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Book Review The Molecular Orbital Theory of Conjugated Systems by L.

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The excellent article by G. F. Springer on the immunochemistry of substances containing amino sugars describes in
detail the structure and immunology of the blood-group
substances, but also deals with other immunologically interesting polymers from higher organisms, bacteria, and protozoa, and describes relationships between the various systems.
Special mention should also be made of the article by A .
Gortschalk, which clearly describes results on virus receptors,
RDE, and analogies between the receptors and various
glycoproteins.
The book is an important addition to the literature, and can
be warmly recommended.
[NB 571 IE]
H , J . Risse
[l] Cf. Angew. Chem. 78, 1027 (1966); Angew. Chem. internat.
Edit. 5 , 979 (1966).
Advances in Free-Radical Chemistry. Vof. 1. Edited by G. H.
Williams. Logos Press - Academic Press, London 1965.
1st Edit., xi. 291 pp., several figures and tables, $12.00;
75s.
The chemistry of free radicals has developed independently
in physical chemistry (gas-phase reactions) and organic
chemistry (solution reactions; stable radicals). It is to be
hoped that the new series “Advances in Free-Radical
Chemistry” will help to bring these two branches together.
In what is probably the most interesting article in the first
volume, A . F. Trotman-Dickenson critically sifts and comments upon the literature on “The Abstraction of Hydrogen
Atoms by Free Radicals”. The articles by N . J. Friswell and
B. G . Gowenlock (“Inorganic Hydrogen- and Alkyl-Containing Free Radicals”) and by E. S. Huyser (“Solvent Effects
in Free-Radical Reactions”) are first interim reports on
current research topics, the object of which is to describe
new departures and to stimulate new work by formulations
that are occasionally rather too subtle.
An important report on the little known but surprisingly
smooth “Vapor-Phase Halogenation of Aromatic Compounds”, which has been studied mainly in the author’s own
laboratory since 1957, is presented by E. C . Kooyman.
R . Kh. Freidlina’s article OR “Rearrangments of Radicals in
Solution” emphasizes the Russian work, and particularly
her own: this article therefore complements a recent review
by Ch. Walling. However, the choice of subject matter is
not always absolutely satisfactory. For example, the important 1,5-hydrogen shifts afe discussed only on the basis
of the earliest examples, while no mention is made of more
recent reviews. “Free-Radical Reactions of Bridged Cyclic
Systems” are discussed by D . 1. Davies and S. J. Cristol.
In contrast to the chemistry of the carbonium ions, these
free-radical reactions show few unusual features; the article
points out some useful relationships.
With a few exceptions, the literature is covered only up to
1964, and even for this period the coverage is unfortunately
not always complete. The authors should have specified the
completeness and the period covered. The presentation and
the index are good, but the references might have been better
C . Riichardt
[NB 574 IE]
inserted as footnotes.
The Molecular Orbital Theory of Conjugated Systems, by
L. Salen?. W. A. Benjamin, Inc., New York-Amsterdam
1966. 1st Edit., xvi, 576 pp., numerous illustrations, cloth
s 22.50.
The MO theory of conjugated systems is probably the most
extended and one of the most successful sectors of quantum
chemistry. Salem makes a commendable attempt to present a
methodically complete description of the theory in its
present state.
This book should not be approached without a previous
knowledge of the elementary theory of chemical bonding.
The first chapter is a recapitulation of, rather than an introduction to, Huckel MO theory. Unfortunately, no serious
foundation is given for the distinction between d and
electrons nor for the fundamentally important 6-TCseparation. This is particularly regrettable since some aspects of
0-TCseparation are currently regarded as very doubtful, and
since joint treatments of D and x electrons (though within the
framework of the c - x separation) are becoming increasingly
important. Among the basic assumptions for which no convincing justification is given are the “neglect of overlap’’ and
of “differential overlap”. The short section on electron
correlation deals only with some aspects of this important
concept.
The review of the refined methods in the second chapter is
arbitrary rather than systematic. The strength of the book
does not lie in the discussion of fundamental questions, but
in the detailed description of the current and possible
applications of the MO theory. The author goes into detail
on the relationship between theoretical delocalization energies and resonance energies, the Huckel rule, and the semiempirical calculation of dipoIe moments, bond lengths,
force constants, and ionization energies Special attention is
given to the magnetic properties of x -electron systems,
particularly to ‘ ring currents”, the theory of “chemical
shifts”, and spin densities and their refation to ESR spectra.
Further chapters deal with the theory of the chemical reactivity and that of the UV spectra of unsaturated molecules.
The author makes extensive and profitable use of the simple
rules derived by the “English school” for the Huckel MO’s
of alternant hydrocarbons, e.g. the scheme for obtaining the
coefficients of a non-bonding MO without calculation.
The final chapter is devoted, apart from the Jahn-Teller
effect, to a phenomenon on which the author himself has
worked successfully, i.e. bond alternation in polyenes and
other conjugated systems.
Though the book is quite extensive and includes treatments
of some uncustomary problems, such as conjugated rings
containing d electrons, the author has omitted the theory of
a number of interesting unsaturated systems, e.g. that of the
non-classical carbonium ions, as well as conjugation in nonplanar systems. The main emphasis is placed on the treatment of alternant hydrocarbons. The reader experiences little
of the special problems of the theory of heteroaromatic
compounds.
The recent literature is abundantly cited, though sometimes
the selection is somewhat arbitrary.
The rather high price of this book may preclude purchase by
individuals, but chemical libraries should not do without
[NB 560 IEI
the information it contains. w.Kurzelnigg
Registered names, trademarks, etc. used in fhis journal, even without specific indication thereof, are not to be considered unprotected by law.
0Verlag Chemie,
GmhH., Weinheim 1967.
- Printed
in Germany by Druckerei Winter, Heidelberg.
All rights reserved. N o part of this journal may he reproduced in any form whatsoever, e.g. by photoprint, microfilm, o r any other means, without
written permission from the publishers.
Editorial office: Ziegelhauser Landstrasse 35, 6900 Heidelberg, Germany, Telephone 24975, Telex 46 1855 kemia d, Cable address: Chemieradaktion
Heidelberg.
Editor: H . Griinewald
. Translation Editors: A. J. Rackstraw
and A . Stimson.
Publishers: Verlag Chemie GmbH. (President Eduard Kreuzhage), Pappelallee 3, 6940 Weinheim/Bergstr., Germany, and Academic Press Inc.
(President Walter J. Johnson), 1 1 1 Fifth Avenue, New York 3, N. Y.,USA, and Berkeley Square House, Berkeley Square, London, W. 1 ., England.
Correspondence concerning advertisements should be addressed to Verlag Chemie, GmhH. (Advertising Manager W . Thiel), Pappelallee 3 ,
6940 Weinheim/Bergstr., Germany, Telephone Weinheim 3635, Telex 4 6 5 5 16 vchwh.. Cable address Chemieverlag Weinheimhergstr.
Angew. Chem. internat. Edit. I Yof.6 (1967) / No. 5
475
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