- Weak C - H ... N≡ C hydrogen bonds in the structures of two poly(cyano)-substituted ring systems
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In benzene-1,2,3-tricarbonitrile, C9H3N3, the packing of the two independent mol-ecules is three-dimensional and complex, involving inter alia bifurcated (C - H)2...N systems from neighbouring CH groups. In [2.2]paracyclo-phane-4,5,12,13-tetra-carbonitrile, C20H12N4, the [2.2]paracyclo-phane systems display the usual distortions, namely lengthened C - C bonds and widened sp 3 angles in the bridges, narrow angles in the six-membered rings at the bridgehead atoms, and flattened boat conformations of the rings. The mol-ecules are linked by a series of C - H...N inter-actions to form layers parallel to the ab plane. International Union of Crystallography 2007.
- Jones, Peter G.,Hopf, Henning,Mlynek, Cornelia,Swaminathan, Vijay Narayanan
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p. o723-o725
(2008/09/18)
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- ESR-investigations on the dynamic solvent effects of degenerate electron exchange reactions. Part I: Cyanobenzenes
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The rates of degenerate electron exchange (electron self-exchange) of various cyanobenzenes have been measured by EPR line broadening technique in nine different solvents at room temperature. The molecules studied comprise besides benzene-1,2-dicarbonitrile, benzene-1,4-dicarbonitrile and benzene-1,2,4,5-tetracarbonitrile, the two isomeric tricyanobenzenes, benzene-1,2,3- tricarbonitrile and benzene-1,2,4-tricarbonitrile, the anion radicals of which have not been characterized before. The experimentally observed rates vary from 4.5 × 108 to 44.0 × 10 8 M-1 s-1 and show the pronounced dependence on the longitudinal relaxation times, τL, of the solvents. The solvent dynamical effect so manifested is confirmed with remarkable clarity using solvents spanning a wide range of τL-values, which comprise acetonitrile (0.2 ps) and o-dichlorobenzene (6.0 ps) at its extremes. The rate constants are compared with Marcus theory using the continuum model (CM) and the mean spherical approximation (MSA) for the outer sphere reorganization energies and Nelson's method for the inner sphere reorganization energies. Furthermore, an estimation of the resonance splitting energies, VRP, is given based on the experimental rates. by Oldenbourg Wissenschaftsverlag.
- Mladenova, Boryana,Kattnig, Daniel R.,Grampp, Guenter
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p. 543 - 563
(2008/02/08)
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- The Effect of Pressure on the Trimerization and Diels-Alder Reaction of Cyanoacetylene. Synthesis and Reactivity of 2,3,5-Tricyanobicyclohexa-2,5-diene ("Tricyano Dewar Benzene")
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The trimerization of cyanoacetylene (1a) and the Diels-Alder reaction of 1a with 1,3-cyclohexadiene (2) show a powerful pressure-induced acceleration which allows the reaction temperature to be reduced from 160 deg C at 1 bar to 40 deg C at 12 kbar or from 100 deg C at 1 bar to room temperature at 7 kbar.At high pressure thermally unstable intermediates like the tricyano Dewar benzene 12 generated in the trimerization of 1a or the primary adduct 3a formed in the Diels-Alder reaction of 1a with 2 were isolated. - Key Words: Diels-Alder reactions / 1,2-Dicyano-1,3-cyclobutadiene / Dewar benzenes / High-pressure reactions
- Breitkopf, Volker,Hopf, Henning,Klaerner, Frank-Gerrit,Witulski, Bernhard,Zimny, Bernd
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p. 613 - 618
(2007/10/02)
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- Process for the preparation of 1,2,3-tricyanobenzene, phthalocyanines which are obtainable from 1,2,3-tricyanobenzene, and their use as pigments
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1,2,3-Tricyanobenzene can be prepared in a good yield from fluorobenzonitriles by reaction with an alkali metal cyanide. This product can be converted into metal-free tetracyanophthalocyanines or into the corresponding metal complexes by tetramerisation,
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- Optical recording elements
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An optical recording element comprising a substrate and as a recording medium a layer comprising a dye having a nucleus of general formula (I): STR1 wherein: each Y and Z is independently selected from the group consisting of hydrogen and --XR wherein X i
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- Photochemical cycloaddition reactions of cyanoacetylene and dicyanoacetylene.
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Photolysis of cyanoacetylene with 185- or 206-nm light yields 1,3,5-tricyanobenzene while 254-nm radiation yields a mixture of tetracyanocyclooctatetraenes, 1,2,4- and 1,3,5-tricyanobenzene. A polymer of cyanoacetylene is the major photoproduct. 1,3,5-Tricarbomethoxybenzene was the only photoproduct identified from the irradiation of methyl propiolate at 254 nm. Mono-, di-, and tricyanobenzenes are formed by irradiation of mixtures of acetylene and cyanoacetylene at 185, 206, and 254 nm along with trace amounts of cyclooctatetraenes. No photoadducts were detected on photolysis of mixtures of cyanoacetylene and CO or HCN. The tetracyanocyclooctatetraene structures were established by UV, MS, and NMR analyses. The 1H NMR of the product mixture exhibited a singlet at delta 7.028 consistent with either 1 or 2 and two singlets at delta 6.85 and 6.91 assigned to 3. Photolysis of mixtures of dicyanoacetylene and acetylene with either 185- or 206-nm light yielded 1,2-dicyanobenzene and (E,Z)-1-buten-3-yne-1,4-dicarbonitrile. These products were also obtained using 254-nm light along with a mixture of tetracyanocyclooctatetraenes. The same three singlets were observed in this product mixture as were observed in the tetracyanocyclooctatetraenes obtained from cyanoacetylene. From this observation it was concluded that the delta 7.02 signal is due to 2 and not 1. The photolysis of cyanoacetylene and dicyanoacetylene in the presence of ethylene with 185-nm light yields 1-cyanocylobutene and 1,2-dicyanocyclobutene, respectively. 2-Cyanobutadiene and 2,3-dicyanobutadiene are the photoproducts with 254-nm light. Reaction pathways are proposed to explain these findings.
- Ferris,Guillemin
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p. 5601 - 5606
(2007/10/02)
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- New Dienophiles and Dienes, III. On the Addition of Cyanoacetylene to Paracyclophane
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Heating a benzene solution of paracyclophane (2) in the presence of excess cyanoacetylene (1b) at 160 deg C in a sealed ampoule provides the novel 2:1-addition product 10, as well as the previously obtained cycloadducts 7-9.It is suggested that these Nenitzescu hydrocarbon systems are formed via the cyclobutadiene intermediates 17 and 18.This hypothesis is supported by the isolation of the side-products 1,2,4- and 1,2,3-tricyanobenzene (11 and 12).When a mixture of 7 and 8 is pyrolyzed at 220 deg C the novel dihydronaphthalene 24 is formed; the mechanism of this isomerization is discussed.The structures of 10 and 24 were confirmed by X-ray structure determination.
- Witulski, Bernhard,Ernst, Ludger,Hopf, Henning,Jones, Peter G.
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p. 2015 - 2022
(2007/10/02)
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