Synthesis of aromatic alcohols and their alkanoic acid esters

Article abstract of DOI:10.1134/S1070427206030141

The reaction of benzene with ethylene and propylene oxides in a helium atmosphere with aluminum chloride as a catalyst and the esterification of the resulting alcohols with saturated monocarboxylic acids in the presence of the heterogeneous catalyst KU-2-8 were studied. Pleiades Publishing, Inc., 2006.

Full text of DOI:10.1134/S1070427206030141

ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 3, pp. 408 410. Pleiades Publishing, Inc., 2006.
Original Russian Text M.K. Mamedov, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 3, pp. 415 418.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Synthesis of Aromatic Alcohols and Their Alkanoic Acid Esters
M. K. Mamedov
Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Received July 26, 2005; in final form, January 2006
Abstract The reaction of benzene with ethylene and propylene oxides in a helium atmosphere with alumi-
num chloride as a catalyst and the esterification of the resulting alcohols with saturated monocarboxylic acids
in the presence of the heterogeneous catalyst KU-2-8 were studied.
DOI: 10.1134/S1070427206030141
Aldehydes, ketones, and higher alcohols have
usually pleasant odor and are synthetic fragrance
compounds [1 3]. Some aromatic alcohols and their
esters are successfully used in perfume industry as
components in preparation of perfume compositions,
eau de Colognes, food essences, and odorants for
detergents [4 6].
hydrins III VI:
RCHCH2 ,
OH
Cl
HCl + RCHCH2
III, IV
RCHCH2 ,
Cl
OH
The procedures of synthesis of aromatic alcohols
by the reaction of benzene with ethylene and propyl-
ene oxides [7, 8], hydrogenation of styrene oxide [9]
and cinnamic aldehyde [10], and oxidation of cumene
[11] are well known.
V, VI
where R is H (III, V), CH (IV, VI).
3
Chlorohydrins III VI adversely affect the yield of
alcohols I and II; therefore, to remove hydrogen
chloride from the system we used an inert gas (heli-
um); by so doing, we significantly increased the yield
of the target products I and II.
Taking account a great practical significance of
aromatic alcohols, we developed an efficient proce-
dure of synthesis of 2-phenylethanol and 1-phenyl-
2-propanol by hydroxyalkylation of benzene with
ethylene and propylene oxides in the presence of alu-
minum chloride as a catalyst [12].
The influence of various factors on the yields of I
and II was studied. We found that the optimum condi-
tions for hydroxyalkylation of benzene are the tem-
perature of 6 7 C, helium flow rate of 2 l min , and
molar ratio benzene : organic oxide : AlCl equal to
5 : 3 : 1. Under these conditions, the yield of alcohols
I and II reaches 90 95% based on organic oxides
(compare to the yield of 30 41% for the procedure
described in [13]).
1
The reaction proceeds in two steps. In the first step,
complexes A and hydrogen chloride are formed:
3
O
(C6H5CH2CHO)3Al
C6H6 + 3CH2CHR + AlCl3
R
A
To make the process waste-free, hydrogen chloride
was passed through aluminum hydroxide to obtain
aluminum chloride and helium was purified to remove
HCl and repeatedly used in the process.
+ 3HCl.
In the second step, decomposition of complexes A
with water yields aromatic alcohols I and II:
A + H2O
C6H5CH2CHOH + Al(OH)3,
The composition and structure of I and II were
1
proved by elemental analysis and IR and H NMR
R
I, II
spectra. In the IR spectra the bands at 3300, 3020,
1
1610, 1500, 745, and 695 cm are assigned to the
where R is H (I) and CH (II).
3
skeleton vibrations of monosubstituted benzene; the
1
Hydrogen chloride formed in the first step reacts
with the initial oxides to give as by-products chloro-
absorption at 900 cm corresponds to bending modes
1
of the C H bond; at 1380 cm , to methyl groups; at
408

SYNTHESIS OF AROMATIC ALCOHOLS AND THEIR ALKANOIC ACID ESTERS
1
409
1
3440 cm , to hydroxy groups; at 1060 cm , to
current 100 mA. The purity of alcohols I and II and
primary hydroxy groups; the absorption in the range
1400 1250 cm belongs to in-plane bending mode of
the bound OH group.
esters VI XIX was 99.0 99.5%.
1
The IR spectra were recorded on a UR-20 device in
1
CCl . The H NMR spectra of solutions of com-
4
1
In the H NMR spectra, phenyl protons give signals
pounds in CCl were recorded on a Tesla BS-487
4
in the range 6.8 7.28 ppm; methyl protons, at
1.38 ppm; and protons at the tertiary carbon atom and
OH group, at 4.75 and 2.60 2.70 ppm, respectively.
spectrometer operating at 80 MHz at 25 C; HMDS
was used as an internal reference; the accuracy of
measuring chemical shifts was 0.05 ppm.
With the aim to synthesize esters of the aromatic
alcohols synthesized, we studied their esterification
with saturated monocarboxylic acids. Contrary to the
existing procedures, in this reaction we used a hetero-
geneous catalyst, ion-exchange resin KU-2-8:
Hydroxyalkylation of benzene was performed
as follows. Benzene was charged into an enameled
reactor and anhydrous AlCl was added in portions
3
over a period of 1 h; then, a helium from a cylinder
was passed through the mixture at a flow rate of
1
2 l min . The released gas was passed through the
O
KU-2-8
other reactor containing a suspension of aluminum
hydroxide. Then, the calculated amount of ethylene or
propylene oxide was fed into the enameled reactor
over a period of 3 h. The reaction was carried out at
6 7 C; this temperature was maintained up to the end
of the process by passing cooled water through the
reactor jacket, since the process is exothermic. After
completion of feeding the oxide, the reaction mixture
was stirred for 1 h and cold distilled water was added
to decompose the resulting complex A. In so doing,
the upper layer was separated, dried over silica gel,
and aromatic alcohols I and II were isolated by frac-
tional distillation.
I, II + R COOH
C6H5CH2CHOCR ,
H O
2
R
_
VII XIX
where R is H (VII XII), CH (XIII XIX); R is CH
3
3
(VII, XIII), C H (VIII, XIV), CH (CH ) (IX, XV),
2
5
3
2 3
2 2
(CH ) CH (X, XIV), CH (CH ) (XI, XVII),
3 2
3
(CH ) CHCH (XII, XIX).
3 2
2
The use of the KU-2-8 catalyst significantly sim-
plifies synthesis of esters (VI XIX), since in this case
neutralization of the catalyzate, its washing, and dry-
ing before distillation are eliminated from the flow-
sheet.
2-Phenylethanol (I). From 1560 g of benzene,
Removal of water formed in the course of esteri-
fication from the system prevents the reverse reaction
and significantly increases the yield of the target com-
pounds (to 82 95%).
528 g of ethylene oxide, and 534 g of AlCl , 1317.6 g
3
of alcohol I was obtained (90%); bp 91 92 C (8 mm
20
20
Hg), d
= 1.0209, n
= 1.5306. IR spectrum,
4
D
1
(cm ): (CH of phenyl radical) 3330, 3020, 1610,
1500, 900, and 745; (CH CH ) 1440 1470; (OH)
The structure of the synthesized esters VI XIX
2
2
was proved by the IR spectra. The strong absorption
1
1
3440, 1060. H NMR spectrum ( , ppm): (OH) 2.60,
(CH ) 2.85, (CH ) 3.26, (CH of phenyl radical) 7.20.
bands at about 1720 and 1200 cm suggest the pres-
1
2
2
ence of the ester group. In the H NMR spectra, the
phenyl protons give a singlet at 7.20 ppm; methyl
protons, at 2.10 ppm; and ethylene (CH CH ) protons,
at 2.75 and 3.82 ppm.
Found, %: C 78.45, H 8.25.
C8H10O. Calculated, %: C 78.65, H 8.25.
2
2
1-Phenyl-2-propanol (II). From 1170 g of ben-
EXPERIMENTAL
zene, 522 g of propylene oxide, and 400.5 g of AlCl ,
3
The initial substances were freshly distilled chemi-
cally pure grade compounds, whose physicochemical
characteristics corresponded to published data [14].
1138.2 g of alcohol II was obtained (93%); bp 92
20
20
93 C (2 mm Hg), d = 1.0047, n = 1.5218. IR
4
D
1
spectrum,
(cm ): (CH of phenyl radical) 3330,
3018, 1605, 900, and 740; (CH ) 1380, (CH and CH)
The composition and purity of alcohols I and II
and their esters VI XIX were determined by gas
liquid chromatography on an LKhM-8 MD chroma-
tograph; stationary phase polyethylene glycol adipate
applied to Sferokhrom (10 wt %), column length 2 m,
vaporizer temperature 250 C, column temperature
120 170 C, detector temperature 120 170 C, and
3
2
1
1440, 1340; (OH) 3440, 1056. H NMR spectrum
( , ppm): (OH) 2.60, (CH ) 1.85, (CH ) 2.80, (CH)
2
2
4.58, (CH of phenyl radical) 7.25.
Found, %: C 79.36, H 8.81.
C9H12O. Calculated, %: C 79.37, H 8.88.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 3 2006

410
Yield, constants, elemental composition, molecular weight, and odor* of esters VII XIX
Found, % Calculated
MAMEDOV
M
Com- Yield,
bp,
C
d240
n2D0
Formula
pound
%
(10 mm Hg)
C
H
C
H
found calculated
VII
VIII
IX
X
XI
93
92
91
90
89
89
93
89
86
84
82
83
82
113
121
135
1.0181 1.5029 73.04 7.30 C10H12O2
1.0101 1.4904 74.10 7.58 C11H14O2
0.9905 1.4905 74.86 8.23 C12H16O2
0.9871 1.4895 74.90 8.26 C12H16O2
0.9864 1.4982 75.59 8.29 C13H18O2
0.9791 1.4878 75.61 8.23 C13H18O2
73.14
74.13
74.97
74.97
75.69
75.69
73.14
74.13
74.97
75.69
75.69
76.33
76.33
7.37
7.92
8.39
8.39
8.38
8.38
7.37
7.92
8.39
8.80
8.80
9.15
9.15
164.20
178.10
192.20
192.11
206.21
206.82
164.10
178.20
192.20
206.28
206.26
220.29
220.28
164.20
178.20
192.23
192.23
206.88
206.28
164.20
178.23
192.26
206.31
206.31
220.31
220.31
128 129
138 139
133 134
127
138
146
157 158
151 152
175 176
171 172
XII
XIII
XIV
XV
XVI
XVII
XVIII
XIX
1.0081 1.5180 73.0
7.25 C10H12O2
1.0028 1.5160 74.03 7.89 C11H14O2
1.0001 1.5167 74.82 8.27 C12H16O2
0.9909 1.5181 75.65 8.62 C13H18O2
0.9825 1.5011 75.61 8.69 C13H18O2
0.9806 1.5099 76.25 9.10 C14H20O2
0.9800 1.5006 76.28 9.05 C14H20O2
* Odor: VII, fruit (tint of greens); VIII, fruit (rose tint); IX, fruit (rose tint); X, weak fruit; XI, delicate fruit; XII, apricot (rose tint);
XIV, grass; XVI, weak flower; XVII, weak fruit; XIX, flower fruit.
1
Organoleptic tests of the synthesized alcohols
show that 2-phenylethanol has rose odor, and 1-phen-
yl-2-propanol, hyacinth odor.
REFERENCES
1. FRG Patent Appl. no. 10226942.
2. FRG Patent Appl. no. 10206771.
3. Challener, C., Spec. Chem. Mag., 2004, vol. 24, no. 6,
Esters VI XIX of alcohols I and II (see table)
were prepared using a Dean Stark trap with KU-2-8
catalyst in an amount of 10 wt % based on the raw
materials in benzene at 80 85 C. The water release
was complete in 4 5 h. The molar ratio of reacting
components I, II : carboxylic acid : solvent was
1 : 1 : 2.
pp. 32 34.
4. Kheifits, L.A. and Dashunin, V.M., Dushistye ve-
shchestva i drugie produkty dlya parfumerii (Fragrance
Compounds and Other Products for Perfumery), Mos-
cow: Khimiya, 1994.
5. Clark, C.S., Perfum. Flavor., 1990, vol. 15, pp. 37 44.
6. Bratus, I.N., Khimiya dushistykh veshchestv (Chemis-
try of Fragrance Compounds), Moscow: Agropromiz-
dat, 1992.
7. Cristol, S., Douglass, J., and Meek, J., J. Am. Chem.
Soc., 1951, vol. 73, pp. 816 818.
8. USSR Inventors’ Certificate no. 433121.
9. Kologrivova, N.E., Shumskaya, I.V., and Khei-
CONCLUSIONS
(1) Aromatic alcohols that are synthetic fragrance
compounds were synthesized by hydroxyalkylation of
benzene with ethylene and propylene oxides in an
inert medium with aluminum chloride as a catalyst
(yield 90 93%).
fits, L.A., Maslozhir. Prom-st., 1983, issue 12, pp. 23
25.
(2) Esterification of the aromatic alcohols syn-
thesized with saturated aliphatic monocarboxylic acids
in the presence of a heterogeneous catalyst, KU-2-8
ion-exchange resin, yields esters (yield 82 95%) with
pleasant odor, which can be used as a component of
perfumes and essences.
10. French Patent 2015475.
11. US Patent 244700.
12. USSR Inventors’ Certificate no. 1778109.
13. Likhterov, V.R. and Etlis, V.S., Zh. Obshch. Khim.,
1957, vol. 27, no. 9, pp. 1867 1869.
14. Goronovskii, I.T., Nazarenko, Yu.P., and Nek-
ryach, E.F., Kratkii spravochnik po khimii (Brief
Handbook on Chemistry), Kiev: Naukova Dumka,
1974.
1
Organoleptic tests were performed at the All-Russian Research
Institute of Synthetic and Natural Fragrance Compounds
(Moscow).
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 3 2006