Carbon tetrachloride, exchange reactions

Barker and Kahn have made a detailed study of the exchange in carbon tetrachloride media using the isotope " Sb to label the Sb(III) species. The reaction was carried out in sealed ampoules covered with A1 foil in the presence of an atmosphere of He or Ar gas. The separation method used involved complexing the Sb(V) with fluoride (brought about by addition of ethanol, HCl and HF) followed by precipitation of the Sb(III) with H2S and finally addition of boric acid and HCl, removal of the CCI4, and treatment with H2S to remove the Sb(V). Zero-time exchange was 5 %. 

Most of the investigations into disproportionation reactions have mainly concentrated on chlorofiuoro derivatives of methane and ethane. When trichlorofluoromethane is refluxed with aluminum trichloride or aluminum tribromide, dichlorodifluoromethane and carbon tetrachloride are obtained. Dichlorofluoromethane yields chlorodifiuoromethane and chloroform chlorofiuoro derivatives of ethane and longer chain homologs exhibit a tendency towards isomerization as well as disproportionation, i.e. intramolecular halogen atom exchange. In this case, both types of reaction take place simultaneously. In other words, disproportionation of l,l,2-triehloro-1.2,2-trifiuoroethane (1) forms l,l,1.2-tetrachloro-2,2-difluoroethane (2) and... 

The stereospecific cis-addition of diboron tetrachloride to alkynes and alkenes (37) may be interpreted as an interaction of the empty 7r-orbitals of the boron atoms with the 7r-orbital of the organic species. According to this picture, boron-boron bond breaking would lag behind boron-carbon bond formation. The transition state is a 4 + 2 Hiickel aromatic ( .=0), and thermal addition is allowed. If bond making and breaking were synchronous, this four-center reaction would be more like the <7-77 exchange reactions, which we shall discuss later. With regard to (37), there is a discrepant case in which an apparent trans addition of diboron tetrachloride to cyclopentadiene has been found (Saha et al., 1967). 

The w,causes electrochemical exchange between the Mg and the Ag ion. The heat of reaction of this exchange provokes the pyrochemical effect. I a peroxide oxidizes Mg powd with incandescence (Ref 5). The mixt explodes when Heated to redness. When the mixt is exposed to moist air spontaneous combustion occurs., When carbon dioxide gas is passed over a mixt of powd Mg and Na peroxide, the mixt explodes (Ref 6). Stannic oxide, heated with Mg, explodes (Ref 13)., A mixt of sulfates and Mg may cause an expln (Ref 17.) It has been detd experimentally that a mixt of Mg powd with trichloroethylene or carbon tetrachloride will flash or spark under, Heavy impact (Ref 2l). Mg alloy powders contg more than 50% Mg readily ignite in air (Ref 20)... 

Hypochlorites are very good oxidizers of alcohols and are frequently selective enough to oxidize secondary alcohols in preference to primary alcohols see equations 288-291). Solutions of sodium hypochlorite in acetic acid react exothermically with secondary alcohols within minutes [693]. Calcium hypochlorite in the presence of an ion exchanger (IRA 900) oxidizes secondary alcohols at room temperature in yields of 60-98% [76 5]. Tetrabutylammonium hypochlorite, prepared in situ from 10% aqueous sodium hypochlorite and a 5% dichloromethane solution of tetrabutylammonium bisulfate, oxidizes 9-fluorenol to fluorenone in 92% yield and benzhydrol to benzophenone in 82% yield at room temperature in 35 and 150 min, respectively [692]. Cyclohexanol is oxidized to cyclohexanone by teit-butyl hypochlorite in carbon tetrachloride in the presence of pyridine. The exothermic reaction must be carried out with due precautions [709]. 

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