Heterogeneous catalytic solvent-free synthesis of 3,3,5-trimethyl cyclohexyl anthranilic acid esters via transesterification

Article abstract of DOI:10.1007/s11696-016-0061-z

The transesterification of anthranilates with both mixtures of cis and trans and pure trans 3,3,5-trimethyl cyclohexanol was studied using 'calcium-oxide- and magnesium-oxide'-based catalysts under 'solvent-free' conditions. The catalysts were characteriz

Full text of DOI:10.1007/s11696-016-0061-z

Chem. Pap.
DOI 10.1007/s11696-016-0061-z
ORIGINAL PAPER
Heterogeneous catalytic solvent-free synthesis of 3,3,5-trimethyl
cyclohexyl anthranilic acid esters via transesterification
Chittaranjan S. Thatte1 Manapragada V. Rathnam1 Ashutosh Namdeo2
Kiran Rane1
•
•
•
Received: 12 June 2016 / Accepted: 5 October 2016
Ó Institute of Chemistry, Slovak Academy of Sciences 2016
Abstract The transesterification of anthranilates with both
mixtures of cis and trans and pure trans 3,3,5-trimethyl
cyclohexanol was studied using ‘calcium-oxide- and
magnesium-oxide’-based catalysts under ‘solvent-free’
conditions. The catalysts were characterized by XRD, CO2-
TPD, BET-surface area, and FEG–SEM analysis. Pure
calcium oxide was found to be the most effective hetero-
geneous catalyst. Pure ‘calcium-oxide’-based catalyst was
recycled five times without appreciable loss in the catalytic
activity. The TOF after five recycles was 10.7 mol/mol of
catalyst/h. The study was further extended for the synthesis
of new anthranilates. The synthesized pure esters have been
Introduction
Transesterification is one of the classic organic reactions
that have enjoyed numerous laboratory uses and indus-
trial applications. The ester-to-ester transformation is
particularly useful when the parent carboxylic acids are
labile and difficult to isolate. Transesterification with
heterogeneous catalyst serves as green and useful means
to synthesize higher homologues of esters. Metal alkox-
ides (Taft et al. 1950; Billman et al. 1947; Haken 1966;
Frank et al. 1944; Wulfman et al. 1972; Rossi and de
Rossi 1974), aluminum isopropoxide (Rehberg and Fisher
1947; Brenner and Huber 1953), tetraalkoxytitanium
compounds (Seebach et al. 1982; Imwinkelried et al.
1987; Blandy et al. 1991), and organotin alkoxides
(Otera et al. 1986) are applied as catalysts for transes-
terification reactions. Heterogeneous catalysts, such as
alkylguanidines (Sercheli et al. 1999), attached to mod-
ified polystyrene or siliceous MCM-41, Na/NaOH/-Al2O3
(Kim et al. 2004), tin complex [Sn(3-hydroxy-2-methyl-
4-pyrone)2(H2O2)] (Abreu et al. 2005) ZrO2, ZnO,
SO42-/SnO2, SO42-/ZrO2, KNO3/KL zeolite and KNO3/
ZrO2 (Jitputti et al. 2006), potassium loaded on alumina
(Xie et al. 2006), potassium loaded on a mesoporous
MSU-type alumina, KF, LiF and CsF (Verziu et al.
2009), and KF/ZnO (Hameed et al. 2009). Heteropoly-
acid (Cs2.5H0.5PW12O40) (Zhang et al. 2010), Cs-ex-
changed NaX faujasites, a commercial hydrotalcite,
magnesium oxide, and barium hydroxide (Leclercq et al.
2001) have been used.
1
characterized by UV–Vis, IR-, H NMR-, and 13C NMR
spectroscopies and mass spectrometry.
Keywords Transesterification Á Methyl anthranilate Á
Trimethyl cyclohexanol Á Calcium oxide Á Mixed
magnesium–calcium oxide
Electronic supplementary material The online version of this
article (doi:10.1007/s11696-016-0061-z) contains supplementary
material, which is available to authorized users.
& Manapragada V. Rathnam
mvrathnam58@rediffmail.com
Chittaranjan S. Thatte
chittthatte@gmail.com
Ashutosh Namdeo
ashutoshnamdeo83@gmail.com
Kiran Rane
kiranrane8@gmail.com
Among the heterogeneous catalysts used, generally,
calcium oxide (CaO) is a candidate for the solid base cat-
alyst from an economical point of view and it has been
used as a catalyst on several occasions (Kouzu and Hidaka
2012; Boeya et al. 2011). In this work, we have used co-
1
Chemistry Research Laboratory, B. N. Bandodkar College of
Science, Chendani Bunder Road, Thane 400601, India
2
Chemical Engineering Division, CSIR-North East Institute of
Science and Technology, Jorhat, Assam 785006, India
123

Chem. Pap.
precipitated calcium oxide and calcium oxide–magnesium-
oxide-type mixed catalyst.
higher flow rate 50 ml/min to ensure that the exposed
catalyst surface is free from the moisture if any.
3,3,5-Trimethyl cyclohexanol (3,3,5-TMCH) finds
application in the preparation of perfumes. However, its
major application is in preparation of various derivatives,
such as acetates and salicylate for cosmetic applications
(Gambaro et al. 2006). The salicylic acid ester of 3,3,5-
TMCH has been reported for sunscreen properties. The
esterification of salicylic or anthranilic acid ester has been
attempted. However, there are no reports of the transes-
terification methodology involving the use of 3,3,5-TMCH
and anthranilic acid ester. It was, therefore, of interest to
study the transesterification reaction of 3,3,5-TMCH and
anthranilic acid esters using various acidic and basic cat-
alysts. The transesterification was eventually extended for
the synthesis of novel potential sunscreens using calcium
oxide as a solid base heterogeneous catalyst, which has not
been reported in the literature.
After the pretreatment sample was saturated with the
CO2 pulses followed by the TPD performed up to 800 °C
under helium flow (20 ml min-1). All areas of sub-peaks
were summed to calculate the total amount of base sites. 1H
NMR and 13C NMR of the pure compounds were deter-
mined using VARIAN 300 MHz USA. Elemental analysis
was performed using Flash EA-1112 Series instrument.
BET-surface area was determined using Tristar 3000 V
6.05 A using nitrogen adsorption.
Catalyst preparation
In the present work, three types of catalysts were prepared.
Catalyst-a is the calcium-oxide-based catalysts prepared
using literature methods (Kontoyannis and Vagenas 2000;
Galmarini et al. 2011) by co-precipitation of calcium
nitrate with sodium carbonate, whereas catalyst-b and
catalyst-c are mixed calcium-oxide–magnesium-oxide-
based catalysts.
Experiment
Materials
Method for the preparation of catalyst-a
All the reagents used for the preparation of catalysts and
for the synthesis and analysis of catalytic activity were pure
and procured from E Merck., Aldrich, and SD fine chem-
icals. Commercially available grades of mix (cis ? trans
ratio 85:15) 3,3,5-trimethylcyclohexanol and pure trans-
3,3,5-trimethylcyclohexanol (99% pure) were procured
from SI-Group (I) Ltd (will be termed in this paper
henceforth as mix TMCH and pure trans TMCH,
respectively).
In a typical procedure for the preparation of catalyst-a,
34.74 g (0.21 mol) of calcium nitrate was dissolved in
50 ml of distilled water, and the solution was heated to
100 °C under efficient stirring. A solution of sodium car-
bonate 23 g (0.21 mol) in 50 ml of distilled water was
added to this solution within 20 min. The mixture was
cooled after complete precipitation of calcium carbonate. It
was filtered, dried for 3 h at 120 °C, and calcined at 950 °C
for 5 h. Theoretical wt% (CaO 100%).
Techniques
Method for the preparation of catalyst-b
Gas chromatograph (Agilent 6890) with FID and Varian
CP 8934 capillary column (10 m length, 100 lm diameter,
and 0.40 lm film thickness) was used to establish the
separation of geometrical isomers with GC parameters,
such as oven, 100–45 °C/min–280 °C—2 min hold, inlet,
250 °C, detector 300°, split ratio 1:500, and sample
injection 0.2 ll.
The XRD analysis of the catalysts was performed using
X’pert Pro (from P analytical) at a wavelength of
260–850 nm. The FT-IR characterization was performed
using Vertex 80 FT-IR System. Temperature-programmed
desorption (TPDRO 1100, Thermo Scientific) of carbon
dioxide (CO2-TPD) was used to determine the base prop-
erties of catalysts. Before the analysis, samples were pre-
treated. In a typical pretreatment procedure, the gas line
was first cleaned by inert gas (Argon), and then, the sample
was exposed to Argon at higher temperature (800 °C) with
For the preparation of catalyst-b, solution containing
23.43 g (0.14 mol) of calcium nitrate in 25 ml of dis-
tilled water and magnesium nitrate 21.07 g (0.14 mol)
dissolved in 25 ml of distilled water was heated to
100 °C under efficient stirring. A solution of sodium
carbonate 30.19 g (0.28 mol) dissolved in 100 ml of
distilled water was added to this solution within 20 min.
The mixture was cooled after complete precipitation of
mixed calcium carbonate–magnesium carbonate. The
precipitate was filtered, dried for 3 h at 120 °C, and
calcined at 950 °C for 5 h. Theoretical wt% of mixed
CaO (58.2):MgO (41.8).
Method for the preparation of catalyst-c
For the preparation of catalysts-c, solution containing
32.82 g (0.20 mol) of calcium nitrate dissolved in 35 ml
123

Chem. Pap.
of distilled water and magnesium nitrate 11.69 g
(0.079 mol) dissolved in 15 ml of distilled water was
heated to 100 °C under efficient stirring. A solution of
sodium carbonate 30.19 g (0.28 mol) dissolved in 100 ml
of distilled water was added to this solution within
20 min. The mixture was cooled after complete precipi-
tation of mixed calcium carbonate–magnesium carbonate.
The precipitate was filtered, dried for 3 h at 120 °C, and
calcined at 950 °C for 5 h. Theoretical wt. % of mixed
CaO (77.85): MgO (22.15).
Results and discussion
Characterization of catalysts
The prepared catalysts were characterized by powder XRD,
elemental analysis, FEG-SEM analysis, and CO2-TPD.
XRD Analysis: From the XRD patterns shown in Fig. 2, it
can be observed that the catalyst-a showed typical diffraction
peaks due to 100% CaO at 2h = 32.40°, 2h = 37.66°,
2h = 54.15°, 2h = 64.41°, and 2h = 67.66°. These diffrac-
tion peaks of CaO are similar to previously published results
(Watcharathamrongkul et al. 2010). The catalyst-b showed
extra peak due to MgO (He et al. 2010) at 2h = 43.23° and
2h = 62.49° in addition to the peaks due to CaO. The cata-
lyst-c also showed the extra peak due to MgO at 2h = 43.04°
and 2h = 62.43°, but in the case of catalyst-c, the peak was
less intense, indicating a subsequent reduction in the com-
position of MgO (22.15 wt%) compared with the catalyst-b
(41.8 wt%). Diffraction peak at 2h = 35° was due to the
formation of calcium hydroxide after moisture absorption,
which followed the order of intensity b [ a.
Catalytic tests
Reaction procedure
The transesterification reaction, as shown in Fig. 1, was
carried out in a 100 ml R.B. flask with a stirrer, con-
denser, thermometer pocket, and dean and stark separator.
Initially, mix TMCH was mixed with catalyst under
stirring with a rate of 600 rpm. The mixture was heated to
190 °C when methyl anthranilate was added for the per-
iod of 20 min. After complete methanol liberation (typi-
cally 1 h), the contents were cooled and the reaction
sample was analyzed by gas chromatography. The con-
version and selectivity for each prepared catalyst were
studied. The catalyst was recycled five times after wash-
ing with acetone, drying at 100 °C, and calcinations at
750 °C.
FT-IR spectra of the catalysts
FT-IR spectra of catalysts were recorded to examine the
influence of change in calcium oxide composition, as
shown in Fig. 3. The background spectrum was recorded at
ambient temperature and was compensated during the
a=
-tr met c c o ex
-m no enzoate
s +trans
Ci
III
III
III
III
III
III
5
2
3 3
, ,
i
h l l h
l
l
i
b
y y
y
(
)
=
-tr met c c o ex
h l l h
-am no enzoate trans+c s
b
i i
( )
3 3
5
i
2
b
, ,
y y
y
c=
3 3
-tr met c c o ex
- met am no enzoate c s +trans
5
2
i
i
h l l h
l
l
h l
y
i
b
b
i
, ,
y y
y
y
(
(
)
(
(
)
=
-tr met c c o ex
h l l h
- met am no enzoate trans+c s
h l
3 3
5
2
i
i
d
, ,
y y
y
)
)
e=
-tr met c c o ex
-am no- -c oro enzoate c s+trans
5
b
i i
(
3 3
5
5
i
h l l h
l
l
2
2
hl
-am no- -c oro enzoate trans+c s
, ,
, ,
y y
y
y
)
)
=
f 3 3
-tr met c c o ex
h l l h
5
i
i
hl
b
i
y y
(
Ia = Methyl anthranilate, Ib = Methyl N-methylanthranilate, IC = 5-chloro methyl anthranilate, IIa = 3,3,5-trimethyl
cyclohexanol (cis +trans), IIb = 3,3,5-trimethyl cyclohexanol (trans)
Fig. 1 Synthesis of 3,3,5-trimethyl cyclohexyl anthranilic acid esters by transesterification
123

Chem. Pap.
absorption of water compared to the catalyst with less
concentration of MgO (catalysts a and c). The intensity of
absorption bands due to water was in the order b [ a [ c.
CO2-TPD of catalysts
The alkalinity (basic nature) of the catalysts was measured
using CO2-TPD technique. The CO2-TPD profiles of cat-
alysts are shown in Fig. 4. The catalysts were subjected to
the test under the conditions mentioned in the experimental
section. The amounts of base sites in the catalysts, as
summarized in Table 1, are calculated from the area below
the curve of TPD profiles. The characteristic peaks of these
TPD profiles are assigned to their desorption temperatures
indicating the strength of base sites. From CO2-TPD pro-
files (Fig. 4), the CO2 desorption peaks appear in all pro-
files at high temperature (C650 °C) suggesting that the
catalysts have strong base sites (see Fig. 4).
In all cases except catalyst-b, single desorption peak was
observed. In case of the catalyst-b, two desorption peaks
were observed (643 and 800 °C). However, for catalyst-b,
643 °C is the major and contributing peak as it represents
73.6% of the peak area (Fig. 4). The order of base sites of
the catalysts after calculations is a [ c [ b. The basicity
increased with the increase in the amount of calcium oxide;
hence, the order of basicity was found to be 100%
CaO [ CaO:MgO,(77.85:22.15) [ CaO:MgO,(58.2:41.8).
Fig. 2 XRD analysis of catalysts: a–c
FEG–SEM analysis of catalysts
FEG–SEM were carried out to see the morphology of the
catalysts. Catalysts b (Fig. 6) and c (Fig. 7) are mixed
MgO/CaO catalysts, which showed finer particle size
compared to catalyst-a (Fig. 5), which is a pure calcium
oxide catalyst.
Fig. 3 FT-IR spectra of catalysts a, b, and c
sample run under atmospheric condition. The spectra were
recorded without any pretreatment of the prepared catalyst.
Catalysts a, b, and c showed bands at 1413, 1437, 1429,
870.75, 876.27, and 870.84 cm-1 which can be attributed
to absorb CO2 and bands at 3639, 3642, and 3642 cm-1 are
due to absorbed water in the calcium oxide and calcium
oxide–magnesium oxide samples (Dan et al. 2001). The
difference in the intensity of absorption bands due to
absorption of carbon dioxide (see Fig. 3); in case of cata-
lysts a, b, and c at 1480, 1474, and 1472 cm-1. The
intensity of absorbance follows the order catalyst-
b [ catalyst-a [ catalyst-c. The catalyst with high con-
centration of magnesium oxide, i.e., catalyst-b, is quite
sensitive towards the atmospheric absorption of carbon
dioxide than catalysts a and c. We also found a difference
in the intensity of absorbed moisture in the catalysts.
Catalyst-b has more intensity of the band at 3642 cm-1
compared to that of catalysts a and c. Therefore, it can be
inferred that catalyst with higher concentration of MgO
(catalyst-b) will show more tendency towards the
A number of heterogeneous and homogeneous catalysts,
such as potassium carbonate, sodium carbonate, barium
hydroxide, hydrotalcite, calcium oxide, magnesium oxide,
zinc oxide, aluminum oxide, sodium methoxide, potassium
tertiary butoxide, and sodium hydroxide, were initially
screened for the transesterification. Sodium methoxide,
potassium carbonate, and calcium oxide were found to be
active. Owing to the reusability limitation of first two
catalysts, calcium oxide was found to be the most effective
and advantageous heterogeneous catalyst for the transes-
terification. Hence, the reaction was only studied using
calcium-oxide-based catalyst. Table 2 shows the conver-
sion and selectivity data. The selectivity values for the
product have been expressed independently as values of cis
and trans isomers. It was observed that the reaction is much
faster when homogeneous alcoholic sodium hydroxide was
used (Entry 7); however, the product selectivity remained
the same as compared with the reaction with heterogeneous
123

Chem. Pap.
Fig. 4 CO2-TPD of catalysts a, b, and c (? represent that a peak observed at the very beginning of the holding temperature 800 °C during the
TPD analysis)
IIa) under otherwise the same reaction conditions (Entry
12, 14, 16). When mix alcohol (IIa) is used in combination
with the electron donating substituent on the ester tend to
decrease the conversion (Entry 13), whereas electron
withdrawing group on the ester has a positive effect on the
conversion (Entry 15). In all the cases, some (cis) product
formations were also observed when the reaction was
conducted with pure trans 3,3,5-TMCH (IIb). Catalyst-a
was recycled five times without a significant loss in cat-
alytic activity. Each time the catalyst was washed with
acetone, oven dried at 100 °C, and calcined at 750 °C and
then reused. This has been represented graphically in terms
of TOF in Fig. 8.
Table 1 BET-surface area and base sites of catalysts
Catalysts
BET-surface area (m2/g)
Base sites (lmole/g)
a
b
c
2.619
12.91
5.742
534.44
104.85
485.71
Effect of molar ratio of alcohol to ester
on conversion and selectivity
The effect of molar ratio of alcohol to ester on transester-
ification using catalyst-a has been presented graphically in
Fig. 9. The molar ratio was studied at four points 2,3,4,5
using Ia and IIa. During this study, the temperature, cata-
lyst loading, and other parameters, such as stirring rate,
were kept constant. At a higher mole ratio 5, the conversion
was the highest (99.2) and the selectivity was the lowest
(97.6). In lower mole ratio 2, the conversion was (95.7) and
Fig. 5 FEG–SEM image of catalyst-a
calcium oxide (Entry 9). It is observed from the reaction
data that pure trans 3,3,5-TMCH (Fig. 1, IIb) has less
reactivity compared with the mixed 3,3,5-TMCH (Fig. 1,
123

Chem. Pap.
Table 2 Conversion and selectivity of different 3,3,5-trimethyl cyclohexyl anthranilates
Entry
Ester used
Alcohol used
Catalyst used
Time (min)
% Conversion
% Product selectivity
% Yield (i)
cis
trans
1
Ia
Ia
Ia
Ia
Ia
Ia
Ia
Ia
Ia
Ia
Ia
Ia
Ib
Ib
Ic
Ic
IIa
IIa
IIa
IIa
IIa
IIa
IIa
IIa
IIa
IIa
IIa
IIb
IIa
IIb
IIa
IIb
No catalyst
Na2CO§3
K2CO§3
NaOMe§
MgO§
KOBu-t§
NaOH*,¥
KOH*,¥
a¥
b¥
c¥
a¥
a¥
60
600
120
600
600
180
20
No reaction
30.7
98.6
94.5
94.2
46.0
98
–
–
2
82.6
88.0
90.3
91.0
90.6
92.0
88.9
91.8
91.9
91.4
12.1
91.4
15.9
92.9
8.97
5.5
10.0
7.0
8.0
9.3
6.2
8.9
6.3
5.7
6.7
84.9
5.3
80.0
6.4
86.83
–
3
–
4
–
5
–
6
–
7
74.2
–
8
60
72.1
95.8
79.6
91.6
73.1
86.6
82.5
89.2
55.1
9
60
72.0
–
10
11
12
13
14
15
16
60
60
–
120
120
540
120
240
63.5
80.2
74.5
79.2
42.3
a¥
a¥
a¥
Reaction conditions: mole ratio of alcohol/ester = 2
% Conversion = [(% of ester consumed)/(% of ester taken)] 9 100
% Selectivity = [(% of product)/(100 - sum of % of reactants)] 9 100
(i) = isolated yield
¥
Catalyst concentration g/total mole of reactants = 2.9, temperature = 190 °C
* Alcoholic solution
§
Catalyst concentration used, g/total mole of reactants = 5.8
Fig. 6 FEG–SEM image of catalyst-b
Fig. 7 FEG–SEM image of catalyst-c
selectivity was (98.1). It can be concluded from the study
that the higher molar ratio improves the conversion but
marginally reduces the selectivity.
reactants (Fig. 10), maintaining the rest of the reaction
conditions, such as temperature, mole ratio, and rate of
stirring constant. We observed that the conversion
increased when the catalyst amount was increased from
1.7, 2.2, 2.6, and 2.9 g/total mole of reactants (Fig. 10). At
2.9 g/total moles, reactants loading the conversion are the
highest (98.4); however, the selectivity values observed to
Effect of catalyst loading on conversion
and selectivity
Effect of catalyst loading was studied at four different
loadings, such as 1.7, 2.2, 2.6, and 2.9 g/total moles of
123

Chem. Pap.
Fig. 10 Effect of catalyst loading on % conversion and % selectivity
of product. Reaction conditions: mole ratio = 2, temperature 190 °C,
time = 1 h
Table 3 Effect of temperature on % conversion
Temperature
% Conversion
Fig. 8 TOF of during five recycles, TOF after five recycles = 10.7
150
160
170
180
190
4
6
9
30
95.7
Reaction conditions: mole ratio = 2, catalyst load = 2.9 g/total,
moles of reactants, time = 1 h
Following Tables 4 and 5 show characterization data of
compounds IIIa and IIIb
Mechanism of transesterification
Fig. 9 Effect of mole ratio on % conversion and % selectivity of
product. Reaction conditions: catalyst concentration g/total moles of
reactants = 2.9, temperature 190 °C, time = 1 h
The mechanism of transesterification with 3,3,5-TMCH
and methyl anthranilate using solid basic calcium oxide
catalyst at higher temperature is quite comparable to the
mechanism of transesterification of oil using calcium oxide
as a catalyst (Kouzu and Hidaka 2012). It involves
abstraction of proton from alcohol by the basic sites to
form cyclohexoxy anion, which is the first step of the
reaction. The cyclohexoxy anion attacks carbonyl carbon in
a molecule of the methyl anthranilate, leading to the for-
mation of the cyclohexoxy carbonyl intermediate. Then,
the cyclohexoxy carbonyl intermediate divides into two
molecules, the product and the methoxy anion. Figure 11
illustrates a mechanism on the catalyzed transesterification
using calcium oxide as a solid base. Although the BET-
surface area of the magnesium-oxide-based prepared cat-
alysts b and c is high compared with the pure calcium-
oxide-based catalyst, it can be emphasized on the basis of
the conversion data using all three catalysts that the
nucleophilic reaction was accelerated by an enhancement
of the basic properties.
be marginally high (97.7). At lower catalyst loading
(1.7 g/total moles of reactants), the conversion was found
to be (96.51) and the selectivity was found to be (97.6). It
can be inferred that, as the catalyst loading is increased,
there is rise in conversion but marginal increase in selec-
tivity. From Fig. 10, it seems that there is a liner increase in
the conversion up to catalysts loading 2.6 g/total moles of
reactants, and furthermore, it is deviated from the linearity.
Therefore, from this experiment, we found 2.6 g/total
moles of reactants as an optimum catalyst loading for the
reaction.
Effect of temperature on conversion and selectivity
Effect of temperature was studied at five different tem-
peratures. Table 3 shows the conversion obtained at the
corresponding temperatures. As a result, 190 °C was cho-
sen as a final reaction temperature.
123

Chem. Pap.
Fig. 11 Mechanism of
transesterification
Table 4 Characterization of compounds
Compound
Formula
Mr
wi (calc.)/%
wi (found)/%
C
Yield (%)
M.p/B.p. (°C)
H
N
IIIa
IIIb
C16H23NO2
261.36
261.36
73.63
73.60
73.63
73.61
8.87
8.85
8.87
8.84
5.36
5.35
5.36
5.33
72.03
63.53
60.1/189
10 mb Hg
196
C
16H23NO2
18 mb Hg
Table 5 Spectral data of compounds
Compound Spectral data
IIIa
U.V, /nm: 253 (benzenoid form), 322, 356 (fine structure band)
ƛ
IR, m/cm-1: 1247 (CN), 1469 (aromatic), 1596 (NH bend primary amine), 1668(C=O), 2943 (CH stretch alkyl), 3370 (NH stretch),
3483(aromatic primary amine)
~
1H NMR (CDCl3), d: 0.781–0.893(m, 1H, a), 0.913–0.935(m, 3H, b), 0.967–0.985 (m, 6H, c, d), 0.999–1.2 (m, 1H, e), 1.18–1.3(m,
1H, f), 1.34–1.39,(m, J 3.29, 1H, g) 1.7–1.82(m, 2H, h, i), 2.09(m, 1H, j), 5.1(dddd, J1 4.44, J2 9.0, J3 11.70, J4 16.2, 1H, k), 5.6
(s,2H, l) D2O exchangeable, 6.582–6.605 (dd, J1 1.50, J2 5.55 1H, m), 6.61–6.65 (m, 1H, n), 7.18–7.254(m, 1H, o),
7.823–7.870(dd, J1 1.65, J2 8.54 1H, p)
13C NMR (DMSO-d6), d: 28.3 (CH2), 129.4 (C), 131.1 (C), 164.2 (CO)
ESI positive mode 262.17 (M?H), C16H23NO2
IIIb
U.V, /nm: 255 (benzenoid form), 322, 360 (fine structure band)
ƛ
IR, m~/cm-1: 3482(aromatic primary amine), 3369 (NH stretch), 2937 (CH stretch alkyl), 1682(carbonyl), 1597 (NH bend primary
amine), 1467, (aromatic ring), 1248 (CN stretch)
1H NMR spectrum of IIIb in (CDCl3, 300 MHz) showed signals at 0.79–0.99(m, 7H, a, b, c), 1.01–1.2(m, 4H, d, e)1.33–1.40(dd, J1
3.6, J2 15.0 1H, f)1.45–1.522(m, 1H, g), 1.76–1.97(m, 3H, h, i, j), 5.3(dd, J1 2.99, J2 6.0, J3 9.3 1H, k), 5.4(bs, 2H, l) D2O
exchangeable, 6.59–6.66(m, 2H, m, n), 7.206–7.271(m, 1H, o), 7.850 (dd, J1 1.50, J2 8.40, 1H, p)
13C NMR (CDCl3, 75.5 MHz) 22.58 (a), 23.62 (b), 27.63 (c), 30.60 (d), 34.02 (e), 38.61 (f), 41.62 (g), 48.20 (h), 71.06 (i), 111.56
(j), 116.29 (k), 116.76 (l), 131.14 (m), 133.85 (n), 150.63 (o), 167.75
ESI positive mode 262.20 (M?H), C16H23NO2
123

Chem. Pap.
neutralization step, which is required in case of esterifica-
tion reaction catalyzed by homogeneous catalyst.
Acknowledgements The authors are thankful to the Indian Institute
of technology, Mumbai, for the support provided for the FT-IR, 13C
1
NMR, H NMR, TPD, Mass, Elemental, and Image analyses.
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