Hydrogenation 4-chlorophenol

Radon forms a series of clathrate compounds (inclusion compounds) similar to those of argon, krypton, and xenon. These can be prepared by mixing trace amounts of radon with macro amounts of host substances and allowing the mixtures to crystallize. No chemical bonds are formed the radon is merely trapped in the lattice of surrounding atoms it therefore escapes when the host crystal melts or dissolves. Compounds prepared in this manner include radon hydrate, Rn 6H20 (Nikitin, 1936) radon-phenol clathrate, Rn 3C H 0H (Nikitin and Kovalskaya, 1952) radon-p-chlorophenol clathrate, Rn 3p-ClC H 0H (Nikitin and Ioffe, 1952) and radon-p-cresol clathrate, Rn bp-CH C H OH (Trofimov and Kazankin, 1966). Radon has also been reported to co-crystallize with sulfur dioxide, carbon dioxide, hydrogen chloride, and hydrogen sulfide (Nikitin, 1939). 

This compound is obtained from phthalic acid and p-chlorophenol with sulfuric acid in the presence of boric acid. The intermediate product is quinizarin, which is sulfonated in oleum or with sodium hydrogen sulfite and oxidants to form 89 ... 

August et al. (1998) conducted kinetic studies for the reaction of chlorobenzene (0.2 mM) and other monocyclic aromatics with Fenton s reagent (8 mM hydrogen peroxide [Fe" ] = 0.1 mM) at 25 °C. They reported a reaction rate constant of 0.0820/min. The following intermediates were identified during this reaction chlorophenol, chlorohydroquinone, chloroquinone, hydroquinone, and quinone. 

Irradiation of an aqueous solution at 296 nm and pH values from 8 to 13 yielded different products. Photolysis at a pH nearly equal to the dissociation constant (undissociated form) yielded pyrocatechol. At an elevated pH, 2-chlorophenol is almost completely ionized photolysis yielded cyclopentadienic acid (Boule et al., 1982). Irradiation of an aqueous solution at 296 nm containing hydrogen peroxide converted 2-chlorophenol to catechol and 2-chlorohydroquinone (Moza et al, 1988). In the dark, nitric oxide (10 vol %) reacted with 2-chlorophenol forming 4-nitro-2-chlorophenol and 6-nitro-2-chlorophenol at yields of 36 and 30%, respectively (Kanno and Nojima, 1979). 

Chemical/Physical. Hypochlorous acid reacted with p bromophenol forming dichlorophenol, 4-chlorophenol, bromochlorophenol, dibromophenol, bromodichlorophenol, and dibromochloro-phenol. The displacement of bromine atom by chlorine yields hypobromous acid which then displaces a hydrogen atom from another brominated compound forming brominated substances, e.g., bromochlorophenol, dibromophenol, etc. (Hwang et al., 1988). 

Chemical/Physical. Chemical oxidation of mono-, di-, and trichlorophenols using Fenton s reagent were investigated by Barbeni et al. (1987). To a 70-mL aqueous solution containing 4-chlorophenol thermostated at 25.0 °C was added ferrous sulfate and hydrogen peroxide solution (i.e., hydroxyl radicals). Concentrations of 4-chlorophenol were periodically determined with... 

Photolytic. When profenofos in an aqueous buffer solution (pH 7.0) was exposed to filtered UV light (X >290 nm) for 24 h at 25 and 50 °C, 29 and 56% decomposed, respectively, to 4-bromo-2-chlorophenol and 4-bromo-2-chlorophenyl ethyl hydrogen phosphate. Both compounds were also identified in soil irradiated with UV light. 

Lipcz3mska-Kochany, E. and Bolton. J.R. Flash photolysis/HPLC applications. 2. Direct photolysis vs hydrogen peroxide mediation photodegradation of 4-chlorophenol as studied by a flash photolysis/HPLC technique. Environ. Sci Technol, 26(2) 259-262, 1992. 

Moza, P.N., Fytianos, K., Samanidou, V., and Korte, F. Photodecomposition of chlorophenols in aqueous medium in presence of hydrogen peroxide, Bull. Environ. Contam. Toxicol, 41(5) 678-682, 1988. 

Fig. 16 Structures of chlorophenols and metabolites of ochratoxin A (OTA) with an OH group [ochratoxin hydroquinone (OTHQ)] and a hydrogen atom [nonchlorinated OTA (OTB)].

Stevani and coworkers prepared and characterized a peracid intermediate, 4-chloro-pheny 1-0,0-hydrogen monoperoxalate (57) and found that no chemiluminescence was observed in the presence of activators (i.e. rubrene, perylene and DPA) and the absence of a base. Based on this result, the authors excluded 57 and similar peracid derivatives as HEI in the peroxyoxalate system. Moreover, 57 only emits light in the presence of an activator and a base with pK > 6, suggesting that a slow chemical transformation must still occur prior to the chemiexcitation step. Kinetic experiments with 57, using mainly imidazole, but also in the presence of other bases such as potassium 4-chlorophenolate, f-butoxide and l,8-bis(dimethylamino)naphthalene , showed that imidazole can act competitively as base and nucleophilic catalyst (Scheme 41). At low imidazole concentrations, base catalysis is the main pathway (steps 1 and 2) however, increasing the base concentration causes nucleophilic attack of imidazole catalyzed by imidazole to become the main pathway (steps la and 2a). Contrary to the proposal of Hohman and coworkers , the... 

The infrared absorption spectrum thus showB that o-chlorophenol in solution in carbon tetrachloride consists of about 91 percent cis molecules and 9 percent trans molecules. The cis molecules are more stable than the trans molecules by a standard free-energy difference of about 1.4 kcal/mole (calculated from the ratio of the areas of the peaks). This is presumably the difference in free energy of the cis molecule with its intramolecular hydrogen bond and the trans molecule with a weaker hydrogen bond with a solvent molecule. 

The weak hydrogen bond in o-chlorophenol stabilizes the gas molecule relative to those of the meta and para isomers, whereas the crystalline and liquid phases of the three substances, in which hydrogen bonds can be formed between adjacent molecules, have about the same stabil-... 

Dehalogenation of chlorinated arenes.3 Palladium (10%) on carbon catalyzes the rapid transfer of hydrogen from ammonium formate to aryl chlorides to provide the parent arene. Dehalogenation of 2,4,6-trichlorophenol proceeds through di-chloro- and chlorophenol and is complete within 10 minutes at ambient temperature and pressure. 

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