Russian Journal of Organic Chemistry, Vol. 37, No. 3, 2001, pp. 446 447. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 3, 2001,
pp. 471 472.
Original Russian Text Copyright
2001 by S. Shchelkunov, Mazakova, Bekenova, Amirkhanova, A. Shchelkunov.
SHORT
COMMUNICATIONS
Chemical Aspects of Electrocatalytic Reduction of Carbonyl
Compounds. Mesityl Oxide
S. A. Shchelkunov, S. V. Mazakova, U. B. Bekenova,
A. K. Amirkhanova, and A. V. Shchelkunov
Institute of Organic Synthesis and Coal Chemistry, Ministry of Education and Science of Kazakhstan Republic,
ul. 40 Let Kazakhstana 1, Karaganda, 470061 Kazakhstan
Received June 2, 2000
Interest in the reduction of mesityl oxide (4-methyl-
3-penten-2-one) originates from the fact that this
process results in formation of either 4-methylpentan-
2-one which is widely used in varnish-and-paint
industry or 4-methylpentan-2-ol which is an efficient
flotation reagent for large-scale coal benefication.
the target product increased almost twofold (see table).
There was no doubt that temperature should strongly
affect the process. Raising the temperature increases
the fraction of isopropyl alcohol among the products,
which indicates increased contribution of the retro-
aldol reaction and subsequent reduction of the acetone
thus formed.
Naturally, it was reasonable to examine electro-
catalytic reduction of acetone itself at various tem-
peratures. We have found that at 20 C the reduction of
acetone is terminated when the fraction of isopropyl
alcohol in the catholyte attains 34%; at 60 C the
corresponding fraction of isopropyl alcohol is 66%.
The electrocatalytic reduction of mesityl oxide
of chemically pure grade was carried out in a two-
chamber Kirilyus electrolyzer [2, 3], whose anode
and cathode spaces were separated by an MA-40
ion-exchange membrane. As anolyte we used a 20%
aqueous solution of sodium hydroxide (50 ml), the
catholyte was 5% aqueous sodium hydroxide (50 ml),
the anode was a platinum network, the cathode was
Kirilyus et al. [1] described a procedure for electro-
catalytic reduction of mesityl oxide to 4-methyl-
pentan-2-one in 92% yield. We believe that aqueous
alkaline medium (where the reaction was carried
out) should necessarily give rise to side processes,
specifically to aldol-like condensation. Our attempts
to reproduce experiments described in [1] showed
that 0.0438 mol of mesityl oxide in 3 h absorbs only
0.066 mol of hydrogen. Moreover, it was impossible
to attain more than 30% yield of 4-methylpentan-
2-one because of concurrent aldol condensation.
Temperature effect on the composition of products of
exhaustive electrocatalytic reduction of mesityl oxide
(substrate amount 0.024 mol)
Catholyte composition, %
T,
C
4-methyl-
4-methyl-
Me2CO i-PrOH
pentan-2-one pentan-2-ol
20
56.4
38.6
41.3
7.2
25.8
27.9
9.2
1.8
6.8
1.5
16.0
26.7
48.1
73.2
45
52
60
When the reaction was performed until hydrogen
was no longer absorbed (contrary to [1]), the yield of
8.4
11.1
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