Dialkyl aluminium chlorides

The polymerization is effected by a complex catalyst system. One such system has three main components. The first of these is typically a halide or acetyl-acetonate of tungsten, molybdenum, tantalum or rhenium the second a trialkyl aluminium or dialkyl aluminium chloride and the third component an activator such as epichlorhydrin or 2-chloroethanol. The polymerization may be carried out in bulk in the temperature range -50 to 0°C. The molecular weight may be regulated by the addition of small amounts of butene. The final polymer molecules are not necessarily macrocyclic in nature due to bond scission. This explanation has been shown to be consistent with the existence of vinyl end-groups even where no chain terminating non-cyclic mono-olefins have been specificaUy added. 

The most valuable and comprehensive kinetic studies of alkylation have been carried out by Brown et al. The first of these studies concerned benzylation of aromatics with 3,4-dichloro- and 4-nitro-benzyl chlorides (these being chosen to give convenient reaction rates) with catalysis by aluminium chloride in nitrobenzene solvent340. Reactions were complicated by dialkylation which was especially troublesome at low aromatic concentrations, but it proved possible to obtain approximately third-order kinetics, the process being first-order in halide and catalyst and roughly first-order in aromatic this is shown by the data relating to alkylation of benzene given in Table 77, where the first-order rate coefficients k1 are calculated with respect to the concentration of alkyl chloride and the second-order coefficients k2 are calculated with respect to the products of the... 

There are several other examples of ZSM-5 being used commercially to reduce waste and give high product selectivity. One of these is the alkylation of benzene with ethene to produce ethylbenzene selectively. The pore size of ZSM-5 successfully minimizes dialkylation reactions whilst the ability to regenerate the catalyst avoids waste issues associated with older catalysts such as aluminium chloride. 

DIALKYLS AND DIARYLS Silver nitrate. DIAMANTANE Aluminium chloride. 

Alkyl phosphorodichloridodithioates and dialkyl phosphorochloridotrithioates react with benzene in the presence of aluminium chloride to give the expected di-and mono-aryl esters. ... 

Carboxylic acid anhydrides or halides normally require the presence of a Lewis acid (often boron trifluoride) for Friedel-Crafts acylation of furans, though trifluoroacetic anhydride will react alone. Aluminium-chloride-catalysed acetylation of furan proceeds 7 x lO times faster at the a-position than at the P-position. 3-Alkyl-furans substitute mainly at C-2 2,5-dialkyl-furans can be acylated at a P-position, but generally with more difficulty. 3-Bromofuran is efficiently acetylated at C-2 using aluminium chloride catalysis. ... 

The ene addition of ethyl propiolate to P-pinene is catalysed by aluminium chloride as expected, the reaction is stereospecific and affords (545) in 82 % yield after 2 days at room temperature in benzene solution. Other 1,1-dialkylethylenes reacted similarly, but 1,2-dialkyl- and monosubstituted ethylenes, however, afforded products of stereospecific [2 +2] addition presumably short-lived dipolar intermediates are formed in the non-ene processes. Reaction of selenium tetrachloride with two equivalents of t-butylamine or toluene-p-sulphonamide in dichloromethane in the presence of four equivalents of an amine base produces solutions thought to contain iminoselenium compounds RN=Se=NR (R = Bu or Ts). Both compounds reacted with P-pinene to afford the allylic amination products (546). An even more... 

Dioxolans and dialkyl ketals are cleaved by the lithium aluminium hydride-aluminium chloride combination, giving hydroxyethyl and alkyl ethers respectively [35, 68]. 

A new method of synthesis of substituted cyclohex-1-enyl alkyl sulphides involves the reaction of the appropriate cyclohexanone with a thioacetal or thiol in the presence of aluminium chloride.Aldehydes and ketones give symmetrical dialkyl disulphides on treatment with hydrogen sulphide in the presence of pyridine and triethylamine. ... 

The purification of diethyl ether (see Chapter 4) is typical of liquid ethers. The most common contaminants are the alcohols or hydroxy compoimds from which the ethers are prepared, their oxidation products (e g. aldehydes), peroxides and water. Dialkyl ethers form peroxides much more readily than other ethers, e.g. ethyl phenyl ethers, on standing in air. Peroxides, aldehydes and alcohols can be removed by shaking with alkaline potassium permanganate solution for several hours, followed by washing with water, concentrated sulfuric acid [CARE], then water. After drying with calcium chloride, the ether is distilled. It is then dried with sodium or with li um aluminium hydride, redistilled and given a final fractional distillation. The drying process is repeated if necessary. 

Trialkyl-lead hydrides and dialkyl-lead dihydrides were made by reducing the corresponding chlorides with lithium aluminium hydride at low temperature (- 78°)36p 37.38,... 

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