Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 7, pp. 1234−1237.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
N.D. Zubareva, A.A. Vedenyapin, E.I. Klabunovskii, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 7,
AND CORROSION PROTECTION OF METALS
Stereoselectivity of Electroreduction
of a Menthone–Isomenthone Mixture
N. D. Zubareva, A. A. Vedenyapin, and E. I. Klabunovskii
Zelinskii Institute of Inorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
Received June 23, 2008
Abstract—Electroreduction of an equilibrium menthone–isomenthone mixture at a controlled potential in a
diaphragm cell on various cathodes was studied. The influence exerted by the nature of a solvent and of an
electrode, electrode material, and various additives on the reduction stereoselectivity of ketones was examined.
Conditions for a predominant formation of the most stable of the four isomeric alcohols being formed, menthol,
The electroreduction of menthone has been rather
extensively studied. This reaction was ﬁ rst performed in
1912 . However, early studies are only of a historical
interest because no reliable chromatographic analyses
had been reported before 1972 in the foreign literature
and before 1962 in domestic publications for the reaction
mixture composed of six components: two starting
ketones (menthone–isomenthone) and four isomeric
alcohols being formed (menthol, neomenthol, isomenthol,
neoisomenthol). Of these, menthol is widely used in
pharmaceutical and food industries. Later, the reaction in
which one of the isomeric ketones (speciﬁ cally, menthone)
undergoes electroreduction to give only two isomeric
alcohols, menthol and neomenthol, was studied [2, 3]. It
was of interest to examine the reduction of an equilibrium
menthone–isomenthone mixture to give four isomeric
alcohols, and to ﬁ nd conditions in which predominantly
one of these, preferably menthol, is formed.
In the industry, menthol is synthesized by catalytic
hydrogenation of thymol (over a Ni/Cr
reaction proceeds in stages via formation of menthones.
Therefore, any information on the reduction of menthones
is also practically important.
It has been shown  that, on the background of
tetrasubstituted ammonium salts at an excess of proton
donors, menthone gives distinct two-electron diffusion-
limited polarographic waves.
In this study, the stereoselectivity of electroreduction
of an equilibrium menthone–isomenthone mixture was
examined at a controlled potential in different solvents
on electrodes of varied nature.
The electrolysis was performed with a potentiostat
developed at the Special Design Bureau of the Institute
of General Chemistry, Academy of Sciences of the
USSR. The potentiostat had the following technical
parameters: potentiostating range at a constant potential,
±3 V; potential sweep range ±3 V; range of polarization
currents, ±500 mA; time constant 1.5 × 10
of maintaining the potential at polarization currents
varied from 1000 mA to 1 μA, 10 mV; precision of
maintaining the polarization current, 0.5% of its value;
stability of maintaining the potential of the working
electrode during 8 h, ±10 mV. The electroreduction was
performed at a controlled potential in a cell with a ceramic
diaphragm. An Ag/AgCl electrode served as reference.
The experiments were carried out at room temperature,
with the electrolyte agitated by a ﬂ ow of argon.
Menthone was produced by oxidation of menthol in
the presence of a chromium catalyst. According to GLC
data, the mixture contained 70% menthone and 30%
isomenthone; bp 207–210°C, n
= 1.45. The menthone