–96
91
is rich in nitrogen and the end product ketene oligomer
does not contain any nitrogen group the detail study in
the structure of the end product is needed. In this paper,
we reported the structure in detail of the oligomer obtained
using glycine as the reactant.
The 2D-HETCOR NMR spectrum was recorded in
CDCl3 on JEOL ECA-500 MHz spectrometer. The 2D-
HETCOR NMR measurements were carried out at the
operating frequency of x is 125.765 MHz and the operating
frequency of y is 500.159; x-acquisition time, xat = 0.14 s;
y-acquisition time, yat = 0.13 s relaxation delay,
d1 = 1.5 s; T = 293 K.
The NMR spectroscopy studies have been used as the
most reliable technique to determine compositional and
stereo chemical structure of the polymers [14–17].
1
In this work, we report the complete H and 13C{1H}
2.3. ESI-MS measurements
NMR spectral assignments, ESI-mass spectrum and
ATR-IR spectrum of the ketene oligomers. The composi-
tions of the ketene oligomers as different structures were
determined from 13C{1H} NMR spectra and the sequence
distribution of the oligomer was done with the help of 2D
NMR spectroscopy. The 13C{1H} NMR and 1H NMR
spectra of the oligomer are quite complex and has been
assigned with the help of DEPT – 135 (distortionless
enhancement by polarization transfer) and 2D heteronucle-
ar (HETCOR) NMR spectroscopy. We have also con-
firmed the absence of nitrogen group in the product
through elemental analysis, 14N and 15N NMR hence the
reactant contains amino group (not reported).
The ESI (electron spray ionization) mass spectrum was
recorded on Micromass QuattroII triple quadrupole mass
spectrometer that was set in the positive ionization mode.
The sample was dissolved in methanol and introduced into
the ESI source through a syringe pump at the rate of 5 ll/
min. The ESI capillary was set at 3.5 kV and the cone volt-
age was 40 V. The source temperature was 120 °C and the
dessolvation temperature was 300 °C. The spectrum was
collected in 6 s scans.
2.4. ATR-FTIR measurements
The ATR-FTIR spectrum was recorded on Thermo
Nicolat – 320 spectrometer (AVATAR model) using the
ATR attachment at room temperature. Sample was placed
in a platinum liquid cell assembled in the ATR attachment.
The spectrum was taken with a resolution of 4 cmꢀ1 and
accumulation of 32 scans. The fourier self-deconvoluted
(FSD) IR spectrum was obtained with bandwidth of 15
and enhancement of 2.5 using EZ OMNIC 6.0 (Thermo
Nicolat) software.
2. Experimental
2.1. Preparation of ketene oligomers
Different weights of Glycine (E-merck, Germany) 25, 50,
75 and 100 mg were dissolved in 1 ml of water separately and
made up to 250 ml with methanol. The above mixture was
fed into the spiral packed bed reactor at the flow rate of
1.0 ml/min. The reactor was comprised of free electron rich
carbon (insoluble catalyst) of different weights such as 6,
12, 18 and 24 g, which was maintained at the temperature
of 10 °C (optimized). The solution collected at the outlet is
subjected to conventional separation such as solar evapora-
tion or vacuum distillation, whereby the alcohol escapes
leaving behind the ketene oligomer. The ketene oligomer
solution is optionally subjected to non-polar solvent
extraction.
3. Results and discussion
3.1. Preparation of ketene oligomers
The formation of ketene from glycine is shown in the
Eq. (1).
NH2ACH2ACOOH ! CH2@C@O þ NH2OH
ð1Þ
The possible pathway of occurrence of the above prod-
ucts through catalytically is discussed below. Because of
the hydrophilic nature of the free electron rich carbon,
when the glycine molecule tries to enter into the pores
of the catalyst it changes its orientation, due to the pres-
ence of the free electrons in the carbon (confirmed by the
EPR studies) it forms an isomer having the two center-
three electron interactions between NH2 and OH groups
as follows:
2.2. NMR measurements
The 1H, 13C{1H} and DEPT NMR spectrum of the ketene
oligomers was recorded in CDCl3 on Bruker AMX-
1
400 MHz spectrometer. The H NMR measurements were
carried out at the operating frequency of 400.134 MHz; spec-
tral width, sw = 7246.381 Hz; acquisition time, at = 1.13 s;
relaxation delay, d1 = 1.0 s; T = 300 K and TMS as the
internal standard. 13C NMR spectrum was recorded at the
operating frequency of 100.614 MHz; spectral width,
sw = 25,000 Hz; acquisition time, at = 0.33 s; relaxation
delay, d1 = 3.0 s; T = 300 K and TMS as the internal stan-
dard. DEPT spectrum was recorded at the operating fre-
quency of 100.614 MHz; spectral width, sw = 26315.789
Hz; acquisition time, at = 0.35 s; relaxation delay,
d1 = 3.0 s; T = 300 K and TMS as the internal standard.
H
H
O
N
H
H
H
O