Aluminum displacement reactions

In the production of a-olefins, ethylene reacts with an aluminum alkyl at relatively low temperature to produce a higher aLkylalumiaum. This is then subjected to a displacement reaction with ethylene at high temperatures to yield a mixture of a-olefins and triethylalumiaum. In an alternative process, both reactions are combiaed at high temperatures and pressures where triethylalumiaum fuactioas as a catalyst ia the polymerization process. 

Only one of these methods, namely the reaction of halides with lithium aluminum deuteride, is a true displacement reaction, following the same course as the previously discussed displacement of sulfonate esters (section Vl-A). Thus, lithium aluminum deuteride treatment of 7a- and 7jS-bromo-3 -benzoyloxy-5a-cholestanes (195) and (196) gives the corresponding deuterium labeled cholestanols (197) and (198) respectively." ... 

In 1954, Ziegler and coworkers observed that the course of the reaction of ethene with trialkylalanes was drastically altered by the presence of traces of nickel salts [25]. Instead of low molecular weight polyethylene, the only product was 1-butene. Obviously, the transition metal strongly supports the displacement reaction of the alkyl group bonded to the aluminum by ethylene, a reaction which can be formally described as transfer of a hydridoalane. 

When the process of chain growth is satisfactorily completed, separation of the three hydrocarbon chains that are connected to the aluminum atom is accomplished by a displacement reaction. The chain-laden aluminum compound (called trialkyl aluminum compounds) is subjected to still higher temperatures and pressure. This causes an ethylene molecule to displace the long linear carbon chain. As the separation is made, triethyl aluminum is reformed, making a recyclable root for another go-around. 

This chemistry is sometimes accomplished simultaneously in one reactor and sometimes in two separate reactors. In the former, the triethyl aluminum catalyst is lost in the latter, it is recycled. Sometimes the displacement compound is butene-1 or hexene-1, depending on the chain length of the final alpha olefin desired and the change in operating conditions necessary to effect the displacement reaction. 

Similarly, aluminum substrate can be activated by a displacement reaction (56,59) ... 

The use of lithium aluminum hydride gives slightly lower yields and probably involves a displacement reaction by hydride ion. The zinc-copper couple technique probably involves formation of an organozinc intermediate. Sodium, magnesium, and aluminum metal may be used to replace the zinc-copper couple [59a, b]. These organometal intermediates react with aldehydes and... 

Another simple oligomerization is the dimerization of propylene. Because of the formation of a relatively less stable branched alkylaluminum intermediate, displacement reaction is more efficient than in the case of ethylene, resulting in almost exclusive formation of dimers. All possible C6 alkene isomers are formed with 2-methyl-1-pentene as the main product and only minor amounts of hexenes. Dimerization at lower temperature can be achieved with a number of transition-metal complexes, although selectivity to 2-methyl-1-pentene is lower. Nickel complexes, for example, when applied with aluminum alkyls and a Lewis acid (usually EtAlCl2), form catalysts that are active at slightly above room temperature. Selectivity can be affected by catalyst composition addition of phosphine ligands brings about an increase in the yield of 2,3-dimethylbutenes (mainly 2,3-dimethyl-1-butene). 

Instead of the displacement reaction, aluminum alkyls may be oxidized with dry air to produce aluminum alkoxides that, after hydrolysis with dilute sulfuric acid or water, yield linear primary alcohols with an even number of carbon atoms (fatty... 

One problem with this method is that the workup must be done carefully as die amine products tend to complex tenaciously with the aluminum salts formed from the LAH upon workup and thus are not recovered easily. There are standard workups which avoid these issues, but these should be followed carefully. Reduction of azides by catalytic reduction, phosphine or phosphite reagents, or Sn(II) chloride are all effective methods. The azides are also available from displacement reactions and give primary amines upon reduction. 

Many metals, such as zinc, iron, lead, copper, and aluminum are found chemically bonded to oxygen in nature. Sometimes, chemists can use single displacement reactions to get the pure metal. 

Figure 4.2 The mixing of a silver sulfate solution with an aluminum chloride solution, results in the formation of aqueous aluminum sulfate and the precipitation of silver chloride. This is an example of a double displacement reaction.

In the example of a double displacement reaction below, a silver sulfate (Ag2S04) solution is mixed with an aluminum chloride (AlCl3) solution. One of the products, silver chloride (AgCl), precipitates out of the solution as a solid. The (s) following the formula for silver chloride shows that it is a solid. 

This reaction could be viewed in terms of a double displacement reaction One of the oxygen atoms and one of the hydrogen atoms have displaced each other. One of the most famous examples of this type of exchange reaction, a single exchange, occurs between iron oxide and aluminum ... 

In the displacement reaction, reversible -hydride elimination of an alkene from an aluminum alkyl (equation 5) is followed by insertion of a different alkene into the Al-H bond of the resulting diaUcylaluminum hydride (equation 6). Three repetitions of this process yield the new trialkylaluminum compound as in equation (7). Tri-wo-butylaluminum obtained from the direct synthesis is a convenient starting aluminum alkyl for this process. 

Aluminum was first prepared by the following displacement reaction. 

Potassium was also expensive because it was made by passing an electric current (from a voltaic cell) through molten KCl. In addition to the great cost of energy required to melt large quantities of KCl, copper and zinc (used in voltaic cells) were also expensive metals in the early 1800s. Thus, the very small amount of aluminum produced by this displacement reaction was extremely expensive. 

ALA-dehydratase, and isocitrate dehydrogenase and decreases Na+, K -ATPase activity, Mg +-ATPase activity, and choline uptake into synaptosomes. In vitro, aluminum displaces magnesium from Mg +-ATP complexes, and it could thus antagonize virtually any phosphatetransferring reaction that uses Mg +-nucleotide triphosphate complexes. 

In the course of these investigations, an experiment was carried out to prepare hexyl and octyl derivatives of aluminum by reaction of triethylaluminum with ethylene. Instead of the anticipated aluminum alkyls, an almost quantitative yield of 1-butene was obtained. After a strenuous investigation, Ziegler and his coworkers found that an extremely small trace of metallic nickel caused this change in the course of the reaction. The nickel, present from a previous hydrogenation experiment, catalyzed the displacement reaction (Reaction 2) of 1-butene from butylaluminum (Reaction 3),... 

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