Aluminum chloride catalyst metals, effect

Studies on the conditions of the reaction have been made using simple compounds as model substances, A comparison of thirty-nine metallic chlorides shows aluminum chloride to be the most effective in the preparation of p-methylacetophenone. Optimum yields result when the molar ratios of aluminum chloride to anhydride, acyl chloride, and acid are 3.3, 1,0, and 2.5, respectively. Halogen and oxyhalogen carriers are not helpful. Inconsistent yields in the Friedel-Crafts reaction have been attributed to the presence of ferric chloride or moisture in the aluminum chloride Catalyst. Prolonged heating causes condensation of the ketone product. 

Use of Metal Halides. Metal halides and particularly izinc and aluminum chlorides have been found to be effective dehydrochlorinating agents. When pentachloroethane is heated with aluminum chloride, tetrachloreth-ylene is obtained. The pentachloroethane is fed continously into a mixture of tetrachloroethylene and aluminum chloride (or metal aluminum particles) at 120 C. The chloroolefin distills over with hydrogen chloride, and the metal halide becomes converted to an organo aluminum chloride complex of diminishing catalytic activity. Fresh catalyst must consequently be added periodically to maintain high conversion rates. 

Catalysts. It was shown by Friedel and Crafts that while aluminum chloride is a very active alkylation catalyst, other metal chlorides (ferric chloride, zinc chloride, etc.) are also effective. They also showed that other aluminum halides (aluminum... 

The redistribution reaction in lead compounds is straightforward and there are no appreciable side reactions. It is normally carried out commercially in the liquid phase at substantially room temperature. However, a catalyst is required to effect the reaction with lead compounds. A number of catalysts have been patented, but the exact procedure as practiced commercially has never been revealed. Among the effective catalysts are activated alumina and other activated metal oxides, triethyllead chloride, triethyllead iodide, phosphorus trichloride, arsenic trichloride, bismuth trichloride, iron(III)chloride, zirconium(IV)-chloride, tin(IV)chloride, zinc chloride, zinc fluoride, mercury(II)chloride, boron trifluoride, aluminum chloride, aluminum bromide, dimethyl-aluminum chloride, and platinum(IV)chloride 43,70-72,79,80,97,117, 131,31s) A separate catalyst compound is not required for the exchange between R.jPb and R3PbX compounds however, this type of uncatalyzed exchange is rather slow. Again, the products are practically a random mixture. 

The isomerization of pentane was carried out with a series of mixtures containing aluminum chloride or bromide with sulfates of metals such as Ti, Fe, Ni, Cu, Al, and others the most effective catalyst was an equimolar mixture of AlBr3 and Ti2(S04)3 with a conversion of 86% and a selectivity to isopentane of 99% at room temperature (50, 51). In the vapor phase conversion, however, the main product was isobutane. 

An exceptional catalyst for isomerization of CFC-113 to CFC-113a is anhydrous aluminum chloride as reported by Miller (28). This isomerization is usually carried out in the liquid phase and under mild conditions. Some disproportionation of CFC-113a to CFC-114a and CF2CICCI3 (CFC-112a) is also observed on prolonged contact with catalyst. The use of trace quantities of metals such as chromium and manganese is claimed to have a beneficial effect in this process (29). There is an initial activation period... 

The decomposition of R6Pb2 to R4Pb has been observed using activated carbon black 331), silica-type catalysts 332), aluminum chloride 249), and ultraviolet light 333), Autocatalysis by metallic lead, though less effective, has also been reported 334). 

Among a number of metal chlorides used in organic synthesis, anhydrous aluminum chloride is undoubtedly one of the most effective of Lewis acid catalysts. During the chloromethylation of polystyrene, using aluminum chloride as catalyst, it was observed that all the aluminum chloride could not be removed, even after repeated washing. This was attributed to the formation of a tightly bound polystyrene-aluminum chloride complex. Complex formation was demonstrated by the increase in color (yellow) intensity of the polymer, and by the development of a new characteristic ir band at 1650 cm This complex could act as a mild Lewis acid catalyst for certain organic preparations. 

Many studies on the direct reaction of methyl chloride with silicon-copper contact mass and other metal promoters added to the silicon-copper contact mass have focused on the reaction mechanisms.7,8 The reaction rate and the selectivity for dimethyldichlorosilane in this direct synthesis are influenced by metal additives, known as promoters, in low concentration. Aluminum, antimony, arsenic, bismuth, mercury, phosphorus, phosphine compounds34 and their metal complexes,35,36 Zinc,37 39 tin38-40 etc. are known to have beneficial effects as promoters for dimethyldichlorosilane formation.7,8 Promoters are not themselves good catalysts for the direct reaction at temperatures < 350 °C,6,8 but require the presence of copper to be effective. When zinc metal or zinc compounds (0.03-0.75 wt%) were added to silicon-copper contact mass, the reaction rate was potentiated and the selectivity of dimethyldichlorosilane was enhanced further.34 These materials are described as structural promoters because they alter the surface enrichment of silicon, increase the electron density of the surface of the catalyst modify the crystal structure of the copper-silicon solid phase, and affect the absorption of methyl chloride on the catalyst surface and the activation energy for the formation of dimethyldichlorosilane.38,39 Cadmium is also a structural promoter for this reaction, but cadmium presents serious toxicity problems in industrial use on a large scale.41,42 Other metals such as arsenic, mercury, etc. are also restricted because of such toxicity problems. In the direct reaction of methyl chloride, tin in... 

Metal triflates can be easily prepared from metal halides and triflic acid at -78 C. They show several unique properties compared with the corresponding metal halides. In an early study, Olah reported the use of boron-, aluminum-, and gallium triflates [M(OTf)J as effective Friedel-Crafts catalysts. In the benzoylation and acetylation of toluene and benzene with acyl chlorides, the relative reactivity is boron triflate > gallium triflate > aluminum triflate, in agreement with the relative acidity strength. 

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