Biomass derived β-cyclodextrin-SO3H as a solid acid catalyst for esterification of carboxylic acids with alcohols

Article abstract of DOI:10.1039/c4ra16699j

A novel β-cyclodextrin-SO₃H carbon based solid acid catalyst was prepared in a convenient and ecofriendly manner and was characterized using FTIR, PXRD, EDAX and NH₃TPD to illustrate that the carbon material has been functionalized with -SO₃H, -COOH and -OH groups. The catalyst was studied for esterification of various carboxylic acids and alcohols under solvent free conditions and showed excellent catalytic performance and gave good yields of esters in the range 78-99% at 70°C. No solvent was used either for catalyst preparation nor for esterification reaction. The catalyst can be easily recovered by simple filtration and reused for subsequent three runs without any significant impact on yields of products. The main advantage of this methodology is easy and ecofriendly catalyst preparation, easy catalyst separation, practical simplicity, safe reaction conditions, recyclable catalyst and high product yields.

Full text of DOI:10.1039/c4ra16699j

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Biomass derived b-cyclodextrin-SO3H as a solid
acid catalyst for esterification of carboxylic acids
with alcohols†
Cite this: RSC Adv., 2015, 5, 12981
Received 19th December 2014
Accepted 16th January 2015
*
Raju S. Thombal, Amol R. Jadhav and Vrushali H. Jadhav
DOI: 10.1039/c4ra16699j
www.rsc.org/advances
A novel b-cyclodextrin-SO3H carbon based solid acid catalyst was and high reusability. In recent reports using heterogeneous
prepared in a convenient and ecofriendly manner and was charac- catalyst for esterication reaction, Zhan et al.4 used GDTCSA
terized using FTIR, PXRD, EDAX and NH3TPD to illustrate that the catalyst (carbon material functionalized with –NH2 and –SO3H
carbon material has been functionalized with –SO3H, –COOH and groups), Minakawa et al.5 used macroporous polymeric acid
–OH groups. The catalyst was studied for esterification of various catalyst, Karimi et al.6 used Bronsted acid ionic liquid, Sakakura
carboxylic acids and alcohols under solvent free conditions and et al.7 and Koshikari et al.8 used diarylammonium pyrosulfates
showed excellent catalytic performance and gave good yields of in water, Chakraborti et al.9 used HClO4–SiO2 and Leng et al.10
esters in the range 78–99% at 70 ꢀC. No solvent was used either for used heteropolyanion-based ionic liquids for esterication
catalyst preparation nor for esterification reaction. The catalyst can be reaction. Though a number of methods have been known for
easily recovered by simple filtration and reused for subsequent three esterication reaction,11 the use of large amounts of acids,
runs without any significant impact on yields of products. The main alcohols, expensive reagents and solvents have been used for
advantage of this methodology is easy and ecofriendly catalyst prep- such type of reactions. Such methods do not promote green
aration, easy catalyst separation, practical simplicity, safe reaction synthesis and atom efficiency. Hence there is still a need to
conditions, recyclable catalyst and high product yields.
develop an efficient process for esterication from both
academic and industrial points of view. Herein, we report direct
esterication of equimolar amounts of carboxylic acids and
alcohols using 10 wt% of b-cyclodextrin-SO3H catalyst under
solvent free conditions.
Introduction
Esterication is a method of condensing carboxylic groups with
alcohols. It is one of the most fundamental yet challenging
reactions in organic chemistry.1 Organic esters are important
products or intermediates in the chemical and pharmaceutical
industries. Most of these industries use a esterication step in
drug synthesis. Traditional liquid acids such as H2SO4 have also
been used as homogeneous catalyst for esterication reaction.
The high acidity of H2SO4 resulted in dehydration of alcohols to
alkenes, thus decreasing the selectivity and yield of ester
formation.2,3 They also suffer from drawback of corrosion,
contamination, have to be neutralized aer the reaction and
hence the workup is tedious. Such catalysts are difficult to
separate from the reaction and they cannot be reused. On
contrary, heterogeneous catalyst are more preferred due to their
low cost, metal-free composition, easy separation, high stability
Results and discussion
An amorphous carbon material consisting of small polycyclic
aromatic carbon sheets with a high density of sulfonic acid
(SO3H) sites are especially attractive heterogeneous catalysts
now-a-days due to their low cost, metal-free composition, and
expected high stability and high reusability. Therefore, we
choose readily available b-cyclodextrin as a carbon precursor
and p-TSA as a sulphonating agent. Naturally occurring b-
cyclodextrin can be prepared by enzymatic hydrolysis of starch
which comes from biomass.12 Cyclodextrins are cyclic oligomers
of seven D-glucose units linked in a a (1–4) manner and have a
pre organized structure. Hence aer sulphonation of b-cyclo-
dextrin we expected more polycyclic aromatic sheets to be
formed and hence high density of sulphonated sites to be
attached on the carbonaceous material ultimately showing
more acidic character of the catalyst. In this study, we have
prepared b-cyclodextrin-SO3H catalyst by one step hydrothermal
carbonization of b-cyclodextrin and p-TSA under mild reaction
Department of Organic Chemistry, National Chemical Laboratory (CSIR-NCL),
Pune-411008, India. E-mail: vh.jadhav@ncl.res.in
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c4ra16699j
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Fig. 1 Preparation of b-cyclodextrin-SO3H carbonaceous catalyst and its application in esterification reaction.
Fig. 2 IR spectra of b-cyclodextrin-SO3H.
Fig. 4 EDAX analysis of b-cyclodextrin-SO3H.
Fig. 3 PXRD spectra of b-cyclodextrin-SO3H.
Fig. 5 NH3TPD curve of b-cyclodextrin-SO3H.
Table 1 The structure and surface properties of the b-cyclodextrin-SO3H catalyst
Surface area
Acid density
SO3H amount
Catalyst
% Sulphur
2.99
(m2 gꢁ1
)
Pore size (A)
(mmol gꢁ1
)
(mmol gꢁ1
)
˚
b-Cyclodextrin-SO3H
0.18
47.4
3.0
1.24
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Table 2 Direct esterification of various alcohols and acids
Entry
Acid
Alcohol
Ester
Temp (ꢀC)
Time (h)
Yielda (%)
1
MeOH
70
3
97
2
70
6
78
3
4
70
70
4
4
91
94
5
6
70
70
3
3
96
96
MeOH
7
70
6
81
8
9
70
70
3
3
94
99
10
11
MeOH
70
70
8
5
94
99
CH3COOH
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Table 2 (Contd.)
Entry
12
Acid
Alcohol
Ester
Temp (ꢀC)
Time (h)
Yielda (%)
CH3COOH
70
6
99
13
CH3COOH
CH3COOH
70
70
7
6
89
99
14
15
CH3COOH
No reaction
16
CH3CH2COOH
70
5
79
a
Isolated yields.
conditions and shown its application in the esterication of analysis (EDAX) analysis (Fig. 4) showed sulphur composition
various acids and alcohols (Fig. 1). The hydrothermal carbon- to be 2.99%. The ammonia desorption studies (Fig. 5) showed
ization promoted the structure to undergo decomposition, the total acid density to be 2.7 mmol gꢁ1
.
hydrolysis, dehydration, and a molecular rearrangement reac-
tion to produce a polycylic aromatic structure embedded with b-cyclodextrin-SO3H based on acid base titration was found to
active –SO3H, –COOH and –OH sites.
be 3.0 mmol gꢁ1 and 1.24 mmol gꢁ1 respectively. BET surface
The total acid density and the sulphonic acid density of
The catalyst thus obtained was characterized with FT-IR areas and pore size were calculated using the standard Bru-
(Spectrum 400), PXRD (Panalytical X'Pert Pro), Elemental anal- nauer–Emmett–Teller (BET) equation and was found to be
ysis from EDAX (Quanta 200 3D, FEI), NH3TPD (Thermo 0.18 m2 gꢁ1 and 47.4 A (Table 1).
˚
Scientic TPD RO 1100) and BET surface area (Micrometrices
The performance of b-cyclodextrin-SO3H as an acid catalyst
ASAP 2020). The acid densities were measured by acid base was tested for direct esterication reaction of acids and alco-
titration (see ESI†). The FT-IR spectrum (Fig. 2) showed char- hols. Variety of different acids and alcohols were tried for
acteristic peaks at 1008 cmꢁ1 and 1032 cmꢁ1 which are attrib- esterication reaction under solvent free condition. In order to
uted to O]S]O stretching vibrations in –SO3H groups and optimize the temperature, the reaction with the test substrate
peak at 1174 cmꢁ1 for SO3H stretching. This indicates that the (benzoic acid and methanol) was carried out at room tempera-
ꢀ
sulfonic acid groups have been successively incorporated on the ture, 50 C, 70 ꢀC and 90 ꢀC. In case of the reaction at room
catalyst surface. Peaks at 1610 cmꢁ1 attributed for C]C temperature and 50 ꢀC the reaction was found to be very slow. At
ꢀ
stretching vibrations in aromatic carbons and peak at 70 C the reaction was clean and good yield of 97% of methyl
1680 cmꢁ1 attributed for C]O stretching. Peak at 1714 cmꢁ1 benzoate was obtained in 3 h (Table 2, entry 1), while at 90 C
ꢀ
attributed to presence of C]O stretching vibration of –COOH not much impact on reaction time and yields was observed. The
group. Bands at 2950 cmꢁ1 to 2875 cmꢁ1 attributed for C–H esterication reaction did not proceed at all in the absence of
stretching band. Bands due to O–H stretching were observed at b-cyclodextrin-SO3H catalyst.
3421 cmꢁ1. The powder X-ray diffraction pattern (Fig. 3) of
b-cyclodextrin-SO3H exhibited
Inspired by this fact, we then tried to explore the reaction on
broad diffraction peak variety of acids and alcohols using b-cyclodextrin-SO3H catalyst
a
(2q ¼ 15ꢀ to 30ꢀ), which can typically be attributed to amor- under solvent free conditions. Benzoic acid was also found to
phous carbon composed of aromatic carbon sheets oriented in react with cyclohexanol using b-cyclodextrin-SO3H catalyst at
ꢀ
considerably random fashion. The energy dispersive X-ray 70 C in 6 h giving 78% yield of cyclohexyl benzoate (Table 2,
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Table 3 Direct esterification of long chain acids and long chain alcohols
Entry
1
Acid
Alcohol
Ester
Temp (ꢀC)
70
Time (h)
3
Yielda (%)
98
CH3COOH
C11H23OH
2
3
70
5
84
C11H23OH
C11H23OH
70
70
4
4
93
89
4
a
Isolated yields.
Table 4 Reusability of b-cyclodextrin-SO3H
entry 2). 2-(o-Tolyl) acetic acid reacted with allyl alcohol, propargyl
alcohol and cyclopentylmethanol at 70 ꢀC to form the corre-
sponding esters with 91–96% yield (Table 2, entries 3–5). 2-Phe-
nylthioacetic acid also reacted smoothly with MeOH, cyclohexanol,
allyl and propargyl alcohols to afford the corresponding esters in
96%, 81%, 94% and 99% yield respectively (Table 2, entries 6–9).
2-(Carboxymethyl)thiobenzoic acid when treated with excess
MeOH as a solvent was found to give 94% yield of the diester in 8 h
(Table 2, entry 10). Cyclohexanol and menthol when reacted with
acetic acid gave about 99% yield of cyclohexyl acetate and menthol
acetate (Table 2, entries 11 and 12). 2-Butene diol when condensed
with excess acetic acid gave about 89% yield of the corresponding
diester (Table 2, entry 13). When a diol containing both secondary
and tertiary alcohol functionality was condensed with excess acetic
acid, monoester of only secondary hydroxyl was formed in 99%
yield (Table 2, entry 14). This method can thus be used for selective
esterication of secondary alcohols in presence of tertiary alcohols.
Reaction of acetic acid with t-butanol gave no ester formation even
aer keeping for longer reaction time (Table 2, entry 15). 1,2-trans-
Cyclohexane diol when reacted with one equivalent of propionic
acid was found to give monoester of cyclohexane diol in 79% yield
(Table 2, entry 16) indicating that selectively one alcohol can be
esteried in presence of other.
Entry
Catalyst reuse
Yielda (%)
1
2
3
1st recycle
2nd recycle
3rd recycle
97
96
96
a
Isolated yields.
the next run. Therefore, the recycled b-cyclodextrin-SO3H cata-
lyst without any regeneration steps was investigated in the
esterication of phenyl thioacetic acid and propargyl alcohol at
70 ꢀC. As shown in Table 4, b-cyclodextrin-SO3H exhibited a 97%
yield of product for the rst run, and the catalytic activity
showed consistency aer repeated use giving 96% yield of the
product aer 2nd and 3rd run.
Conclusion
In conclusion, a carbonaceous b-cyclodextrin-SO3H catalyst was
efficiently prepared and was found to show excellent catalytic
activity for esterication of variety of acids and alcohols under
mild reaction conditions giving high reactivity and selectivity.
No solvent was used for both catalyst preparation and esteri-
cation reaction. The yields for the esterication reaction were
excellent in the range of 78–99%. The catalyst could also be
recovered and reused without any loss of activity. This catalytic
system is environmentally green and can be used as an ideal
method for esterication in future.
Esterication was also carried out successively on long chain
acids and long chain alcohols under solvent free conditions at
ꢀ
70 C (Table 3). Esterication of acetic acid with 1-undecanol
proceeded smoothly to give 98% of 1-acetylundecanol in 3 h
(Table 3, entry 1).
Palmitic acid was found to react with cyclohexanol in 5 h
giving 84% yield of cyclohexylpalmitoyl ester (Table 3 entry 2).
Both long chain palmitic acid and stearic acid reacted smoothly
with long chain 1-undecanol to give the corresponding esters in
93 and 89% yield respectively (Table 3, entries 3 and 4).
As it is very convenient to recover the catalyst at the end of
the reaction, the solid catalyst le could be readily reused for
Experimental section
Preparation of catalyst b-cyclodextrin-SO3H
Typically 4 g of b-cyclodextrin powder was mixed with 18 g of
p-TSA (18 g of p-TSA was used so as to have maximum
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sulphonation on the b-cyclodextrin surface) and was heated in
an oil bath at 180 C for 24 h under nitrogen. Aer 24 h, the
2 A. Sakakura, Y. Koshikari and K. Ishihara, Tetrahedron Lett.,
2008, 49, 5017–5020.
ꢀ
catalyst was kept open to air and further heated for 24 h to
remove all the volatile compounds adsorbed on the surface of
the material. Deionised water was added to it and the catalyst
was ltered and further washed several times with deionised
water to remove the excess sulphate ions and then nally
washed with ethanol. The catalyst obtained was called as
b-cyclodextrin-SO3H.
3 K. Ishihara, Tetrahedron, 2009, 65, 1085–1109.
4 S. Zhan, X. Tao, L. Cai, X. Liu and T. Liu, Green Chem., 2014,
16, 4649–4653.
5 M. Minakawa, H. Baek, Y. M. A. Yamada, J. W. Han and
Y. Uozumi, Org. Lett., 2013, 15, 5798–5809.
6 B. Karimi and M. Vafaeezadeh, Chem. Commun., 2012, 48,
3327–3329.
7 A. Sakakura, Y. Koshikari, M. Akakura and K. Ishihara, Org.
Lett., 2012, 14, 30.
Typical procedure for esterication
8 Y. Koshikari, A. Sakakura and K. Ishihara, Org. Lett., 2012,
14, 3194–3197.
9 A. K. Chakraborti, B. Singh, S. V. Chankeshwara and
A. R. Patel, J. Org. Chem., 2009, 74, 5967–5974.
10 Y. Leng, J. Wang, D. Zhu, X. Ren, H. Ge and L. Shen, Angew.
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11 (a) K. Ishihara, S. Nakagawa and A. Sakakura, J. Am. Chem.
Soc., 2005, 127, 4168; (b) K. Ishihara, S. Ohara and
H. Yamamoto, Science, 2000, 290, 1140; (c) C. Chen and
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The mixture of 0.1 mmol of acid, 0.1 mmol of alcohol and 10
wt% of b-cyclodextrin-SO3H catalyst in a round bottom ask
were stirred magnetically at 70 ꢀC for a stipulated time until the
complete consumption of starting material. The reaction was
monitored by TLC. Aer completion of the reaction, the reac-
tion mixture was diluted with ethyl acetate and the catalyst was
ltered. The ltrate was then washed with saturated solution of
NaHCO3, water and dried over Na2SO4, concentrated and
loaded on silica and puried by column chromatography to
obtain the pure ester.
Acknowledgements
V.H.J. thanks DST, New Delhi for the INSPIRE Faculty Award
and Fast Track Grant. V.H.J also thanks Dr Sourav Pal, Director,
NCL for providing all the infra-structural facilities.
12 J. N. Schoffer, M. P. Klein, R. C. Rodrigues and P. F. Hertz,
Carbohydr. Poly., 2013, 98, 1311–1316.
References
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12986 | RSC Adv., 2015, 5, 12981–12986
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