SbF5-graphite

Electrophilic chlorination and bromination of methane over supported noble metals9-11 (Pt on A1203, Pd on BaSC ) and solid superacid catalysts9-13 (e.g., TaOF3 on alumina, Nafion-H, zeolites, SbF5-graphite, sulfated zirconia) have been studied (see Section 3.4.2). Monosubstitution with selectivities better than... 

The catalytic properties of SbF5-graphite have been investigated.205 208 The chemistry is basically the same as that of SbF5 itself with two major differences (i) As a solid, it can be more easily separated from the reaction mixture, and (ii) the... 

Olah and Bukala404 have developed a method for the oxidative carboxylation of methyl halides with CO and copper oxides or Cu and oxygen over SbF5-graphite [Eq. (5.156)]. Time-dependence studies indicated that the three products—methyl acetate, dimethyl ether, and methyl fluoride—were formed in parallel reactions. The reactivity of methyl halides shows the decreasing order MeBr > MeCl > MeF. 

Subsequently, selective ionic chlorination of methane to methyl chloride was achieved in the gas phase over solid superacid catalysts.526 For example, chlorination of methane in excess chlorine over Nafion-H and SbF5-graphite gave methyl chloride with 88% and 98% selectivity, respectively (185°C and 180°C, 18% and 7% conversion).527 Similarly, electrophilic bromination of alkanes has also been carried out528 (Scheme 5.53). 

The intramolecular nature of most carbocationic isomerization was proved by means of labeling experiments. [l-13C]-Propane was isomerized in the presence of aluminum bromide promoted by hydrogen bromide to form [2-13C]-propane. None of the propane product contained more than one l3C atom per molecule.64 Similarly, very little label scrambling was observed in the isomerization of labeled hexanes over SbF5-intercalated graphite.65 Thus simple consecutive 1,2-methyl shifts can account for the isomerization of l3C-labeled methylpentanes (Scheme 4.3). 

The isomerization of cycloalkanes over SbF5-intercalated graphite can be achieved at room temperature without the usual ring opening and cracking reactions, which occur at higher temperatures and lower acidities.110 In the presence of excess hydrocarbon after several hours, the thermodynamic equilibrium is reached for the isomers. Interconversion between cyclohexane (20) and methylcyclopentane (21) yields the thermodynamic equilibrium mixture [Eq. (5.46)]. 

As a model for cracking of alkanes, the reaction of 2-methylpentane (16, 2MeP) over SbF5-intercalated graphite has been studied in a flow system, with the hydrocarbon being diluted in a hydrogen stream.104,105 A careful study of the product... 

It was shown that the SbF5-intercalated graphite efficiently promotes disproportionation of various alkylbenzenes by simple mixing at room temperature (41). The isomerization of methylpentanes was carried out over the catalyst at room temperature, -30, and - I7°C in a continuous flow system a careful study of the kinetically controlled product distribution was performed to obtain information for the reaction path (42, 43). The skeletal rearrangements of l3C- abeled 2-methyl, 3-methylpentane and... 

Antimony(v) Compounds. The standard heat of formation of SbFj from fluorine combustion experiments is —319.5 kcal mol , and the intercalation of this compound into graphite has been discussed in two reports. The first considers the formation of Ce.sSbFj as the first product while the second reports the existence of C SbF5, where n 4, 6, or 12. A wide-line n.m.r. investigation of... 

The difficulties encountered in handling liquid superacids and the need for product separation from catalyst in batch processes have stimulated research in the isomerization of alkanes over solid superacids. The isomerization of 2-methyl- and 3-methylpentane and 2,3-dimethylbutane, using SbF5-intercalated graphite as a catalyst, has been studied in a continuous flow system. ... 

Thompson TE, Falardeau ER, Hanlon LR. The electrical conductivity and optical reflectance of graphite-SbF5 compounds. Carbon. 1977 15 39. 

Fuzellier H, Melin J, Herold A. Conductibilite electrique des composes lamellaires graphite-SbF5 et graphite-SbC15. Carbon. 1977 15 45. 

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