ISSN 0965-5441, Petroleum Chemistry, 2007, Vol. 47, No. 1, pp. 55–60. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © P.Sh. Mamedova, V.M. Farzaliev, F.M. Velieva, E.R. Babaev, 2007, published in Neftekhimiya, 2007, Vol. 47, No. 1, pp. 58–63.
Optimization of Phenol ortho-Alkylation with Styrene
P. Sh. Mamedova, V. M. Farzaliev, F. M. Velieva, and E. R. Babaev
Kuliev Institute of Chemistry of Additives, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
e-mail: hafizalimardanov@yahoo.com
Received April 6, 2006
Abstract—The results of statistical treatment of experimental data on phenol alkylation with styrene in the
presence of aluminum phenoxide as a catalyst are presented. The optimization of the process provides the max-
imum yield of 2,6-di-α-methylbenzylphenol. The structures of the synthesized compounds were determined on
1
the basis of mass spectrometric, IR, and H NMR data.
DOI: 10.1134/S0965544107010070
1
0.1134/S0965544107010070Sterically hindered
We have previously described the results of synthe-
phenols, being effective inhibitors of free-radical pro- ses of α-methylbenzyl-substituted phenols with effi-
cesses, are widely used as antioxidants for the stabiliza- cient antibacterial properties revealed later [4]. The
tion of fuels, oils, polymeric materials, food stuff, etc. optimization of the synthesis of these alkylphenols and
[
1]. It is noteworthy that these phenols combine their investigation of their structure and functional properties
high efficiency with a much lower toxicity as compared are of theoretical and practical interest.
to their unsubstituted analogs. It is this circumstance
In this paper, we present the results of statistical
that has stirred the interest of researchers in compounds
of this class in recent years.
treatment of experimental data on the optimization of
the synthesis of 2-, 2,6-, and 2,4,6-substituted α- meth-
ylbenzylphenols via the alkylation of phenol with sty-
rene in the presence of aluminum phenoxide. Taking
into account that the introduction of bulky radicals that
screen the hydroxyl group into the phenol molecule
enhances the functional properties of compounds of
this class, we attempted to obtain 2,6-di-α-methylben-
zylphenol at the highest yield.
The inhibiting activity of these antioxidants is
mainly due to steric hindrance of the hydroxyl group
and depends on the size of ortho-substituents. The
introduction of bulky substituents (e.g., tert-butyl) that
optimally shield the hydrogen atom of the hydroxy
group enhances the stability of the phenoxyl radicals
formed and, correspondingly, their inhibiting activity.
Therefore, phenol derivatives with tert-butyl substitu-
ents in the ortho-position (for example, ionol) are the
most popular as high-performance antioxidants. Spe-
cific difficulties in the preparation of sterically hindered
phenols, in particular, with the unsubstituted para-posi-
tion, are caused by the selectivity of introduction of
alkyl groups into the ortho-position of phenol, because
some amounts of 2-, 2,4-, and 2,4,6-substituted phenols
EXPERIMENTAL
Synthesis and Physicochemical Properties of 2-, 2,6-,
and 2,4,6-Substituted α-Methylbenzylphenols
Freshly distilled phenol (47 g, 0.5 mol) was placed
are formed along with 2,6-dialkylphenol, which is the into a four-necked reaction flask equipped with a
most interesting for syntheses of antioxidants [1].
mechanical stirrer, a reflux condenser with a calcium
chloride tube, a thermometer, and a tubing for the with-
drawal of nitrogen gas. Aluminum chips (0.65 g) were
added in portions for 1 h at 140°ë in a nitrogen atmo-
sphere. Then the temperature was increased to
The hydroxyl group in substituted phenols can effi-
ciently be screened, along with the widely used tert-
butyl radical, by the introduction of α-methylbenzyl
substituents into the [ortho]-position of a phenol mole-
cule.
1
80−190°ë, and styrene (57.2 g, 0.55 mol) was added
from a dropping funnel for 1 h. The reaction mixture
There are some data in the literature on the use of was stirred for 4 h under nitrogen. The product was
α-methylbenzyl-substituted phenols obtained from treated with a 1% hydrochloric acid solution, washed
available feedstock (phenol, styrene) as rubber stabili- with water to the neutral reaction, and dried over anhy-
zers [2]. These phenols are mainly applied as a techni- drous sodium sulfate. After solvent removal by vacuum
cal mixture consisting of 2- and 4-α-methylbenzyl-, distillation, mono-, di-, and trisubstituted α-methylben-
2
,4- and 2,6-di-α-methylbenzyl-, and 2,4,6-tri-α-meth- zylphenols were separated by column chromatography
ylbenzylphenols. Disubstituted α-methylbenzylphe- (adsorption column 36 cm long, diameter 3 cm, Al O
2
3
nols were shown to be the most effective [3].
as adsorbent, hexane–ethyl ether (3 : 1) as an eluent).
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