Fille 2566 (15).qxd


Alkylation of Cresols with Cyclohexene in the Presence of 
p-Toluenesulphonic Acid

Manoranjan Saha*, Haradhan Chandra Dey, Mohammad Ziaul Karim,
Mohammad Ismail and Dipti Saha 

Department of Applied Chemistry and Chemical Technology, University of Dhaka,
Dhaka-1000, Bangladesh.

Abstract

Isomeric cresols have been cycloalkylated with cyclohexene in the presence of p-toluenesulphonic acid
as catalyst. The effects of the variation of temperature, molar ratio of cresol to cyclohexene, time of
reaction and amount of p-toluenesulphonic acid on the reactions have been studied and cyclohexyl
cresols have been obtained in high yield.

Bangladesh J. Sci. Ind. Res. 43(2), 277-282, 2008
Short Comuunication

Introduction

Alkylated phenols and their derivatives are
outstanding antioxidants and stabilizers in
fuels, lubricating oils and polymeric materi-
als (Babakhanov et al. 1968; Lebedev, 1984;
Paul, 1950; Ravikovich, 1964; Shreve and
Brink, 1977).Some of their derivatives are
also used as herbicides, bactericides and
insecticides (Melinikov et al. 1954;
Nemetkin et al. 1951). Cresols have been
alkylated by different normal, iso- and
cycloolefins (Karim et al.2005; Kharchenko
and Zavgorodni, 1964; Saha and Ghosh,
1989; Saha et al.1994; Saha et al.1996; Saha
et al. 1998; Saha et al.2000;  Shulov, 1969). 

But no attempt has ever been made to inves-
tigate the reactions with cyclohexene in the
presence of p-toluenesulphonic acid.

In the present work, reactions of isomeric
cresols (ortho-, meta- and para-) have been
investigated with cyclohexene in the pres-
ence of p-toluenesulphonic acid as catalyst.

Materials and Methods

Reaction was carried out in a flask fitted
with a stirrer, a condenser, a thermometer
and a dropping funnel for the addition of
cyclohexene. Cresol and p-toluenesulphonic

* Corresponding author, E-mail : manoranjansaha2005@yahoo.com

BCSIR

Avaiable online at www.babglajol.info BANGLADESH JOURNAL
OF SCIENTIFIC AND 

INDUSTRIAL RESEARCH

E-mail: bjsir07gmail.com



278 Alkylation of Cresols with Cyclohexene 43(2) 2008

acid were charged into the flask and heated
to desired temperature and cyclohexene was
introduced into the mixture gradually over a
certain period of time (time of addition) with
constant stirring. After the addition of total
amount of cyclohexene, the reaction mixture
was stirred for another period of time (time
of stirring) at the same temperature. Reaction
mass was then cooled to the room tempera-
ture, dissolved in petroleum ether, neutral-
ized and washed with distilled water several
times. Unconverted reactants and solvent
were distilled off by distillation at atmos-
pheric pressure. The residual product was
finally distilled and characterized by spectral
means.

Results and Discussion

A. Reaction of o-cresol with cyclohexene:

Table I records the results of the reaction of
o-cresol with cyclohexene in the presence of  

p-toluenesulphonic acid. The reaction gave
the mixture of isomeric cyclohexyl o-
cresols. The yield of the products increased
with the increase of temperature (Expt. No. 1
- 5), molar ratio of o-cresol to cyclohexene
(Expt. No. 6 - 8), time of reaction (Expt. No.
3 and 8) and the amount of catalyst (Expt.
No. 3 and 9). But the increase in the yield
was negligible when the temperature was
raised from 130 to 160OC (Expt No. 3 - 5).
Thus cyclohexyl o-cresols could be obtained
in 95.5% yield under the following reaction
conditions: temperature = 130OC, molar ratio
of o-cresol to cyclohexene = 5:1, time of
addition = 2h, time of stirring = 2h and the
amount of catalyst = 10% by wt. of o-cresol. 

B. Reaction of m-cresol with cyclohexene

Reaction of m-cresol with cyclohexene had
been investigated in the presence of p-tolue-
nesulphonic acid over the temperature range
of  100-130OC.  Molar  ratio  of  m-cresol to 

1 70 5:1 2 2 10 28.3
2 100 5:1 2 2 10 70.1
3 130 5:1 2 2 10 95.5
4 155 5:1 2 2 10 95.9
5 160 5:1 2 2 10 96.0
6 130 3:1 2 1 10 72.0
7 130 4:1 2 1 10 80.2
8 130 5:1 2 1 10 89.4
9 130 5:1 2 2 5 81.0

Table I. Alkylation of o-cresol with cyclohexene in the presence of p-toluenesulphonic acid

Expt.
No. Temp.,OC Molar ratio of 

o-cresol to
cyclohexene

Time of addi-
tion, h

Time of stir-
ring, h

Amount of cata-
lyst, % by wt.

of o-cresol

% Yield of
cyclohexyl

o-cresol

Reaction conditions



cyclohexene was varied from 3:1 to 4:1,
reaction time from 2 to 4h and the amount of
catalyst was varied from 5 to 10% wt. of m-
cresol. Table II records the results. The yield
of products (cyclohexyl m-cresols) increased
with the increasing temperature (Expt. No.1
and 2), molar ratio of m-cresol to cyclohex-
ene (Expt. No. 3 and 4), time of reaction
(Expt. No.2, 4 and 5; 6 and 7) and the
amount of catalyst (Expt. No. 4 and 6). Thus
the best yield of cyclohexyl m-cresols was
obtained under the following conditions:
temperature = 130OC, molar ratio of m-
cresol to cyclohexene = 4:1, the amount of
catalyst = 10% by wt. of m-cresol, time of
addition = 2h and time of stirring = 2h.

C. Reaction of p-cresol with cyclohexene:

The influence of variation of the parameters,
viz. temperature, molar ratio of p-cresol to
cyclohexene, time of reaction and amount of
p-toluenesulphonic acid on the reaction of p-

cresol with cyclohexene has been shown in
Table III. The reaction gave only 2-cyclo-
hexyl-4-methylphenol. The yield of the
product increased with the increasing tem-
perature (Expt. No. 1 - 3), molar ratio of p-
cresol to cyclohexene (Expt. No. 4, 5 and 6),
time of reaction (Expt. No. 2, 4 and 7 ; 8 and
9) and the amount of catalyst (Expt. No. 4
and 8). But the increase in the yield was
insignificant when the temperature was
increased above 130OC (Expt No. 2 - 3). At a
molar ratio of p-cresol to cyclohexene = 4:1,
the maximum yield could be obtained by
increasing the time of additional stirring
(Expt No. 2).The best yield of the product
was  obtained when the reaction was carried 

out under the following conditions: tempera-
ture = 130OC, molar ratio of p-cresol to
cyclohexene = 4:1, the amount of catalyst =
10% by wt. of p-cresol, time of addition = 2h
and time of stirring = 2h.

Saha, Dey, Karim,  Ismail and  Saha 279

1 100 4:1 2 2 10 61.2
2 130 4:1 2 2 10 96.4
3 130 3:1 2 1 10 82.3
4 130 4:1 2 1 10 86.0
5 130 4:1 2 0 10 72.5
6 130 4:1 2 1 5 75.1
7 130 4:1 2 3 5 87.5

Table II. Alkylation of m-cresol with cyclohexene in the presence of p-toluenesulphonic acid

Expt.
No. Temp.,OC Molar ratio of 

m-cresol to
cyclohexene

Time of addi-
tion, h

Time of stir-
ring, h

Amount of cata-
lyst, % by wt.

of m-cresol

% Yield of
cyclohexyl
m-cresol

Reaction conditions



280 Alkylation of Cresols with Cyclohexene 43(2) 2008

1 100 4:1 2 2 10 64.5
2 130 4:1 2 2 10 96.6
3 160 4:1 2 2 10 96.7
4 130 4:1 2 1 10 88.7
5 130 5:1 2 1 10 95.9
6 130 6:1 2 1 10 96.2
7 130 4:1 2 0 10 76.1
8 130 4:1 2 1 5 76.9
9 130 4:1 2 3 5 95.2

Table III. Alkylation of p-cresol with cyclohexene in the presence of p-toluenesulphonic acid

Expt.
No. Temp.,OC Molar ratio of 

p-cresol to
cyclohexene

Time of addi-
tion, h

Time of stir-
ring, h

Amount of cata-
lyst, % by wt.

of p-cresol

% Yield of 2-
cyclohexyl-4-
methylphenol

Reaction conditions

Table IV. 1H NMR-spectrum of cyclohexyl cresols

Products Observed signals of the protons Chemical shift δ in ppm
Cyclohexyl Three protons on the aromatic ring 6.01 - 7.0
o-cresol One proton on the -OH group 4.06

Three protons on the -CH3 group 2.0 - 2.02
All the protons (10) on the cyclohexane ring 
except one on the α-position relative to the aromatic ring 1.05 - 2.16
One proton on the cyclohexane 
ring on the a-position relative to the aromatic ring 2.4 - 2.8

Cyclohexyl Three protons on the aromatic ring 6.06 - 7.1
m-cresol One proton on the -OH group 4.6 - 5.3

Three protons on the -CH3 group 2.05 - 2.5
All the protons (10) on the cyclohexane ring except one 
on the a-position relative to the aromatic ring 1.06 - 2.0
One proton on the cyclohexane ring on the α-position 
relative to the aromatic ring 2.5 - 3.1

2-Cyclohexyl- Three protons on the aromatic ring 6.3 - 7.1
4-methylphenol One proton on the -OH group 4.5

Three protons on the -CH3 group 2.233
All the protons (10) on the cyclohexane ring except one
on the a-position relative to the aromatic ring 1.20 - 2.17
One proton on the cyclohexane ring on the α-position 
relative to the aromatic ring 2.633



Saha, Dey, Karim,  Ismail and  Saha 281

Cyclohexyl group is substituted into the aro-
matic ring to the ortho- or para-position with
respect to the -OH group. Therefore, the
reaction of p-cresol with cyclohexene gave
only one product, while the reactions of
ortho- and meta-cresols gave mixtures of
isomeric cyclohexyl cresols.

In the IR-spectrum of cyclohexyl o-cresol
bands at 740-770 cm-1 accounted for the
1,2,3-trisubstituted benzene ring, while
bands near 800-900 cm-1 were the character-
istics of the 1,2,4-trisubstituted benzene ring.
Bands near 3400 cm-1 indicated the presence
of -OH group.

Absorption band at 3400 cm-1 in the IR-
spectrum of cyclohexyl m-cresols showed
the presence of -OH group. Bands near 800-
900 cm-1 were the characteristics of the
1,2,4-trisubstituted benzene ring. Bands at
740-780 cm-1 accounted for the 1,2,3-trisub-
stituted benzene ring.

IR-spectrum of 2-cyclohexyl-4-methylphe-
nol showed  absorption  band  at  3350 cm-1

(-OH). Bands at 800-900 cm-1 accounted for
the 1,2,4-trisubstituted benzene ring.

The 1H NMR-spectrum of cyclohexyl
cresols Table IV.

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Received : October, 10, 2005;
Accepted : August, 28, 2007