ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 9, pp. 1837–1840. © Pleiades Publishing, Ltd., 2014.
Montmorillonite K10 and KSF Clays as Acidic
and Green Catalysts for Effective Esterification
of Phenols and Alcohols under MWI1
O. Marvi, L. Z. Fekri, and M. Takhti
Department of Chemistry, Payam Noor University, PO Box 19395-3697 Tehran, Iran
e-mail: omid_marvi@pnu.ac.ir
Received July 19, 2014
Abstract—Montmorillonite K-10 and KSF clays catalyze esterification of phenols and alcohols under
microwave irradiation and solvent-free conditions in high yields within seconds.
DOI: 10.1134/S1070363214090333
Esterification is a widely used technological
process [1]. Most procedures require acidic or basic
conditions. Development of simple environmentally
friendly and atom-efficient methods of direct
esterification under mild conditions is of high demand
[2]. Since the Pollution Prevention Act of 1990 was
passed chemists made a significant enefort to develop
more environmentally friendly methods for a variety of
organic compounds. This approach often referred to as
“Green Chemistry,” has produced an array of
improved methods including the use of clays as
chemical catalysts [3]. Natural alumosilicates, such as
zeolites and clays, are solid acids that could act as an
efficient alternative to liquid acids. Natural and
modified clays have attracted attention due to their
extremely versatile properties and high potential in
green chemistry [4]. Many clay based catalysts such as
claycop, clayzinc, clayfen, envirocat, etc. are com-
mercially available and two most common modified
clays applied in organic synthesis are K-10 and KSF
montmorillonites. Though the physicochemical proper-
ties of the clays are similar their BET surface areas
differ. K-10 Has a higher surface area (about 250 m2 g−1)
compared to that of KSF (10 m2 g−1). Microwave-
assisted (MW-assisted) organic synthesis has become a
rapidly developing method [5]. It provides a number of
advantages over the conventional approaches such as
environmentally clean reactions, higher yields, shorter
reaction time, easy work-up, and solvent free reaction
media.
In continuation of our efforts on the microwave-
assisted reactions on solid surfaces under solvent free
conditions [6], herein, we have presented a fast and
simple method for reaction of esterification of benzoic
acid with phenols and alcohols on montmorillonite
KSF and montmorillonite K-10 clays.
KSF or K10 montmorillonite
R1COOR2.
R1COOH + R2OH
Microwave
A variety of esters was synthesized using the above
procedure with no by-products detected (see the table).
Yields of the products based on KSF clay were higher
than those synthesized with K-10 clay and the reaction
time with the latter catalyst was shorter due to more
developed surface of K-10 and higher acidic character
of KSF clay [7]. Enhanced selectivity and lamellar
swelling structures of K-10 and KSF make these solid
supports of certain potential in synthetic organic
chemistry.
EXPERIMENTAL
Melting points were measured by an Electro
Thermal 9100 apparatus. 1H NMR spectra were
recorded by a FTNMR BRUKER DRX 500 Avence
spectrometer. Chemical shifts were measured in ppm
with TMS internal standard in CDCl3 solutions. The IR
spectra were recorded by a Perkin Elmer FT-IR GX
instrument in KBr tablets. Montmorillonite KSF clay,
surface area 15±10 m2/g, surface acidity: 0.75 meq.
H+/g (determined in our laboratory by temperature
programmed desorption of ammonia gas (NH3-TPD);
chemical composition (average value): SiO2 (54.0%),
Al2O3 (17.0%), Fe2O3 (5.2%), CaO (1.5%), MgO
1 The text was submitted by the authors in English.
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