Aluminums redistribution

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

Aluminum resinate particles, ie, size precipitate, are attracted to the fiber surfaces because of a difference in charge and thus are retained (45,46,54). In general, the particles of size precipitate are small and are distributed fairly uniformly over the sheet. However, on drying, there is some sintering of the particles which helps to redistribute them on the fibers. 

Prepa.ra.tlon, Diorganotin dichlorides are the usual precursors for all other diorganotin compounds three primary methods of manufacture are practiced. Dibutyltin dichloride is manufactured by Kocheshkov redistribution from cmde tetrabutyltin and stannic chloride and usually is cataly2ed with a few tenths of a percent aluminum trichloride ... 

Rate law and mechanism. The redistribution of alkyl groups on silanes in benzene is catalyzed by aluminum bromide. Suggest a scheme for it on the basis of the rate equation given. 

The 27Al MAS-NMR spectrum of an alkaline treated sample is comparable to the spectrum of the parent sample (Fig. 2a). This can be expected, since primarily the Si-atoms are leached from the zeolite framework, while the Al-atoms will hardly be removed and/or redistributed. The remaining presence of aluminum in the framework may be beneficial for the catalytic activity. 

The product undergoes a redistribution to produce R4A1C12 and R2A1C14. The reaction of aluminum with HgR2 results in transfer of alkyl groups,... 

Another striking chemical feature that methylchlorodisilanes and -polysilanes display is their ability to undergo the aluminum chloride-catalyzed redistribution reaction much more rapidly than do the related methylchloromonosilanes. Thus, when an equimolar mixture of 1,2-dichlorotetramethyldisilane and hexamethyldisilane is stirred at room temperature in the presence of a catalytic amount of anhydrous aluminum chloride, equilibrium is established between chloropentamethyldisilane and its original components within 1.5 hours (154a). 

In addition to the redistributions discussed above which involve exchanges on aluminum atoms only, there is a great deal of literature available on the exchange reactions of aluminum alkyls with halides, oxides, and alkoxides of other elements which undoubtedly are also equilibrium reactions. These, however, have found great interest as methods for the syntheses of organometallic compounds in general 129, 130). It appears that the equilibria in these systems lie almost completely at the side of the alkyl compound of the other element. 

The redistribution and cleavage reaction of mixtures of tetramethylgermane and tetrabutylgermane with excess of aluminum chloride give di- as well as trichlorogermanes having mixed alkyl groups. 

In electrophilic catalysis, the metal ion acts as a Lewis acid. An example from organic chemistry is the formation of an acylium ion from aluminum chloride and an acid chloride in Friedel-Crafts acylation reactions (Figure 2). In this case substrate activation results in cleavage of the C—Cl bond. In most cases, however, substrate activation by Lewis acids involves electron redistribution without bond breaking (Figure 3). 

Aluminum occurs naturally in soil, water, and air. It is redistributed or moved by natural and human activities. High levels in the environment can be caused by the mining and processing of its ores and by the production of aluminum metal, alloys, and compounds. Small amounts of aluminum are released into the environment from coal-fired power plants and incinerators. Virtually all food, water, and air contain some aluminum, which nature is well adapted to handle. 

These theoretical results discussed in the preceding paragraph are fully consistent with the experimental XPS and UPS data. Indeed, the new features appearing on the C(ls), S(2p), and Al(2p) XPS spectra constitute dear evidence of the charge transfer from aluminum to carbon and sulphur. Other model configurations, where the aluminum atoms are made to interact either only with the sulphur atoms or only with the 0-carbon atoms, are calculated to be much less stable than the Al—C structure described above, and do not result in any electron density redistribution consistent with the XPS results. The inert character of the 0-carbons, and of the adjacent thiophene units, upon reaction of aluminum with a given thiophene unit also is reflected in the spectra, as the major part of the C(ls) and S(2p) contribution remains unshifted when aluminum is deposited... 

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. 

Redistribution of halogens in chloroform and bromoform is taking place in presence of aluminum trichloride226 and also in presence of sodium hydroxide under PTC227. Bromotrichloromethane isomerizes to a mixture of all the possible five isomers in presence of traces of chloroform and Bu4NF (TBAF) catalyst (equation 28)228 ... 

The work of Petrov (288) and of Moldavskil (236) on the isomerization of some paraffins in the presence of aluminum chloride points to the similarity in temperature required for cracking and for isomerization of these paraffins in the presence of the catalyst used. Moldavskil used aluminum chloride-hydrogen chloride for isomerization of butanes and pentanes and observed a redistribution of methyl groups (241). 

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