Methyl halides, acid catalysed

Typical base-catalysed reactions that occur over alkali metal-exchanged zeolites include dehydrogenations, double bond isomerisations, side-chain alkylation of aromatics, conversion of methyl halides and a range of condensations. The reaction of alcohols over zeolites can be used to determine whether acid or base catalysis predominates. Whereas acid forms of zeolites catalyse dehydrations, leading to alkenes and the products of their subsequent reactions, basic sites catalyse dehydrogenations, leading to aldehydes and ketones. 

Carbonylation and decarbonylation reactions of alkyl complexes in catalytic cycles have been reviewed . A full account of the carbonylation and homologation of formic and other carboxylic acid esters catalysed by Ru/CO/I systems at 200 C and 150-200 atm CO/H2 has appeared. In a novel reaction, cyclobutanones are converted to disiloxycyclopentenes with hydrosilane and CO in the presence of cobalt carbonyl (reaction 4) . The oxidative addition of Mel to [Rh(CO)2l2] in aprotic solvents (MeOH, CHCI3, THF, MeOAc), the rate determining step in carbonylation of methyl acetate and methyl halides, is promoted by iodides, such as Bu jN+I", and bases (eg 1-methylimidazole) . A further kinetic study of rhodium catalysed methanol carbonylation has appeared . The carbonylation of methanol by catalysts prepared by deposition of Rh complexes on silica alumina or zeolites is comparable with the homogeneous analogue . 

Preliminary results of the reaction between vanadium(iii)-tetrasulpho-phthalocyanine complex with oxygen have been reported these data were compared with those obtained for the corresponding reaction of the hexa-aquo complex ion. The oxidation of methyl ethyl ketone by oxygen in the presence of Mn"-phenanthroline complexes has been studied Mn " complexes were detected as intermediates in the reaction and the enolic form of the ketone hydroperoxide decomposed in a free-radical mechanism. In the oxidation of 1,3,5-trimethylcyclohexane, transition-metal [Cu", Co", Ni", and Fe"] laurates act as catalysts and whereas in the absence of these complexes there is pronounced hydroperoxide formation, this falls to a low stationary concentration in the presence of these species, the assumption being made that a metal-hydroperoxide complex is the initiator in the radical reaction. In the case of nickel, the presence of such hydroperoxides is considered to stabilise the Ni"02 complex. Ruthenium(i) chloride complexes in dimethylacetamide are active hydrogenation catalysts for olefinic substrates but in the presence of oxygen, the metal ion is oxidised to ruthenium(m), the reaction proceeding stoicheiometrically. Rhodium(i) carbonyl halides have also been shown to catalyse the oxidation of carbon monoxide to carbon dioxide under acidic conditions ... 

Base-catalysed formation of ethers and esters has been carried out by reaction of the relevant alcohol or carboxylate with an alkyl halide in the presence of a phase transfer catalyst such as PEG methyl ether or Bu4Cl. The results of these investigations are summarised below [209] (Scheme 97). The esterification reaction is particularly suited to reaction with highly lipophilic acids, when the products can be obtained in high yield, uncontaminated by side products. 

THF may also be polymerized in the presence of 30% oleum, chlorosulfonic acid and silver salts (e.g. silver carbonate but not silver halides) to give a good yield of polytetramethylene glycol. Chlorosulfonic acid also catalysed the polymerization of 3-methyltetrahydrofuran at 0 C to give a low molecular weight polymer, demonstrating that, in spite of the hindrance of the methyl group, polymerization was still possible. ... 

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