1,2-Dicyanobenzene

P 32] Pyrene (20 mM), 1,4-dicyanobenzene (40 mM) and sodium cyanide (1 M) were reacted in propylene carbonate and water. A 100 pi solution of pyrene (20 mM), 1.4-dicyanobenzene (40 mM) in propylene carbonate and a 100 pi solution of sodium cyanide (1 M) in water were fed by programmable dual-syringe pumps via fused-silica capillary tubes into a micro-channel chip [29]. Both solutions were fed with equal flow velocity. A 300 W high-pressure mercury lamp was used as light source. After passing an optical filter made of a CUSO4 solution, the whole chip was irradiated after formation of a stable oil/water interface inside. The oil phase was collected at the exit. 

OS 43] [R 14] [P 32] Experiments rrm without NaCN did not yield the cyanated photoproduct ]29]. Therefore, NaCN and not 1,4-dicyanobenzene has to be considered as the source of the CN anion that is incorporated into the pyrene moiety. 

PET reactions [2] can be considered as versatile methods for generating radical cations from electron-rich olefins and aromatic compounds [3], which then can undergo an intramolecular cationic cyclization. Niwa and coworkers [4] reported on a photochemical reaction of l,l-diphenyl-l, -alkadienes in the presence of phenanthrene (Phen) and 1,4-dicyanobenzene (DCNB) as sensitizer and electron acceptor to construct 5/6/6- and 6/6/6-fused ring systems with high stereoselectivity. 

A novel nitrilase was purified from Aspergillus niger K10 cultivated on 2-cyanopyridine. It was found to be homologous to a putative nitrilase from Aspergillus fumigatus Af293. The nitrilase exhibited maximum activity at 45 °C and pH 8.0 with much less activity observed at slightly acid pH. Its substrate preference was for 4-cyanopyridine, benzonitrile, 1,4-dicyanobenzene, thio-phen-2-acetonitrile, 3-chlorobenzonitrile, 3-cyanopyridine, and 4-chlorobenzonitrile. ( )-2-Phenylpropionitrile was only poorly converted by this enzyme and with minimal enantioselectivity. The enzyme was shown to be multimeric (>650 kDa) and be stabilized in the presence of sorbitol and xylitol [57]. 

Calibration of the ion-trap detector for quantification of tetrafluor-1.4 dicyanobenzene and 2,6 dichloro-4-nitroaniline. Finnigan MAT Application Data Sheet ADS 27. 

Interactions between aliphatic amines (n-donors) and benzonitrile139 or dicyanoben-zenes140,141 (jr-acceptors), in n-hexane, are mainly electron donor-acceptor interactions. It is reasonable to assume that the lone-pair of the donor is perpendicular to the plane of the acceptor as reported in 42 for 1,4-dicyanobenzene. 

This relationship also conveys one of the reasons why the sensing of explosives can be so effective with this method. Most explosives, especially TNT and other nitroaromatic compounds, are highly electron deficient and have favorable reduction potentials. For instance, the reduction potential of TNT and DNT are only —0.7 and—1.0 V (versus SCE) respectively, quite favorable when compared with other electron acceptors, such as 1,4-dicyanobenzene (—1.7 V versus SCE). This means that if the sensory material emits hght, for example, at 460 nm, the oxidation... 

With respect to photoinitiation, generally, it is important to be very careful in one s choice of sensitizers. For example, attempts to initiate the cyclization of homobenzylic ethers failed if 1,4-dicyanobenzene was used as a sensitizer. Rapid regeneration of the starting material by back-electron transfer from the dicyanobenzene anion-radical to the substrate cation-radical was the cause of cyclization inefficiency. To slow this unproductive process, a mixture of A-methylquinolinium hexafluorophosphate (sensitizer), solid sodium acetate (buffer), and tert-butylbenzene (cosensitizer) in 1,2-dichloroethane was employed. This dramatically increased the efficiency of the reaction, providing cyclic product yields of more than 90% in only 20 min (Kumar and Floreancig 2001, Floreancig 2007). 

Another example of stereoselective radical cation addition was presented by Hirano and co-workers. The reaction of 1,1-diphenyl-l,n-alkadienes employing 1,4-dicyanobenzene as a sensitizer yielded intramolecular tandem cyclization products in up to 60% yield (Scheme 29) [40]. 

Alkene radical cations may transfer protons to cyanoaromatic radical anions, followed by coupling of the resulting radicals. For example, 1,4-dicyanobenzene and other cyano-aromatic acceptors form substitution products (e.g., 73) with 2,3-dimethylbutene via coupling and loss of... 

Synthetic applications of both intermolecular5-6 and intramolecular7 PET initiated cyclodimerizations have been reported. Common electron acceptors (A) arc neutral compounds such as 1,4-dicyanobenzene, 1,4-dicyanonaphthalene or 9,10-dicyanoanthracene usually dissolved in polar solvents like acetonitrile, or arc cationic compounds such as methylacridinium hexafluorophosphate which is soluble in dichloromcthane. 

Therefore, we have developed a pump/pump-probe experiment to obtain more informations on the structures of these geminate ion pairs. It allows the investigation of the excited states dynamics of the transient species at different time delays after photo-triggering the charge transfer, by monitoring the ground state recovery (GSR) of those transient species (Fig. lb). In the present study, we have used perylene (Pe) as fluorescer (electron donor) and either trans-l,2-dicyanoethylene (DCE) or 1,4-dicyanobenzene (DCB) as quencher (electron acceptor) in acetonitrile (ACN). 

The photo-induced electron transfer of l,4-bis(methylene)cyclohexane in acetonitrile-methanol solution with 1,4-dicyanobenzene (DCB) affords two products, both consistent with nucleophilic attack on the radical cation followed by reduction and protonation or by combination with DCB ).63 In the absence of a nucleophile, the product mixture is highly complex, as is the case under electro-oxidative conditions. Under UV irradiation, /nmv-stilbene undergoes dimerization and oxygenation (to benzaldehyde) by a single-electron mechanism in the presence of a sensitizer such as 2,4,6-triphenylpyrilium tetrafluoroborate (TPT).64 This reaction was found to yield a similar product mixture with the sulfur analogue of TPT and their relative merits as well as electrochemical and photophysical properties are discussed. 

Organic constituents that may be found in ppb levels in WP/F smoke include methane, ethylene, carbonyl sulfide, acetylene, 1,4-dicyanobenzene, 1,3-dicyanobenzene, 1,2-dicyanobenzene, acetonitrile, and acrylonitrile (Tolle et al. 1988). Since white phosphorus contains boron, silicon, calcium, aluminum, iron, and arsenic in excess of 10 ppm as impurities (Berkowitz et al. 1981), WP/F smoke also contains these elements and possibly their oxidation products. The physical properties of a few major compounds that may be important for determining the fate of WP/F smoke in the environment are given in Table 3-3. 

In several photochemical electron transfer reactions, addition products are observed between the donor and acceptor molecules. However, the formation of these products does not necessarily involve direct coupling of the radical ion pair. Instead, many of these reactions proceed via proton transfer from the radical cation to the radical anion, followed by coupling of the donor derived radical with an acceptor derived intermediate. For example, 1,4-dicyanobenzene and various other cyanoaromatic acceptors react with 2,3-dimethylbutene to give aromatic substitution products, most likely formed via an addition-elimination sequence [140]. 

In some cases the nucleophilic capture of a radical cation is followed by coupling with the radical anion (or possibly with the neutral acceptor), resulting ultimately in an aromatic substitution reaction. Thus, irradiation of 1,4-dicyanobenzene in acetonitrile-methanol (3 1) solution containing 2,3-dimethylbutene or several other olefins leads to capture of the olefin radical cation by methanol, followed by coupling of the resulting radical with the sensitizer radical anion. Loss of cyanide ion completes the net substitution reaction [144]. This photochemical nucleophile olefin combination, aromatic substitution (photo-NOCAS) reaction has shown synthetic utility (in spite of its awkward acronym). 

In 1966, Walker, Bednar, and Lumry postulated the formation of a 1 2 excited complex state in the system indole-pentane- butanol [101]. Two years later, Beens and Weller found fluorescence emission at 475 nm from an excited complex composed of two molecules of naphthalene and one of 1,4-dicyanobenzene. They postulated the unsymmetrical structure (DD+ A- ) from the solvent dependence of the wavelength of the peak maximum (high dipole moment in contrast to DAD structure) [102]. Later, several other groups detected such termolecular species. For a review on earlier contributions, see Ref. [103]. 

The electron transfer photochemistry of geraniol (42) employing DCA and 1,4-dicyanobenzene (DCB) as sensitizers has been examined by Roth et al. [45]. The course of the reaction is controlled by the energy of the electron transfer step and thus by the sensitizer applied (Sch. 23). 

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