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Eighth European Congress on Molecular Spectroscopy.

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from acid chlorides and t-butyl hydroperoxide by the
Schotten-Raumann procedure or with pyridine in pentane,
ether, methylene chloride, or benzene at -20 "C. They have
been characterized by their spectra and elemcntal analyses.
They undergo thermolysis up to 50000 times faster
than t-butyl peracetate or other simple peresters and thus
have significance as low-temperature initiators. Product
analyses, dependence of the reaction rate on solvent
and concentration, activation parameters, and polymerization
experimentswith styrene and acrylonitrile indicate a homolytic
fragmentation 111 as the rate-determining step.
Since dccomposition of thc compounds with oxygencontaining substituents is faster than that of those with thc
corresponding sulfur-containing substituents, and that of
alkoxy compounds is faster than that of aryloxy compounds,
it is concluded that a polar effect [ I ] is responsible for the
therniolability of these substances. Acyloxy groups have a
similar but weaker effecl. The compounds should bc prepared
only with special precautions and in small quantities (grams),
since some of them deflagrate at room temperature. Explosions have not yet occurred [?].
Received: December 14th, 1965
[ Z 125/956 IE]
German version: Angew. Chern. 78, 268 (1966)
[I] Review and references: Ch. Riichordr, Fortschr. chem.
Forsch., in the press.
[2] The compounds listed in the Table under 70.5"C can be
prepared and handled in 50- 100 g lots if the temperature is
maintaincd at or below 0°C by efficient cooling. Larger amounts
have so far not been prepared. The more labile a-peroxyacetates
should be prepared and stored only in dilute solution at -20OC
exccpt in dealing w i t h small amounts.
Eighth European Congress on Molecular Spectroscopy
The Eighth European Congress on Molecular Spectroscopy
was held in Copenhagen from August 14th to 20th, 1965.
Four hundred lectures were delivered to about 800 participants in up to ten simultaneous sessions.
From t h e lectures:
M . Zawder (Castrop-Rauxel, Germany) discussed the continued interest in the systematic changes in absorption, fluorescence, and phosphorescence bands, brought about by systematic variation of the basic structure of a molecnie. In
single or multiple ortho-fusion to carbazole, for example,
fusion in the 2,3-position and the 6,7-position leads to an appreciable bathochromic shift, whereas the latter is small when
fusion takes place in the 3,4-position and the 5,6-position.
J . H. Eggers et a/. (Aarhus, Denmark) used the dichroism of
molecules oriented in stretched films to determine the transition moment directions of individual bands.
This parameter is increasingly used in the classification of
spectra and electronic excitation states. F. Durr and G. Hohlnrichrr (Munich, Germany) determined the relative transition
moment directions of biphenylene derivatives from the emission anisotropy, and compared the results with thosc of model
calculations. Until recently only the energies of excited molecular states were known, and only now have attempts been
made to determine other physical parameters of these states.
Thus D. E. Freeman and W. A . Klernperer (Cambridge, Mass.,
USA) have determined the dipole moment of formaldehyde
in the ~ A state
z
(excited at 339 mp) from the Stark shift of
single rotational lines and obtained a value of 1.57 D (the
dipole moment in the ground state is 2.34 I)). There is a lack
of detailed data o n the intramolecular transitions between the
energy levels, and this problem requires thorough quantitative investigations of the type carried out by H . Lablznrt
(Zurich, Switzerland) to determine the probability of singlettriplet transitions occurring when optically excited molecules
return to the ground state. This new technique can also be
applied to the measurement of triplet-triplet absorption
spectra. M. A . El-Snjwd (Los Angeles, USA) discussed a
further means of studying the singlet-triplet transition probabilities by the perturbation of phosphorescence through incorporation o f a heavy atom, or by resonance effects in the
host lattice. R. M. Hocltstrasser (University of Pennsylvania,
USA) investigated the line splitting, often caused by lattice
defects, in the singlet-triplet transitions taking place in crystalline derivatives of benzene and naphthalene. H . H. Jtrffi
254
(Cincinnati, USA) used the Parker-Parr-Pople method to
interpret the electronic spectra of trans-stilbene and trnnsazobenzene.
The results of the Pariser-Parr-Pople calculations and similar
approximations are known to depxid on the choice of the
parameters (one-electron one-center and two-center integrals
and two-electron one-center integrals), and I. Fisclzer-Hjrrlmars (Stockholm, Sweden) attempted to deduce from theoretical considerations parameters applicable to as many compounds as possible, particularly to sr-electron systems containing heteroatoms. By contrast, M . Klcssiizger (Gottingcn.
Germany) estimated the parameters from experimental data
(transition energies, oscillator strengths, dipole moments) for
simple molecules such as aniline, so as to improbe the agreement between experimental values and the resulis of the
Pariser-Parr-Pople treatment. These calculations were used
to interpret the electronic spectra of merocyanines and indigoids. F. F. Seelig (Marburg, Germany) reported on the use
of digital computers in further developments of the theory of
r-electron systems on the basis of the Kuhn model of a twodimensional electron gas. J. Liwderbrrg and Y. Ohrn (Uppsala, Sweden) investigated a new model for the spectra of xelectron systems, particularly alternant aromatic hydrocarbons, the model being based on Green's Functions.
The model used in most theoretical treatments is still based
on the assumption that the nuclear configuration does not
change in the course of electronic transitions. The fact is,
however, that excitation rnay be accompanied by a change in
the nuclear configuration and even in the syinnietry of the
molecule. Non-vertical transitions are then determined by
Franck-Condon factors. W. L. Smith and P . A . Worsop
(Dundee, U. K.) calculated these factors for HCN, and compared the results with those obtained from the analysis of
molecular rotations. The theoretical investigations of L.Ilro.iielle (Balto, Md., USA) confirmed that, in the lowest triplet
state, the CH2 groups in ethylene are staggered and tilted
with respect to each other.
As can be seen from the last example, the applicability of the
Pariser-Parr-Pople method is not restricted to the interpretation of electronic spectra. Thus J. Hinze (Stuttgart, Germany)
developed a theory for the excimers of alternant hydrocarbons. H. Dreesknmp (Stuttgart) calculated the indirect,
heteronuclear spin-spin coupling, and compared his results
with experimental values. M. J. S. Dewor et crl. (University of
Texas, USA) calculated the x-electron densities in nionofluorinated aromatic hydrocarbons and correlated the results
with the fluorine-NMR spectroscopic data. E. A . C. Lztckeii
Aiigew. Clzeni. iiitermt. Edit. / Vol. 5 (1966)
/ No. 2
(Geneva, Switzerland) reported on the ESR spectra of conArbor, Mich., USA) reported on the diethyl sulfide-iodine
jugated free radicaIs containing a bivalent sulfur atom. He
complex, and J , Procliorov and A. Tromer (Warsaw, Poland)
found that, when the 3d orbitals of the sulfur are taken into
on charge transfer complexes formed by carbonyl cyanid
account, the experimental data are in very poor agreement
CO(CN)z with a number of electron donors. In comparison
with the theoretical values.
with the charge-transfer bands in the gaseous state, those in
solution exhibit a relatively strong red-shift (1500 to
One application of infrared spectroscopy is the determination
3000 cm--l), as cxpccted on the basis of the great increase in
of molecular symmetry. F. A. Millei- and I. Mnfszrl2nrn(Pittsdipole moment o n exciiation. Resides the extinction of the
burgh, Pa., USA) showed definitely that the butatrjene molefhoresccnce of aromatic hydrocarbons by electron donors
cule, HzC=C=C=CNz. is planar (D~J,).In the analysis of
such as anilines or amines, A. Wcllrr et rrl. (Amsterdam) obnormal coordinates and calculation of the force constants in
served the appearance of a new long-wavelength fluorescence
molecules of the type (CH&CX and (CH&C-- CECX
band in solvents of low polarity. This may be expkdined by
(X = H, D, F, CI, Br, I), W. Z d et nl. (Kiel, Germany) found
the formation of a charge-transfer complex from an excited
that, owing to strong coupling, a number of vibrations can
molecule of hydrocarbon and an electron-donor. The new
no longer be considered lo be localired on onc bond alone.
emission band is due to fluorescence of the complex. The forWith the improvcnient of experimental tcchniqnes, the longmation of charge-transfer complexes from an excited molewavelength I R region (up to 10 cni--j) has assumed a certain
cule and an electron-donor has also been observed in the case
interest. W. G. Fabeley and F. A. Miller (Pittsburgh, Pa.,
of the excimers of aromatic hydrocarbons such as implithatJSA) carried out comparative measurements with a Michellene, and M:D.Lrmzh and D. A. Weyl (Manchester, England)
son interferometer and with a lattice-filter spectrophotometer
discussed the excimer fluorescence of al kylated benzenes.
concluding that the latter i s gcnerally a more suitable instrument. N. T. McDevirl, F. F. Bentley, and A . D. Davidso~~ Short-lived (10 to 100 psec) ions of organic compounds have
been studied by A . Terenin et ai. (Leningrad, USSR), together
(Wright Patterson Air Force Base, Ohio, USA) showed that
with the kinetics of decomposition of these ions. ‘These
the far IR spectra of inorganic compounds such as simple
authors fouitd that, by the use of a “superfast” spectrophotonietat oxides, sulfides, and halides are generally complex and
meter, the spectra (300 t o 1200 mp) of ions formed by 11flash
depend on the crystal structure, the coordination number,
can be recorded in 20 p e e on an oscillograph.
and the lattice constant. I. J . Wick (Morse Laboratories,
USA) has obtained some information from long-wavelength
Systematic investigations carried out by W. Briigel (Ludwigs1R absorption in connection with the molecular configuration,
hafen, Germany) on the N MR spectra of numerous derivaparticularly the cis-trms configuration of double bonds and
tives of naphthalene and anthracene have led to a more acthe Configuration of cyclohexane derivatives. G. C . Htrywr?rd
curate picture of the influence of substituents on the N M R
and P. J . Weiidr~i(London, England) showed that the spectra
parameters. 6. / ~ ~ ~ ~ i g u(I;reibtirg,
~ / ? f ~ s Germany) studied the
of charge-transfer complexes in the s h o r ~ - ~ ~ ~ ~ 1R
~ ~region
e l e i ~ g ~ NhifR
h
spectra of adsorbed nioiecules.
arcessentially superpositions ofthe spectra of ti~ecoI~porie~its, Of the many possible applicAtions of lasers in molecular
but in the long-wavelength I R region new lines may appear.
spectroscopy, the excitation of Raman spcctra is of particular
This phenomenon may be due partly to the activation of forimportance and has been extensively investigated by W. W.
bidden transitions. Theabsorption lines appearing in the region
Ward, K. P. George, and R. C. Hnwes (Monrovia, Calif.,
of 20 to 50 cm-1 in polar liquids such as nitriles, ketones, and
USA) and by R. C. Gove (Norwalk, Conn., USA). R. Deer2
nitro compounds were attributed by G. W. Chnnfry and H .
(Delft, The Netherlands) reported on the vibrational structure
A. Gebbie (Teddington, England) to the “lattice” of the liquid
associated with the n +x* transitioiis manifested in the abc t ~ r ~ Park, ~ ~ a r y l a n dUSA)
,
to
and by E. R. ~ i ~ ~ J i n(Coliege
sorption and the circular dichroism of optically active kethe stretching vibrations of dipole complexes (diniers or
tones. The results will be useful in interpreting many of the
clusters). The investigations may provide detailed informacomplicated circular dichroism and optical rotational distion on the intermolecular attraction between polar molepersion spectra. R . Brinf, M. B i l l d o n , and J. Bndtiz (Paris,
cules, and possibly also on the structure of polar liquids. The
France) designed an instrument for recording niagneto-optilong-wavelength I R absorption of molecules linked by hycal rotation (Faraday effect).
drogcn bonds can contribute to the elucidation of such bondParticularly many lcctures dealt exclusively or predominantly
ing. K . Nnkrrnzoto (Chicago, USA) determined the force
with theoretical problems. Thus many groups are engaged in
coii~tantsand i d e n ~ i ~ ethe
d bands of dimeric acetic and
calcLilations based on sinipli[~edmodels. I n this connection,
formic acid. R. J. J~kabsenand J. W. Brnsch (Colunibus,
the HUcket method is being increasingly superseded by the
Ohio, USA) found a splitting in the OH-stretching and the
Pariser-Parr-Pople treatment. It appears that satisfactory apOH-deformation vibrations of several hydroxy compounds,
proximations can now be obtained for many problems with
and attributed it to intermolecular association.
the aid of computers, although the theoretical prerequisites
H. E. Hdliinz and D. Jones (Swansea, Wales, U. K.) used
(and hence the limitations of the methods) are not entirely
short-wavelength I R absorption to investigate the interniolecunderstood. While we may either welcome or regret the inular association of alcohols and ~ ~ i o r i n a alcohols
~ed
and the
creasing theoretical trend i n chemistry, we certainly cannot
formation of hydrogen bonds with various proton-acceptors
ignore it in research and particularly in the training of studin the gaseous state. L. P. Kziiln and E. E. Bowman (Abcrdeen
[VB 9621271 IE]
ents of chemistry.
Proving Ground, Md., USA) used a similar method for deterGerman vorsion: Angew. Chem. 7b‘, 270 (1966)
mining the equilibrium constants and the frequency shifts of
Translated by Express Translation Service, London
the hydrogen-bonded complexes of phenol with unsaturated
hydrocarbons. W. Luck Kudwigshafen, Germany) obtained
data o n the variation of the hydrogen-bond energy with the
bond angle by investigating the formation of hydrogen bonds
P~otoalkyla
tions
between pyrrolidone and various ~ 3 r o to n - a c ~ p t o as
r s a function of concentration and temperature. On the basis of theoD. Etird, Rehovot (Israel)
retical and experimental studies, K. Szczepiznink (Warsaw,
The photoamidation of terminal olefins “1 (addition of
Poland) concluded that charge-transfer interactions must be
forinarnide to the olefin induced directly by light or initiated
basically responsible for the bonding forces in hydrogen-bond
photochemically by acetone w i t h higher yields) has ako been
complexes iii which a x-electron-donor acts as a proton-acapplied to non-terminal olefins. Were, it leads to a mixture
ceptor, whereas in complexes in which the proton-acceptor is
of‘ the two possible aniides resulting from addition of the
a non-bonding electron-donor, electrostatic attractions are
csrbimoyl group, CONH?, to either carbon atom of the
also signific~~i~t.
double bond.
The formation of charge-transfer coniplexes has recently been
studied on many electron donors and acceptors i n solutions.
Cyclic olefins, such as cycioliexene and norbornene, as well
This work has now been extended to gases. R4.Tunires (Ann
as dienes, like 4-viriylcyclohexene and 1,5-cyclooctadiene,
Angetv. Cilem. internnt. Edit.
/
Vol. 5 (1966) No. 2
255
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