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Book Review Determination of Organic Reaction Mechanisms. By B. K. Carpenter

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9
5 : X=Br
6 : X=SH
CH2X
7
With the synthesis of 7, it has been shown for the first
time that more than fivefold bridge formation is possible
in one step if steric factors are carefully taken into account. Owing to the “six-coordination of the benzene
ring”, the sixfold bridging, particularly with longer bridges
to give molecules with large cavities suitable for the encapsulation of organic guest molecules, opens u p novel aspects: According to model considerations, the cavity of 7
is, as it were, tailor-made for the accommodation of a benzene molecule, whereas longer, flexible bridges are
stretched after passage of the guest molecule; due to the
widening of the cavity the guest becomes “trapped”.
Received: May 6, 1985 [Z 1293 1E]
German version: Angew. Chem. 97 (1985) 782
trum ( m / z 1416 ( M + ) ) shows the molecular ion as an intense peak. The ’H-NMR absorptions of the previously
purified crystalline crude product are considerably broadened in CD2C12 as solvent. The polycondensation productl’l formed at the same time in the reaction, which is responsible for the broad signals, is removed by chromatography on silica gel with dichloromethane as eluent
( R , =0.61). The ‘H-NMR spectrum then shows a n AB system for the CH2 protons ( ~ 5 ~ = 2 . 6 5aB=3.2,
,
JAB=15 Hz)
and sharp signals at 6 = 6.85-7.05 for the aromatic protons
(in CD2C12).These findings are consistent with an all-anti
conformation for 7.Iy1It is easily seen on comparison with
the conformationally flexible 2-thia[3]ortho-terphenylophane 8,‘”’’that 7 can be fixed conformationally, due to
strain; according to model considerations the hexaphenylbenzene skeleton is present in a six-bladed propeller arrangement. This now raises the question whether 7 is sufficiently ridgid (and thus helical) in solution that it can be
separated into enantiomers. Analytical separation on
“Okamoto” resin‘”’ would indicate that this is indeed the
case.
The successful one-step sixfold bridging realized with 7
throws light on the reasons why 4 was hitherto unobtainable: The last CHzX groups in the intermediate 9 may no
longer achieve the conformation requisite for the sixth
bridging span.
CAS Registry numbers:
5, 952 16-95-5: 6, 97877-67-3; 7, 97877-68-4: thiourea, 62-56-6.
[I]F. Vogtle, Liebiys Ann. Chem. 735 (1970) 193; F. Vogtle, P. Neumann,
Chem. Commun. 1970, 1464.
(21 B. Klieser, F. Vogtle, Angew. Chem. 94 (1982) 632; Angew. Chem. f r r t .
Ed. Engl. 21 (1982) 618; Anyew. Chem. Suppl. 1982. 1392.
[3] P. Neumann. Di.ssertution, Universitat Heidelberg 1970; B. Schelcher,
Diplomarbeit, Universitat Bonn 1983: E. Koepp, Diplomarbeir. Universitat Bonn 1985.
[4] The six bridges of the known “superphane” were coupled in a multistep synthesis: V. Boekelheide, Top. Curr. Chem. 113 (1983) 89: V. Boekelheide in T. Lindberg (ed.): Strutegies and Tacrics in Organic Synrhesis, Academic Press, New York 1984, p. I : H. Hopf, S . El-Tamany,
Chem. Ber. 116 (1983) 1682.
[5] K. Meurer, F. Vogtle, A. Mannschreck, G. Stuhler, H. Puff, A. Roloff, J .
Org. Chem. 49 (1984) 3484.
[6] W. Kissener, F. Vogtle, Angew. Chem. 97 (1985) 227; Angew. Chem. Inr.
Ed. Engl. 24 (1985) 222.
[71 Prepared from 5 by the thiourea method. ‘ H - N M R (90 MHz), CDC13/
TMS int.): 6= 1.22 (t. S H ) , 3.3 (d, CH,S), 6.75 (s, aryl, m-H). MS: m / z
810 ( M + ) .
[S] The crystallinity of this product is remarkable; the product is possibly a
high-molecular-weight cyclic oligomer. Due to poor solubility, an osmometric molecular weight determination could not he carried out.
191 Cf. K. Bockmann, F. Vogtle, Chem. Ber. 114 (1981) 1065.
[I01 Cf. E. Hammerschmidt, F. Vogtle, Chem. Ber. 113 (1980) 1125.
[ I l l Cf. [6] and K. Meurer, A. Aigner, F. Vogtle, J . Inclusion Phmom. 3
(1985) 51. Due to solubility problems (cyclohexane/l% THF), difficulties were encountered in the preparariue separation of the enantiomers.
BOOK R E V I E W S
Determination of Organic Reaction Mechanisms. By B. K .
Carpenter. Wiley, Chichester 1984. xi, 247 pp., bound,
E 32.20.-ISBN 0-471-89369-2
This short, compactly-written, introductory textbook on
the methods of investigating the reaction mechanisms of
organic chemical reactions is based o n a one-semester lecture course for new graduate students.
One could wish that such a lecture course were compulsory for all chemistry students at our universities after
Anyew. Chem. Inr. Ed. Enql. 24 (IYSS)N o . 9
completion of their undergraduate work. It is true that the
most important reaction classes and their mechanisms are
treated in most general lecture courses, but additional
knowledge concerning the experimental and theoretical
basis of reaction mechanisms and their general limitations
is needed in order to b e able to understand them and their
information content in a critical manner.
This book is capable of closing this gap. After a short introductory chapter, in which the scientific method of learn795
ing is generally described in brief, there are seven chapters
in which the most important methods of investigating reaction mechanisms are described with brief treatments of
their limitations and areas of application: isotopic labeling, chirality and stereochemistry, kinetics, isotope effects,
acid-base catalysis, the interpretation of activation parameters including the elements of thermochemistry and
bringing in linear free enthalpy relationships, methods of
detecting reactive intermediates. Then follows a chapter
which describes the combined application of these techniques with the aid of examples of investigations taken
from recent literature. An appendix explains a range of
mathematical techniques for the analysis of kinetics and
symmetry problems; then follow tables of Benson group
increments.
Almost all recent methods u p to and including picosecond spectroscopy and laser methods are described briefly
and in a way that is easily followed u p and critically discussed upon the basis of a few chosen examples from the
literature. An overemphasis on pericyclic reactions can be
detected in the choice of examples, but account is also
taken of classical fields, such as solvolysis and arene chemistry, while radical chemistry is dealt with too briefly. Unfortunately, little account is taken of the German literature.
Topics which are omitted from the examples are steric effects including the force field method, the Curtin-Hammett
principle, the interrelationships between selectivity and
reactivity, and, finally, the isoselective relationship.
Is it necessary to know the treasure house of methods
for studying reaction mechanisms in the era of preparative
chemistry which we are now experiencing? In my opinion
yes! It was the development of “physical organic chemistry” over the last 30 years that first made possible the new
breakthroughs in preparative chemistry. It is only quantitative investigation methods that make possible the purposeful optimization of synthesis.
It is in this sense that the present book, which can only
be criticized on the basis of a somewhat one-sided choice
of examples, is thoroughly to be recommended. A German
translation is to be desired.
Christoph Riichavdt [NB 674 IE]
Chemisches Laboratorium
Universitat Freiburg (FRG)
Sources and Applications of Ultraviolet Radiation. By R .
Phillips, Academic Press, New York 1983, xvi, 434 pp.,
bound, $ 60.00.--ISBN 0- 12-553880-4
Normally, a book review begins with a short description
of the contents. It seems more appropriate in the case of
this book to start with the story of its origins. The author
candidly admits in his foreword that his original intention
was to write a monograph concerning (A) “Photopolymerization of Organic Surface Coatings” with emphasis on the
chemical aspects. However, it soon became clear to him
that there was already sufficient review literature covering
this field and he thought it more useful and original to emphasize (B) “Sources of Radiation Suitable for Photopolymerization”. Then that seemed to him to be too restricted
and he became fascinated by the idea of writing a book entitled (C) “Radiation Sources in Applied Photochemistry”.
But this was also too specialized for him (or his publisher)
and thus he came to the very general and sales-promoting
796
title (D) “Sources and Applications of Ultraviolet Radiation”.
The illogical construction of this book and its repetitions, shortcomings, and errors have two basic causes.
Firstly, the various texts that had already been written
ought to have been rewritten on going from (A) through
(B) and (C) to (D). However, the author made it easy for
himself and simply added sections or subsections to what
had already been written. Secondly, in the course of the
transition from (A) to (D) the author concerned himself
with fields in which he was no longer competent. The
eleven friendly helpers who checked the parts of the original manuscript and whom the author thanks in his foreword have probably avoided the worst. This help is evident
in the text because of competently and fluently written
passages, which pleasantly distinguish themselves from the
often clumsy, imprecise or simply false formulations of the
author.
One would actually expect in a book entitled “Sources
and Applications of Ultraviolet Radiation” firstly to learn
something about sources of UV light and afterwards something about their applications. The first chapter (37 pp.,
274 refs.), however, is concerned with “Applications of Ultraviolet Radiation”. It is not surprising that the applications furthest from the interests of the author consist in
practice of pure enumeration, that many concepts are employed which are only explained in later chapters and that
it is very seldom mentioned which U V source was employed.
The main purpose of Chapter 2 (“The Nature of Light”,
10 pp., 2 refs.) is to introduce some concepts from atomic
spectroscopy, which are required later for the discussion of
gas discharge lamps.
Chapter 3 (“Photochemistry and Photopolymerization”,
50 pp., 205 refs.) corresponds to the originally planned
monograph (A). The subsection 3.1.4.3 (“The Jablonski Diagram”) provides a whole range of examples of clumsy or
false formulations. The keyword “UV curing” provides an
example of unnecessary repetition and illogical ordering.
It already appears in many places in Chapter 1 and in the
titles of subsections 1.6.1, 1.6.1.10 and 1.6.11 and then it
reappears in subsections 3.4.4 and 3.5. The explanation of
what is understood by “cure”, however, is first to be found
i n the layt and obviously subsequently added section of
Chapter 3 (3.6 “The Concept and Measure of Cure”).
Chapters 4 (“Radiometry”, 45 pp., 154 refs.), 5 (“Incandescent Sources”, 8 pp., 2 refs.) and 6 (“Gas Discharges”,
14 pp., 14 refs.) lead then to the main portion of the book:
Chapter 7 (“The Low Pressure Mercury Lamp”, 19 pp., 62
refs.), 8 (‘The Medium Pressure Mercury Lamp”, 66 pp.,
53 refs.), 9 (“Metal Halide Lamps”, 16 pp., 71 refs.), 10
(“Electrodeless Lamps”, 16 pp., 16 refs.) and 11 (“Xenon
Lamps”, 33 pp., 91 refs.). Of these, chapter 8 is the most
important because it includes results of the author’s own
investigations. Considerable knowhow is to be expected of
the author here. But, once again one must cast doubts
upon his competence, when on page 208 in connection
with
the
Richardson-Dushmann
equation
J = A T 2 e x p ( - e(v’kT) for thermal electron emission, it is
stated “. .. where ... e is the electronic charge (1.60 x 10
e.s.u.), (I is the work function ... with units of electron
volts, k is Boltzmann’s constant (1.372 x 10” J K - . ..” I t is
almost a work of art to introduce an error into each of the
three definitions! On page 239 of the same chapter the author reveals that he has no notion of optical spectroscopy.
He maintains that the dispersion of a grating monochromator is independent of the wavelength and that the asym~
’’
’
Anyew. Cliem. Int. Ed. Erxql. 24 11985) N o . 9
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