Ethylene oxidation with CuCl

Compared with these methods, the palladium-catalyzed oxidation of 1-olefins described here is more convenient and practical. The industrial method of ethylene oxidation to acetaldehyde using PdCl2-CuCl 2-O2 original reaction of this type. The oxidation of various olefins has been carried out. ... 

Starting from Benzene. In the direct oxidation of benzene [71-43-2] to phenol, formation of hydroquinone and catechol is observed (64). Ways to favor the formation of dihydroxybenzenes have been explored, hence CuCl in aqueous sulfuric acid medium catalyzes the hydroxylation of benzene to phenol (24%) and hydroquinone (8%) (65). The same effect can also be observed with Cu(II)—Cu(0) as a catalytic system (66). Efforts are now directed toward the use of Pd° on a support and Cu in aqueous acid and in the presence of a reducing agent such as CO, H2, or ethylene (67). Aromatic... 

Other Methods. A variety of other methods have been studied, including phenol hydroxylation by N2O with HZSM-5 as catalyst (69), selective access to resorcinol from 5-methyloxohexanoate in the presence of Pd/C (70), cyclotrimerization of carbon monoxide and ethylene to form hydroquinone in the presence of rhodium catalysts (71), the electrochemical oxidation of benzene to hydroquinone and -benzoquinone (72), the air oxidation of phenol to catechol in the presence of a stoichiometric CuCl and Cu(0) catalyst (73), and the isomerization of dihydroxybenzenes on HZSM-5 catalysts (74). 

The Wacker-Hoechst process has been practised commercially since 1964. In this liquid phase process propylene is oxidized to acetone with air at 110-120°C and 10-14 bar in the presence of a catalyst system containing PdCl2. As in the oxidation of ethylene, Pd(II) oxidizes propylene to acetone and is reduced to Pd(0) in a stoichiometric reaction, and is then reoxidized with the CuCl2/CuCl redox system. The selectivity to acetone is 92% propionaldehyde is also formed with a selectivity of 2-4%. The conversion of propylene is more than 99%. 

The essence of the Wacker process is the invention of the reoxidation process for Pd° by using CuCh as a cocatalyst. Cu" salts are good reoxidants, but chlorination of carbonyl compounds takes place with CuCh. For example, chloroacetaldehyde is a by-product of the Wacker process. Chlorohydrin is another by-product from the reaction of ethylene with PdCh and CuCb. - Thus, a number of other reoxidants were introduced. When CuCl, pretreated with oxygen, is used, no chlorination of ketones takes place and the rate of the reaction is higher. - Also Cu(N03)2 and Cu(OAc)2 have been used. Oxidation of cy-clopentene with PdCl2/Fe(C104)3 combined with electrochemical oxidation was carried out. Benzoqui-none was used at first by Moiseev et al and later by many other researchers as a good reoxidant, but a stoichiometric amount is necessary. The oxidation of alkenes can be carried out smoothly with catalytic... 

The Wacker process for the oxidation of ethylene to acetaldehyde with PdClj/CuCls at 100°C (212°F) with 95 percent yield and 95 to 99 percent conversion per pass. 

This is an interesting situation in organic technology and synthesis. Examples are the dissolution of acetylene in an aqueous slurry of CuCl as a step in the manufacture of propylene oxide and the alkylation of naphthalene with ethylene in a liquid medium in the presence of BF3-phosphoric acid as a dissolved catalyst. Note that the presence of the dissolved catalyst does not in any way alter the physical features of the system. 

Zirconacyclopentene 1-5 could also be applied in synthetic reaction (Scheme 1.8). For example, in the presence of CuCl and iodine, oxidative demetallation of 1-5 gives cyclobutene derivatives [34]. Reaction of 1-5 with acid chloride gives tri-subslimted cyclopentadiene derivatives [35]. This research group also reported zirconocene-mediated cyclization of alkyne, ethylene, and two molecules of aldehyde toward synthesis of 2-alkenyl tetrahydrofuran [36]. 

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