Kinetics and mechanism of the chlormethyloxirane reaction with phenols catalyzed by tertiary amines and pyridine derivatives

Full text of DOI:10.1023/A:1013922017887

Russian Journal of Organic Chemistry, Vol. 37, No. 12, 2001, pp. 1723 1725. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 12, 2001,
pp. 1804 1806.
Original Russian Text Copyright
2001 by Shved, Petrenko, Pozhidaev.
Kinetics and Mechanism of the Chlormethyloxirane
Reaction with Phenols Catalyzed by Tertiary Amines
and Pyridine Derivatives
E. N. Shved, E. N. Petrenko, and M. A. Pozhidaev
Donetsk National University, Donetsk, 83055 Ukraine
Received October 21, 1999
Reaction of phenols with 1-chloro-2,3-epoxy-
propane (epichlorohydrin, ECH) proceeds along a
scheme [1]:
d[A]
k1 k2[B]0
(2) k1[A] << k + k2[B]0,
=
[A][M]0;
1
dt
k + k2[B]0
1
(3)
.
d[A]
k1 k2[B]0[A][M]0
(3) k1[A] k + k2[B]0,
=
1
dt
k [A]+ k + k2[B]0
1 1
(4)
(1)
In the majority of the studied cases of reactions
belonging to type (1) according to literature data [4,
6] operates the second case (3).
It was important to find out the possibility of
realization for the first case (2) in order to support
our assumptions. To increase the equilibrium constant
(Kc = k1/k ) we selected phenols with low pKa
values [3-chl1orophenol (Ia) and 4-nitrophenol (Ib)].
As catalysts are applied pyridine derivatives (2,5-di-
methylpyridine, 2,4,6-trimethylpyridine, N-methyl-
pyridinium iodide) that are characterized by high
polarizability [7], and also tributylamine.
Although a great number of patents demonstrates
the practical importance of reaction (1) its catalysis,
kinetics, and selectivity is poorly understood [1 3].
The most important for investigation is the first reac-
tion stage, formation of chlorohydrin ether, since just
this stage is rate-limiting [4]. Some published data
indicate that the first stage of reaction (1) is first order
with respect to each reagent [5]. However our preced-
ing studies [6] showed that the calculation of the ap-
parent rate constant by the law of the overall second
order was not always satisfactory: in some cases the
rate constants monotonically increased. It was
established [1, 6] that amines and ammonium salts in
reaction (1) play the role of basic catalysts. Therefore
the catalysis mechanism in phenols reaction with
compound II may be represented by a scheme [7]:
From the experimental kinetic curves of phenol
Ia, b consumption was graphically estimated the zero
order of reaction in phenol concentration (Fig. 1).
A set of straight lines was obtained in coordinates
(a x) vs t with correlation factors r > 0.98 and
phenol conversion on the average up to 80%. Taking
into account the pseudo-first order of the reaction
in epoxy compound II the apparent rate constants
(kapp) were calculated by the following equation with
the use of the least-squares method:
k1
k2
A + M
AM, AM + B
AB + M
k 1
kapp
=
x/tb,
(5)
where A is phenol, B is epichlorohydrin, M is catal-
yst.
where x is the quantity of the reacted phenol Ia, b,
mol l , b is the concentration of compound II,
mol l , t is reaction time, s. From the relation of
kapp to the catalyst concentration (m, mol l ) (Fig. 2)
1
In the framework of quasi-stationary approxima-
tion using the material balance with respect to phenol
and catalyst three cases are presumable:
1
1
was established the first order of reaction in catalyst
and were calculated the rate constants for catalytic
(kc) and noncatalytic (k0) reaction flows:
d[A]
(1) k1[A] >> k + k2[B]0,
= k2[B]0[M]0;
(2)
1
dt
1070-4280/01/3712-1723$25.00 2001 MAIK Nauka/Interperiodica

1724
SHVED et al.
(6) rate of complex formation between the phenol and the
kapp
= k0 + kcm.
catalyst is higher than the rate of phenol consumption
at the start of the reaction. This is apparently due to
formation of associate through a hydrogen bond or of
an ion pair from phenol and the catalyst [7]. The
zero order in 4-nitrophenol for the uncatalyzed reac-
tion is most likely related to formation of a phenoxide
anion because of high acidity of phenol Ib.
With catalyst of such high basicity as tributylamine
and methyl-substituted pyridine derivatives reaction
(1) is of zero order with respect to phenol. It is
interesting that N-methylpyridinium iodide having
iodide ion I as an active site is intermediate in
catalytic activity between the aliphatic amine (tributyl-
amine) and heteroaromatic amines (di- and trimethyl-
pyridines) which may be related to its high basic
properties. The data in table permit the conclusion
that the first kinetic case (2) is observed when the
Thus within the framework of the general
mechanism of basic catalysis assuming primary
interaction of phenol with catalyst we can suggest the
following path of the first stage in reaction (1):
Fig. 1. Phenol consumption as a function of time in
reaction with epoxy compound II at 80 C: (1) 4-nitrophenol
(Ib), (a) 0.498, catalyst 2,6-dimethylpyridine; (2) 4-nitro-
phenol (Ib), (a) 0.525, catalyst 2,4,6-trimethylpyridine; 3,
4-nitrophenol (Ib), (a) 0.505, catalyst N-methylpyridinium
iodide; (4) 3-chlorophenol (Ia), (a) 0.192, catalyst tributyl-
amine.
Catalysis with N-methylpyridinium iodide occurs
analogously but instead of the nitrogen the part of the
nucleophilic site plays the iodide anion; the reaction
order with respect to phenol depends on the ratio of
the rate constants of individual reaction stages that in
their turn are related to acidic and basic character-
istics of the phenol and the catalyst.
Compound II was dried on solid sodium hydroxide
and then it was distilled at the atmospheric pressure,
bp 116.5 C [8]. Compound Ia and amine catalysts
were distilled at reduced pressure. The corresponding
boiling points are as follows: compound Ia, 214 C
[8]; 2,6-dimethylpyridine, 144 C [8], 2,4,6-tri-
methylpyridine, 170.4 C [8], tributylamine, 213 C
[8].
Compound Ib was twice recrystallized from
benzene with filtering the hot solution through a layer
of alumina, mp 113 C [8].
N-Methylpyridinium iodide was recrystallized
from a mixture ethanol ethyl ether, dried in desic-
cator over P2O5, mp 123 125 C [8].
Fig. 2. Dependence of the apparent rate constants of reac-
tion (1) at 80 C on catalyst concentration: (1) 4-nitro-
phenol (Ib), catalyst 2,6-dimethylpyridine; (2) 4-nitro-
phenol (Ib) catalyst 2,4,6-trimethylpyridine; 3, 4-nitro-
phenol (Ib), catalyst N-methylpyridinium iodide;
(4) 3-chlorophenol (Ia), catalyst tributylamine.
Procedure for kinetic measurements. The catal-
yst and the phenol were dissolved in compound II (in
1 and 2 ml respectively). The solutions obtained were
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 12 2001

KINETICS AND MECHANISM OF THE CHLORMETHYLOXIRANE REACTION
1725
1
Rate constants kapp and kc of reaction between epichlorohydrin (II) (b 12.4 mol l ) and phenols Ia, b at 80 C in the
presence of different catalysts
1
1
1
1
1
Phenol no.
Ib, pKa 7.15 [8]
Ib
a, mol l
Catalyst
m, mol l
kapp b 107, s kc 104, l mol s
0.747
0.390
0.498
0.990 0.024a
0.940 0.010
2,6-Dimethylpyridine, pKa 6.62 [8]
0.00498
0.00378
0.00245
0.00119
6.02 0.27
4.87 0.08
3.72 0.09
2.58 0.03
6.66 0.06
5.17 0.01
3.55 0.05
2.42 0.01
7.02 0.14
5.37 0.10
2.01 0.10
1.64 0.01
1.22 0.04
0.87 0.04
9.03 0.13
11.1 0.3
Ib
0.524
2,4,6-Trimethylpyridine, pKa 7.43 [8] 0.00512
0.00365
0.00234
0.00124
0.00500
0.00375
0.00125
0.00500
0.00375
0.00250
Ib
0.505
0.192
N-Methylpyridinium iodide
1.34 0.00
3.10 0.16
Ia, pKa 9.02 [8]
Tributylamine, pKa 10.89 [8]
a
The given rate constants correspond to uncatalyzed reaction.
kept in a thermostat at 80 0.1 C for 10 min, then
the solutions were mixed, and this moment was
considered as the initial moment of reaction. After a
definite time interval the reaction was stopped by
quenching with 10 ml of aqueous 2-propanol (1: 1)
and cooling to room temperature. The mixture was
quantitatively transferred into the titration cell and
diluted with water. The amount of unreacted com-
pound I was determined by potentiometric acidimetric
titration with 0.2 N NaOH solution.
3. Valetskii, P., Khimiya i tekhnologiya polimerov
(Chemistry and Technology of Polymers), 1996, no. 2,
pp. 54 77.
4. Medzhitov, D.R., Konovalova, E.A., and Shode, L.G.,
Dep. VINITI, Moscow, 1991, no. 4266-V91; Ref. Zh.
Khim., 1992, 4B4047.
5. Lidarzhik, M., Mlezieva, I., Beranova, D. et al.,
Khimicheskaya promyshlennost’, 1960, no. 3, pp. 33 37.
6. Perepichka, I.V. and Shved, E.N., Scripta Fac. Sci.
Nat. Univ. Masaruk. Brun. Chemistry, 1996, vol. 26,
pp. 15 19.
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 12 2001