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Investigations of Cyanine Dyes by P.M.R. Spectroscopy

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whereas the newly discovered disproportionation according
to route B can be regarded as a hydrogenation of an azo
double bond [4]. The structure (3) can be considered as a
transition state, especially since diimide produced from
benzenesulfonylhydrazide hydrogenates added tolane stereospecifically to gibe cis-stilbene in at least 95 "/, yield, according
to infrared analysis.
The consequences of this auto-hydio~eii:rtion ore currently
being investigated.
[Z 449/279 IE]
Received, February 13th. 1963
[ I ] S . Hiinig and H. R . Muller, Ph. D. thesis, Universitiit Wurzburg 1962.
121 S. Hiinig and W. Thier, Diplom thesis, Universitat Wurzburg
[3] S. Hiinig et al., Tetrahedron Letters 11, 353 (1961); E. J.
Corey et al., ibid. 11, 341 (1961); E. E.van Turnelen et al., J.
Amer. chem. SOC.83, 3725 (1961).
[4] F. Raschig, Angew. Chem. 23, 972 (1910).
New Heptafulvene Derivatives
By Prof. Dr. K . Hafner, Dr. H. W. Riedel, and
Dip1.-Chem. M . Danielisz
1,2-Dimethyltropylium fluoroboratc ( 6 ) reacts with ethyl
orthoformate in acetic anhydric!c to give the known
azuienium fluoroborate (7) [51.
i 71
Received, February 13tI1, 1963
[ Z 448/278 IE]
[11 Cf. H. Meerwein et al., Liebigs Ann. Chem. 641, 1 (1961).
[2] Compound ( 3 ) has also been prepared by another route by
T. Noroe el al., see J . W. Cook, Progr. org. Chemistry 5, 159
131 K . Hafner et al., Liebigs Ann. Chern. 624, 37 (1959); 650, 80
(1961); Angew. Chem. 71, 378 (1959).
[4] K. Hufner and H . Pelster, Angew. Chern. 73, 342 (1961).
[ 5 ] K . Hafner et al., Liebigs Ann. Chcm. 650, 62 (1961).
Chemische? Institut der UniversitLt Marburg (Germany)
We have found that the ieactivity of the carbony1 group in
cycloheptatrienone ( I ) can be increased by 0-alkylation.
With triethylosonium fluoroborate [I], ( I ) gives a quantitative 3ield of ethoxytropylium fluoroborate (2) (m.p.
40"C), which reacts smoothly with malonic dinitrile in the
presence of bases t o form thermostable orange P&dicyano-,
heptafulvene (3) (m.p. 200°C; Amax = 252 (log E = 3.98).
368 (4.26), 374 (4.27), and 381 (4.27) m p in n-hexane) [2].
Other reactive methylene compounds also react thus with
compound (2) to yield heptafulvene derivatives.
Investigations of Cyanine Dyes by
P.M.R. Spectroscopy
By Dr. ff. J . Friedrich
Chemisches Jnstitut der Universitiit Wiirzburg (Germany)
Cyanine dyestuffs of type ( I ) can occur i n geometrically
isomeric forms and for steric reasons mostly exist i n one
fixed configuration under normal conditions [I]. Proton
resonance of the 6 0 j)N-CH3 group is particularly suitable
for determining this configuration and for investigating its
geometric isomerism [2].
Symmetrical metliinecyanines with a planar structure and a n
all - trans configuration [ I ] e.g. N,N'- dimethylpseudoisocyanine or N,N'-dimethyl-dibenzoxazolo-monomethinecya'\
nine, give a single 8e ),N-CH3 proton - resonance signal.
Two different 6 0 j,N-CH3 resonance signals are observed
with formally symmetrical, but for steric reasons non-planar
derivatives, e . g . meso-substirutcd N,N'-dimethyldibenzthiazolomonomethinecyanines. Similarly, formally symmetrical
planar cyanines with a mono-cis-configuration [l], e . g . N,N'dimethyldipyridomonomethinecyanine, give two different
8 0 ,i,N-CH3 signals.
The P.M.R. spectra show that all the azacyanines so far
investigated exist (for a n as yet unknown reason) in the
mono-cis-form (2), e.g. the N,N'-dimelhylmono-azacyanines
containing pyridine, quinoline, and benzthiazole rings. This
surprising result is supported even further by ultraviolet and
infrared spectroscopic findings.
Heptafulvene derivatives also result from condensation of
methylated tropylium salts with orthoesters of carboxylic
acids or their vinylogs in acetic anhydride [3]. Methyltropylium perchlorate ( 4 ) and triethyl orthoformate yield the
deep blue [3-(cycloheptatrienylidene)allyl]tropylium perchlorate ( 5 ) (decomp. > 200°C; Amax = 604 m p ; log E =
4.1 in acetonitrile), a non-benzenoid isomer of the diarylpolymethine-carbonium salts [4].
Analogous colored salts are formed from.compound ( 4 ) and
azulene- 1 -aldehyde (deep blue crystals, decomp. > I50 "C;
Amax = 632 m p ; log E = 3.7 in acetonitrile) andp-dimethylaminobenzaldehyde (deep blue crystals, decomp. > 150 "C;
Amax = 657 m?; log E = 3.76 in acetonitrile).
Angew. Chem. internut. Edit.
Vol. 2 (1963)
No. 4
These results supply information on the fine structure of the
cyanines and contribute to the theoretical interpretation of
these dyes. Our investigations are therefore continued on a
broad basis.
Received, February 15th, 1963
NM R-Spectrometer.
Preparation of 1-Hydroxypropane-2-sulfonicAcid
By Dr. Heinz Schmitz, Dr. H. Grosspietsch,
Dr. H. Kaltenhiiuser, and Dr. H.Wendt
Farbwerke Hoechst AG. vormals Meister Lucius & Bruning,
FrankfurtIMain-Hiichst (Germaiiy)
I-Hydroxypropane-2-sulfonicacid is said to have been
prepared by Raschig and Prahl [l] bq treating chloropropylene glycol acetate with K2SO3 (synthesis I) and by Manecke [2]by hydrolysis of an anhydride of the acid made by
treating sulfuryl chloride with n-propanol and dehydrochlorinating the propyl chlorosulfonate obtained (synthesis
11). As rearrangements may possibly occui in these syntheses,
we have prepared 1-hydroxypropane-2-sulfonicacid by
reduction of cr-sulphonylpropionic acid with LiAIFI4 in
dioxan (synthesis 111).
The infrared spectrum of the barium salt of this acid was
different from those of the barium hydroxypropanesulfonates
made by syntheses I and 11, which corresponded. The
hydroxypropancsulfonic acid made by the othei authors
must therefore be either 2-hydroxypropane-1-sulfonicacid
or 1 -hydroxypropane-3-sulfonic
acid. The latter is obtainable
by hydrolysis of 1,3-propanesultone; the infrared spectrum
of its barium salt differs from the spectra of the barium salts
obtained by syntheses I, 11, and 111. 2-Hydroxypropane-lsulfonic acid was made by reduction of acetonesulfonic acid
(synthesis IV); its barium salt had the same infrared spectrum
as that of the barium salts from syntheses J and 11.
I t can also be shown by comparison of the melting points of
the phenylhydrazonium salts and of the N-methylaminopropanesulfonic acids (obtained by reaction with methylamine) that the hydroxypropanesulfonic acids described both
by Raschig and Piahl and by Manecke are in fact 2-hydioxypropane- 1 -sulfonic acid.
Method of
Phenylhydrazoniurn salt
rn.p.[ “C];
By Dozent Dr. Ulrich Schmidt and
Dip1.-Chem. Asmus Muller
[Z 454/292 IE]
[ l ] G. Scheibe, H . J . Friedrich, and G. Hohlneicher,Angew. Chem.
73, 383 (1961).
[2] The investigations were carried out with a Varian A 60 Mode
Detection of the Phenylsulfur Radical [11
N-Methylaminopropanesulfonic acid
m.p. [ T I ; mixed m.p. I “Cl
Chemisches Laboratorium
der Universitit FreiburgIBreisgau (Germany)
Ionic radicals of doubly-bonded sulfur (R--S-R) were
detected by us in oxidized solutions in sulfuric acid of di-pmethoxyphenyl sulfide, p-di(arylthio)benzenes, and tetraphenylthiophenes [l]. Free radicals of singly-bonded sulfur
(R-So) have been sought repeatedly, but were not found
hitherto [2]. However, the existence of the phenylsulfur
radical (Ph --SO)has now been demonstrated by us.
On irradiating diphenyl sulfide vapor with short-wave ultraviolet light at 1 mm. Hg pressure and high carrier-gas (N2)
speeds, phenylsulfur radicals were detected as thiophenol by
dehydrogenation of injected cumene 10 cni from the irradiated
Irradiation of diphenyl sulfide vapor without carrier-gas at
0.1 mm Hg pressure resulted in the formation of a red
coating of Ph -S. a few cm away on a finger cooled with
liquid nitrogen. This was stable for some hours in vcicuo at
-2OO”C, but disappeared within a few minutes at -100°C.
Thiophenol was formed by disproportionation or dehydrogenation of diphenyldisulfide.
Measurement of the electron spin resonance spectrum at
-200 “C showed a strong signal with a typically anisotropic
g factor. The g tensor is almost axisymmetrical with limiting
values g I = 2.006 and gi 1 = 2.012 as far as can be determined
from the powder spectra. This indicates that the unpaired
electron is associated mainly with the sulfur, since such a
large degree of g anisotropy can only be explained by an
electron which is strongly localized.
Received, February 25th, 1963
[Z 453/281 IE]
[ l ] Communication No. 2 on Organosulfur Radicals; Communication No. 1 : Angew. Chem. 72, 708 (1960).
[2] For literature references, see Communication No. 3, Liebigs
Ann. Chem., in the press.
Proton-Resonance Investigations of
“4 (or 5)-Substituted Imidazoles”
By Prof. Dr. H. A. Staab and Dr. A. Mannschreck
Organisch-chemisches Jnstitut
der Universitat Heidelberg (Germany)
Tautomeric forms A and B of 4 (or 5)substituted imidazoles
cannot be isolated [I]. It has also not been possible to determine whether these compounds exist as either structure A or
structure B.
I1 f IV
Willems [3] also designated a substance he obtained from 2bromopropanol and N a ~ S 0 3 as 1-hydroxypropane-2-sulfonic acid, as it proved to be identical with the acid described
by Manecke. It appears from our work that Willems too
obtained 2-hydroxypropane-1-sulfonicacid.
Received, February 21st, 1963
[Z 451/280 IE]
[ I ] F. Raschig and W. Prahl, Ber. dtsch. chem. Ges. 61, 185
[2] G. Manecke, Chem. Ber. 85, 160 (1952).
[3] J. Willerns, Bull. SOC.chim. Belg. 64, 409 (1955).
Concepts, such as the hypothesis of a special “mesohydric
tautomerism” [2], or the postulate [3] based on spectroscopic
results that, in both the crystalline state and non-polar solvents, imidazoles exist as ion-pairs made up of imidazole
anions and imidazole cations led to the assumption that it is
impossible to differentiate between 4-and 5-substituted imidazoles [3,4]. Our proton-resonance experiments show that
such postulates do noi apply to the 4(or 5)-substituted
imidazoles investigated in the present work. They demonstrate that these compounds exist predominantly in one
definite form, for which distinction can be made between 4and 5-substitution on the basis of the respective spin-spin
coupling constants.
Angew. Chem. internat. Edit. / Vol. 2 (1963) No. 4
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dyes, investigation, spectroscopy, cyanine
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