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Computer-Aided Structure Elucidation. Spectra Interpretation and Structure Generation. By Ern Pretsch Gbr Tth Morton E

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Angewandte
Chemie
whereas the sample treated with biodiesel looks very healthy. S. Horn, H. J.
Bader, and K. Buchholz discuss plastics
made from renewable raw materials and
describe some very nice experiments,
including the vulcanization of natural
rubber, and making films from starch,
plastics from lactic acid, and solid foams
from castor oil. Student experiments are
also described in the chapter by A.
L#hken and H. J. Bader on the absorption of microwaves and ultrasound in
different materials. Problems associated
with solvents in the laboratory are discussed by A. Eickhoff and R. Kreuzig,
by considering the example of the analysis of pesticide residues in plants.
These chapters in the German version, which are provided as material to
be used by the teacher, are absent from
the American version, and are included
in the British version only as additional
material. That is probably because the
English-language versions are explicitly
described as material for students of
about 16 years and above. The American students are instead given a very
nice experiment to illustrate the principle of “Using Safer Materials for Chemical Reactions”, in which Vitamin C is
used as an alternative to a mercury salt.
Also, to illustrate “Using Renewable
Resources”, they carry out some experiments on biodiesel. “Safer Solvents for
Chemical Processes” is illustrated by the
use of liquid CO2 for the purification of
chemicals; the same experiment is
included in the German version under
the title “New Methods for Chemical
Purification”. This version also includes
student experiments to illustrate the
basic principles of the action of soaps
and detergents, chemical purification,
and lastly even the method of purification using liquid CO2, a technology that is
sadly neglected in Europe. An important
principle of green chemistry is the avoidance of wastes in chemical processes by
choosing the best reaction from the
standpoint of atom economy. This principle is very clearly illustrated in all three
versions, beginning with simple examples, then considering a more complex
one, the synthesis of ibuprofen. In the
course of working through the different
activities, the student will also learn quite
a lot about stoichiometry. In the RSC
version the ibuprofen example is treated
in even greater detail than in the others.
Angew. Chem. Int. Ed. 2004, 43, 659 – 662
The principle of “Using Lower
Amounts of Energy for Chemical Processes” is only given a dedicated chapter
in the ACS version, whereas “Returning
Safe Substances to the Environment” is
dealt with in the ACS and RSC versions
in a chapter entitled “The Need to
Green our Wastes”. The RSC's Internet
version, which is freely accessible and
well-organized, is alone in containing a
very useful glossary, which is linked to
the expressions used in the text, so that
students and teachers can work comfortably with it.
All three versions conclude with a
statement by P. Anastas and J. C.
Warner summarizing the “twelve principles of green chemistry”. Unfortunately, the translation in the German
version contains a serious error that
must be corrected: the ninth principle
there states that catalytic reactions are
preferable to stoichiometric ones. Even
green chemistry has not yet overcome
the law of conservation of mass! In fact,
Anastas and Warner wrote simply that
“catalytic reagents are superior to stoichiometric reagents”. Even that statement is not universally true, but at least
it does not contradict the fundamental
principles of chemistry.
It is to be hoped that this cooperative project by the three leading chemical societies will be energetically
applied in basic chemistry courses in
schools, colleges, and universities
throughout the world, that its contents
will be increasingly incorporated into
the curriculum, and above all that the
project as a whole will be further
developed, both nationally and internationally. Finally, a word on a personal
note: in 1997, in my review of the book
Green Chemistry—Designing Chemistry
for the Environment (Angew. Chem.
1997, 109, 812; Angew. Chem. Int. Ed.
Engl. 1997, 36, 783), I expressed the
view that one could not use the expression “gr#ne Chemie” in German as it
had political overtones. The passage of
time has changed that, and the term
“green chemistry” is now accepted
throughout the world.
Jrgen O. Metzger
Institut fr Reine und
Angewandte Chemie
Universitt Oldenburg (Germany)
www.angewandte.org
Computer-Aided Structure
Elucidation
Spectra Interpretation and Structure
Generation. By Ern
Pretsch, Gbr Tth,
Morton E. Munk
and Martin
Badertscher. WileyVCH, Weinheim
2002. xi + 279 pp.,
softcover
E 42.90.—ISBN
3-527-30640-4
Every chemist engaged in organic synthesis encounters this problem soon
after graduation, if indeed not earlier:
a reaction has not gone according to
plan. The task then is to determine the
structure of a new, unexpected compound, which develops into a puzzle
game. Depending on one's attitude and/
or imagination, the game can be a
pleasurable exercise or an irksome
task. In either case, however, it can
often be quite costly in time expended,
and in the computer age that may not be
justified. This book is a valuable source
of help in that respect.
Within its 279 pages it offers a
combination of guidance and practical
examples, backed up by software that is
included. The central core of the book is
based on the software package “Assemble” produced by the Swiss software
house Upstream. It is a structure-generating program, which requires as input
the molecular formula of the compound
(determined from the mass spectrum).
The book begins with an introduction describing the input masks of the
Assemble program. That is followed by
the main part of the book, consisting of
18 worked problems. Here, in a cleverly
didactic presentation, the book explains
how information from “classical” interpretation of spectral data (IR, 1H NMR,
13
C NMR, DEPT, COSY, HMQC/
HSQC, HMBC) can be combined with
the Assemble program to obtain an
unequivocal structure for the unknown
compound in the shortest possible time.
The spectra presented are of first-class
quality. The solutions to these problems
are given in the form of a table at the
end of the book. A further chapter
5 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
661
Books
entitled “Additional Remarks” summarizes some basic principles and concepts
under various headings: double-bond
equivalents, mass spectrometry, NMR
spectroscopy. The concepts of homotopic, enantiotopic, and diastereotopic
groups are clearly and rigorously
defined, and the system for nomenclature of spin systems is explained with the
help of examples. The final chapter
(45 pp.) is a comprehensive tutorial on
the use of Assemble, and is really
excellent. Here, at last, one learns all
about the possibilities for narrowing
down the search for the correct structure
by using knowledge about the functional
groups and fragments present, and thus
speeding-up the analysis. Such information may include, for example, the
minimum and maximum number of
rings, the number of peaks in the
13
C NMR spectrum (which determines
the molecular symmetry), the hybridization of individual atoms, or whether a
primary, secondary, or tertiary hydrocarbon group is present. One learns how
“post-processing”, imposing additional
boundary conditions, can reduce the
number of possible structures so that
only a few are left, or even just one. The
resulting structures can be shown individually in a three-dimensional repre-
sentation and stored in two-dimensional
format (sdf).
An additional software aid, “NMRPrediction”, is provided in the book. By
using the editor facility “JUME” (which
is common to both this software and
Assemble), one can draw a structure
and subsequently calculate the 1H and
13
C NMR chemical shifts. Although
these estimates are based on incremental systems, much care and effort has
been applied to their programming. The
results are surprisingly accurate and
certainly better than those from most
of the “Freeware-Tools” programs.
Obviously, however, this software
cannot compete with larger packages
that include access to databases. Also, it
does not allow one to distinguish diastereotopic atoms or groups.
The Assemble and NMR-Prediction
software packages are provided here as
demonstration versions, and therefore
they have limited functionality. For
example, the maximum number of heteroatoms that can be accommodated is
15, and some of the tools in the package
are limited to the examples in the book.
The full version of Assemble costs
E 2400.00 (for industrial users) or
E 1200.00 (noncommercial) per single
license, and the corresponding prices for
NMR-Prediction are E 490.00 and
E 245.00.
The book is a pleasure to work with,
even for experienced spectroscopists. If
one has already analyzed the spectroscopic data for a compound “by hand”
and believes that one has covered all
possible and rational structures, Assemble then always finds a better answer
and reveals the limitations of one's
imagination. This is a very useful book,
both as a teaching resource through its
didactic structure, and, through its many
practical comments and tips, as a valuable aid for solving real problems in
the organic chemistry laboratory. Our
only criticism is that the “Selected
References” are indeed very selective,
consisting of only six citations. One
would certainly have liked much more
information here, including references
to other software packages such as ACD
and SpecInfo. However, it is a splendid
book, which fills a gap in the market and
should be in every library.
Walter Bauer, Anselm H. C. Horn
Institut fr Organische Chemie
Computer-Chemie-Centrum
Universitt Erlangen-Nrnberg
(Germany)
DOI: 10.1002/anie.200385101
662
5 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 659 – 662
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