Synthesis of ethyl benzoate by ozonolysis of styrene in the presence of ethanol

Article abstract of DOI:10.1023/A:1016103023539

Ozonolysis of styrene in the presence of ethanol was studied as a route to ethyl benzoate.

Full text of DOI:10.1023/A:1016103023539

Russian Journal of Applied Chemistry, Vol. 75, No. 3, 2002, pp. 441 443. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 3,
2002, pp. 452 454.
Original Russian Text Copyright
2002 by Gaifutdinova, Beresnev.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Synthesis of Ethyl Benzoate by Ozonolysis of Styrene
in the Presence of Ethanol
E. K. Gaifutdinova and V. V. Beresnev
Kazan State Technological University, Kazan, Tatarstan, Russia
Received July 11, 2001
Abstract Ozonolysis of styrene in the presence of ethanol was studied as a route to ethyl benzoate.
Thanks to the high reactivity of ozone and its
selective action on C=C bonds, ozonolysis of unsatu-
rated organic compounds shows promise for industrial
synthesis of various compounds with oxygen-contain-
ing functional groups [1].
254 nm. Oxidation was performed to ozone break-
through, which was detected by coloration of a 15%
aqueous KI solution in a wash bottle placed at the
reactor outlet (with starch as indicator). In the course
of ozonolysis, we withdrew samples to determine the
content of available oxygen [11] and of carboxy,
carbonyl, and ester groups [12].
Recently the demand for benzoic acid and its deriv-
atives increased. These compounds are widely used
in various branches of the national economy. Benzoic
acid esters are used in production of dyes [2], heat-
resistant lubricants [3], herbicides [4], alkali-resistant
polyester coatings [5], and also as plasticizers for
synthetic resins, cellulose ethers and esters, rubbers,
and paper, as additives for dyeing fabrics made from
manmade fibers [5], as polymerization catalysts [3],
drugs [6 8], active ingredients of plant growth regu-
lators [9], and cosmetic means [10].
The thermal decomposition of ozonides was per-
formed by heating the reaction solutions at 90 100 C
for 2 4 h. In the resulting products, we determined
the content of carboxy, ester, and carbonyl groups.
The IR spectra were recorded on an IFS-113V
1
Fourier spectrometer in the range 400 4000 cm
1
with a resolution of 2 cm ; samples were prepared
as films cast from solution on KBr plates, or as KBr
pellets. The GC MS study of ozonolysis products was
performed with a Finnigan-MAT 212 device (INCOS
50 mass spectrometer, Varian 3400 gas liquid chro-
matograph, capillary column with grafted SE-30,
carrier gas helium, heating from 40 to 300 C at a rate
High selectivity of ozonolysis of unsaturated hy-
drocarbons gives reasons to hope that synthesis of
benzoic acid esters by ozonolysis starting from styrene
and alcohols would be commercially feasible.
1
of 15 deg min , injector temperature 250 C). The
13
EXPERIMENTAL
C NMR spectra of ozonolysis products were taken
on a Bruker MSL 400 spectometer at 100.62 MHz; the
chemical shifts were measured relative to TMS [13].
Ozonolysis was performed in a glass bubbler with
a porous bottom; it was charged with a styrene (I)
solution. Ozone was generated by passing oxygen
through a glow discharge at 10 kV. The ozone con-
centration was determined spectrophotometrically at
According to the experimental results, ozonolysis
of styrene in the presence of ethanol can be described
by the following scheme:
O
_
O
O
O
O
O
O
O
1
3
C6H5 C+H + CH5O
C6H5 CH CH2
C6H5 CH=CH2
C6H5 CH CH2
ROH
I
II
III
IV
O
V
C H OH
2
5
O
OH
C6H5 CHOC2H5 + CH2O
C6H5 CO2C2H5 + CH2O,
_
H O
VI
2
VII
1070-4272/02/7503-0441$27.00 2002 MAIK Nauka/Interperiodica

442
GAIFUTDINOVA, BERESNEV
O
_
O
O
O
O
O
O
O
3
2
C6H5 CH CH2
C6H5 CH CH2
C6H5 CH CH2
HC+H + C6H5 CHO
ROH
I
VIII
IX
II
O
V
C H OH
O
OH
2
5
HCHOC2H5 + C6H5 CHO
HCO2C2H5 + C6H5 CHO.
_
H O
2
XI
X
According to this scheme, addition of ozone to the
double bond in styrene I yields unstable molozonide
II; in the presence of a terminal double bond the aro-
matic system remains intact [14]. Molozonide readily
decomposes into two fragments: bipolar ion III or
VIII and carbonyl compound IV or IX. Presumably,
owing to the positive inductive effect of the phenyl
ring in styrene I, formation of the bipolar ion at the
phenyl-substituted carbon atom [reaction (1)] is pre-
ferable [15]. The pair bipolar ion carbonyl compound
arising in decomposition of molozonide rapidly re-
combines in the solvent cage to form ozonide V.
Formation of this compound is preceded by a change
in the mutual orientation of fragments III and IV
[reaction (1)], or VIII and IX [reaction (2)] (turn by
180 ). Decomposition of ozonide V also yields bipolar
ion III or VIII and carbonyl compound IV or IX.
Thermal decomposition of alkoxy hydroperoxides
VI and X was performed at 90 100 C. It is advisable
to perform the reaction at elevated temperatures, be-
cause at low temperatures formation of esters is too
slow. The reaction is accompanied by release of low-
molecular-weight inorganic products (e.g., water,
which is formed by hydrogen abstraction by the hy-
droxy radical).
The IR spectra of reaction products contain ab-
1
sorption bands at 1260 [ (C O)] and 1715 cm
[ (C=O)], confirming the presence of ethyl benzoate.
1
1
The bands at 1680 and 1690 cm belong to benzoic
acid, and the band at 1700 cm is characteristic of
aromatic aldehydes (in particular, benzaldehyde IX).
13
The C NMR spectrum of the reaction product (after
vacuum distillation) confirms its identification as
ethyl benzoate [ , ppm: 166 (C=O), 125 135 (Ph),
C
Bipolar ion III or VIII is stabilized by reaction
with an added active compound (ethanol) to form
ethoxy hydroperoxides VI and X. In pathway (1),
which is apparently preferable (see above), the second
reaction product is formaldehyde IV. However, its
content in the reaction mixture was low, probably
because of easy volatilization.
61.4 (CH ), 14.6 (CH )].
2
3
The major reaction products are ethyl benzoate VII
[63.4 wt %, isolated by vacuum distillation (68 C at
15 mm Hg)] and ethyl formate XI (20.4 wt %); the
by-products are formaldehyde (6.0 wt %), benzalde-
hyde (6.3 wt %), formic acid (1.8 wt %), and benzoic
acid (2.1 wt %).
We found that the content of available oxygen
increases with the progress of styrene oxidation. We
found that at the molar ratio styrene : ethanol = 1 : 1.5
the yield of available oxygen reaches a maximum
(8.14 wt %); at the ethanol content increased further,
the content of available oxygen decreases.
CONCLUSION
A procedure was suggested for preparing ethyl
benzoate by ozonolysis of styrene in the presence of
ethanol, followed by thermal decomposition of the
intermediate ozonolysis products.
The IR spectra of alkoxy hydroperoxides contain
1
the following absorption bands (cm ): 2980 [ (CH )];
3
2950 [ (CH )]; 2890 [ (CH )]; 1310 [ (C O)]; 1110
[ (CO)]; 990, 910, and 840 [ (O O)] [15].
2
3
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Alkoxy hydroperoxides are unstable and readily
decompose even at room temperature [16]. After stor-
age of a mixture of ethoxy hydroperoxides VI and X
for 2 months at 20 C, the content of available oxygen
decreased from 8.1 to 1.9%.
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