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Book Review Ostwalds Klassiker der exakten Wissenschaften 265. Jacobus Henricus van't Hoff Studien zur chemischen Dynamik (Etudes de dynamique chimique) 1884. Translated by L. Dunsch

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transverse arrangement and of those with a vicinal arrangement of the inner protons is removed in the crystal
due to intermolecular interactions."x1 Since only one type
of porphycene molecules is observed in the crystal at room
temperature,"' there is a high probability that case (ii) is
realized.["' If one further assumes that the state of lowest
energy is characterized by a transverse arrangement of the
inner hydrogen atoms one can, tentatively, assign the observed nitrogen lines to the atom positions shown in
Scheme 2. The observation that K.,h=pb/p., and K,, = p c / p d
are different means that the proton motion in both proton
transfer units is asynchronous. A similar situation has been
found recently for a tetraaza[l4]annulene derivative.""]
We conclude that the two inner H-atoms in crystalline
porphine 1 move with measurable rates in a double minimum potential which is symmetric within the margins of
experimental error. In the seven-membered ring H-chelate
porphycene 2 an energy barrier exists between the four NH
tautomers, which, however, is very small because of the
short NH . . .N distances. The pairwise equivalence of the
tautomers is destroyed due to crystal effects. In contrast to
the case of 1 , the mutual interconversion of the tautomers
is, therefore, so fast that it is no longer possible to measure
rate constants for the proton motion by lineshape analysis
of the "N-CPMAS-NMR spectra.
Received: March 12, 1987 [Z 2137 IE]
German version: Angew Chem. 99 (1987) 914
C A S Registry numbers:
I , 101-60-0: 2, 100572-96-1
[ I ] E. Vogel, M. Kocher, H. Schmickler, J. Lex, Angew. Chem 98 (1986)
262; Angew. Chem. Int. Ed. Engl. 25 (1986) 257.
12) 8 . Bock, K. Flatau, H. Junge, M. Kuhr, H. Musso, Angew. Chem. 8 3
(1971) 239; Angew. Chem. In/. Ed. Engl. lU(1971) 225; S. Bratan-Mayer,
F. Strohhusch, W. Hansel, Z. Nuturfor.rch. 831 (1976) 1106; H. M. Pickett, J . Am. Chem. Soc. 95 (1973) 1770; H. L. Ammon, U. Mueller-Westerhoff, Tetrahedron 30 (1974) 1437; U. Mueller-Westerhoff, J .
Am. Chem. Soc. 92 (1970) 4849; H. A. Staab, T. Saupe, C. Krieger, Anqen'. Chem 95 (1983) 748; Angew. Chem. lnt. Ed. Engl. 22 (1983) 731.
[3] C . B. Storm, Y. Teklu, Ann. N. Y. Acad. Sci. 206 (1973) 63 I ; H. H. Limhach, J. Hennig, D. Gerritzen, H. Rumpel, Faruduy Discuss. Chem. Soc.
74 (1982) 229; H. H. Limbach, J. Hennig, J. Stulz, J. Chem. Phys. 78
(1983) 5432; H. H. Limhach, ibid. 80 (1984) 5343: M. Schlahach, B.
Wehrle, H. H. Limbach, E. Bunnenberg, A. Knierzinger, A. Y. L. Shu, B.
R. Tolf, C . Djerassi, J A m . Chem. SOC. 108 (1986) 3856.
[4] H. H. Limhach, J. Hennig, R. D. Kendrick, C. S. Yannoni, J . Am. Chem
Soc. 106 (1984) 4059; H. H. Limhach, D. Gerritzen, H. Rumpel, B.
Wehrle, G. Otting, H. Zimmermann, R. D. Kendrick, C . S. Yannoni in
H. Sixl, J. Friedrich, C. Brauchle (Eds.): P/?otoreaktrce Fc.rtkorper. M.
Wahl Verlag, Karlsruhe 1985, p. 19-43.
[5] R. D. Kendrick, S. Friedrich, B. Wehrle, H. H. Limbach, C. S. Yannoni,
J . Mugn. Reson. 6 5 (1985) 159.
I61 L. E. Wehh. E. B Fleischer, J. Chem. Phys. 43 (1965) 3 100.
171 B. M. L. Chen, A. Tulinsky, J. Am. Chem. So<,.94 (1972) 4144; A. Tulinsky, Ann. N . Y Acad. Scr 206 (1973) 47.
I81 S. Volker, J. H. van der Waals, Mu/. Ph?.s. 32 (1976) 1703: J. Friedrich,
D. Haarer, Angen,. Chem. 96 (1984) 96; Angew. Chem. I n / . Ed. Engl 23
(1984) 113.
191 J. Almlof, In,. J . Quantum Chem. 8 (1974) 915. A. Sarai, J . Chem. Phys.
76 (1982) 5554: h i d . 80 (1984) 5341 ; V. A. Kuzmitsky, K. N. Solovyov, J .
Mo/. Struct. 65 (1980) 219; G . I.Bersuker, V. Z. Polinger, Chem. P h w 86
(1984) 57.
[ l o ] H. H. Limhach, 8. Wehrle, H. Zimmermann, R. I). Kendrick, C. S. Yannoni, J . Am. Chem. SOC.109 (1987) 929; H. H. Limhach, 8. Wehrle, H.
Zimmermann, R. D. Kendrick, C. S. Yannoni, Anyew. Chem. 99 (1987)
241 ; Angew. Chem. Int. Ed. Engl. 26 (1987) 247.
[II] C P 3 cross polarization, MAS = magic angle spinning. For reviews o n
the C P M A S - N M R method see C. A. Fyfe: Solid State N M R f o r Chemists. C. F. C. Press, Guelph. Ontario 1983; J. R. Lyerla, C. S. Yannoni,
C . A. Fyfe, Acc. Chem. Res. 15 (1982) 208. Review on "N-NMR spectroscopy: W. von Philipshorn, R. Miiller, Angen,. Chem. 98 (1986) 381:
Angew. Chem. In/. Ed. Engl. 25 (1986) 383.
[I?] P. D. Ellis, F. I). Doty, Rec. Sci. Insrr. 52 (1981) 1868.
1131 "N-enriched 1 and 2 were synthesized from "NH,CI [A. H. Hempel
G m h H , D-4000 Diisseldorf (FRG)] using slightly modified versions of
the procedures described for the unlabeled compounds. See: R M. Silverstein, E. E. Ryskiewicz, S . W . Chaikin, J . Am. Chem. Soc. 76 (1954)
4485: F. R. Longo, E. J. Thorrie, A. D. Adler, S. Dym, J H e r e r o c d .
Chem. 12 (1975) 1305: see also Ref. [I]. Impurities d u e to metal complexation could not he detected in the mass-spectra o f I and 2.
[I41 T h e larger linewidth of the N H signal at low temperatures is not caused
instrunlentally hut, probably, by slightly different chemical shifts o f the
two N H atoms in 1 arising from a reduced molecular symmetry in the
monoclinic crystal.
[IS] R. J . Butcher, G . B. Jameson, C. B. Storm, J. A m . Chem. Soc. 107 (1985)
1161 P. DuBois Murphy, J . Mayn. Reron. 70 (1986) 307.
[I71 E. Fukushima, S. B. W. Roeder, J Magn. Rrron. 33 (1979) 199.
[IS] K.,h dnd K,, are equilibrium constants in case (i). I n case (ii). K,,h a n d
K,,, are complex quantities which are related to the equilibrium constants K,,,,, m. n = A, D of tautomerism by
K,,,=K,M ( l + K < i > ) ' ( l + K , < H ) ;
[I91 A differentiation of both cases by two-dimensional spin diffusion ex-
periments as in the case of 5,14-dihydro-6,8,15,17-tetrdmethyl-5,9,14,l8tetraazadibenzo~a,h]cyclotetradecene(tetramethyldihenzotetraaza[
I41annulene) [lo] w i l l be attempted in a future study.
Ostwalds Klassiker der exakten Wissenschaften 265. Jacobus Henricus van't Hoff: Studien zur chemischen Dynamik (Etudes de dynamique chimique) 1884. Translated
by L. Dunsch. Akademische Verlagsgesellschaft Geest &
Portig, Leipzig 1985. 236 pp., paperback, DM 31.00.In the report "Opportunities in Chemistry" (the Pimentel Report, a successor to the Westheimer Report), pub-'
lished recently in the USA, the first item in a list of the
most important chemical research tasks suggested for intensive study in the rest of this century is: "Understanding
chemical reactivity (. .. clarification of factors that control
the rates of reactions ... to sustain international leadership
for the US at the major fundamental frontier of chemis-
try)". The award of the Nobel Prize for Chemistry last year
to D. Herschbach, Y. Lee and J. Polanyi for their work on
the dynamics of chemical reactions underlines this view of
the importance of reaction kinetics.
J . H. van't H o f f s "Etudes de dynamique chimique" was
published in 1884. These studies of the dynamics of chemical processes are probably the first comprehensive account of reaction kinetics. It is a happy circumstance that
this classic work has now been published again (for the
first time in German), and it provides a good opportunity
to look back o n 100 years of growth in the quantitative understanding of chemical reactions, an understanding
which, as indicated above, is still open to much further improvement.
Angew Chem. Int Ed Engl 26 11987) No 9
H o f f s studies were published at
a time when the
atomic theory had become common ground to (almost) all
chemists, and when thermodynamics was slowly beginning
to establish a foothold in chemistry. The measurements by
WiIhemy on the time-dependence of the inversion reaction
in cane sugar, which constitute the first ever study of reaction kinetics in the modern sense, had been made about
thirty years previously.
The book begins with a quantitative description of the
time-scale of chemical reactions, under the following headings:
Normal reactions: unimolecular, bimolecular, multimolecular-in each case with examples of suitably chosen reactions from the known chemistry of the day, whose kinetics
were carefully measured .by the author and his collaborators, presented to the reader in such a way that he could
follow the evaluation of the data.
Factors influencing reactions: a section which is still as relevant today as then, and from which uan’t Hoff s working
methods and experimental techniques come out especially
Applications: this section is concerned with “multimolecular” reactions and the use of rate measurements to derive
reactant properties. In studying reactions of the type
4AsH3-As4+6H2, it occurred to van’t Hoffthat “the majority of these (chemical) equations give only a very distorted idea of the mechanism of the reaction ... and the
actual mechanism is nearly always uni- or bimolecular”.
Unfortunately this point does not appear to have become
more widely understood at the time.
The effect of temperature on chemical reactions, in
terms of the (correct) thermodynamic expressions for temperature dependence of rate constants, is given in this section, and the essential features of the theory of thermal explosions are presented through discussion and diagrams.
This too did not become a part of generally accepted
knowledge until much later.
The second half of the book is concerned with chemical
equilibria, vaporization equilibria, and other matters. Included here are the effects of external variables on such
equilibria, and chemical affinity, topics which are still associated today with the name of van? HofJ He introduced
the use of twin arrows for describing a chemical equilibrium, to indicate “that the chemical reaction proceeds in
two opposing directions simultaneously”.
Many of van’t Hoff s ideas which are recorded in his
“Etudes” were of a pioneering nature, and are now generally accepted knowledge, and some could have been written today. Just a few of these will be cited here, either literally or in summarized form. Time plays a special role in
the chemist’s thinking, it is usually not perceived. Van’t
Hqff thus concentrated on studying those reactions whose
progress could be directly followed. “Reactions which occur in immediate succession o r simultaneously make the
process complicated, and these must be avoided in order
to obtain a clearer understanding of reactions.” He thereby
defined a problem which still concerns reaction kineticists
today. For simple reactions he states the important principle that “The progress of a chemical reaction is characterized entirely by the number of molecules whose interaction
produces that reaction.”
The extent to which he contributed to ideas about detailed reaction mechanisms does not emerge from the text
of this book. In 1884 his papers on the size and shape of
molecules had already been published ten years before.
Anger,. Chem. In,. Ed. Engl. 26 119871 No. 9
Possibly he held back from discussing this topic because
conclusive experiments had only been carried out much
more recently.
Since 1884 chemists have been able to obtain much further insight into the progress of chemical reactions. Numerous proposed models have been investigated, and in
many cases have had to b e rejected. The desire which is
expressed in the Pimentel Report, perhaps almost impatiently, for more progress in “Understanding chemical
reactivity”, shows that uan’t Hoff s view that “the understanding of chemical reactions has not yet been put on to
such a firm basis as that of thermodynamics” is still relevant 100 years later. Nevertheless the prospects for attaining this objective have never been so good as they are today.
Herr L. Dunsch deserves praise for his translation, and
for his explanatory notes to the German edition.
Heinz-Georg Wagner [ N B 8 1 8 I El
Institut f u r Physikalische Chemie
der Universitat Gottingen (FRG)
Aspects of Chemical Evolution. XVIIth Solvay Conference
on Chemistry. Edited by G . Nikolis. Wiley, Chichester
1985. xvi, 286 pp., bound, L 52.25.--1SBN 0-471-88405-7
The international physics and chemistry institutes
founded in 1912 by the Belgian industrialist Ernest Soluay
can be viewed as unique catalysts in the development of
modern science. With a minimum of organization these famous institutes have succeeded again and again up to the
present day in bringing together prominent scientists from
every conceivable discipline to discuss their work, thereby
providing a significant impetus for the progress of
The seventeenth Solvay Conference on Chemistry,
which was held jointly with the US National Academy of
Sciences on the occasion of the 150th anniversary of the
Belgian state, was concerned with the current research situation in chemical evolution, a fundamental problem area
of modern science, whose development has been greatly
influenced by the theoretical work of the Director of the
Solvay Institutes, Professor I . Prigogine.
This volume in the series “Advances in Chemical Physics” contains the lectures presented by the international
experts, together with a brief look back at the history of the
Solvay Institutes ( E . Amaldi and A. R . Llbbelokde) and an
introduction by I . Prigogine on the theme “Nonequilibrium Thermodynamics and Chemical Evolution”. We
find brilliant essays on “Atmospheric Chemistry” (M.Nicolet), “The Prebiotic Synthesis of Organic Molecules and
Polymers” ( S . L. Miller), “The Origin and Evolution of
Life at the Molecular Level” ( M . Eigen), “Optimization of
Mitochondria1 Energy Conversions” (J. W . Stucki). “Bifurcations and Symmetry Breaking in Far-from-Equilibrium
Systems: Towards a Dynamics of Complexity” (C. Nicoiisj.
“Bifurcation in Insect Morphogenesis” ( S . A . Kauffman),
’and “Logical Description, Analysis, and Synthesis of Biological and other Networks Comprising Feedback Loops”
( R . 7horna.s). The volume also includes brief commentaries
on problems of chirality, stochastic models, and oscillatory
chemical systems. Altogether, this volume truly reflects the
breadth of the interdisciplinary fields which are now involved in research on chemical evolution.
Benno Hess [NB 814 IE]
fur Ernahrungsphysiologie, Dortmund (FRG)
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