Preparation of triethylaluminum

The separation of the process into two stages is explained by fact that the reaction takes place at a temperature above 100 °C and triethylaluminum reacts with ethylene, forming higher aluminumtrialkyls and higher olefines  

the conditions for the formation of by-products are close to the conditions of the main process, which impairs one-stage synthesis. However, the one-stage production of triethylaluminum is more convenient due to the simplicity of the technological process. The one-stage production of triethylaluminum nevertheless requires the speed of the main reaction to be much higher than the speed of secondary reactions. 

The one-stage synthesis should be conducted at 135 °C, 5 MPa, the 0.71 1 ratio of aluminum and triethylaluminum and the 1 1 ratio of ethylene and hydrogen. First, aluminum power is activated to eliminate the ox- 

The activation can be carried out by the chemical technique (with various reagents), the physical technique (with ultrasound with inert gas used to disperse liquid aluminum) or the mechanical technique (fine dispersion in a cavity, ball or vibration mill). 

The chemical activation of aluminum. The reactor is loaded with a suspension of aluminum in petrol and activating additive (triethylaluminum or triethylaluminum mixed with aluminum chloride). The mixture is agitated and heated in hydrogen to 160-200 °C and held at this temperature for 10 hours. After the activation the reactor is cooled, the excess hydrogen is withdrawn and the synthesis is started. 

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Since the Conoco ALFOL alcohol process has already been described in detail, only those areas where the two processes are different will be covered. Preparation of triethylaluminum appears similar in both processes. Ethyl s scheme is believed to use a ballmilling procedure to obtain an active aluminum... 

With the development by Ziegler of an accessible method for the preparation of triethylaluminum [71,72] interest in the use of this compound for the synthesis of other alkyl metallic compounds increased considerably. As already mentioned above, melts of mixtures of the MX AlRs or MR-AlRs types (where M is a monovalent metal and X is halogen or hydrogen) possess sufficient electrical conductivity. 

Polymerizations catalyzed with coordination compounds are becoming more important for obtaining polymers with special properties (linear and stereospecific). The first linear polyethylene polymer was prepared from a mixture of triethylaluminum and titanium tetrachloride (Ziegler catalyst) in the early 1950s. Later, Natta synthesized a stereoregular polypropylene with a Ziegler-type catalyst. These catalyst combinations are now called Zieglar-Natta catalysts. 

A 10% molar excess of hydrogen cyanide was employed, and the quantity added at this point was determined by the amount of triethylaluminum collected. See Note 4 in Part III of this preparation for the preparation of hydrogen cyanide. 

The exact volume of the triethylaluminum added at this point is not critical, since the exact weight is determined later. I he use of a 25% solution of triethylaluminum in benzene, available from the Stauffer Chemical Company, 299 Park Avenue, New York, eliminates the tedious preparation of the triethylaluminum solution described in this procedure. 

The "symmetrisation" of triethylaluminum sesquichloride takes place in reactor 8. The suspension of sodium in petrol is prepared there sesquichloride enters the reactor from collector 7 through batch box 9 at 125-135 °C and agitation. Then the mixture is agitated at the synthesis temperature for 2-3 hours to complete the reaction then it is cooled to ambient temperature. The obtained diethylaluminumchloride solution is settled for 2-3 hours to separate dirt the purified product enters container 12. 

This technique for preparing diethylaluminumchloride presents few problems. However, aluminum powder should be activated, otherwise the formation of triethylaluminum sesquichloride starts much later but proceeds autocatalytically, releasing a lot of heat, which greatly increases the pressure in the reactor and even causes explosions. The formation stage of diethylaluminumchloride is not so active however, the process should be strictly controlled (because the reaction releases heat) and the ion should be supplied from the components gradually. 

A preparation of fra/ -[Mo(N2)2(dppe)2] (dppe = Ph2PCH2CH2PPh2) that uses triethylaluminum as reductant has already been reported in Inorganic Syntheses,3 but it is less convenient and gives much lower yields than that described below. Other reported methods, using sodium amalgam as reductant, involve a more difficult work-up procedure.4... 

Claisen rearrangement of allyl vinyl ethers. " Allyl vinyl ethers undergo Claisen rearrangement at 25° in CICHiCHiCl in the presence of 2 equiv. of (CjH liAlSQH, (prepared from triethylaluminum and thiophenol) or (C3H5)2AICI/P(CftH,),. 

Ci2-Cig olefins are prepared by a modified Ziegler a-olefin process based on ethylene and triethylaluminum. The process consists of five steps buildup, displacement, separation, alkylation, and recycle. The major chemical and economic problems encountered are wide molecular weight distribution of the products and incomplete recovery of triethylaluminum. Catalysts consisting of alkyl-aluminums and colloidal nickel are needed for the alkylation-displacement steps however, the omount of nickel has to be very low because in the other process steps, nickel favors side reactions. The yield of a-olefins in the C 2" i8 creased by using coordination compounds of triethylaluminum with a Lewis base followed by azeotropic distillation. In the Chlorex process, (bis-a-chloroethyl) ether is used because of easy availability and low cost. 

Silylated cyanohydrins have found considerable utility in the regioselective protection of p-qui-nones, as intermediates for the preparation of 3-amino alcohols and as precursors to acyl anion equivalents. Such compounds are typicdly prepared in high yield by either thermal or Lewis acid catalyzed addition of TMS-CN across the carbonyl group. This cyanosilylation has a variety of disadvantages and modified one-pot cyanosilylation procedures have been reported. - The carbonyl group can be regenerated by treatment with acid, silver fluoride or triethylaluminum hydrofluoride followed by base. ... 

Preparation. A solution of triethylaluminum in benzene is stirred magnetically with ice cooling during dropwise addition of a solution of hydrogen cyanide in benzene. When the evolution of ethane ceases, the solvent is evaporated and the product distilled. 

The above reaction may be carried out using diethylaluminum ethoxide in place of triethylaluminum. The title compound can also be prepared by the reaction of Ni(cod)2 with triphenylphosphine [9] or by the reduction of NiCf with Zn powder in the presence of triphenylphosphine [61]. 

Diethylzinc was prepared by treating one molar equivalent of anhydrous zinc chloride with two molar equivalents of triethylaluminum. A turbid solution was formed with little heat evolution. Fractional distillation of the mixture through a Vigreux column gave a 77% yield of colorless diethylzinc boiling at 24-25X under 17 mm of pressure. 

Oxidation is carried out with air. In the preparation of the catalyst, the residual nitrogen serves to maintain an inert atmosphere in the storage of the aluminum powder required to produce triethylaluminum. Heat can be removed by water. 

Other methods have also been used for the synthesis of macromonomers. For example the synthesis of poly(D,L)-lactide macromonomers was reported [225]. It is known that aluminum alkoxides can be used as initiators for the polymerization of lactides via a coordination-insertion mechanism. A functional initiator was prepared by the reaction of triethylaluminum with 2-hydroxyethyl-methacrylate (HEMA) as shown in the following Scheme 71. 

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),... 

Until recently ethylene itself could be polymerized only at high pressure and high temperatures. Ziegler and his colleagues27 have, however, shown that ethylene, which is otherwise so inert, can be polymerized at atmospheric pressure by use of a triethylaluminum-titanium tetrachloride catalyst in a suitable solvent details for the laboratory preparation of this interesting and technically important variety of polyethylene have been given by Ziegler and Martin.28... 

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