Conversion of phenylacetonitrile in supercritical alcohols within a system containing small volume of water

Article abstract of DOI:10.1515/chempap-2015-0047

The reaction of phenylacetonitrile in supercritical methanol and ethanol in a system containing a small volume of water was studied. The effects of various operating conditions, such as reaction temperature, reaction time, the mole ratio of phenylacetonitrile/water/methanol or ethanol on the product yield were systematically investigated. The optimal yield of methyl phenylacetate for phenylacetonitrile in supercritical methanol in a system containing a small volume of water was 70 % at 583 K and 2.5 h. The optimal yield of ethyl phenylacetate for phenylacetonitrile in supercritical ethanol with a small volume of water was 80 % at 583 K and 1.0 h. At the same time, a feasible mechanism was proposed for phenylacetonitrile in supercritical methanol and ethanol in a system containing a small volume of water.

Full text of DOI:10.1515/chempap-2015-0047

Chemical Papers 69 (3) 490–494 (2015)
DOI: 10.1515/chempap-2015-0047
SHORT COMMUNICATION
Conversion of phenylacetonitrile in supercritical alcohols
within a system containing small volume of water
Zhi-Qiang Hou, Rui-Zhe Zhang, Li-Gang Luo, Jing Yang, Chun-Ze Liu,
Yuan-Yuan Wang*, Li-Yi Dai
Department of Chemistry, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
Received 14 April 2014; Revised 9 July 2014; Accepted 3 August 2014
The reaction of phenylacetonitrile in supercritical methanol and ethanol in a system containing
a small volume of water was studied. The effects of various operating conditions, such as reaction
temperature, reaction time, the mole ratio of phenylacetonitrile/water/methanol or ethanol on
the product yield were systematically investigated. The optimal yield of methyl phenylacetate for
phenylacetonitrile in supercritical methanol in a system containing a small volume of water was 70 %
at 583 K and 2.5 h. The optimal yield of ethyl phenylacetate for phenylacetonitrile in supercritical
ethanol with a small volume of water was 80 % at 583 K and 1.0 h. At the same time, a feasible
mechanism was proposed for phenylacetonitrile in supercritical methanol and ethanol in a system
containing a small volume of water.
ꢀ
c 2014 Institute of Chemistry, Slovak Academy of Sciences
Keywords: phenylacetonitrile, supercritical methanol/ethanol, methyl phenylacetate, ethyl pheny-
lacetate, alcoholysis reaction mechanism
Methyl and ethyl phenylacetates are widely used in
daily life and industry. Karlsson et al. (2009) reported
that flowering plants released large amounts of methyl
phenylacetate, and that this compound had a strong
honey-like floral fragrance with earthy tones. Ethyl
phenylacetate has long been known as a synthetic
honey flavour (Buttery et al., 1980). At the same time,
methyl phenylacetate (Pinheiro et al., 2000; Nomura
et al., 2002) and ethyl phenylacetate (Periasamy et
al., 2003) have been used as reactants in organic re-
actions. Ethyl phenylacetate has also been used as an
effective solvent for organic materials (Caruso et al.,
of the most promising due to milder reaction condi-
tions, such as its higher solubility and high ionic prod-
uct, which was commonly used in the alcoholysis re-
action. Researchers have paid increasing attention to
supercritical alcohol and a series of studies have been
conducted (Demirba ¸s , 2002; Kusdiana & Saka, 2004;
Bicker et al., 2005; Minami & Saka, 2006; Song et al.,
2008; Kamitanaka et al., 2008; Goto et al., 2009; Šk-
erget et al., 2011; Trivedi et al., 2013). Kamitanaka
et al. (2008) investigated the non-catalytic alcoholy-
sis of benzonitrile in supercritical methanol. A 95 %
yield of methyl benzoate was obtained at 623 K after
12 h. This study suggested that supercritical alcohols
possessed high reactivity toward unsaturated bonds.
The present study sought a useful method for effec-
tively transforming phenylacetonitrile into a valuable
chemical. However, Vieitez et al. (2010) reported that
adding water to a level of 10 mass % to the reaction
medium afforded an increase in both the methyl and
ethyl ester contents by increasing the reaction rate
and reducing the degradation of fatty acids; He et
2
008).
Traditionally, the nitrile was allowed to react with
an aqueous alcohol in the presence of large amounts
of sulphuric acid. In this reaction, the nitrogen from
the nitrile was converted to relatively valueless am-
monium sulphate, while separation of the sulphuric
acid entailed a difficult and costly process, hence ren-
dering this method commercially limited (Gasson &
Hadley, 1960). However, supercritical alcohol was one
*Corresponding author, e-mail: yywang@chem.ecnu.edu.cn, lydai@chem.ecnu.edu.cn
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/9/15 8:25 PM

Z. Q. Hou et al./Chemical Papers 69 (3) 490–494 (2015)
491
Fig. 1. Effects of reaction time and reaction temperatures on phenylacetonitrile conversion (a) and methyl phenylacetate yield (b).
Mole ratio of reactant/water/methanol = 1 : 13 : 75, at different temperatures: 533 K ( ), 553 K (
), 573 K (ꢀ), and
83 K (ꢁ).
•
5
al. (2004) also reported that the water and alcohol-
assisted alcoholysis of N-methyl-1,2-thiazetidine-1,1-
dioxide greatly reduced the active energy in compar-
ison with the non-assisted reaction. Hence, the re-
action of phenylacetonitrile in supercritical methanol
and ethanol with a small content of water was investi-
gated, and the addition of a small volume of water was
found to promote the reaction which produced excel-
lent results. At the same time, a feasible mechanism
was proposed for the reaction of phenylacetonitrile in
supercritical methanol and ethanol in a system con-
taining a small volume of water.
ature when the desired reaction time had elapsed. It
was then cooled in an ice-water bath to terminate the
reaction and the reactor was rinsed with ethanol at
least three times using a microlitre syringe to recover
the product.
The uncertainty in the results was determined as
the 95 % confidence interval, on the basis of at least
three independent experiments conducted under nom-
inally identical conditions. The results reported here
represent the mean values for the independent trials.
The reaction solution was subjected to analysis by
gas chromatography (Shimadzu, Japan; GC-2014, RT-
10223; capillary column, i.d. 0.25 mm, film thickness
0.25 m, length 30 m). The sample was quantitatively
analysed using the area normalisation method. Iden-
tification of the products was performed using a GC–
MS (Saturn 2100 T, Varian 3900, USA; Factor Four
Capillary column VF-5ms; i.d. 0.25 mm, film thickness
0.25 m, length 30 m).
All the experiments were conducted within a time
range of 0.5–2.5 h, temperatures in a range of 533–
583 K, and phenylacetonitrile/water/methanol mole
ratio of 1 : 13 : 75, and the major product was
methyl phenylacetate. The effect of time on the pheny-
lacetonitrile conversion and the methyl phenylacetate
yield is shown in Figs. 1a and 1b, respectively. Fig. 1a
shows that the phenylacetonitrile conversion gradually
increased with the increasing reaction time at tem-
peratures of 533–583 K. The phenylacetonitrile con-
version achieved 97 % at 583 K and 2.5 h. As shown
in Fig. 1b, the methyl phenylacetate yield gradually
increased with the increasing reaction time at temper-
atures of 533–583 K. The methyl phenylacetate yields
were clearly higher at 573 K and 583 K than those
In this work, the critical conditions of methanol
and alcohol were (Tc = 513 K, pc = 8.1 MPa and
−
3
ρc = 0.272 g cm ) for methanol and (Tc = 516 K,
−
3
pc = 6.3 MPa and ρc = 0.276 g cm ) for ethanol,
respectively (Kamitanaka et al., 2008).
Phenylacetonitrile, methanol and ethanol (all ana-
lytical reagents) were sourced from Sinopharm Chem-
ical Reagent (China) and used as received. Pure water
was redistilled after deionisation.
Experiments were conducted in a 316 stainless steel
batch reactor (Shandong Precision and Scientific In-
strument, China) with a volume of 500 L. The to-
tal amount of stock mixture solutions was calculated
to drive the pressure inside the reactor to the satu-
rated water vapour pressure at any given temperature
(Duan et al., 2009; Chang et al., 2012). The pheny-
lacetonitrile, methanol, ethanol and water were fed
into the reactor using different microlitre syringes at
the mole ratio. The loaded reactor was placed in the
salt bath (consisting of NaNO2, NaNO3 and KNO3
(Sinopharm Chemical Reagent) at a mass ratio of
4
0 : 7 : 53) which was preheated to the desired temper-
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/9/15 8:25 PM

4
92
Z. Q. Hou et al./Chemical Papers 69 (3) 490–494 (2015)
Fig. 2. Effects of reaction time and reaction temperatures on phenylacetonitrile conversion (a) and ethyl phenylacetate yield (b).
Mole ratio of reactant/water/ethanol = 1 : 13 : 51, at different temperatures: 533 K ( ), 553 K (
), 573 K (ꢀ), and
83 K (ꢁ).
•
5
at 533 K and 553 K corresponding to the same re-
action time. At the same time, the methyl phenylac-
etate yields were close at 573 K and 583 K but high
at 533 K and 553 K. This indicated that the longer
reaction time was beneficial to the phenylacetonitrile
conversion and the methyl phenylacetate yield.
Table 1. Effects of mole ratio of reactant/water/methanol on
phenylacetonitrile conversion and methyl phenylac-
etate yield at 583 K and 2.5 h
Mole ratio
Conversion Yield
%
Phenylacetonitrile/Water/Methanol
Figs. 1a and 1b also show the effect of temper-
ature on the phenylacetonitrile conversion and the
methyl phenylacetate yield, respectively. Fig. 1a in-
dicates that the phenylacetonitrile conversion was low
at 533 K and 553 K. However, the phenylacetonitrile
conversion clearly increased at 573 K and 583 K. No
obvious difference in the conversion of phenylacetoni-
trile was observed at 573 K and 583 K. As shown
in Fig. 1b, the methyl phenylacetate yields increased
with the increasing temperatures of 533–583 K. The
methyl phenylacetate yields were low at 533 K and
1
1
1
1
: 7 : 78
: 13 : 75
: 20 : 72
: 26 : 69
93
97
96
96
95
67
70
64
63
54
1 : 33 : 66
tively. This indicated that the optimal phenylacetoni-
trile/water/methanol mole ratio was 1 : 13 : 75.
All the experiments were conducted within a time
range of 0.5–2.5 h, temperatures in a range of 533–
583 K, and phenylacetonitrile/water/ethanol molar
ratios of 1 : 13 : 51; the major product was ethyl
phenylacetate. The effect of time on the phenylace-
tonitrile conversion and the ethyl phenylacetate yield
is shown in Figs. 2a and 2b, respectively. Fig. 2a shows
that the phenylacetonitrile conversion gradually in-
creased with the increasing reaction time at 533 K and
553 K. However, the phenylacetonitrile conversion in-
creased up to 1.5 h at 573 K and 583 K, then remained
unchanged. From Fig. 2b, it may also be observed that
the ethyl phenylacetate yield increased gradually with
the reaction time at temperatures of 553–573 K. but
the ethyl phenylacetate yield increased up to 1.0 h
at 583 K, then it decreased. This indicated that the
optimal reaction time was 1.0 h for the reaction of
phenylacetonitrile in supercritical ethanol in a system
containing a small volume of water.
5
53 K. The methyl phenylacetate yield clearly in-
creased at 573 K and 583 K compared with 533 K
and 553 K, but there were also no obvious differences
at 573 K and 583 K. A high yield of 70 % was achieved
at 583 K and 2.5 h. This indicated that temperature
greatly affected the phenylacetonitrile conversion and
the methyl phenylacetate yield.
Table 1 shows the effect of phenylacetonitrile/wa-
ter/methanol mole ratios on the phenylacetonitrile
conversion and the methyl phenylacetate yield at
5
83 K and 2.5 h. As shown in Table 1, all the
phenylacetonitrile conversions were around 95 % at
different phenylacetonitrile/water/methanol mole ra-
tios, 583 K and 2.5 h. However, the phenylacetoni-
trile/water/methanol mole ratios had a slight effect
on the methyl phenylacetate yield. For instance, the
methyl phenylacetate yields were 67 %, 70 %, 64 %,
6
3 %, and 54 % at a phenylacetonitrile/water/ethanol
mole ratio of 1 : 7 : 78 to 1 : 33 : 66, respec-
Figs. 2a and 2b also show the effects of temper-
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/9/15 8:25 PM

Z. Q. Hou et al./Chemical Papers 69 (3) 490–494 (2015)
493
Fig. 3. Possible reactions of phenylacetonitrile in supercritical methanol and ethanol in system containing small volume of water.
R = benzyl, R’= methyl or ethyl).
(
Table 2. Effects of mole ratio of reactant/water/ethanol on
phenylacetonitrile conversion and ethyl phenylacetate
yield at 583 K and 1.0 h
phenylacetonitrile/water/ethanol mole ratios. How-
ever, the phenylacetonitrile/water/ethanol molar ra-
tio had a great effect on the ethyl phenylacetate
yield. For instance, the methyl phenylacetate yields
were 64 %, 64 %, 67 %, 80 %, and 72 % at phenyl-
acetonitrile/water/ethanol mole ratio of 1 : 7 : 53–
Mole ratio
Conversion
%
Yield
Phenylacetonitrile/Water/Ethanol
1
: 33 : 45, respectively, showing the optimal phenyl-
1
1
1
1
1
: 7 : 53
: 13 : 51
: 20 : 49
: 26 : 47
: 33 : 45
93
98
97
91
89
72
80
67
64
64
acetonitrile/water/ethanol mole ratio to be 1 : 13 : 51.
Reeve et al. (1979) reported that the relative acid-
ity of methanol and ethanol were pH 4.4 and pH 1.0,
respectively. Kamitanaka et al. (2008) also reported
that the concentration of alkoxide ion in methanol
was much higher than that in ethanol, which might
also be valid for the alcohols in the supercritical state,
suggesting that the alkoxide ion concentration was re-
sponsible for the rapid formation of esters. These sup-
ported the greater reactivity of methanol compared to
ethanol. However, Madras et al. (2004) reported that
the conversion of sunflower oil was higher in super-
critical ethanol than the conversions obtained in su-
percritical methanol, because the solubility parameter
of ethanol was lower than that of methanol and was
closer to the solubility parameter of the oil. Hence, it
may be presumed that the difference in the solubility
parameters of methanol, ethanol and phenylacetoni-
trile resulted in the yield of ethyl phenylacetate being
higher than that of methyl phenylacetate.
ature on the phenylacetonitrile conversion and the
ethyl phenylacetate yield, respectively. Fig. 2a indi-
cates that the phenylacetonitrile conversions were high
at 573 K and 583 K. However, the phenylacetonitrile
conversions were low at a shorter reaction time but
high after a longer reaction time. Fig. 2b shows that
the ethyl phenylacetate yields gradually increased at
temperatures of 533–573 K; however, the ethyl pheny-
lacetate yields began to decrease after 1.0 h at 583 K.
The optimal ethyl phenylacetate yield was 80 % at
5
83 K and 1.0 h. This indicated that temperature had
a great effect on the phenylacetonitrile conversion and
ethyl phenylacetate yield, indicating that the optimal
reaction temperature was 583 K for the reaction of
phenylacetonitrile in supercritical ethanol in a system
containing a small volume of water.
Table 2 shows the effect of the phenylacetoni-
trile/water/ethanol mole ratios on the phenylacetoni-
trile conversion and ethyl phenylacetate yield at 583 K
and 1.0 h. As shown in Table 2, all the phenylace-
tonitrile conversions were around 90 % at various
Based on the mechanism for the Pinner reaction
(Lee & Crayston, 1996; Schneekloth et al., 2009),
Fig. 3 shows a possible reaction mechanism for pheny-
lacetonitrile in supercritical alcohol in a system con-
taining a small volume of water. This may be de-
scribed as follows: H originating from H2O was do-
nated to the C—N bond, and the primary alcohol
functioned as an alcoholysis agent for the C—NH
+
—
—
+
—
—
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/9/15 8:25 PM

4
94
Z. Q. Hou et al./Chemical Papers 69 (3) 490–494 (2015)
bond. The alcohol molecule attacked the carbon
atom of RC —NH to form II (RC—NH(OH R )).
507. DOI: 10.1016/j.supflu.2008.10.011.
+
+
ꢀ
He, M. X., Feng, D. C., Zhu, F., & Cai, Z. T. (2004) Alcoholysis
of N-methyl-1,2-thiazetidine-1,1-dioxide: DFT study of water
and alcohol effects. Journal of Physical Chemistry A, 108,
+
Subsequently, II eventually formed III (RC—NH2
ꢀ
(
OR )). Then, III was attacked by H2O to form
IV (RC(NH )(OH)(OR )). IV was further converted
to V (RC—OH (OR )). Finally, V formed VI
RC—O(OR )). At the same time, a small volume of
water directly attacked the RC —NH carbon com-
peting with alcohol to form phenylacetic acid. Hence,
some by-products were afforded, such as NH3, ammo-
nium phenylacetic acid or phenylacetic acid.
7702–7708. DOI: 10.1021/jp048374s.
+
3
ꢀ
Kamitanaka, T., Yamamoto, K., Matsuda, T., & Harada, T.
(2008). Transformation of benzonitrile into benzyl alcohol
and benzoate esters in supercritical alcohols. Tetrahedron,
64, 5699–5702. DOI: 10.1016/j.tet.2008.04.029.
Karlsson, M. F., Birgersson, G., Prado, A. M. C., Bosa, F.,
Bengtsson, M., & Witzgall, P. (2009). Plant odor analysis
of potato: Response of guatemalan moth to above- and be-
lowground potato volatiles. Journal of Agricultural and Food
Chemistry, 57, 5903–5909. DOI: 10.1021/jf803730h.
+
ꢀ
ꢀ
(
+
The treatment of phenylacetonitrile in supercrit-
ical methanol and ethanol in a system containing a
small volume of water was proposed. The effects of
such operating parameters as reaction temperature,
reaction time and molar ratio on product yield were
investigated. The optimal yield of methyl phenylac-
etate from phenylacetonitrile in a system containing
supercritical methanol with a small volume of water
was 70 % at 583 K and 2.5 h. The optimal yield of
ethyl phenylacetate from phenylacetonitrile in a sys-
tem containing supercritical ethanol with a small vol-
ume of water was 80 % at 583 K and 1.0 h. This indi-
cated that the supercritical ethanol was a more suit-
able alcohol for the reaction of phenylacetonitrile. A
feasible mechanism was proposed on the basis of the
experimental results.
Kusdiana, D., & Saka, S. (2004). Effect of water on biodiesel fuel
production by supercritical methanol treatment. Bioresource
Technology, 91, 289–295. DOI: 10.1016/s0960-8524(03)00201-
3.
Lee, G. R., & Crayston, J. A. (1996). Hydrolysis of acetonitrile
in the presence of NbCl5. Polyhedron, 15, 1817–1821. DOI:
10.1016/0277-5387(95)00432-7.
Madras, G., Kolluru, C., & Kumar, R. (2004). Synthesis of
biodiesel in supercritical fluids. Fuel, 83, 2029–2033. DOI:
10.1016/j.fuel.2004.03.014.
Minami, E. J., & Saka, S. (2006). Kinetics of hydrolysis and
methyl esterification for biodiesel production in two-step
supercritical methanol process. Fuel, 85, 2479–2483. DOI:
10.1016/j.fuel.2006.04.017.
Nomura, K., Ogura, H., & Imanishi, Y. (2002). Ruthenium cat-
alyzed hydrogenation of methyl phenylacetate under low hy-
drogen pressure. Journal of Molecular Catalysis A: Chemi-
cal, 178, 105–114. DOI: 10.1016/s1381-1169(01)00281-3.
Periasamy, M., Babu, N. K., & Jayakumar, K. N. (2003). A
novel arylation of arylacetic acid esters using tertiary ary-
lamines and TiCl4. Tetrahedron Letters, 44, 8939–8941. DOI:
Acknowledgements. The authors wish to acknowledge the fi-
nancial support provided by the National Natural Science Foun-
dation of China (nos. 21073064, 21003049).
1
0.1016/j.tetlet.2003.10.009.
Pinheiro, S., Lima, M. B., Gon c¸ alves, C. B. S. S., Pedraza, S. F.,
de Farias, F. M. C. (2000). Control of diasteroselectivity
References
&
in the aldolization of methyl phenylacetate. Tetrahedron Let-
ters, 41, 4033–4034. DOI: 10.1016/s0040-4039(00)00582-7.
Reeve, W., Erikson, C. M., & Aluotto, P. F. (1979). A new
method for the determination of the relative acidities of al-
cohols in alcoholic solutions. The nucleophilicities and com-
petitive reactivities of alkoxides and phenoxides. Canadian
Journal of Chemistry, 57, 2747–2754. DOI: 10.1139/v79-444.
Schneekloth, J. S., Jr., Kim, J., & Sorensen, E. J. (2009). An in-
terrupted Ugi reaction enables the preparation of substituted
indoxyls and aminoindoles. Tetrahedron, 65, 3096–3101. DOI:
Bicker, M., Kaiser, D., Ott, L., & Vogel, H. (2005). Dehydration
of D-fructose to hydroxymethylfurfural in sub- and supercrit-
ical fluids. Journal of Supercritical Fluids, 36, 118–126. DOI:
10.1016/j.supflu.2005.04.004.
Buttery, R. G., Ling, L. C., & Teranishi, R. (1980). Volatiles
of corn tassels: possible corn ear worm attractants. Jour-
nal of Agricultural and Food Chemistry, 28, 771–774. DOI:
1
0.1021/jf60230a020.
Caruso, M. M., Blaiszik, B. J., White, S. R., Sottos, N.
R., Moore, J. S. (2008). Full recovery of francture
&
10.1016/j.tet.2008.08.055.
toughness using a nontoxic solvent-based self-healing sys-
tem. Advanced Functional Materials, 18, 1898–1904. DOI:
Škerget, S., Knez, Ž., & Knez-Hrnčič, M. (2011). Solubility
of solids in sub- and supercritical fluids: a review. Jour-
nal of Chemical & Engineering Data, 56, 694–719. DOI:
10.1002/adfm.200800300.
Chang, Y. J., Wang, Z. Z., Luo, L. G., & Dai, L. Y. (2012).
Additive-assisted Rupe rearrangement of 1-ethynylcyclo-
hexan-1-ol in near-critical water. Chemical Papers, 66, 33–
1
0.1021/je1011373.
Song, E. S., Lim, J. W., Lee, H. S., & Lee, Y. W. (2008).
Transesterification of RBD palm oil using supercritical
methanol. Journal of Supercritical Fluids, 44, 356–363. DOI:
10.1016/j.supflu.2007.09.010.
Vieitez, I., da Silva, C., Alckmin, I., Borges, G. R., Corazza,
F. C., Oliveira, J. V., Grompone, M. A., & Jachmanián, I.
(2010). Continuous catalyst-free methanolysis and ethanoly-
sis of soybean oil under supercritical alcohol/water mixtures.
Renewable Energy, 35, 1976–1981. DOI: 10.1016/j.renene.
2010.01.027.
38. DOI: 10.2478/s11696-011-0093-3.
Demirba ¸s , A. (2002). Biodiesel from vegetable oils via trans-
esterification in supercritical methanol. Energy Conver-
sion and Management, 43, 2349–2356. DOI: 10.1016/s0196-
8904(01)00170-4.
Duan, P. G., Li, S., Yang, Y., Wang, Z. Z., & Dai, L. Y. (2009).
Green medium for the hydrolysis of 5-cyanovaleramide.
Chemical Engineering & Technology, 32, 771–777. DOI:
1
0.1002/ceat.200800607.
Trivedi, V., Bhomia, R., Mitchell, J. C., Coleman, N. J.,
Douroumis, D., & Snowden, M. J. (2013). Study of the effect
of pressure on melting behavior of saturated fatty acids in liq-
uid or supercritical carbon dioxide. Journal of Chemical &
Engineering Data, 58, 1861–1866. DOI: 10.1021/je400260c.
Gasson, E. J., & Hadley, D. J. (1960). U.S. Patent No. 2,921,088.
Washington, D.C., USA: U.S. Patent and Trademark Office.
Goto, M. (2009). Chemical recycling of plastics using sub- and
supercritical fluids. Journal of Supercritical Fluids, 47, 500–
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/9/15 8:25 PM