Progress in Electrochemistry of Organic Compounds 1

441 Pages·1971·12.749 MB·English

by  Ya. P. Stradyn’, R. A. Gavar (auth.), A. N. Frumkin, A. B. Érshler (eds.)

PROGRESS IN
ELECTROCHEMISTRY OF
ORGANIC COMPOUNDS
Volume 1
Edited by
A. N. Frumkin and A. B. Ershler
Institute of Electrochemistry, Acade,my
of Sciences of the U.S.S.R .. Moscow
This new series contains review articles sum
marising, assessing and assimilating recent
research on the electrochemistry of organic
compounds. ranging from the kinetics of
electrode processes, electrosynthesis, the effect
of electrode metal on adsorption processes.
electrolytic oxidation and electroreduction of
organic substances to polarography.
Problems reviewed include the electrosynthesis
of organometallic compounds and electrolytic
oxidation of organic substances in fuel cells.
Also considered are the possibilities of using
electrochemical methods to investigate catalytic
processes in solutions and electrochemical
gene. dllon of free radicals.
Providing an invaluable reference source and
guide to recent research. this series will be useful
for specialists in the field of theoretical and
applied electrochemistry, analytical and organic
chemists. and those working in the chemical and
fuel industries.
Progress in Electrochemistry
1
of Organic Compounds
Progress in Electrochemistry
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of Organic Compounds ...
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Edited by A. N. Frumkin and A. B. Ershier
Institute of Electrochemistry,
Academy of Sciences of the U.S.S.R.,
Moscow
Translated from Russian by D. E. Hayler
Translation edited by P. Zuman
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Plenum Press London and New York· 1971
Plenum Publishing Company Ltd.,
Donington House,
30 Norfolk Street,
London, W.C.2.
U.S. Edition published by
Plenum Publishing Corporation,
227 West 17th Street,
New York, N.Y. 10011
© 1971 by Plenum Publishing Company Ltd.
Softcover reprint of the hardcover 1st edition 1971
All rights reserved
No part of this publication may be reproduced
in any form without written permission
from the publisher.
Library of Congress Catalog Card Number 77-137739
ISBN-13:978-1-4684-3341-8 e-ISBN-13:978-1-4684-3339-5
DOl: 10.1007/978-1-4684-3339-5
The original Russian text was first published by Nauka Press in Moscow in 1969.
The present translation is published under an agreement with Mezhdunarodnaya
Kniga, the Soviet book export agency.
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PROGRESS ELEKTROKHIMII ORGANICHESKIKH SOEDINENII
Set in Cold Type by Plenum Publishing Company Ltd.
Foreword
In the Soviet Union, investigations of electrochemical changes in
organic substances are being conducted on a comparatively large
scale and a large number of specialists are involved. This arises to a
large extent from the necessity to solve problems in the applied fields,
e.g. in the development of new improved methods for the analysis
and synthesis of organic compounds or in the work on fuel cells. The
attainment of substantial successes in this field has been linked
inseparably with a deeper understanding of the mechanism and
kinetics of electrolytic organic reactions and the utilization of modem
research methods based on the latest achievements in instrumentation.
The theory of organic electrode processes is therefore now developing
rapidly. However, the propagation of information on this work has
been relatively slow.
The Series of reports on Progress in Electrochemistry of Organic
Compounds should stimulate systematic treatment and propagation
of information in this field of science. It is proposed that each volume
of the series will be compiled on the same lines as the book Advances
in Electrochemistry of Organic Compounds published by Nauka in
1966. They will form collections of original review articles on the most
important aspects of the subject, prepared by competent authorities.
This collection represents the first volume of the series. The
reviews published here are based on reports read at the Sixth Con
ference on Electrochemistry of Organic Compounds held in Moscow
in January, 1968. In the review, use is made of the results from the
authors' own investigations, the latest information gathered from the
world literature, and the contents of reports covering new original
investigations in this field which were sent to the Sixth Conference.
In selecting the scope of topics covered by. these reviews the
Organizing Committee of the Sixth Conference has endeavoured to
include problems which interest a large number of Soviet scientists
v
vi FOREWORD
and which have not been considered in sufficient detail at earlier con
ferences on the electrochemistry of organic compounds.
The collection opens with an examination of the methods,
achievements, and potentialities of electron paramagnetic resonance
in the electrochemistry of organic compounds. Attention has been
paid to the current work on electrosynthesis, investigations with solid
electrodes, and investigation of the role of adsorption in electrode
processes involving organic substances. Papers on classical polaro
graphy are also included. Because the contribution by V. S. Bagotskii
and Yu. B. Vasil'ev on the behaviour of organic substances at a
platinum electrode was published earlier, another review on this topic,
prepared by O. A. Petrii, has been included in the present collection.
This departure from the otherwise followed procedure is due both to
the need to analyse results obtained since 1965 and to the endeavour
to represent as completely as possible the various approaches to this
important problem.
The collection can be recommended to the attention of specialists
working in the field of theoretical and applied electrochemistry and
also to those active in analytical and organic chemistry.
A. N. Frumkin
Contents
Electrochemical Generation of Free Radical Ions and Use of
Electron Paramagnetic Resonance for their Investigation.
Ya. P. Stradyn' and R. A. Gavar •.....••..•..••.••. 1
Polarographic Reduction of Azomethine Compounds.
Yu. P. Kitaev and T. V. Troepol'skaya ......•.......•. 43
Electrode Processes Complicated by Chemical Reactions
and by Adsorption on Mercury Electrodes.
S. G. M airanovskii ..•.••....•.•.•••.....••.... 85
Stereochemistry of Electrode Processes.
L. G. Feoktistov ....•......•....•.•••.......•• 135
Prewaves in Reversible Systems.
G. A. Tedoradze, E. Yu. Khmel'nitskaya,
and Ya. M. Zolotovitskii . . . • • . . . . . . • . . • . • . . . • . . .• 171
Reduction of Organic Molecules in Region of Low Electrode
Surface Coverages.
A. B. Ershler ..•......••..............•..•..• 203
Electrochemical Synthesis of Organometallic Compounds.
A. P. Tomilov and l. N. Brago ..• . • . • . . • . • . . . . . . • .. 241
Electrolysis of Organic Compounds with Use of
Ion-Exchange Membranes.
M. Ya. Fioshin •••••••.•••...•••.•.•.•.•.•.•• 287
Electrochemical Oxidation of Organic Compounds at
Metals of the Platinum Group.
O. A. PetrU . . . . . • . • . . • • . • • . . . • . • . • • • • • . • • . .. 319
Electrochemical Methods for Investigation of Catalytic
Hydrogenation Mechanism in Solutions.
D. V. Sokol' skU . . . • • • . • . • . . . • • • • • • . . . . • . • . • .• 377
Electrochemical Reduction Mechanism in Organic Peroxides.
E. S. Levin and A. V. Yamshchikov ....•.•...•...•.• 411
vii
Electrochemical Generation of Free
Radical Ions and Use of Electron
Paramagnetic Resonance for Their
Investigation
Ya. P. Stradyn' and R. A. Gavar
Among the numerous methods used for the preparation of
organic free radicals the most widespread have been the following
[1-6]: 1) Thermal decomposition; 2) electric discharge in gases;
3) electron bombardment; 4) radiolysis with ')I-rays; 5) photolysis.
Alongside these methods in the last 10 years there has also been
a rapid development of the electrochemical methods for generation
of free radicals, which has a number of special characteristics
and advantages over the other methods. Most frequently used for
electrolytic generation of free radicals is electrolytic reduc
tion, and more rarely electrolytic oxidation; as a rule radical
anions are obtained in the first case and radical cations in the
second:
+
R e .... .R'-; R-e->R·+.
Detection of unchanged (neutral) free radicals produced in
electrochemical processes is difficult owing to their short life
under the conditions of the electrochemical experiment, and the
discussion will therefore be mostly concerned with radical ions.
1. METHODS FOR DEMONSTRATING THE
FORMATION OF FREE RADICALS AND RADICAL
IONS IN ELECTROCHEMICAL PROCESSES
The electrochemical method for generating particles with un
paired spins is based on the appearance of these particles as inter
mediate or final products in the electrochemical reaction. Trans
ferof a single electron to a particle (which may be a neutral molecule
1
2 YA. P. STRADYN· AND R. A. GAVAR
or an ion) should result in the formation of a free radical as initial
product ['7, 8].
As a rule free radicals formed during electrochemical proces
ses are short-lived kinetic particles; they determine the course and
kinetics of a series of electrochemical reactions but themselves
undergo further rapid chemical or electrochemical changes and
cannot be isolated from the solution by preparative means.
Methods for their detection and investigation are limited and
include the following:
1. Detection indirectly from the nature of the final large-scale
electrolysis products [8-10] or by the use of free-radical acceptors,
such as unsaturated compounds (styrene, 1,3-butadiene, acryloni
trile, etc.) for example, which readily enter into reaction with the
radicals [7]; this also applies to the observation by Bezuglyi and
Ponomarev that radical anions formed during electrolysis of acrylic
and methacrylic acids can act as initiators of polymerization of the
original monomeric depolarizers, which was discovered from the
suppression of polarographic maxima [11);
2. Appearance of one-electron steps on polarograms or on
potentiometric titration curves [12), as well as the indirect effect
of free-radical formation on the polarographic wave parameters
(the slope of the wave, the half-wave potential, and others) [13-26);
3. Change in the spectral characteristics of the solution and,
in particular, the development of intense coloration due to the free
radicals if their life is long enough for them to allow diffusion from
the layer adjacent to the electrode into the bulk of the solution [22,
27-30];
4. Direct recording of the EPR spectra of the radical ions;
unlike the preceding methods, EPR makes it possible not only to
demonstrate the existence of free radicals clearly and unambiguously
but also to study the electron-density distribution in these species
quantitatively from the hyperfine structure of the spectra, i. e. to
identify the nature and structure of the generated radical ions
[31, 32].
ELECTROCHEMICAL GENERATION OF FREE RADICAL IONS 3
Historically the earliest indirect evidence for the formation
and interaction of free radicals in electrolytic organic chemistry
was the establishment of the nature of some electrolysis macro
products, e. g. the products obtained from the classical Kolbe elec
trosynthesis [10]. The first direct evidence for electrochemical
one-electron transfers was provided by the discovery of semiqui
nones, made independently in 1931 by Michaelis and Friedheim [33]
and by Elema [34]. While studying oxidation - reduction potentio
metric titration curves for some quinoid systems these investiga
tors noticed the appearance of two one-electron steps and gave the
correct interpretation of their observation. Numerous papers by
the Michaelis school [35, 36] were devoted to further investigation
of semiquinones and their biological role.
Evidence for the formation of free radicals from the shape of
potentiometric titration curves can only be obtained for reversible
electrochemical systems, the number of which in organic electro
chemistry is rather limited. The use of polarography was therefore
an important step forward. In the course of a systematic investiga
tion of current - voltage curves for organic compounds at the dropping
mercury electrode it was found that in a number of cases, in partic
ular aqueous alkaline solutions and aprotic media, one-electron
waves appeared on the polarograms or the analysis of the slope of
multielectron waves indicated the transfer of a single electron in
the potential..,determining step. Evidence for the formation of free
radicals during electrolysis is also provided by oscillographic
polarography [37] and cyclic current - voltage curves on a suspend-
ed mercury drop [38]. By these methods, for example, the forma
tion of free radicals in the electrolytic reduction of benzophenone
or nitrobenzene has been demonstrated. The method of cyclic
voltammetry was used by n 'yasov, Kargin and co-workers [39] to
establish the precedence and stability of radical anions formed
from carboxylic esters.
2. ONE-EL,ECTRON POLAROGRAPHIC WAVES:
PRINCIPLES OF ELECTROCHEMICAL
GE NE RA TION
Among cathodic reactions which take place within the potential
range attainable by means of the dropping mercury electrode, the