Reac$. Kinet. Cata~. LetS., Vol. $3, No. 2, 471-476 (1987)
ISOMERIZATION OF EUGENOL TO ISOEUGENOL
L. ~erven~, A. Krej~ikov~, A. Marhoul and V. R ~ i d k a
Department of Organic Technology,
Technology,
Institute of Chemical
166 28 Prague 6, Czechoslovakia
Received June 6, 1986
Accepted July 9, 2986
The isomerization of eugenol to isoeugenol was investigated by employing catalysis by KOH in amyl alcohol or
glycerol, or by RhCl 3. A number of factors which affect
the reaction (solvent, temperature, molar ratios, presence of water) were examined.
Hccne~osaHa HSOMepH3auH~ 9BreHo~a B H30~BPeHO~ B ~e-
noqaoR cpe~e (KOH B aMH~0BOM cnHpTe HnH rn~uepHHe) H
B npHcyTcTSHH KaTanHsaTopa (RhCI3). H3yqeH p ~ SaKTOp0S, B~HH~mHX Ha XO~ peaKRHH (paCTBOpHTe~H, TeMnepaTypa, MO~HpHMe OTHOmeHHs, ~pHCyTCTBHe BOOM).
Isoeugenol is widely used in the fragrance industry. Synthetically,
it is obtained by the isomerization of eugenol:
OH
~
OH
OCH3
~
CH2-CH=CH2
~ C H 3
CH=CH-CH3
The reaction is carried out either by the so-called alkaline procedure
[i-6] (heating with KOH,
most often in higher
Akad~miai Kiadd, Budapest
~ERVENY et al. : ISOMERIZATION OF EUGENOL
alcohols),
pounds
or by the action of group VIII metals or their com-
serving as catalysts
[7-14]. Both of these procedures
have been studied in order to assess the effect of reaction
parameters
on the process of isomerization~
EXPERIMENTAL
Chemicals:
eugenol,was a commercial
/1.6 kPa~ density=0.5425g/ml,
potassium hydroxide,
purity grade
grade,
(b.p.=122~
[20]
Astrid Praha) t
were analytical
Ethanol denaturated with methanol
dried and distilled
Rhodium(III)
Apparatus
sample
amyl alcohol and glycerol
(Lachema Brno).
was technical
Prague).
nD=1.5409
(united Distilleries,
chloride was commercial
and working procedure:
(Safina,
The reactions
were carried out
in a 15 ml flask provided with a reflux condenser,
thermometer
and placed in thermally
with controlled
temperature.
insulated
introduced
into the reactor,
ing the reaction
by rhodium(III)
ing an ethanolic
thermostated
Samples
flame-ionization
detection.
AND
The introductory
4?2
taken
of the sam-
with dilute H2SO 4) and
using a Chrom 5 apparatus
A glass column
with
(1.2 m x 2.5 mm)
NAW-HMDS
was used.
at 190~
by KOH
the literature
(ixl0-2mol),
into the
DISCUSSION
Isomerization
hol
chloride
(neutralization
20M on Chromaton
The analyses were performed
RESULTS
were
catalyzed
of the reaction mixture
isomerization
analyzed by gas chromatography
packed with 15 % Carbowax
hydroxide
In the isomerization
during the reaction were adjusted
ples from the alkaline
isomeriza-
the reaction was started by introduc-
solution of rhodium(III)
eugenol.
aluminium block
and eugenol was added after reach-
temperature.
chloride
stirrer and
In the case of alkaline
tion, amyl alcohol or glycerol and potassium
Vestec).
experiments
were carr/ed out according
[2]. The reaction mixture consisting
potassium hydroxide
(6.7x10-2mol)
(7.3xi0 -2 mol)
was heated to 150~
to
of eugenol
and amyl alco-
for i0 h. The mixture
~EHVENY et ul. : ISOMERIZATION OF EUGENOL
was very viscous,
and the samples solidified in cooling.
In an
effort to prevent this, the amount of potassium hydroxide was
gradually reduced
(to 4.4 or 2.2 mol/mol).
reaction was slowed down
: with 2~
As a result,
the
mol/mol KOH the degree of
conversion after !0 h was only 0.6, with 4.4 mol/mol KOH~ it
was 0.95~
In further experimentsn
amyl alcohol was replaced by gly-
cerol which led to an improved consistency while at the same
time enabling the reaction temperature
reaction courses can be seen in Fig.
to be raised. Typical
I.
100
X
c"
9
U)
L.
5O
>
c"
0
t~
I
10
5
t(h}
Fig.
i.
Alkaline isomerization of eugenol in glycerol
Temperature:
150~
molar ratios
eugenol :KOH :glycerol
From Fig.
@
1
9
1
2.2
4.4
9
9
O
1
7.3
9
i, a rise in the r~s_ction rate w i t h increasing
amount of KOH can be seen. An increase in the reaction temperature to 173~
about
or 195~
(amount of KOH 4.4 moi/mol)
brought
an increase i n t h e reaction rate; the activation energy
4?3
~ERVENY e~ al. : ISOM~'RIZATION OF EUGENOL
~-~
.~
O
O
U
,-,4
0
r~
N N ~
N
P4
0
P~
O
C~
O
{n
-H
H
NO
A
O
•
0
0
I
~
1
1
1
1
.,4
0
O,
t~
0
r.4
N
O
0
.H
Ia
.H
('4
H
X
,"t
|
~.~
,H
+
CERVEN~ et al. : ISOMERIZATION OF EUGENOL
as determined from three points was 94.5 kJ/mol.
In these cases
too, however, the viscosity cf the reaction mixture was quite
high. With respect to difficulties in manipulation such procedure is not adequate for application.
Catalytic isomerization
The experiments are summarized in Table I.
It is known from the litera~Ee
[15-17]that rhodium(III)
chloride used as the isomerization catalyst in this study appears in both hydrated and anhydrous form, and that samples of
different provenance differ greetly from each other
(in color,
solubility, catalytic activity, etc.). All experiments were
performed with anhydrous rhodium(III)
chloride dissolved in
ethanol or isopropyl alcohol.
The first three experiments in Table 1 demonstrate the
negative effect of the addition of water to the reaction mixture. Moreover,
the effect of the potentially present free h y -
drogen chloride
(in an amount comparable with added water) was
also tested. The result again was negative.
Experiments 4 and 5 show that the replecement of ethanol
by isopropyl alcohol leads to a considerable slowing down of
the reaction. The activation energy of the reaction estimated
from the reaction rates in experiments
1 and 4 was 42.6 kJ/mol.
Experiment 7 was carried out so that after completion of the
reaction in experiment 6, the same amount of eugenol was again
added to the reaction mixture and the heating was continued.
It can be seen from a comparison that the activity of rhoditm(III)
chloride decreases considerably during the reaction. The reactlon course remained unaffected if the experiments were carried
out in nitrogen.
~t may bo inferred from the experlmonts that the best
procedura for the i,omerization of ~ugonol is the on~ in which
th~ reaction i, catalyzed by rhodium(ZZ~)
in ethanol, by rhodium(IZ~)
chloride in an amount of 1 mmol
p@r i mol of th~ starting ougenol
about 140~
when as
~onvo~slon la auhi~ved.
chloride dissolved
(order of magnitude),
at
about throe hour, a virtually total
4?4
~ERVENY et al. : ISOMERIZATION OF EUGENOL
REFERENCES
I. T.F. West: J. Soc. Chemo
Ind.,
59~ 275
2. F. Tiemann~
Be, o, 2__4/ 2872
(1891).
3. A. Einborn,
Co Trey: Ber.~
27~ 2455
4o Mo Palgi:
Zhur. Obscho Khim.~
5o R. Horiuchi;
J. Chem.
6. R.H. Boots: Brit.
7. D.V. Sokolskii,
8. A. Halasz: Compt.
Komarovskaya,
Rend.,
L.S. Lapikova:
D.H.R.
Trans i, ~, 359
12. P. Grandilhon,
14. M. Martan,
(1925)~
React. Kinet. Cata!.
232, 2329
LoAo Chejfish~
Barton,
(1951) o
L-P. Faleeva, N.A.
UdSSR 791; 728
(1951).
H. Partin: J. Chem. Soc. Perkin
(1977).
II. A.Jo Chalk, N.Y. Kinnelon:
13. R.Y. Levina:
209
(1981).
9o A.K~ Moryshayev,
10. J. Andrieux,
(1958) o
(1926)~
N.P~ Truchasheva:
Lett., 17, 393
(1891).
28~ 2239
SOCo Japan, 45t
271 819
(1940)o
R. Charly:
Ger. Offen 2,508,347
Ger. Offen 1,936,727
Zhur. Obsch. Khim., ~, 1092
P.H. Reichenbacher:
U.S.
(1975).
(1970).
(1936).
4,038,325
15. Gmelins Hendbuch der anorganischen Chemie, 64,
(1975).
54 (1938).
16. L. W6hler, W. MUller:
Z. anorg. ~llgem. Chem., 149,
(1925).
17. J. Meyer, M. Kawczyk:
Z. anorg. ~llgem.
(1936).
4?6
125
Chem. -, 228, 297