Brown-Walker reaction

Seb cic Acid. Sebacic acid [111-20-6] C QH gO, is an important intermediate in the manufacture of polyamide resins (see Polyamides). It has an estimated demand worldwide of approximately 20,000 t/yr. The alkaline hydrolysis of castor oil (qv), which historically has shown some wide fluctuations in price, is the conventional method of preparation. Because of these price fluctuations, there have been years of considerable interest in an electrochemical route to sebacic acid based on adipic acid [124-04-9] (qv) as the starting material. The electrochemical step involves the Kolbn-type or Brown-Walker reaction where anodic coupling of the monomethyl ester of adipic acid forms dimethyl sebacate [106-79-6]. The three steps in the reaction sequence from adipic acid to sebacic acid are as follows ... 

Such reactions usually are called Brown-Walker reactions. They are of practical importance for the synthesis of higher carboxylic acids. 

Tricarballylic Acid.—The potassium salt of the diester of this acid was subjected by von Miller 2 to the Brown-Walker reaction, but without success. The ester-acid was in part regenerated. When potassium acetate, however, was added to the anode solution the expected reaction occurred ethylsuc-cinic ester was produced ... 

Brown-Walker reaction — Important generalization and extension of the Kolbe reaction (1891) (- Kolbe synthesis) leading to the synthesis of a variety of long-chain dicarboxylic acids and esters using monoesters of dicar-boxylic precursors. Among the most used application belongs the production of sebacic acid diethylester from hydrogen ethyladipate... 

Crum Brown-Walker reaction, 4 Cuprous chloride, 42, 121 1-Cyanocyclopropanecarboxylic acid, 69... 

Chromium trioxide, 60, 21 Clemmensen reaction, 60, 111 Copper chloride (CuCl) [7758-89-6], 61, 122 Crotonic acid, ethyl ester, ( )-, 61, 85 18-Crown-6-potassium cyanide complex, 60,129 Crum Brown-Walker reaction, 60, 4 Cuprous chloride, 60, 42, 121 61, 122 CYANIC ACID, PHENYL ESTER [1122-85-6], 61, 35... 

The Brown-Walker Electrosynthesis.—The salts of normal dicar-boxy lie acids do not undergo an oxidation similar to the Kolbe reaction, but alkali metal salts of the semi-esters, viz., C02Et(CH2)nC02K, do, however, give a reaction of the same type this process was discovered by Crum Brown and Walker (1891) and is generally referred to as the Brown-Walker reaction. The over-all anodic process may be represented by... 

Actually, this modification, the Brown-Walker reaction, is a well-established method for the synthesis of long-chain carboxylic acids ... 

Monomethyl adipate is fed into the electrolysis loop. This specific variation of the Kolbe reaction is known as the Brown-Walker reaction. The electrodes are bipolar (the anode is platinum-plated titanium). 

Kolbe Electrolytic Synthesis Crum Brown-Walker Reaction... 

The dimerization of half-esters is known as the Crum Brown-Walker reaction A. Crum Brown, J. Walker, ibid. 261,107 (1891). 

In aqueous and related media, most of the chemistry of organic electrode reactions is concerned with species resulting from the eventual uptake of one electron and one proton or, more usually, two electrons and two protons (in cathodic reactions) and the reverse processes in some anodic reactions. However, in the latter reactions, the formation of radical intermediates as a result of de-electronation may lead to other chemical changes, e.g., in the total oxidation of hydrocarbons to carbon dioxide in aqueous media and in other ways in the Kolbe, Hofer-Moest and Crum Brown-Walker reactions, and some other carbonium ion type rearrangements. 

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