Russian Journal of Applied Chemistry, Vol. 74, No. 2, 2001, p. 350. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 2, 2001,
pp. 342 343.
Original Russian Text Copyright
2001 by Osadchenko, Tomilov.
BRIEF
COMMUNICATIONS
Alkylation of p-Cresol with Isohexyl Alcohol
I. M. Osadchenko and A. P. Tomilov
State Research Institute of Organic Chemistry and Technology, Moscow, Russia
Received June 23, 2000
Abstract The feasibility of p-cresol alkylation with isohexyl alcohol, using phosphotungstic heteropoly acid
as catalyst, was examined.
Alkyl derivatives of p-cresol find application as
antioxidants, surfactants, and perfumes. In particular,
products of p-cresol alkylation with isohexyl alcohol
are used in synthesis of vetinone perfume (see scheme).
The experiment with phosphomolybdic acid
H7PMo12O42 failed, because the catalyst appeared
to be reactive toward the starting compounds.
Below is given a typical procedure for condensa-
tion of p-cresol with isohexyl alcohol.
OH
A reactor equipped with a reflux condenser with
a Dean Stark trap, a stirrer, a thermometer, and a drop-
ping funnel was charged with 102 g (0.982 mol) of
p-cresol and 2.0 g of H7PW12O42. The mixture was
heated on an oil bath to 85 95 C, and 51 g (0.50 mol)
of isohexyl alcohol was added dropwise at this tem-
perature over a period of 40 min. The temperature was
gradually raised to 105 120 C, and the mixture was re-
fluxed for 4 h 40 min. In the process, water was sepa-
rated in the Dean Stark trap. After the reaction was
complete, the content of the target product was de-
termined by GLC to be 50.5%. To isolate the product,
the mixture was neutralized with 3 g of sodium carbon-
ate. The neutralized mixture was vacuum-distilled.
The target fraction (bp 125 140 C/8 10 mm Hg) con-
tained, according to GLC, 97% 4-methyl-2-isohexyl-
phenol. The product yield was 53 g (55.2% in terms of
loaded isohexyl alcohol), and the amount of bottoms,
7.2 wt % relative to the target fraction (with sulfuric
acid as catalyst, the amount of bottoms was 15 wt %).
+ (CH3)2CH C(CH3)2
OH
CH3
OH
OH
O
R
R
R
H2
O2
,
H2O
CH3
CH3
CH3
where R = (CH3)2C CH(CH3)2.
Kheifits et al. [1, 2] studied the alkylation of
p-cresol in the presence of various catalysts including
Fe2(SO4)3, ZnCl2, BF3, and H2SO4. Sulfuric acid ap-
peared to be the most suitable. At a 2 : 1 molar ratio
of p-cresol to alcohol and a temperature of 110
120 C, the target product was obtained in about 50%
yield. A major drawback of the process is the ap-
preciable tarring of the reaction mixture containing
about 15 wt % tar.
The alkylation of p-cresol with 2-methyl-2-pentan-
ol was performed similarly. The yield of the condensa-
tion product, 4-methyl-2-(2-methyl-2-pentyl)phenol,
was 50%.
The tarring, and also the high corrosive activity
of sulfuric acid stimulated us to look for new cata-
lysts for this process. We decided to test heteropoly
acids which have recently found use as catalysts
in many processes [3]. Among the tested heteropoly
acids, the best results were obtained with reagent-
grade phosphotungstic acid H7PW12O42 [TU (Techni-
cal Specifications) 6-09-4376 78]. With this catalyst,
the formation of tars under the conditions recom-
mended for the process with sulfuric acid decreased
by more than a factor of 2.
REFERENCES
1. Kheifits, L.A. and Podberezina, A.S., in Problemy or-
ganicheskogo sinteza (Problems of Organic Synthesis),
Moscow: Nauka, 1965, pp. 124 132.
2. Kheifits, L.A., Podberezina, A.S., Klimakhina, S.T.,
and Grigor’eva, L.T., Maslozhir. Prom st., 1976, no. 7,
pp. 32 34.
3. Kozhevnikov, I.V., Usp. Khim., 1987, vol. 56, no. 9,
pp. 1417 1442.
1070-4272/01/7402-0350 $25.00 2001 MAIK Nauka/Interperiodica
Osadchenko
