Diazo Chemistry I: Aromatic and Heteroaromatic Compounds

460 Pages·1994·10.49 MB·English

by  Prof. Dr. Drs. h. c. Heinrich Zollinger(auth.)

H. Zollinger
Diazo Chemistry I
VCH
Diazo Chemistry I: Aromatic and Heteroaromatic Compounds. By Heinrich Zollinger
Copyright © 1994 VCH Vertagsgesellschaft mbH
ISBN: 3-527-29213-6
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ISBN 3-527-29213-6
Heinrich Zollinger
Diazo Chemistry I
Aromatic and Heteroaromatic
Compounds
Weinheim • New York
Basel • Cambridge • Tokyo
Prof. Dr. Drs. h. c. Heinrich Zollinger
Technisch-Chemisches Laboratorium
Eidgenossische Technische Hochschule
CH-8092 Zurich
Switzerland
This book was carefully produced. Nevertheless, author and publisher do not warrant the information
contained therein to be free of errors. Readers are advised to keep in mind that statements, data,
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A catalogue record for this book is available from the British Library.
Die Deutsche Bibliothek - CIP-Einheitsaufnahme
Zollinger, Heinrich:
Diazo chemistry / Heinrich Zollinger. - Weinheim ; New York
; Basel ; Cambridge ; Tokyo : VCH.
1. Aromatic and heteroaromatic compounds. -1994
ISBN 3-527-29213-6 (Weinheim...)
ISBN 1-56081-878-6 (New York)
© VCH Verlagsgesellschaft mbH, D-69451 Weinheim (Federal Republic of Germany), 1994
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Dedicated in friendship
to Paul D. Bartlett
Je distingue deux moyens de cultiver les sciences: 1'un
d'augmenter la masse de connaissances par des decouvertes;
Pautre de rapprocher les decouvertes et de les ordonner entre
elles afin que plus d'hommes soient eclairer. *
Diderot (1747)
Preface
During the last twenty years several colleagues have approached me suggesting that
I write a second edition of my book Diazo and Azo Chemistry. Aromatic and
Aliphatic Compounds (Interscience/Wiley, 1961). One of them was a consultant for
a leading publisher. For many years I was unable to consider such suggestions
seriously since, besides my primary duties of teaching and research, I had numerous
commitments in the management of the ETH and of Swiss and international scien-
tific organizations. Nevertheless, the unexpectedly positive response to my book
Color Chemistry (VCH, 1987; second edition 1991), and the observation that the
1961 book is still cited quite frequently** in papers published by well known authors,
convinced me that I should start work on a new book on diazo (not azo) chemistry
after my retirement from the ETH.
But there was another and more appealing impetus — even challenge — for me to
write a book on diazo compounds. The chemistry of these compounds had started
to cross the classical border between organic and inorganic chemistry in the 1960s
with the discoveries of completely inorganic diazonium ions, of the reactivity of
transition metal complexes with molecular nitrogen, and of the ability of organic
diazo and diazonium compounds to act as ligands in metal complexes.
However, the inclusion of these new areas obviously increases the number of
chemical compounds to be described and therefore brings the danger that such a
book may degenerate into a compilation of data — an accusation that representatives
of the humanities quite often make about scientific monographs. I agree with such
censure because this is indeed the case for many books in chemistry. Such mere
reference books are outdated nowadays, when comprehensive data are becoming
available in computerized data bases. What is needed, however, is a personal inter-
pretation of a selected group of experimental and theoretical data, which should be
capable of providing the reader with a basis for their understanding. Correlations
between apparently independent problems, classes of compounds, or reactions
should be highlighted in order to deepen our understanding of nature.
* I differentiate two ways of developing the sciences: one by increasing the understanding of fun-
damentals through discoveries; the other by making discoveries more widely known and coor-
dinating them so that more people understand them.
** The 1961 book appeared 30-40 times per year in the Science Citation Index in the 1970s and
between 1990 and 1992 still 16 times per year on average.
VIII Preface
I think that such a book may become a little like a real organism, which is the non
plus ultra of an extremely complex combination of biological and psychic reactions.
What we need today in chemistry is not more ponderers, but more people capable
of disentangling a complex web of information and of making connections between
apparently unconnected ideas or data. Chemistry is the science of molecules,
reagents, and products, but chemical research should — like all research — create not
only chemical products but also ideas. Chemistry becomes innovative through the
combination of products and ideas.
During the first phase of working on the manuscript I realized, however, that it
is hardly possible to cover the entire sequence of defining goals, interpreting results,
and finally understanding within the limits of one resonably sized book. I had to
split it into two volumes, the present book containing aromatic and heteroaromatic
diazo compounds. The second volume will deal with aliphatic and inorganic diazo
compounds, and all metal complexes (including those with aromatic diazo ligands).
It is planned that the second book will be available one year after the first. The two
volumes will be independent of each other with respect to content, index, etc. It
should be possible to understand the context of one book without having to consult
the other. There are very few repetitions in the books. For the reader interested in
a really in-depth understanding, it is, of course, beneficial to consult the analogous
parts of both books.
This book contains what I call an "interlude" on the logic, the psychology, and
the serendipity of scientific discoveries. Readers may wonder what the correlation is
between that short Chapter 9 and diazo chemistry. The specific reason for including
it was to elucidate the dediazoniation mechanism of aromatic diazonium ions, but
I expanded this mechanistic discussion (Sec. 8.3) in the interlude by including general
aspects originating in the philosophy of science as developed by Karl Popper and
Thomas S. Kuhn, ideas which, in my opinion, should be better known by all scien-
tists working in chemical research.
The reader will also recognize in the interlude one of my scientific hobbies, namely
linguistics. In that context I should like to draw attention to the growing inac-
cessibility of science in general. Large areas of the scientific literature are becoming
more and more difficult to understand for nonspecialists. Hayes proposed in Nature
(1992) an objective way of measuring this and applied it to science journals over the
past 145 years. With a difficulty scale based on the choice of words from the full
English lexicon and used in sample texts one finds a considerable increase in dif-
ficulty, not only for journals such as Nature, Science, and Scientific American (all
since 1930), but also for the Journal of the American Chemical Society (1900-1990).
I agree with Hayes' conclusion that these "higher barriers to the comprehension of
scientific affairs must surely diminish science itself". I have therefore tried to write
as clearly as possible, and to give references to elementary literature, but not explana-
tory descriptions for certain subjects because that would require too much space
(e. g., MO methods, toxicological investigations, etc.). I think also that the readabi-
lity of a scientific book is increased by occasional violations of three taboos, namely
the use of T, of metaphors, and of a narrative style.
For the same reasons I make relatively frequent reference to historically important
and pioneering investigations (including relevant bibliographic information). I agree
Preface IX
with Postman's recommendation (1991) that general acceptance of science and
technology can be improved by teaching such subjects with a historical background.
By giving some space to historical remarks on diazo chemistry and by inclusion of
the interlude mentioned above, I hope to make a modest contribution to better links
between science and the humanities.
Another aspect of our present scientific language was raised by Caserio (1993) at
the 1992 IUPAC Conference in Geneva celebrating the centenary of the so-called
Geneva Nomenclature of Organic Chemistry. She proposed a further reduction in
the number of trivial names used for relatively simple organic compounds compared
with those listed in the current 'Blue Book' (IUPAC, 1979), because it is easier and
less boring for science students to learn somewhat longer, but more logical, system-
atic names.
In this book I will follow these recommendations as far as is reasonable and SI
units will be used throughout. * I cannot accept the argument of some of my col-
leagues who are twenty or more years younger than I that they are 'accustomed' to
(for example) kcal, and that they think it sufficient just to tell students in courses
once that the SI unit is kJ, that 1 kJ = 0.239 kcal, and to suggest that students con-
vert units if they want!
I dedicate this book to Paul D. Bartlett, one of the grand pioneers of physical
organic chemistry, who investigated perceptively several basic problems in organic
chemistry at a time when the chemical community did not yet see their crucial
aspects, for example, in the mechanism of the diazo coupling reaction (Wistar and
Bartlett, 1941). I learned much from him when he invited me to attend his Friday
seminars at Harvard University in 1951-1952.
I thank my former coworker, Dr. M. D. Ravenscroft (now with Dow Deutschland
Inc., Rheinmtinster) for reading the entire manuscript, for improving its English,
and for making suggestions and comments on the contents of this book. I am also
thankful to Dr. M. V. Kisakiirek, Editor of Helvetica Chimica Acta, who read
critically Section 1.2 (nomenclature), to Mr. J. Meienberger, Head of the Chemistry
Library of ETH for his help in database literature search, and to two former
secretaries, Mrs. S. Braun and Mrs. M. Gray, who typed all the manuscript, and to
Dr. P. Skrabal who helped me read the galley proofs. I am very grateful to my wife
Heidi for understanding that even a retired chemistry professor may still have a vivid
interest in his former subjects of teaching and research, no longer with students and
a laboratory, but in the library and at home.
Kusnacht, Zurich, February 1994 Heinrich Zollinger
* e.g. kJ instead of kcal or Hartree (or ...!), pm instead of A (see Sec. 1.2).
Contents
1 Introduction 1
1.1 History of Aromatic and Heteroaromatic Diazo Compounds 1
1.2 Nomenclature 3
1.3 General References 9
2 Methods for the Preparation of Aromatic and Heteroaromatic Diazo Com-
pounds 11
2.1 Diazotization of Amines with Alkali Nitrite in Dilute Aqueous
Mineral Acids 11
2.2 Diazotization in Concentrated Mineral Acid 20
2.3 Isolation of Diazonium Salts 24
2.4 Diazotization of 2- and 4-Aminophenols 25
2.5 Formation of Diazonium Salts under Anhydrous Conditions 30
2.6 Other Reactions Involving Formation of Aromatic Diazonium Ions 32
3 Kinetics and Mechanism of Diazotization 39
3.1 Historical Development 39
3.2 Influence of Acidity on the Rate and Mechanism of Diazotization in
Aqueous Sulfuric and Perchloric Acids 44
3.3 Nucleophilic Catalysis of Diazotization 54
3.4 Transformation of the 7V-Nitrosoamine Intermediate into the
Diazonium Ion 58
4 The Structure of Diazonium Compounds 65
4.1 Introductory Remarks 65
4.2 Structure of Arenediazonium Salts 66
4.3 Theoretical Investigations 82
5 Acid-Base and Isomerization Reactions of Diazo Compounds in Water 89
5.1 The Aromatic Diazonium Ion as a Dibasic Acid 89
5.2 The Combined System of Acid-Base Addition, (Z)/(E)- and Pro-
totropic Isomerization Reactions of Arenediazonium Ions 96
5.3 Kinetics and Equilibria of Arenediazonium Ions in Water 98
6 Additions of Other Nucleophiles to Arenediazonium Ions 107
6.1 Introduction 107
6.2 O-Coupling 108
XII Contents
6.3 5-Coupling 116
6.4 TV-Coupling 120
6.5 P-Coupling 126
6.6 C-Coupling 127
6.7 Intramolecular Coupling 131
6.7.1 Introduction 131
6.7.2 TV-Coupling 131
6.7.3 O-Coupling 136
6.7.4 S-Coupling 136
6.7.5 C-Coupling 137
7 Structural and Mechanistic Aspects of Additions of Nucleophiles to
Diazonium Ions 143
7.1 (Z)/(£)-Isomerism 143
7.2 Investigations on Reactivities by the Interpretation of Substituent Ef-
fects: The Hammett and Related Equations 148
7.3 The Electronic Influence of the Diazonio Group as a Substituent 151
7.4 Influence of Substituents on the Addition of Nucleophiles to
Arenediazonium Ions 153
8 Dediazoniation of Arenediazonium Ions 161
8.1 Introduction to Dediazoniation in General 161
8.2 Multiplicity of Pathways and Products 162
8.3 The D + A Mechanism of Dediazoniation 166
N N
8.4 Molecular Orbital Investigations on Heterolytic Dediazoniations and on
Aryl Cations 177
8.5 Dediazoniations via Aryne Intermediates 183
8.6 Dediazoniation Initiated by an Electron Transfer 188
8.7 Solvent Effects in Competitive Homolytic and Heterolytic
Dediazoniation 197
8.8 Dediazoniation in Alkaline Aqueous Solutions 200
8.9 Dediazoniation in Highly Nucleophilic Solvents and in the Presence of
Good Nucleophiles 205
8.10 Dediazoniation in Alcohols 208
9 Logic, Psychology, and Serendipity of Scientific Discoveries
- An Interlude 213
10 Applications of Heterolytic and Homolytic Dediazoniations in Organic
Syntheses 221
10.1 Introductory Remarks 221
10.2 Hydro-de-diazoniation 222
10.3 Hydroxy- and Mercapto-de-diazoniations and Related Reactions 225
10.4 Fluoro-de-diazoniation 228