Catalytic and Kinetic Waves in Polarography

Catalytic and Kinetic Waves in Polarography

Stal' G. Mairanovskii Institute of Organic Chemistry

Academy of Sciences of the USSR, Moscow

Translated from Russian by

Bela M. Fabuss Technical Director, Environmental Pollution Division Lowell Technological Institute Research Foundation

Lowell, Massachusetts

Translation Editor

Petr Zuman Heyrovsky Institute of Polarography

Czechoslovak Academy of Sciences Prague, Czechoslovakia

<±' Springer Science+Business Media, LLC 1968

Stal' Grigor'evich Mairanovskii was born in 1926. He studied at the Lomonosov Institute of Fine Chemical Technology and pursued his post­graduate studies at the Institute of Chemical Physics of the Academy of Sciences of the USSR, obtaining his doctorate in 1962. Currently Dr. Mairanovskii is the leader of the polarographie group at the Institute of Organic Chemistry of the Academy of Sciences of the USSR in Moscow . . Mairanovskii developed the theory of catalytic hydrogen evolution and has published more than 110 papers dealing with the polarographic behavior of different classes of organie compounds and with the kinetics of electrode processes and chemical reactions occurring at the electrode .. While at the Institute of Organic Chemistry, he also took part in the work performed at the Institute of Electrochemistry of the Academy of Sciences of the

USSR under the guidance of Academician A. N. Frumkin.

Tbe Russian text, originally publisbed by Nauka Press in Moscow in 1966 for the Institute of Organic Cbemistry of the Academy of Sciences of

the USSR, was corrected by the author for tbis edition.

CATALYTIC AND KINETIC WAVES IN POLAROGRAPHY

KATALITICHESKIE I KINETICHESKIE VOLNY V POLYAROGRAFII

RATAJIRTlNECRHE H RHHETHqECRHE BOJIHLI B nOJIflPOrPAG>HH emu!> rpueOpM8UQ Maüpan08C"uü

Library of Congress Catalog Card Number 67-10535

ISBN 978-1-4899-2833-7 ISBN 978-1-4899-2831-3 (eBook) DOI 10.1007/978-1-4899-2831-3

© 1968 Springer Science+Business Media New York

Originally published by Plenum Press in 1968.

All rights reserved

No part of this publication may be reproduced in any form without written permission from the publisher

Preface

As our knowledge of the mechanism of electrode processes increases, it becomes more and more apparent that the kinetic currents first observed by R. Brdicka and by K. Wiesner in the 1940's are very widely encountered. Very many electrode pro­cesses contain a chemical stage.* This is true primarily of elec­trode processes that involve organic compounds. Therefore, to understand the mechanism of electrode processes and, particular­ly, to correctly interpret the results of polarographic investiga­tions, it is important to know the characteristics and relationships controlling the chemical reactions taking place at the electrode surface. Generally, these reactions are substantially different from ordinary chemical reactions taking place in the bulk of the solution, since the reactions at the electrodes are often affected by the electric field of the electrode and the adsorption of the par­ticipating compounds .

The fact that hydrogen ions usuallY take part in the electro­chemical reduction of organic compounds makes possible the use of electrochemical methods, particularly polarography, for the study of protolytic reactions. These reactions play an important role in organic chemistry: the majority of reactions of organic compounds in solutions go through a stage in which a hydrogen ion is removed or added (see, for example, [1, 2]). Therefore, the polarographic study of protolytic reactions can supply much important information to theoretical organic chemistry.

• By electrode processes we mean the combination of electrochemical and chemical stages as weIl as the supply and removal of compounds, while the term "electro­chemie al reaction" will denote only the process of electron transfer.

v

vi PREFACE

The present work deals mainly with the polarographic in­vestigation of fast protolytic reactions, i.e., with reactions of hy­drogen ion addition to the anions of weak acids and to un-ionized organic bases. In the latter case, the so-called catalytic hydro­gen wave is used for the determination of the constant. A sepa­rate chapter is devoted to the description and theory of catalytic hydrogen wa ves.

Because of its complexity, catalytic hydrogen evolution on a dropping mercury electrode represents aseparate, extremely interesting area of polarography. This process consists of the protolytic reaction, electron transfer, and the bimolecular inter­action of the products of the electrode reaction. Therefore, a chapter dealing with the theory of catalytic hydrogen waves fol­lows chapters dealing with the processes taking place with ante­cedent protonation and processes in which the electrochemical stage is followed by a fast dimerization of the products that form.

Certain stages of the catalytic reaction cycle are substan­tially affected by the adsorption of the compounds at the mercury electrode, by the structure of the electric double layer, by stir­ring under the conditions of the polarographic maximum of the second kind, etc. Therefore, a study of catalytic polarographic hydrogen waves makes it possible to investigate relatively simple processes and phenomena that are hardly (or not at all) accessible by other methods: the rate constants for fast protolytic reactions, adsorption phenomena at extremely low coverage of the electrode surface by adsorbed particles (less than 0.50/0), the rate of bi­molecular reactions of certain free radicals, and certain other phenomena.

The catalytic hydrogen waves are important from a practi­cal standpoint, too. Their application makes possible the attain­ment of a sensitivity of 10- 7 M for analytical purposes using or­dinary polarographic equipment. This means that the sensitivity can be increased by several orders of magnitude compared with "classical n polarography where diffusion currents are used. Par­ticularly interesting is the application of catalytic waves in biology and medicine, where several diagnostic methods have been de­veloped. The well-known serological polarographic test for can­cer developed by Brdicka [3] is an example.

PREFACE vii

The objectives of this book are: first, to show examples and methods of investigations of electrode processes occurring at the dropping electrode that are complicated by chemical reactions tak­ing place at the electrodes and, second, to demonstrate how the kinetic parameters of fast reactions in solutions can be calculated on the basis of investigation of electrode processes • Finally, we intend to show how the reacti vity of organic compounds can be de­termined from the value of the polarographic half-wave potential (E1j2), taking into consideration the effect of the structure of the electric double layer, adsorption, and accompanying chemical re­actions on the half-wave potential.

This work does not discuss all published material on kinetic waves; instead, its aim is to demonstrate, with selected charac­teristic examples, the importance of kinetic currents and their re­lationships. The book is based mainly on the data from investiga­tions conducted over aperiod of several years at the N. D. Zelin­skii Institute of Organic Chemistry of the Academy of Sciences of the USSR.

In the first chapters of the book some aspects of the theory of polarography and the kinetics of electrode processes are dis­cussed, and a short review of the investigations dealing with ki­netic currents is given. General information on the theory of the polarographic method and also of electrochemical kinetics can be found in polarography handbooks [4-6] and also in the well-known monographs of Frumkin, Bagotskii, Iofa, and Kabanov [7].

The author wishes to use this occasion to express his deep gratitude to Academician Aleksandr Naumovich Frumkin, for his interest and helpful criticism, and for his evaluation of experi­mental data which helped to clarify a number of phenomena of the kinetics of electrode processes that were complicated by chemical reactions and adsorption. The author further acknowledges the help for several years of Doctor of Chemical Sciences Valentina Alekseeva Klimova, who carried out many of the experiments de­scribed in this book. The author also acknowledges the assistance of B. 1. Khaikin, G. A. Tedoradze, A. B. Ershler, and E. D. Belo­kolos for valuable suggestions and evaluations of certain results and also the help of S. I. Zhdanov, B. D. Bezuglyi, and L. G. Fe­oktistov in reading the manuscript. L. K. Gladkova helped in the preparation of the manuscript and proof.

Contents

Chapter 1. Basic Principles of the Polarographic Method................. 1

Chapter 11. Currents Limited by the Rate of Chemical Reaction............. 7

A. The Meaning of Kinetic Currents . • • • • • • • • • 7 B. Discussion of Kinetic Currents on the Basis

of the Reaction-Layer Concept. • • • • • • • • • . • 8 C. The Rigorous Solution of the Depolarization

Scheme; Comparison of the Exact and Approximate Methods. • . • . • • . • • • • • • • • • . 12

D. Examples of Polarographic Currents Limited by the Rate of Chemical Reactions. • • 17

1. Catalytic Processes • • • . • • • . • • • • • . • • • 17 2. Kinetic Currents Limited by the Rate of

Recombination of Acid Anions • • • • • • . • • • 25 3. Kinetic Currents Limited by the Rate· of

Dehydration of Carbonyl Groups • • • • • • • • • 35 4. Kinetic Currents in the Polarography of

Solutions of Complexes . • • . . • • • . • • . • . . 43 E. Methods of Investigation of Kinetic Currents • • 47

Chapter 111. Adsorption on the Electrode and the Electrode Processes.. ......... 57

A. Basic Relationships of Adsorption . • • • • . • • • 57 B. Methods for the Investigation of Adsorption

on the Electrodes . . • • • • • • • • • • • • • • . • • • 65 C. The U se of Specific Properties of the Dropping

Mercury Electrode for the Determination of Adsorption of Organic Compounds • • • • • . • . • 73

ix

x CONTENTS

D. The Effect of Adsorption of the Depolarizer in Reversible Redox Systems; Adsorption Prewaves and Postwaves • • • • • . . . • • • • • . • 85

E. The Effect of the Adsorption of Compounds Not Taking Part Directly in the Electrode Process on the Rate of Electron Transfer. • • . 93

F. Inhibition of Electrode Processes by Adsorption of Depolarizer and Electrochemical Reaction Products; Formation of Adsorption Pseudoprewaves • • • • • • . • • • . • • • • • • . • . • 106

Chapter IV. Electrode Processes with Antecedent Protonation Reaction . . • . • • • 115

A. Protonation in the Electrochemical Reduction of Orgarric Compounds • • • • . • • • • • • • • • . . . 115

1. General Remarks .•••••••••••••••.• 115 2. Electrode Processes with a Reversible

Electrochemical Step • . • • . • • • • • • • • • • • 116 3. Protonation Preceding a Slow Electron

Transfer: Quasidiffusion Waves. • • • • • • • • 119 B. Antecedent Chemical Reactions at the Surface

and in the Volume: The Effect of Adsorption of Reaction Components in the Electrode Layer on Kinetic Currents . . • • • • . • . • • • • . • . • . . 128

C. Protonation Reactions in the Volume. • • • • • . . 132 1. Volume Character of Kinetic Currents

Limited by the Recombination of Maleic Acid Diani ons. . • • • • . • . • • • • • • . • • • . • • • • • 132

2. Calculation of Rate Constants from Polarographic Data Measured in Buffer Solutions . • • • • • • • • • • • • . • . . • . . • • . • 133

3. Determination of the Protonation Rate Constant of Maleic Acid Dianions Under the Irrfluence of the Components of the Buffer System. • . • • . • • • . . • . . . • • • . • . • . . • • 135

4. Development of Equations for Kinetic Volume Waves Observed in the Polarography of Salts of Weak Acids in Unbuffered Solutions • • • . . 140

CONTENTS xi

5. Kinetic Waves of Maleic Acid Dianions in Unbuffered 1 M Potassium Chloride Solutions; Determination of the Protonation Rate Constant of Maleic Acid Dianions by Water •••••••••• 0 ••••••••••••••• 144

6. The Relationship Between the Acid ,Strength and Its Proton-Donor Effect •••••••••••• 146

7. The Effect of Temperature on the Protonation Rate of Maleic Acid Dianions ••• 148

8. Certain Other Processes with Fast Antecedent Volume Protonation Reaction ••• 152

Chapter V. The Effect of the Double-Layer Structure on Electrode Processes 155

A. Introduct ion • • • • • • • • • • • • • • • • • • • • • • • • 155 B. Irreversible Electrode Processes with

Participation of Uncharged Compounds without Antecedent Protonation. • • . • • • • • • • • • • • • • 156

C. The Effect of the Double Layer on Ion Discharge . . . . . . . . . . . . . . . . . . . . . . . . . 160

D. Some Peculiarities of Anion Reduction • • • • • • 163 E. Change of pH in the Electrode Layer as

Compared to Its Value in the Bulk Solution. • • • 164 F. The Effect of Double-Layer Structure on

Processes with Antecedent Protonation. • • • • • 166 G. The Effect of the Nature of Supporting

Electrolytes • • • • • . • • • • • • • • • • • • • • • • • • 172 H. Change of Reactivity of Particles Polarized

in the Electrode Field • • • • • • • • • • • • • • • • • 183 I. Consideration of the Effects of the Double­

Layer Structurein Determining the Relation­ship Between the Structure of Organic Molecules and the Half-Wave Potentialof Their Reduction Wave • • • • • • • • • • • • • • • • • 185

Chapter VI. Electrode Processes with Participation of Adsorbed Compounds... 187

A. Characteristics of Electrode Processes with Adsorption of the Components Taking Part in Chemical and Electrochemical Reactions. • • • • 187

xii CONTENTS

B. Equations of Surface Kinetic Waves • • • . • • • • 189 C. The Shape of Surface Kinetic Waves . • • . . • • . 194 D. The Effect of Double-Layer Structure on the

Adsorption of Components of Antecedent Reactions. • • . • • • • . . • • • • • . . • . • . • . • • • 201

E. Quasidiffusion Surface Kinetic Waves and Electrode Processes with Adsorbed Depolarizer without Antecedent Reactions. • • . • • . • • • • • • 208

F. Difference in the Properties of Depolarizer Formed at the Electrode and Transported from the Solution (Effect of Succession in Multistage Electrode Processes). • . • • • • . • . . • . • • • . • 217

Chapter VII. Mixed Volume - Surface W ave s ..•••.•.. 0 • • • • • • • • • • • • • • • • • • • • • 221

Chapter VIII. The Effect of Dimerization of Electrode Products on Processes w i t h Re ver s i bl e Eie c t r 0 ehe m i c alS tag e. 227

A. The Effect of Subsequent Chemical Reaction on Electrode Processes . . . . • . . . • . . . . . . . 227

B. Second-Order futeraction of the Products of a Reversible Electrochemical Reaction • • • • • • • 229

1. General Relationships and Equations • • . • • • 229 2. Polarography of N-Alkyl Pyridinium Salts . • 231 3. The Effect of Dimerization of Free Radicals

on Polarographic Reduction Waves of Aromatic Aldehydes and Ketones in Acid Medium • • • • • • . . • • . • • • . • . • • . • . . . • 232

4. Electrode Processes with Second-Order Reaction, Parallel to the Electron Transfer. 235

5. Certain Other Reversible Processes with Dimerization of Electrode Products • • • • . • 238

Chapter IX. Catalytic Hydrogen Evolution at the Dropping Mercury Electrode Ca u se d b Y 0 r ga ni c C at a I y s t s • • • • • • • • • • • 241

A. futroduction......... . • • . • • . . • • • • • • • 241 1. Certain Properties of Catalytic Hydrogen

Waves ....................... 0 • • 241

CONTENTS xiii

2. Mechanism of Catalytic Hydrogen Wave Formation Under the Effect of Organic Bases 245

B. Volume Catalytic Hydrogen Waves with a Reversible Electrochemical Step • • • • • • • • • • 249

1. Reversible Catalytic Hydrogen Waves with Volume Chemical Reactions • • • . • • • . 249

2. Reversible Volume Catalytic Hydrogen Waves in Buffer Solutions • • • • . • • • • • • • . 251

3. Determination of the Protonation Rate Constant of the Catalyst; The Effect of Double-Layer Structure on the Protonation Occurring in the Reaction-Layer Volume • • . 255

4. The Effect of Temperature on Volume Catalytic Wavesin Buffer Solutions. • • • • . • 258

5. Reversible Volume Catalytic Hydrogen Waves in Unbuffered Solutions • • • • • • • • • • 259

C. Surface Catalytic Waves of Hydrogen. • • • • • • 261 1. The Shape and Properties of Surface

Catalytic Waves. • • • • . • • • . • • • • • . • • . • 261 2. Mixed Volume-Surface Catalytic Waves • • • 266 3. The Effect of Double- Layer Structure on

Surface Catalytic Waves • • . • • . • • • • . • • • 267 D. Catalytic Waves Caused by Sulfur-Containing

Compounds. • . • • • • • • • • • • . • • • . . • • • • . • 269 1. The Mechanism of the Process. • • • . • . . • • 269 2. The Nature of the Doubling of Protein Waves 273 3. The Form of Double Waves on Polarographic

Curves of Protein Solutions in the Presence of Cobalt Salts. • • • . . • • • • . • • • • • . . • • • 277

E. The Dependence of Catalytic Hydrogen Waves from the Structure of Organic Catalysts . . • • • 280

1. General Remarks. • • • • • • • • • • . • • • • • • • 280 2. Reversible Volume Catalytic Waves • • • • • • 281 3. Irreversible Surface Waves • • • . • . • • • • • • 283 4. Catalytically Active Organie Compounds 285

Chapter X. The Effect of Composition of Aqueous Organic Solvents on the Pol a r 0 g rap h i c B eh a v i 0 r 0 f 0 r ga ni c Compounds •••••••••.•.••••..•••.••••. 287

A. General Remarks • • • • . • . • • • • • • . • . • • • . 287

xiv CONTENTS

B. Electrode Processes without Participation of Protons in the Potential Determining Stage . • • 290

C. Electrode Processes with Antecedent Protonation . • • • • • • • • • • • • • . • . • • • • . . • 297

D. Processes with Adsorption of the Electro-chemical Reaction Products • • • • • . . • • • • • . 304

E. Interaction of the Depolarizer with the Components of the Solution. • • • • • • . • • • • • • 308

Chapter XI. The Effect of Antecedent Metal Ion Discharge on Polarographic Reduction Waves of Organic Compounds. 311

A. Introduction................ . . • . . . • • 311 B. Electrode Processes without Antecedent

Protonation . • • . • • • • • • . • • • • . • . • • • • . • 312

Li te rat ure • • • • • • • • . • • • • • . . . • • • • • . . • • • • • 323

Ind ex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 349