Titanium chloride-Aluminum

As shown in Table IV, the highest catalytic activity of metal halides used as Lewis acid for the alkylation reaction of ferrocene with 2 was observed in methylene chloride solvent. Among Lewis acids such as aluminum chloride, aluminum bromide, and Group 4 transition metal chlorides (TiCl4, ZrCU, HfCU), catalytic efficiency for the alkylation decrea.ses in the following order hafnium chloride > zirconium chloride > aluminum chloride > aluminum bromide. Titanium chloride... 

So you can see why branching in the polymerization process can be a problem—the symmetry is affected. And you can get a hint why PP was commercialized long after polyethylene. The chemistry and catalysis are a lot more demanding. Thats why Giulio Natra won the Nobel Prize for his contribution to the field of stereo-catalysis, the discovery of the effects of titanium chloride and organo-aluminum compounds. 

The surveyed data also indicate that there were net increases in all of the following compounds total dissolved solids, total suspended solids, total organic carbon, total residual chlorine, free available chlorine 2,4-dichlorophenol, 1,2-dichlorobenzene, phenolics, chromium, lead, copper, mercury, silver, iron, arsenic, zinc, barium, calcium, manganese, sodium, methyl chloride, aluminum, boron, and titanium. 

Solutions of low-valence titanium chloride (titanium dichloride) are prepared in situ by reduction of solutions of titanium trichloride in tetrahydrofuran or 1,2-dimethoxyethane with lithium aluminum hydride [204, 205], with lithium or potassium [206], with magnesium [207, 208] or with a zinc-copper couple [209,210]. Such solutions effect hydrogenolysis of halogens [208], deoxygenation of epoxides [204] and reduction of aldehydes and ketones to alkenes [205,... 

For the reduction to pinacols aluminum amalgam [825] or low valence state titanium chloride [207] were used. Under different conditions the titanium... 

The metal halide catalysts include aluminum chloride, aluminum bromide, ferric chloride, zinc chloride, stannic chloride, titanium tetrachloride and other halides of the group known as the Friedel-Crafts catalysts. Boron fluoride, a nonmetal halide, has an activity similar to that of aluminum chloride. 

The catalytic activity of certain of the Friedel-Crafts catalysts was shown to decrease over a very wide range in the series boron fluoride, aluminum bromide, titanium tetrachloride, titanium tetrabromide, boron chloride, boron bromide and stannic chloride (Fairbrother and Seymour, mentioned in Plesch al., 83). When boron fluoride is added to isobutylene at dry ice temperatures, the olefin is converted to a solid polymer within a very few seconds. The time required for complete polymerization with aluminum bromide hardly extends to a few minutes while reaction times of hours are required with titanium chloride and periods of days with stannic chloride. 

Although several Lewis Acids were evaluated, including titanium(lV) chloride, aluminum(lll) chloride and tin(lV) chloride, ferric(lll) chloride proved to be the most effective co-catalyst. We believe that in the presence of a Lewis Acid, the rate of j3-palladium hydride elimination (H-Pd-X) from the -allyl carbomethoxy palladium complex 4 can be enhanced. A good leaving group such as iodide attached to -allyl carbomethoxy palladium complex 4 would facilitate iodopalladium hydride elimination to selectively form methyl, -pentadienoate (Equation 11.). 

Tin(II) chloride-Aluminum, 299 Titanium(IV) chloride-Diethyl-aluminum chloride, 309 Titanium(III) chloride-Diisobutyl-aluminum hydride, 303 Titanium(IV) chloride-Lithium aluminum hydride, 310... 

ZIEGLER CATALYST. A type of stereospedfre catalyst, usually a chemical complex derived from a transition metal halide and a metal hydride oi a metal alkyl. The transition metal may be any of those in gioups IV to VIII of the periodic table the hydride or alkyl metals are those of groups I, II. and III. Typical, titanium chloride is added to aluminum alkyl in a hydrocarbon solvent to form a dispersion or precipitate of ilie catalyst complex. These catalysts usually operate at atmospheric pressure and are... 

The chemistry of Lewis acids is quite varied, and equilibria such as those shown in Eqs. (28) and (29) should often be supplemented with additional possibilities. Some Lewis acids form dimers that have very different reactivities than those of the monomeric acids. For example, the dimer of titanium chloride is much more reactive than monomeric TiCL (cf., Chapter 2). Alkyl aluminum halides also dimerize in solution, whereas boron and tin halides are monomeric. Tin tetrachloride can complex up to two chloride ligands to form SnCL2-. Therefore, SnCl5 can also act as a Lewis acid, although it is weaker than SnCl4 [148]. Transition metal halides based on tungsten, vanadium, iron, and titanium may coordinate alkenes, and therefore initiate polymerization by either a coordinative or cationic mechanism. Other Lewis acids add to alkenes this may be slow as in haloboration and iodine addition, or faster as with antimony penta-chloride. 

Benzenesulfenyl chloride alkene adducts may be transformed to many useful molecules. Intermediates, such as (3), can be treated with base to pi uce vinyl or allyl sulfi s (equation 2). Alternatively, the adducts can be oxidized and treated with base to yield vinyl sulfones in high overall yield (equation 3). The thiirane intermediates or adducts, i.e. (3), may be alkylated with alkyl-titanium and -aluminum reagents which replace the chloride substituent with retention of configuration. 

Exhaustive extraction involves the quantitative removal of a solute, and selective extraction, the separation of two or more solutes from each other. One classical application of an exhaustive analytical extraction is the ether extraction of iron(III) chloride from hydrochloric acid solutions. The extraction is not strictly quantitative in that a small fraction remains unextracted. Therefore the method is best suited to the removal of relatively large amounts of iron (several grams) from small amounts of such metals as nickel, cobalt, manganese, chromium, titanium, or aluminum. It is of interest that iron(II) remains unextracted. 

Natta catalyst. A stereospecific catalyst made from titanium chloride and aluminum alkyl or similar materials by a special process that includes grinding the materials together to produce an active catalyst surface. 

Two years later, in October of 1953, another accidental discovery was made by Karl Ziegler of the Max-Planck Institut, Mulheim, Germany [10]. His catalyst consisted of titanium chloride combined with aluminum alkyl. The first patents were filed quickly, on October 17,1953. A polymer density of about 0.94 g mL 1 was reported. Ziegler licensed it within a year, offering only a laboratory method that each licensee then had to develop and scale up independently. Hoechst was one of the first licensees. One of the early problems, which was apparently not addressed in the license, was how to control the MW of the polymer [2]. 

With aluminum-chloride catalysts, the polymer structure is 80% cyclobutane units and about 5% cyclopropane units, the remainder being polyene units. With stannic chloride, we do not observe any cyclopropane units the polymer consists mainly of cyclobutane units (75%). The presence of methyl groups on cyclohexane shows that the other units possess partially isomerized and cyclized polyene structures. When using titanium chloride or ethyl aluminum chloride with traces of water as cocatalyst, the polymer consists mainly of cyclobutane units—that is, 60%, the demainder being cyclized see Equation 17. 

There are also examples for which there is no need to separate a catalyst, because it can be left in the product without adverse effects. Magnesium chloride-supported catalysts for the polymerization of propylene attain such high mileage that they can be left in the polymer. Earlier less-efficient catalysts had to be removed by an acidic extraction process that produced titanium- and aluminum-containing wastes. The earlier processes also produced heptane-soluble polymer that had to be removed, and, sometimes, ended up as waste. The newer processes produce so little that it can be left in the product. Thus, improved catalysts have eliminated waste. 

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