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Book Review Organomagnesium Methods in Organic Synthesis. (Series Best Synthetic Methods.) By B. J. Wakefield

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BOOKS
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one of the pioneers in the development
and application of the theory of crossing
potential curves, usually called the valence
bond configurational mixing (VBCM)
theory or the curve-crossing model. The
book contains ten chapters which are
grouped under three main sections:
“Theoretical Principles”, “Principles of
Physical Organic Chemistry”, and “Reaction Types”. The first section introduces
some basic concepts of molecular quantum mechanics. Here the author avoids
using mathematical formalism as far as
possible. The comparison between the
molecular orbital and valence bond theories is well presented and instructive. The
fourth chapter starts from simple potential energy curves and develops the theory
to discuss reaction profiles using the
VBCM method. The three most important “ingredients” of the VBCM theory
are explained here, namely the initial excitation energy C, the fraction fact0r.f; and
the resonance energy B. Chapter 5 continues this theme with scarcely a perceptible
break, explaining a number of well-established reactivity concepts such as the
Hammond postulate, the Bell-EvansPolanyi principle, and the Marcus theory.
Both these chapters make easy reading as
the arguments follow a clear sequence.
However, they could have been improved
by including a little more detail, especially
in the treatment of the Marcus theory.
Chapter 6 discusses empirical structurereactivity relationships that are not based
on a theoretical model, such as the
Hammett and Brernsted relationships. In
Chapter 7 the author provides the reader
with all the theoretical tools needed to
apply the VBCM theory qualitatively: the
excitation energies, electron affinities,
and ionization potentials. Chapter 8 then
deals with solvent effects on reaction
rates, describing various classical procedures for quantifying such effects, and finally considering solvent effects in terms
of the VBCM theory.
The third section of the book is entirely
devoted to applications of the VBCM theory to various types of reactions. In accordance with the historical development of
the theory it is natural that the greatest
emphasis is given to nucleophilic substitution reactions and to general considerations regarding the reactivity of nucleophiles. The last chapter describes recent
work by the author on the reactivity of
free radicals and carbenes and the application of the VBCM model to pericyclic
reactions.
The author writes in an excellent and
didactically clear style, both in explaining
fundamental concepts and in discussing
the many well-chosen examples; thus the
A f i g c ~Chem.
.
In[. Ed. Engl. 1996, 35. No. 16
central features of the VBCM theory
come out especially clearly. Pross confines
the discussion to considerations of energy
level diagrams and variations in the initial
excitation energy, and thus all aspects are
treated qualitatively and in a comparative
way. This makes the book especially suitable for the readership intended by the
author, defined as “advanced undergraduate and graduate students as well as researchers in organic chemistry”. The
quantitative application of the VBCM
theory has already been treated in a
monograph by S. Shaik et al. published in
1992 and reviewed in this journal (Angew.
Chern. 1993, 105,1277; Angew. Chem. Int.
Ed. Engl. 1993, 32, 1106). Perhaps the
only complaint about this excellent introduction is that nearly all the publications
on the VBCM theory cited here originate
either from the author himself or from S.
Shaik. Proposed extensions to the VBCM
theory, such as those discussed in the literature by V. Parker, are not mentioned.
Also the chosen examples are rather onesided, in that they illustrate the scope but
not the limitations of the VBCM theory.
These become especially evident in reactions with very low energy barriers, such
as those between nucleophiles and radical
cations, and generally in bimolecular reactions where intermolecular attractive
forces come into play.
Hendrik Zipse
Institut fur Organische Chemie
der Technischen Universitat Berlin
Berlin (Germany)
Organomagnesium Methods in Organic Synthesis. (Series: Best Synthetic Methods.) By B. J. Wakefeld.
Academic Press, London, 1995.
249 pp., hardcover E 50.00.-ISBN
0-1 2-730945-4
Like the other volumes of this series,
the book reviewed here is designed to inform synthetic organic chemists about the
capabilities, advantages, and limitations
of a particular class of synthetic methods
from a practical standpoint. The approach is based not only on describing
many examples from the literature but also on giving detailed laboratory procedures for carrying out the preparations.
From this the reader can quickly gain a
comprehensive picture of the reaction
conditions, the techniques used, and the
work-up procedures.
The first of the 16 chapters in this volume deals with general aspects, beginning
with a fairly brief account of the structures and reactive properties of organo-
Q VCH Verlagsgesellschafr m b H , 1)-69451 Weinheim,1996
magnesium compounds, then discussing
in more detail the methods for handling
and using them. The author discusses the
different solvents used and describes the
techniques for working in an inert environment and performing titrations. This
is followed by a chapter of more than fifty
pages on the preparation of organomagnesium compounds, including detailed descriptions of 25 laboratory procedures. As
well as methods based on activation of
magnesium metal, this includes routes
that start from other organomagnesium
or organolithium compounds, and ligand
exchange reactions. The chapters that follow describe applications of organomagnesium compounds in synthesis. The list
includes addition reactions of alkenes,
alkynes, carbon-nitrogen multiple bonds,
carbony1 compounds, and thiocarbonyl
compounds, followed by substitutions at
carbon atoms, reactions yielding carbenes
and arynes, reactions with acidic compounds, methods for forming carbon-nitrogen, carbon-oxygen, carbon-sulfur,
carbon - selenium, carbon - tellurium, and
carbon-halogen bonds, and methods for
synthesizing organoboron. organophosphorus, organosilicon, and various
organometallic compounds.
Reaction mechanisms are also explained in some cases, but the emphasis
remains firmly on practical synthetic applications. The great value of the book lies
in its presentation of the broad scope of
applications of organomagnesium compounds, in the wealth of examples that are
described, and in the detailed descriptions
of experimental procedures. The examples
from the literature are closely integrated
with the selected laboratory recipes. In addition there are tables referring the reader
to other published examples. Unfortunately the laboratory procedures are not
easily distinguished at a glance from the
main text, which would have made for
easier reading. However, a very positive
aspect of these descriptions is the attention to the detailed needs of the user, including not only valuable advice about
special points concerning the reactions,
but also about possible difficulties, such
as side-reactions that may occur, or the
extent to which the reaction is or is not
compatible with the presence of certain
functional groups. The coverage of the literature is very thorough, including some
references as recent as 1994. The inclusion
of the laboratory recipes in the list of contents is a useful aid, but it would also have
been helpful to provide in addition a
“graphic abstract” for quick access to the
information.
To summarize, this should not be regarded as a textbook (nor is it intended to
0570-083319613S16-1867 S IS.OOi 2S!U
1867
BOOKS
be), but it can be thoroughly recommended as a very useful reference source for
libraries and for all chemists wishing to
use organomagnesium compounds in synthetic work.
Sabine Laschat
Organisch-chemisches Institut
der Universitlt Miinster (Germany)
Multidimensional NMR in Liquids.
Basic Principles and Experimental
Methods. By F: J. M. van der Ven.
VCH Verlagsgesellschaft, Weinheim/
VCH Publishers, New York, 1995.
400 pp., hardcover DM 85.00.ISBN 1-56081-665-1
This book is an up-to-date introduction
to multidimensional N M R spectroscopy
as applied to biomolecules. It has been
written for chemists, biochemists, and biologists interested in problems of molecular structure, who wish to gain a deeper
understanding of N M R spectroscopy and
have the necessary background in physical chemistry. The mathematical and
physical fundamentals of N M R spectroscopy are presented in an exemplary
way, without assuming a great deal of previous knowledge. The theoretical tools introduced are later used repeatedly and
consistently in the applications part of the
book to describe pulsed N M R experiments, thus enabling the reader to relate
them directly to practical situations. A
particular peptide (His-Val-Tyr) and a
protein (the Pf3-DNA binding protein)
appear frequently thoughout the book as
standard example molecules to illustrate
and explain the various N M R experiments used in determining the structures
of biomolecules.
The first of the six chapters begins by
explaining the vector formalism used for
N M R spectroscopy, and basic concepts
such as radiofrequency pulses, the rotating frame, off-resonance effects, the free
precession of a spin, and Bloch-Siegert
effects. This is followed by a more technically-orientated description of the main
components of an N M R spectrometer
and of data processing methods. At the
end of this chapter the author introduces
the density matrix, and discusses the relationship between the quantum-mechanical description of a spin in Liouville space
and the vector formalism.
Chapter 2 is concerned with the fundamental properties of multi-spin systems,
introducing the scalar coupling and the
chemical shift as the dominant parameters. The role of these parameters in the
development of a spin system as a func1868
tion of time is described using the product
operator formalism, according to the theory formulated by the author simultaneously with the work of Serrensen,
Bodenhausen, and Ernst. The product operator formalism using Cartesian basis operators plays a central role in the description of N M R experiments throughout the
book. The phenomenological description
of relaxation in the product operator formalism is briefly discussed. The chapter
ends by introducing and explaining the
most important terms in the spin Hamiltonian operator (the chemical shift, the
spin-spin coupling, and the interaction
with the r.f. field).
Chapter 3 shows how a one-dimensional N M R experiment can be described as
an assembly of modules in which the basic
building blocks are a 90’ pulse and a 180’
pulse. These can produce many different
effects, such as refocussing of the precessing spins, modulation of the J-coupling,
the appearance of a spin-echo, etc. This
chapter also describes experiments for
measuring the longitudinal and transverse
relaxation times and for calibrating pulses, and various types of experiments using
heteronuclear detection, such as the wellknown INEPT and DEPT procedures.
Lastly some more complicated building
blocks are described, such as “composite”
pulses and decoupling sequences. Because
ever more new and improved pulse sequences are continually being introduced,
the author is here less concerned with
evaluating the existing sequences than
with showing the reader what factors
should be considered in assessing the usefulness of any newly developed pulse or
decoupling sequence.
Chapter 4 is concerned with two-dimensional N M R spectroscopy. The first
60 pages of the chapter are devoted to the
COSY experiment, which was the earliest
type of 2D experiment and is the simplest.
The underlying philosophy here may have
been that once one has understood the.
COSY experiment one has the key to the
whole of 2D N M R spectroscopy. This
method serves as an example for explaining various tools of 2D N M R spectroscopy, including phase cycles, field gradients, the BIRD pulse sequence, sign
differentiation in indirect dimensions
(TPPI, states, states-TPPI, etc.), multiquantum filters, and small flip-angle pulses. The other basic mixing schemes for
magnetization transfer are then described:
Hartmann-Hahn mixing, NOESY via the
nuclear Overhauser effect, then ROESY
and TOCSY. This is followed by a discussion of heteronuclear correlation experiments with proton detection (HSQC,
HMQC, HMBC). Correlation experi-
Q VCH Verlug.~gesells~lIufft
m h H , 0-69451 Wcinhcim, 1996
ments with heteronuclear detection are
now scarcely used at all for applications to
biomolecules, and are therefore not discussed further. The chapter ends with a
detailed discussion of “coherence order
pathways”, which form the basis for the
design of phase cycles and pulsed gradient
sequences for suppressing unwanted signals.
Chapter 5 moves on to n-dimensional
N M R spectroscopy. Many different experiments of this kind have been developed during the last six years. The author
describes the most useful of these, using
the product operator formalism. These
are arranged in order of the complexity of
the pulse sequences rather than according
to the spectral or chemical information
that they yield. A number of important
experiments are described, including 3D
and 4 D versions of NOESY-HMQC,
HCCH-TOCSY, HNCO, HN(CO)CA,
and CBCA(C0)NH. Those treated here
are only a selection of the many different
methods that can be applied to tasks such
as determining the structure of a protein.
However, the author clearly explains the
principles on which the sequences are
based, so as to enable the reader to understand the original publications and to
evaluate new sequences. The spectral information yielded by these methods plays
only a secondary role in the discussions.
The final chapter is devoted to relaxation. This is undoubtedly the most difficult topic to treat. The author first sets out
the fundamental principles of relaxation
using the example of stochastic fields,
leading to simple derivations of the most
important mathematical expressions for
dipolar relaxation (NOE, ROE, T I , and
T,). He then goes on to derive a formalism
for relaxation in terms of the density
matrix. After a brief resume of the
Wangsness-Bloch-Redfield
relaxation
theory he then calculates the double commutators needed to describe the most important magnetic interactions, namely the
dipolar relaxation and the chemical shift
anisotropy, and the cross-correlation between these interactions. In contrast to
the previous chapters, this chapter on
relaxation devotes relatively little attention to relating the results to spectroscopic
practice. However, the bibliography for
this chapter includes references to review
articles and other publications describing
relevant experiments and the types of information that they can give about the
dynamic structures of biomolecules.
The book can be thoroughly recommended for everyone who wishes to gain a
deeper understanding of the applications
of N M R spectroscopy to biomolecules in
solution. It is unrivalled in its up-to-date
aS70-a833/96/3516-1868 $ 15.00f .2S/O
Angeu. Chem. I n ! . Ed. Engl. 1996, 35, N o . 16
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