Microwave-assisted NaHSO4-catalyzed synthesis of ricinoleic glycol ether esters

Article abstract of DOI:10.1080/00397911.2016.1268695

The synthesis of several ricinoleic acid glycol ether esters by high-pressure microwave radiation is described. Ricinoleic acid which is from castor oil reacted fastly with glycol ethers in the presence of NaHSO₄· H₂O and dichloromethane (DCM) in special microwave reactor. The influences of reaction factors such as catalyst and solvent type, reaction temperature, and time were investigated and the optimal reaction conditions were obtained. The activity of catalyst had a higher performance up to the 10th cycle and the excellent values of turnover numbers and turnover frequency were obtained. Compared with the traditional esterification in reflux heating systems., the microwave-assisted process has many advantages such as shorter reaction time, less side effects, higher yield, which is a great potential for the development of green chemistry.

Full text of DOI:10.1080/00397911.2016.1268695

Microwave-Assisted NaHSO4-Catalyzed Synthesis of Ricinoleic Glycol Ether Esters
Haifei Zhang1, Fengfan Zhu2, Yuan Xu1, Xiaoxiang Zhang1, Xinbao Zhu1,2
1College of Chemical Engineering, Nanjing Forestry University, Nanjing, China, 2Jiangsu
Province Glycol Ether Engineering Technology Research Center, Jiangyin, China
Address correspondence to X. Zhang. E-mail: zhuxinbao@njfu.com.cn
Project supported by the State Forestry Administration 948 project foundation(No. 2015-
4-55)
The Priority Academic Program Development of Jiangsu Higher Education Institutions
(PAPD)
Abstract
The synthesis of several ricinoleic acid glycol ether esters (RAGEE) by high-pressure
microwave radiation is described. Ricinoleic acid which is from castor oil reacted fastly
with glycol ethers in the presence of NaHSO4•H2O and DCM in special microwave
reactor. The influences of reaction factors such as catalyst and solvents type, reaction
temperature and time were investigated and the optimal reaction conditions were
obtained. The activity of catalyst had a higher performance up to the tenth cycle and the
excellent values of turnover numbers (TON) and turnover frequency (TOF) were
obtained. Compared with the traditional esterification in reflux heating systems., the
microwave(MW)-assisted process has many advantages such as shorter reaction time,
less side effects, higher yield, which is a great potential for development of green
chemistry.
GRAPHICAL ABSTRACT
1

KEYWORDS: microwave-assisted; ricinoleic acid; glycol ether; esterification;
NaHSO4•H2O.
INTRODUCTION
Plasticizer is one of the most important additives in polymer materials, especially in PVC,
which contains more than 60% of the total production of plastics additives[1,2]. Traditional
petroleum-based phthalate plasticizer has still the largest production and sale in the
current plasticizer industry. However, due to the potential threat to human health and
environment, the usage is gradually decreasing in the recent years[3-4]. Since the global
environmental regulations become more stringent, people start to pay more attention on
the eco-friendly technologies and products. The development of new alternative phthalate
plasticizer has become the focus of attention worldwidely.
Transforming castor oil into high value-added energy and new materials is a hot topic
nowadays. Castor oil is commonly used in the field of plasticizers by many ways[5,6]
.
Castor oil is well known as a source of ricinoleic acid, a monounsaturated, 18-carbon
fatty acid. Among those fatty acids, ricinoleic acid is unique because it has a hydroxyl
group on the 12th carbon which causes ricinoleic acid to be more polar than other fatty
2

acids and presents some peculiar chemical properties, At the meanwhile, the chemical
reactivity of the hydroxyl group also allows chemical derivatization in castor oil, but it is
impossible for other seed oils. RAGEE is non-toxic and biodegradable and eco-friendly
which has excellent cold resistance and high-plasticized efficiency[7–11]. The synthesis of
RAGEE has rarely be reported. One common method is obtained by the reaction of castor
oil transesterification (Scheme 1). Such methods require long reaction time and also
produce byproducts which is difficult to separate from the product[12]
.
Microwave heating technology is a new green chemistry method that was developed in
recent years[13]. Gedye first introduced microwave-heating synthesis into organic
synthesis researches[14]. Unlike the synthesis at normal atmospheric pressure, the
synthesis of RAGEE microwave radiation requires to heat the reactants to a high pressure
in a sealed reactor. This method is easy to operate and eco-friendly which will not destroy
the sample structure. Moreover, it can shorten the reaction time and improve the
selectivity and product yield[15–19]
.
In the past few years, our group has studied the synthesis of RAGEE by ionic liquids
catalyzed esterification[20], following green and sustainable chemistry principles[21]. As a
continuation of our studies, we reported herein the preparation of RAGEE from ricinoleic
acid and glycol ethers by microwave radiation method, which is in a faster and more
efficient way and can be applied in a wide range of applications [22–24].and the catalyst can
be reused for up to 10 runs with a higher performance on its activity. In addition, the
TON and TOF values were higher than in reflux heating systems.
3

RESULTS AND DISCUSSION
Optimization Of Reaction Conditions
Our initial efforts were focused on the preparation of the ricinoleic acid ethylene glycol
butyl ether ester (RAEGBEE) 3c which was derived from ricinoleic acid 1a and ethylene
glycol butyl ether (EGBE) 2c. We examined the effects of the reaction time and
temperature, use of solvent, catalyst on the esterification yields, the results were shown in
the Table 1.
Aiming to reduce the reaction time and to improve the yield, we first tested several
catalysts (Table 1 Entries 1-5), as well as some different solvents (Table 1 Entries 5-12),
the best result was obtained when the reaction was performed in the presence of
NaHSO4•H2O and DCM. The reason why NaHSO4•H2O had such excellent catalytic
performance was that it has strong electrolytes and hydrogen ions can be ionized without
adding water to forward the reaction. Then, NaHSO4•H2O can not only be easily
separated after the reaction complete which make post-treatment simple, but also can
reduce equipment corrosion. DCM was preferred due to its low boiling point. At 100 C,
it form a higher steam pressure than other solvents, which was conducive to carry out the
reaction to the positive direction.
Then, the impact of the reaction temperature was examined (Table 1 Entries 13-16). The
higher temperature, the better performance. However, when it exceeded 150 C, the yield
decreased. Finally, the effect of reaction time on the yield (Table 1 Entries 15-20) was
studied. When the reaction time was longer than 25 min, the yield almost didn’t increased.
4

Thus, when ricinoleic acid 1a (10.0 mmol) and EGBE 2c (12.0 mmol), catalyst (0.01%
mol) were simply mixed in the presence of DCM (5.0 ml) at 150 C under the microwave
radiation, the desired RAEGBEE 3c was obtained in 98% yield after 25 min (Table 1
entry 15).
TON and TOF values which were calculated for all the reactions are given in Table 1,
these TON and TOF values which were achieved under MW were higher than those in
reflux heating systems.
Substrate Scope
In order to demonstrate the efficiency of our protocol, ricinoleic acid 1a was treated with
other glycol ethers 2a–2i according to the optimal synthesis method of RAEGBEE 3c
above. the results are summarized in Table 2. We observed that the reaction worked well
for a variety of glycol ethers.
As shown in Table 2, in the same type of glycol ether, the longer the chain, the lower the
yield. For example, among the ethylene glycol ethers (Table 2 entries 1-7), The ethylene
glycol methyl ether 2a reacted with ricinoleic acid 1a to afford the Ricinoleic acid
ethylene glycol methyl ether ester 3a in higher yield than ethylene glycol ethyl ether 2b.
Similarly, among the propylene glycol ethers (Table 2 entries 8-9), dipropylene glycol
methyl ether 2h (Table 2 entry 3) than dipropylene glycol elthyl ether 2i. Ricinoleic acid
and glycol ether occurred bimolecular nucleophilic substitution reaction (SN2). The
increasing volume of the alkyl group caused steric hindrance, which lowered the yield.
5

The ethylene glycol ethers 2a-2g (Table 2 entries 1-7) gives the respective esters 3a-3g in
slightly superior yield to propylene glycol ethers 2h-2i (Table 2 entries 8-9) after the
same reaction time. These results from the electron correlation effect.
In conclusion, an improved, microwave-assisted technology to prepare RAGEE directly
from ricinoleic acid was developed. Ricinoleic acid 1a (10.0 mmol) and glycol ethers 2a-
2i (12.0 mmol) reacted in the presence of NaHSO4•H2O (0.01% mol) and DCM (3.0 ml)
at 150 C under the microwave irritation, after 25 min, the desired product 3a-3i were
obtained in satisfactory yields, which can be valuable to the future scaling-up research for
the pilot or industry[27].The minimization of the reaction time and the increase of
selectivity and yields are important advantages of this improved procedure. Besides, the
obtained esters can be explored as the vegetable oil glycol esters in the synthesis of more
complex biomass plasticizers.
Reusability Of Catalyst Nahso4•H2O
The reusability was investigated on model reaction at optimum reaction conditions and
are given in Table 3, NaHSO4•H2O can be used economically for several applications
since the activity of catalyst has a higher performance after 10 cycles.
Mercury test
As been well known, if the catalytic reaction stops and the catalyst lose activity after
mercury is added, it is considered to be a heterogeneous catalyst. Meanwhile, if mercury
addition does not affect the catalytic reaction, it is a homogenous catalyst . The mercury
6

test showed that the catalyst had a heterogeneous nature because it lost activity upon the
addition of mercury.
EXPERIMENTAL
Instruments and Reagents
Monowave 300 Microwave reactor (Canada Antonpear Company); RE-2000B rotary
evaporator (Shanghai Yarong Shenghua Instrument Factory); DF-101S solar collector
thermostat heating magnetic stirrer (Zhengzhou Greatwall Scientific Industrial and Trade
Co, Ltd.); FTS-135 type Fourier transform infrared spectrometer (BIO-RAD company);
PHS-25 pH meter (Shanghai precision scientific instrument Co, Ltd.); Bruker Ascend
400 MHz NMR measurement; Agilent 6540 UHD Q-TOF LC/MS.
All reagents were analytical grade, purchased from Aladdin Co, Ltd.
Mercury Poisoning Test
The model coupling reaction was conducted in the absence of mercury for 25min under
microwave heating (yield: 98%). Then 300 molar equivalents of mercury, with relation to
the catalyst (NaHSO4•H2O), were added into the reaction media, and the reaction was
allowed to continue for 25min. After the allowed time, the yield of 96% of the expected
product was obtained.
General Procedure For The Synthesis Of RAGEE
7

Ricinoleic acid (10.0 mmol) 1a, glycol ethers 2a-2i (12.0 mmol) and DCM (5.0 mL) and
NaHSO4•H2O (0.01% mol) were added into a dry 10.0 mL microwave reaction tube,
which was put into a microwave reactor. The desired product was afforded after 25 min
at 150 C (Scheme 2).
The reaction progress was followed by thin-layer chromatography (TLC) and the crude
product was purified on column chromatography of silica gel using ethyl acetate-
petroleum ether(1:7) as eluent. All products were characterized by 1H NMR, 13C NMR,
FT-IR and HRMS and spectrum data of 3a-3i were listed.
Ricinoleic acid ethylene glycol methyl ether ester (3a), pale yellow liquid, yield 99%.
1H NMR ( 400 MHz, CDCl3), δ: 5.54-5.52 (m, 1H), 5.39-5.36 (m, 1H), 4.37 (t, J = 7.2
Hz, 2H), 3.69 (t, J = 7.2 Hz, 2H), 3.60 (s, 1H), 3.57 (s, 3H), 3.51-3.44 (m, 1H), 2.32-2.30
(t, J = 7.4 Hz, 2H), 2.28-2.24 (m, 2H), 2.18 (t, J = 7.2 Hz, 2H), 1.72-1.64 (m, 2H), 1.46-
1.41 (m, 2H), 1.32-1.28 (m, 16H), 0.87 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3),
δ: 173.9, 132.5, 125.3, 71.4, 70.3, 69.1, 67.7, 65.8, 63.6, 56.4, 36.8, 34.0, 31.9, 29.1, 26.9,
26.7, 25.7, 22.4, 19.1, 14.0, 13.8; (KBr) ν: 3386, 3009, 2931, 2851, 1744, 1651, 1543,
1454, 1372, 1278, 1251, 1217, 1121, 1109, 1031, 1000, 866, 729, 714, 702, 611 cm-1;
(ESI) calcd for C21H40NaO4 [M+Na]+: 379.2824, found: 379.2820.
Ricinoleic acid ethylene glycol ethyl ether ester (2b), pale yellow liquid, yield 98%. 1H
NMR (400 MHz, CDCl3), δ: 5.52-5.50 (m, 1H), 5.38-5.36 (m, 1H), 4.55 (t, J = 7.2 Hz,
2H), 3.88 (t, J = 7.2 Hz, 2H), 3.65 (t, J = 7.2 Hz, 2H), 3.60 (s, 1H), 3.42-3.40 (m, 1H),
8

2.54 (t, J =7.4 Hz, 2H), 2.42-2.38 (m, 2H), 2.35 (t, J = 7.4 Hz, 2H), 1.80-1.74 (m, 2H),
1.59-1.51 (m, 2H), 1.32-1.28 (t, 16H),1.21 (t, J = 7.2 Hz, 3H), 0.87 (t, J = 7.2 Hz, 3H);
13C NMR (100 MHz, CDCl3), δ: 173.9, 132.7, 125.2, 70.5, 68.2, 67.6, 60.5, 43.4, 36.7,
35.2, 32.2, 31.7, 31.3, 30.8, 29.0, 27.3 25.7, 23.9, 22.5, 19.3, 14.0, 13.9; FT-IR (KBr) ν:
3381, 3008, 2930, 2850, 1744, 1651, 1541, 1455, 1372, 1279, 1252, 1217, 1121, 1106,
1032, 1001, 866, 727, 710, 702, 610 cm-1; HRMS (ESI) calcd for C22H42NaO4 [M+Na]+:
393.2981, found: 393.2985.
Ricinoleic acid ethylene glycol butyl ether ester (2c), pale yellow liquid, yield 98%. 1H
NMR (400 MHz, CDCl3), δ: 5.54-5.50 (m, 1H), 5.43-5.39 (m, 1H), 4.23 (t, J = 7.2 Hz,
2H), 4.13-4.11 (m, 1H), 3.63 (t, J = 7.2 Hz, 2H), 3.60 (s, 1H), 3.48 (t, J = 7.2 Hz, 2H),
2.34 (t, J = 7.4 Hz, 2H), 2.27 (m, 2H), 2.05-2.03 (m, 4H), 1.61-1.58 (m, 8H), 1.31-1.25 (t,
J = 7.2 Hz, 16H), 0.92 (t, J = 7.6 Hz, 3H), 0.88 (t, J = 7.2 Hz, 3H); 13C NMR (400 MHz,
CDCl3), δ: 173.8, 133.6, 125.1, 70.7, 68.4, 63.6, 61.9, 36.8, 35.4, 34.1, 33.8, 31.4, 29.5,
26.9, 26.7, 25.7, 24.6, 22.3, 19.6, 14.5, 13.9; FT-IR (KBr) ν: 3387, 3004, 2932, 2853,
1745, 1653, 1545, 1465, 1379, 1280, 1251, 1220, 1106, 1045, 1010, 867, 729, 718, 709,
611 cm-1; HRMS (ESI) calcd for C24H46NaO4 [M+Na]+: 421.3294, found: 421.3292.
Ricinoleic acid diethylene glycol methyl ether ester (2d), pale yellow liquid, yield 96%.
1H NMR ( 400 MHz, CDCl3), δ: 5.55-5.52 (m, 1H), 5.38-5.36 (m, 1H), 4.26 (t, J = 7.6
Hz, 2H), 3.71-3.68 (m, 2H), 3.65-3.63 (m, 2H), 3.60 (s, 1H), 3.53-3.44 (m, 1H), 3.40 (t, J
= 7.6 Hz,2H), 2.35 (t, J = 7.4 Hz, 2H), 2.29-2.26 (m , 2H), 2.13 (t, J = 7.4 Hz, 2H), 1.62-
1.55 (m, 2H), 1.48-1.43 (m, 2H), 1.31-1.25 (m, 16 H), 0.89 (t, J = 7.2 Hz, 3H); 13C NMR
9

(100 MHz, CDCl3), δ: 173.9, 132.6, 125.3, 74.6, 71.4, 70.2, 69.1, 67.7, 65.8, 63.6, 56.4,
36.8, 34.0, 31.8, 29.1, 26.9, 26.7, 25.7, 22.4, 19.1, 14.1, 13.8; FT-IR (KBr) ν: 3381, 3008,
2930, 2850, 1744, 1651, 1541, 1455, 1372, 1279, 1252, 1217, 1121, 1106, 1032, 1001,
866, 727, 710, 702, 610 cm-1; HRMS (ESI) calcd for C22H42NaO4 [M+Na]+: 393.2981,
found: 393.2980.
Ricinoleic acid diethylene glycol butyl ether ester (2e), pale yellow liquid, yield 93%.
1H NMR ( 400 MHz, CDCl3), δ: 5.49-5.46 (m, 1H), 5.35-5.32 (m, 1H), 4.17 (t, J = 7.2
Hz, 1H), 3.91 (t, J = 7.2 Hz, 2H), 3.66-3.44 (m, 6H), 3.60 (s, 1H), 2.33 (t, J = 7.2 Hz,
2H), 2.26 (d, 2H), 1.86 (m, 2H), 1.72 (m, 2H ), 1.61-1.55 (m, 6H), 1.32-1.28 (t, 16H),
0.87 (t, J = 7.2 Hz, 3H), 0.83 (t, J = 7.2 Hz, 3H); 13C NMR(100 MHz, CDCl3), δ: 173.9,
132.2, 125.3, 71.6, 70.8, 69.6, 67.5, 65.8, 63.7, 56.4, 50.3, 36.9, 34.6, 31.8, 30.7, 29.1,
28.7, 27.2, 26.5, 26.4, 25.7, 22.4, 19.4, 14.3, 13.6; FT-IR (KBr) ν: 3390, 3012, 2921,
2850, 1746, 1646, 1545, 1460, 1390, 1280, 1246, 1220, 1120, 1105, 1012, 1013, 867, 726,
702, 618 cm-1; HRMS (ESI) calcd for C25H48NaO4 [M+Na]+: 435.3450, found: 435.3454.
Ricinoleic acid triethylene glycol methyl ether ester (2f), pale yellow liquid, yield 95%.
1HNMR ( 400 MHz, CDCl3), δ: 5.57-5.50 (m, 1H), 5.39-5.37 (m, 1H), 4.21 (t, J = 7.2 Hz,
2H), 4.01 (t, J = 7.2 Hz, 2H), 3.74 -3.70 (m, 2H), 3.68-3.64 (m, 2H), 3.62-3.58 (m ,4H),
3.55 (s, 1H), 3.51-3.44 (m, 1H), 3.38 (t, J = 7.2 Hz, 2H), 3.30 (t, J = 7.2 Hz, 2H), 2.34 (t,
J = 7.2 Hz, 2H), 2.28-2.20 (m, 2H), 2.03 (t, J = 7.2 Hz, 2H), 1.62-1.54 (m, 2H), 1.48-
1.42 (m, 2H), 1.30-1.25 (t, 16H), 0.87 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3),
δ: 173.7, 132.3, 125.2, 71.5, 71.4, 71.0, 70.8, 70.5, 70.3, 69.8, 36.9, 35.4, 34.2, 31.8, 29.6,
10

29.3, 29.2, 29.1, 29.0, 28.7, 28.6, 27.4, 25.7, 22.6, 14.1; FT-IR (KBr) ν: 3381, 3008, 2930,
2850, 1744, 1651, 1541, 1455, 1372, 1279, 1252, 1217, 1121, 1106, 1032, 1001, 866, 727,
710, 702, 610 cm-1; HRMS (ESI) calcd for C25H48NaO5 [M+Na]+: 451.3399, found:
451.3398.
Ricinoleic acid triethylene glycol propyl ether ester (2g), pale yellow liquid, yield 93%.
1HNMR ( 400 MHz, CDCl3), δ:5.56 (m, 1H), 5.37 (m, 1H), 4.21 (t, J = 7.2 Hz, 2H), 3.67
(t, J = 7.2 Hz, 2H), 3.60 (s, 1H), 3.54-3.51 (m, 8H), 3.38 (t, J = 7.2 Hz, 2H), 2.75 (t, J =
7.2 Hz, 2H), 2.28-2.20 (m, 4H), 2.03 (t, J = 7.2 Hz, 2H), 1.62-1.56 (m, 4H), 1.48-1.42 (m,
4H), 1.35-1.25 (m, 16H), 0.89 (t, J = 7.2 Hz, 3H), 0.86 (t, J = 7.2 Hz, 3H); 13C
NMR(100MHz, CDCl3), δ:173.9, 133.3, 125.2, 72.5, 71.9, 71.5, 71.4, 71.0, 71.0, 70.6,
69.2, 63.4, 61.7, 36.9, 35.4, 34.2, 31.8, 31.7, 31.6, 29.6, 29.3, 29.1, 27.4, 25.7, 22.6, 19.3,
14.1, 13.9; FT-IR (KBr) ν: 3381, 3008, 2930, 2850, 1744, 1651, 1541, 1455, 1372, 1279,
1252, 1217, 1121, 1106, 1032, 1001, 866, 727, 710, 702, 609 cm-1; HRMS (ESI) calcd
for C28H54NaO5 [M+Na]+: 493.3869, found: 493.3866.
Ricinoleic acid dipropylene glycol methyl ether esters (2h), pale yellow liquid, yield
91%. 1HNMR ( 400 MHz, CDCl3), δ: 5.52-5.50 (m, 1H), 5.42-5.38 (m, 1H), 4.85 (t, J =
7.2 Hz, 2H), 3.93 (t, J = 7.2 Hz, 2H), 3.60 (s, 1H), 3.59 (m, 2H), 3.48 (t, J = 7.2 Hz, 2H),
3.16 (t, J = 7.2 Hz, 2H), 2.26 (t, J = 7.2 Hz, 2H), 2.24-2.20 (m, 2H), 2.03 (t, J = 7.2 Hz,
2H), 1.48-1.42 (m, 2H), 1.35-1.25 (m , 22 H), 0.85 (t, J = 7.2 Hz, 3H ); 13C NMR (100
MHz, CDCl3), δ: 173.9, 133.3, 125.2, 71.3, 71.2, 70.3, 71.0, 69.2, 63.4, 61.7, 36.9, 35.4,
34.2, 31.8, 31.7, 31.6, 29.6, 29.3, 29.1, 27.4, 25.7, 22. 6, 19.3, 14.1, 13.9; FT-IR (KBr) ν:
11

3389, 3067, 2938, 2850, 1755, 1656, 1547, 1460, 1370, 1280, 1252, 1280, 1144, 1128,
1046, 1022, 867, 710, 611 cm-1; HRMS (ESI) calcd for C25H48NaO4 [M+Na]+: 435.3450,
found: 435.3453.
Ricinoleic acid dipropylene glycol elthyl ether esters (2i), pale yellow liquid, yield
89%. 1H NMR ( 400 MHz, CDCl3), δ:5.52 (m, 1H), 5.39 (m, 1H), 3.99 (t, J = 7.2 Hz,
2H), 3.61 (t, J = 7.2 Hz, 2H), 3.60 (s, 1H), 3.50-3.47(m, 2H), 3.42 (t, J = 7.2 Hz, 2H),
3.35-3.32 (m, 2H), 2.33-2.29 (m, 2H), 2.18 (t, J = 7.2 Hz, 2H), 2.04-2.02 (m, 2H), 1.35-
1.32 (m, 26H), 1.12-1.08, (m, 2H), 0.85 (t, J = 7.2 Hz, 3H); 13C NMR(100 MHz, CDCl3),
δ: 178.9, 133.3, 125.2, 71.3, 71.2, 71.0, 71.0, 70.6, 69.0, 65.8, 61.7, 31.8, 31.6, 29.6, 29.3,
29.1, 28.9, 25.7, 24.7, 22.6, 18.3, 17.2, 16.8, 15.0, 14.1, 13.9; FT-IR (KBr) ν: 3389, 3010,
2932, 2855, 1746, 1657, 1546, 1465, 1379, 1280, 1258, 1230, 1127, 1116, 1045, 1024,
869, 738, 719, 711, 616 cm-1; HRMS (ESI) calcd for C26H50NaO4 [M+Na]+: 449.3607,
found: 449.3609.
ACKNOWLEDGEMENT
The authors would like to thank the State Forestry Administration 948 project
foundation for financial support under the Grant No 2015-4-55 and the Priority Academic
Program Development of Jiangsu Higher Education Institutions (PAPD).
REFERENCES
12

1.
Erythropel, H. C.; Maric, M.; Nicell, J. A. Leaching of the plasticizer di(2-
ethylhexyl)phthalate (DEHP) from plastic containers and the question of human exposure.
Appl. Microbiol. Biotechnol. 2014, 24, 9967.
2.
Rahman, M.; Brazel, C.S. The plasticizer market: an assessment of traditional
plasticizers and research trends to meet new challenges. Prog. Polym. Sci. 2004, 12, 1223.
Lithner, D.; Larsson, A.; Dave, G. Environmental and health hazard ranking and
3.
assessment of plastic polymers based on chemical composition. Scie. Total. Environ.
2011, 18, 3309.
4.
Hines, C. J.; Hopf, N.B.; Deddens, J.A. Occupational exposure to diisononyl
phthalate (Di NP) in polyvinyl chloride processing operations. Int. Arch. Occup. Environ.
Health. 2012, 3, 317.
5.
Perin, G.; lvaro, G. A.; Westphal, E. Transesterification of castor oil assisted by
microwave irradiation. Short communication. 2008, 87, 2838.
Manuel, Sánchez-Cantú.; Federico, M.; Reyes-Cruz. Direct synthesis of calcium
6.
diglyceroxide from hydrated lime and glycerol and its evaluation in the transesterification
reaction. Fuel. 2014, 18, 126.
7.
Wang, B.; Wang, K. Z.; Kong, Y. L. Research Progressof Environment-friendly
Plasticizers. China plastics industry. 2013, 5, 12.
Huang, X. F.; Huang, W. B.; Li, X. D.; Li, Z. Studies on the preparation of 10-
hydroxy decanonic acid from the caster oil, You Ji Hua Xue. 1996, 2, 175.
Ranu, B. C.; Jana, R.; Dey, S. S. An Efficient and Green Synthesis of 2-
8.
9.
Arylbenzothiazoles in an Ionic Liquid [pmIm]Br under Microwave Irradiation, Chem.
Lett. 2004, 2, 274.
13

10.
Black, Brenna. A.; Sun, C. X.; Zhao, Y. Y.; Ganzle, Michael. G.; Curtis, Jonathan,
M. Antifungal Lipids Produced by Lactobacilli and Their Structural Identification by
Normal Phase LC/Atmospheric Pressure Photoionization–MS/MS. J. Agric. Food. Chem,
2013, 22, 5338.
11.
Lin, Jiann.Tsyh.; Arcinas, Arthur ; Harden, Leslie. A. Identification of
Acylglycerols Containing Dihydroxy Fatty Acids in Castor Oil by Mass Spectrometry.
Lipids. 2009, 4, 359.
12.
Xu, H.; Zhou, Q.; Wang, J. F. Treatment of Sebacic Acid Industrial Wastewater
by Extraction Process Using Castor Oil Acid as Extractant, Chin. J. Chem. Eng. 2013, 9,
967.
13.
(a) Baran, Talat.; Aciksoez, Eda.; Mentes, Ayfer. Highly efficient, quick and
green synthesis of biaryls with chitosan supported catalyst using microwave irradiation in
the absence of solvent. Carbohydr Polym, 2016, 142, 189. (b) Baran.; Ayfer, Menteş.;
Talat, Baran.; Ayfer, Mente. Highly efficient Suzuki cross-coupling reaction of
biomaterial supported catalyst derived from glyoxal and chitosan, Journal of
Organometallic Chemistry, 2016, 803, 30. (c) Talat, Baran.; Tülden, Inanan.; Ayfer,
Menteş. Synthesis, characterization, and catalytic activity in Suzuki coupling and
catalase-like reactions of new chitosan supported Pd catalyst ,Carbohydrate Polymers,
2016, 145, 20. (d) Talat, Barana.; Idris, Sarginb.; Murat, Kayab.; Ayfer, Menteşa. An
environmental catalyst derived from biological waste materials for green synthesis of
biaryls via Suzuki coupling reactions, Journal of Molecular Catalysis A:2016, 420, 216;
(e) Talat, Baran.; Ayfer, Mentes. Microwave assisted synthesis of biarlys by C-C
coupling reactions with a new chitosan supported Pd(II) catalyst, Journal of Molecular
14

Structure, 2016, 1122, 111; (f) Talat, Barana.; Idris, Sarginb.; Murat, Kayab.; Ayfer,
Mentes. Green heterogeneous Pd(II) catalyst produced from chitosan-cellulose micro
beads for green synthesis of biaryls, Carbohydrate Polymers, 2016, 152,181; (g) Baran,
Idris Sargin.; Ayfer, Menteşa.; Murat, Kaya. Exceptionally high turnover frequencies
recorded for a new chitosan-based palladium(II) catalyst, Applied Catalysis A: General
2016, 523, 12.
14.
(a) Gedye , R.;Smith, F.;Westaway , K. The use of microwave ovens for rapid
organic synthesis. Tetrahedron Lett .1986; 3, 279. (b) Gedye , R.;Smith, F.;Westaway ,
K . The rapid synthesis of organic compounds in microwave ovens, Can .J. Chem .1988,
4, 17.
15.
Li, Y.H.; Guo, Y.b.; Tang, T.; Deng, Z. L.; Zhao, K. Q. Gang CuI-catalyzed
domino reactions for the synthesis of benzoxazine-fused isoquinolines under microwave
irradiation, Synthetic Commun. 2016, 4,355.
16.
Sharifi, Ali.; Ghonouei, Nima.; Abaee, M. Saeed Ethylene glycol, an efficient and
recoverable medium for copper-catalyzed N-arylation of diazoles under microwave
irradiation, Synthetic Commun. 2016, 3, 249.
17.
Mariappan, Arumugam; Rajaguru, Kandasamy; Muthusubramanian, Shanmugam;
Bhuvanesh, Nattamai. Microwave-assisted catalyst-free synthesis of tetrasubstituted
pyrroles using dialkyl acetylenedicarboxylates and monophenacylanilines, Synthetic
Commun. 2016, 46, 805.
18.
Pei, W.; Dong, Z. G.; Yao, C. P.; Chen, Q. Application of Solid Base Catalysts of
Metal Oxide In Organic Synthesis, Chinese. J. Org. 2010, 9, 1410.
15

19.
Weber, Harald.; Scholten, Frank.; Leinz ,Gerhard. Arzneimittelinformation und
Beratung in der Apotheke, Deut Lebensm-Rundsch. 2005, 10, 425.
Zhang, H. F.; Liu, D. M.; Kang, T. T.; Wang, Y.; Zhang, X. X.; Zhu, X. B.
20.
Synthesis of Novel Benzothiazolium Ionic Liquids and Research on Their Catalytic
Esterification for Ricinoleic Acid, Chinese. J. Org. 2016, 5, 1104.
21.
Lenardao, E. J.;Trecha, D. O.; Ferreira, P. C.; Jacob, R. G.; Perin, G. Green
Michael addition of thiols to electron-deficient alkenes using KF alumina and recyclable
solvent or solvent-free conditions, J. Braz. Chem. Soc. 2009, 20, 93.
22.
Pelle, Lidstrom.; Jason, Tierney.; Bernard, Wathey. Microwave assisted organic
synthesis—a review, Tetrahedron, 2001, 45, 9225.
liver, Kappe. Microwave Reactor for Batchwise Organic Synthesis, Angew. Chem.
Int. Edit. 2004, 46, 6250.
23.
24.
He, P.; Haswell, S. J.; Fletcher, P. D. I. Microwave-assisted Suzuki reactions in a
continuous flow capillary reactor, Applied Catalysis A. Genera. 2004, 1,111.
25.
Xu, R.; Xie, H.; Huang, L. Curing Kinetics of Dehydrated Castor-oil Polyamide-
epoxy Resin System, Chemistry and Industry of Forest Products. 2009, 2, 59.
Lin, Jiann.Tsyh.; Arcinas, Arthur.; Harden, Leslie. R.; Fagerquist, Clifton.K.
26.
Regiospecific Analysis of Diricinoleoylacylglycerols in Castor (Ricinus communis L.)
Oil by Electrospray Ionization−Mass Spectrometry. J. Agric. Food Chem. 2006, 10, 3498.
16

Table 1. Optimization reaction conditions of ricinoleic acid and EGBEa
Entr Catalyst
y
Solvent
DCM
DCM
DCM
Time/mi
n
Yield/% TO
TOF
Temp/
C
b
N
1
2
3
4
5
6
7
8
9
10
TsOH
25
25
25
25
25
25
100
91
85
90
80
93
80
89
87
91
79
9100 2184
0
HCl
100
100
100
100
100
100
100
100
100
8500 2040
0
H2SO4
9000 2160
0
SnCl2•2H2O DCM
8000 1920
0
NaHSO4•H2
DCM
9300 2232
O
0
NaHSO4•H2
acetonitrile
8000 1920
O
0
NaHSO4•H2
dichloroethane 25
8900 2136
O
0
NaHSO4•H2
toluene
hexane
25
25
8700 2088
O
0
NaHSO4•H2
9100 2184
O
0
7900 1896
0
NaHSO4•H2
tetrahydrofura 25
n
O
17

11
12
13
14
15
16
17
18
19
20
21c
NaHSO4•H2
chlorobenzene 25
100
100
75
85
81
79
95
98
97
87
89
98
97
90
8500 2040
O
0
NaHSO4•H2
DMSO
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
toluene
25
25
25
25
25
15
20
30
35
300
8100 1944
O
0
NaHSO4•H2
7900 1896
O
0
NaHSO4•H2
125
150
160
150
150
150
150
110
9500 2280
O
0
NaHSO4•H2
9800 2352
O
0
NaHSO4•H2
9700 2328
O
0
NaHSO4•H2
8700 3480
O
0
NaHSO4•H2
8900 2670
O
0
9800 1960
0
NaHSO4•H2
O
NaHSO4•H2
9700 1662
9
O
NaHSO4•H2
9000 1800
O
18

aReaction conditions: ricinoleic acid (10.0 mmol), EGBE (12.0 mmol), catalyst (0.01%
mol), solvent (5.0 mL), under MW, bYield: the esterification yields.
cReaction conditions: ricinoleic acid (10.0 mmol), EGBE (12.0 mmol), catalyst (0.02%
mol), solvent (5.0 mL), in reflux heating systems.
19

Table 2. Synthesis of RAGEE from ricinoleic acids 1a and glycol ethers 2a-2ia
Entries Ricinoleic acid glycol ethers Product
2a
Yield b
99%
2b
2c
98%
98%
2d
2e
2f
96%
93%
95%
93%
2g
2h
2i
91%
89%
aReaction conditions: ricinoleic acid (10 mmol), glycol ether (12mmol), catalyst
(0.01%mol), solvent (5.0mL), 150 C, 25min, under MW; bYield: the esterification yield.
20

Table 3. Reusability of catalyst NaHSO4•H2O
The number of cycle
TON
Yield (%）
1st
98
97
97
96
95
95
94
93
92
92
9800
9700
9700
9600
9500
9500
9400
9300
9200
9200
2nd
3rd
4th
5th
6th
7th
8th
9th
10th
Reaction conditions: ricinoleic acid (10.0 mmol), EGBE (12.0 mmol), catalyst (0.01%
mol), solvent (5.0 mL), 150 C, 25.0 min, under MW; bYield: the esterification yield.
21

Table 4 Optimization of reaction conditions of ricinoleic acid and binary alcohol ether
Entry Catalyst
solvent
Time/min
25
Temp/℃
100
100
100
100
100
100
100
100
100
100
100
100
75
Yield/%b
91
1
TsOH
dichloromethane
dichloromethane
dichloromethane
dichloromethane
2
HCl
25
85
3
H2SO4
SnCl2•2H2O
25
90
4
25
80
5
NaHSO4•H2O dichloromethane
NaHSO4•H2O acetonitrile
25
93
6
25
80
7
NaHSO4•H2O dihloroethane
NaHSO4•H2O toluene
25
89
8
25
87
9
NaHSO4•H2O hexane
25
91
10
11
12
13
14
15
16
17
18
19
20
NaHSO4•H2O tetrahydrofuran
NaHSO4•H2O chlorobenzene
NaHSO4•H2O DMSO
25
79
25
85
25
81
NaHSO4•H2O dichloromethane
NaHSO4•H2O dichloromethane
NaHSO4•H2O dichloromethane
NaHSO4•H2O dichloromethane
NaHSO4•H2O dichloromethane
NaHSO4•H2O dichloromethane
NaHSO4•H2O dichloromethane
NaHSO4•H2O dichloromethane
25
79
25
125
150
160
100
100
100
100
95
25
98
25
97
15
87
20
89
30
98
35
97
aricinoleic acid (10 mmol) and glycol ether (12 mmol) and sodium bisulfate monohydrate
(30 mg), dichloromethane (3ml) 150W 25 min.
bthe esterification rate.
22

Table 5 Synthesis of Castor oil Derivativesa
Product R2
Yield
99%
98%
98%
96%
93%
95%
93%
91%
2a
2b
2c
2d
2e
2f
CH3OCH2CH2
CH3CH2OCH2CH2
CH3(CH2)3OCH2CH2
CH3 (OCH2CH2)2
CH3(CH2)3(OCH2CH2)2
CH3(OCH2CH2)3
2g
2h
2j
CH3(CH2)2(OCH2CH2)3
CH3[OCH (CH3)CH2]2
CH3CH2[OCH(CH3)CH2]2 89%
aricinoleic acid (10 mmol) and glycol ether (12 mmol) and add sodium bisulfate
monohydrate (30 mg), dichloromethane (3 ml) 150 W 25min.
bthe esterification rate.
23

Scheme 1.
24

Scheme 2.
25