c. Jpn.
e Chemical © 2002 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 75, 123–126 (2002)
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Ultrasonic Effects on Electroorganic Processes. Part 22. Cathodic
Crossed Hydrocoupling of Acetone with Acrylonitrile
Ultrasonic Effect on the Crossed Coupling
M. Atobe et al.
Mahito Atobe,* Sou Fujiwara, and Tsutomu Nonaka†
0
3
6
2
Department of Electronic Chemistry, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502
Tsuruoka National College of Technology, 104, Aza-sawada, Oaza-ioka, Tsuruoka 997-8511
†
SJA8
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9-2673
(
Received July 25, 2001)
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0
39
The ultrasonic effects on the cathodic-crossed hydrocoupling of acetone with acrylonitrile were examined. The to-
1
1
tal current efficiency of all products in the cathodic reduction of a mixture of acetone and acrylonitrile was little influ-
enced by ultrasonic irradiation, while the product selectivity for crossed hydrocoupling products formed in the cathodic
reduction was significantly increased by irradiation. This ultrasonic effect could be rationalized as being due to mass-
transport promotion of acrylonitrile molecules as an electrophile to the cathode surface from the bulk of the electrolytic
solution by the ultrasonic irradiation. Thus, the ultrasonic effect can be purposively applied to control the product selec-
tivity in the crossed coupling reaction.
0
.3
3
The application of ultrasound to chemical processes has re-
ceived much attention from both fundamental and practical as-
to the following procedure. A catholyte (100 cm of 0.5 M H
2
SO
4
−
3
aqueous solution; 1 M = 1 mol dm ) containing acetone (10 M)
and acrylonitrile (10 mM) was kept constant at 25 °C by using a
cooling bath. Electrolysis was galvanostatically conducted by
passing 3.0 × 10 F mol based on acetone at a current density
of 20 mA cm− . A stepped horn (titanium rod with 1.9 cm diame-
ter) connected with a PZT oscillator (20 kHz) was inserted into the
catholyte. The output power of ultrasound was determined by an
adiabatic measurement of the temperature raise of sonicated wa-
ter. The working electrode surface was positioned perpendicu-
larly to the propagating direction of ultrasonic waves, 2.0 cm apart
from the top of the horn. The reduction products were analyzed
by GC with a PEG 1540 column at 60–160 °C.
1–10
pects.
A high-speed micro-jet stream generated by ultra-
sonic cavitation in a liquid is known to accelerate heteroge-
neous reactions on a solid surface by promoting mass transport
−
3
−1
2
1–3,5,8
in the solid-liquid interface.
An electrochemical reaction
is one of the typical heterogeneous processes; therefore, ultra-
sonic effects on it seem to be very attractive to be investigated.
In fact, recent sonoelectrochemical studies have been exten-
sively reported in variety of areas, such as electrochemical
measurement, kinetics, deposition (including electroplating),
20
7,8
synthesis, and gas evolution.
On the other hand, a number of electrochemical bimolecular
reactions have been developed, some of which were used for
syntheses in laboratories and industries, since the processes are
effective means for not only constructing carbon-carbon
bonds, but also for introducing functional groups into a carbon
Results and Discussion
It is known that the cathodic reduction of acetone with acry-
lonitrile gives a mixture of the corresponding crossed hydro-
coupling products (ꢀ and ꢁ), as shown in Scheme 1.
21–23
In ad-
11,12
skeleton.
From this point of view, we have been interested
dition, non-crossed hydrocoupling products (ꢂ and ꢃ) are
also formed by the one- and two-electron reduction of acetone,
respectively. In the present work, this reaction was used to ex-
amine the ultrasonic effects on the crossed-coupling reaction.
Table 1 shows the total current efficiency of all products (ꢀ,
, ꢂ, and ꢄ) and the product selectivity for the crossed hydro-
coupling products (ꢀ and ꢁ) based on the total yield of products
, ꢁ, ꢂ, and ꢄ. The current efficiency and product selectivity
were examined under three different conditions, such as still
standing, mechanical stirring, and ultrasonic irradiation. The
high, medium, and low selectivities were obtained under the
following reaction modes: ultrasonic irradiation, mechanical
stirring, and still standing, respectively, although the efficiency
was little influenced by the reaction mode. In addition, the se-
lectivity was greatly increased with an increase in the ultrason-
ic power. This result implies that the selectivity apparently de-
pends on the agitation intensity of the solution; i.e. mass trans-
port in a solid–liquid interface is particularly and remarkably
in the application of ultrasounds to electrochemical bimolecu-
lar reactions, such as the cathodic hydrocoupling of carbonyl
13–18
13,19
compounds
and olefins.
We have so far found signifi-
cant ultrasonic effects upon an increase in the current efficien-
cy and product selectivity. In this paper we report that the
product selectivity for crossed hydrocoupling products, formed
in a cathodic reduction of a mixture of acetone and acryloni-
trile, is clearly increased under ultrasonic irradiation. Thus,
this paper represents the first report of ultrasonic effects on a
crossed-coupling reaction between two different kinds of com-
pounds.
ꢁ
ꢀ
Experimental
An H-shaped divided cell equipped with a lead (99.9% pure)
disc cathode (Diameter, 3.3 cm) and a platinum plate anode was
used for the reduction of acetone in the presence of acrylonitrile.
Unless otherwise stated, the electrolysis was carried out according