Henkel reaction

In a similar process, potassium benzoate heated with cadmium salts dispropor-tionates to benzene and 44. The term Henkel reaction (named for the company that... 

In a similar process, potassium benzoate heated with cadmium salts disproportionates to benzene and 43. The term Henkel reaction (named for the company that patented the process) is used for these rearrangements.451 An SeI mechanism has been suggested.452 The ter-phthalate is the main product because it crystallizes from the reaction mixture, driving the equilibrium in that direction.453... 

Henkel reaction. Industrial-scale thermal rearrangement or disproportionation of alkaline salts of aromatic acids to symmetrical diacids in the presence of cadmium or other metallic salts. 

Other references related to the Henkel reaction are cited in the literature. 

Position shift of carboxyl Disproportionation of arylcarboxylic acids Henkel reaction or Raecke process... 

Henkel reaction 13, 699 Herz ring closure 21, 646 Helerocyclics (s. a. Ring closure)... 

Haworth Methylation Haworth Phenanthrene Synthesis Hayashi Rearrangement Heck Reaction Helferich Method Hell-Volhard-Zelinsky Reaction Henkel Process Henkel Reaction Henry Reaction... 

Mitsubishi Chemical Industries, Ltd. practiced a Henkel II technology starting with toluene to produce benzoic acid. Reaction of benzoic acid with potassium hydroxide resulted in potassium benzoate, which was subjected to a disproportionation reaction to produce dipotassium terephthalate and benzene. Dipotassium terephthalate reacted with sulfuric acid, and the resulting terephthahc acid was recovered by filtration and drying (65,66). Here, dipotassium sulfate was the by-product. 

In addition to the nitrile and alcohol routes for fatty amine preparation, processes have been described by Unocal and Pennwalt Corporation, using an olefin and secondary amine (14—16) by Texaco Inc., hydrogenation of nitroparaffins (17—20) by Onyx Corporation, reaction of an alkyl haUde with secondary amines (21,22) by Henkel Cie, GmbH, reduction of an ester in the presence of a secondary amine (23) by catalytic hydroammonolysis of carboxyhc acids (24) and by the Hofmann rearrangement (25). 

The first representative of the acetylenic derivatives, 3(5)-ethynylpyrazole, was obtained by condensation of diacetylene with diazomethane by Kuhn and Henkel (41LA279) and later by other authors (69IZV2546), and by reaction of acetylene with diazopropyne (62AG252 68LA113) (Scheme 2). 

The reaction is conducted in the melt, in the presence of carbon dioxide under pressure, catalyzed by zinc or cadmium compounds. Invented by B. Raecke at Henkel, Germany. Improved variations of this process, known as Henkel I and Henkel II, were operated by several other companies, but by 1975 had been abandoned in favor of various other methods of oxidizing /j-xylcne. 

Molecular graphics (Henkel and Clarke, 1985) refers to a technique for the visualization and manipulation of molecules on a graphical display device. The technique provides an exciting opportunity to augment the traditional description of chemical structures by allowing the manipulation and observation in real time and in three dimensions, of both molecular structures and many of their calculated properties. Recent advances in this area allow visualization of even intimate mechanisms of chemical reactions by graphical representation of the distribution and redistribution of electron density in atoms and molecules along the reaction pathway. 

Among the various reactions catalyzed by bases, we have selected (i) the polymerization of ethylene oxide catalyzed by MgO (260), (ii) the closely related reaction of ethylene oxide with alcohols on basic hydrotalcites to give polyoxyethylene polymer (the Henkel process), (iii) the phenol alkylation with methanol on MgO (General Electric and BASF processes) (261), and (iv) phenol animation to give aniline on MgO (the USS process) (262). 

The same mechanism can be postulated for the reaction of ethylene oxide and an alcohol ROH (as in the Henkel process) (261), leading to the catalytic formation of the polymeric R0(CH2CH20) H (with a narrow molecular weight range). In this case it is the alcohol molecule (instead of water) that displaces the polymer from the surface and gives the final product. 

Hoechst and Henkel first attempted ethoxylation of these materials in 1989 with alkali/alkali earth and aluminium hydroxycarbonates respectively but these catalyst activities were too low for commercial application [24, 25]. Vista, in 1990, patented [26] the use of activated calcium and aluminium alkoxides and Lion Corporation, in 1994, filed a patent using magnesium oxide [27]. There was a flurry of activity in the 1990s and Michael Cox and his co-workers have written most of the literature [28-30]. The proprietary catalysts are more expensive than those for standard alcohol ethoxylates and generally have to be removed from the final product. They are more reactive than the standard alkali catalysts with the result that the reaction proceeds faster and at lower temperature and uses less catalyst. 

Direct synthesis is simple and covered by patents with all major producers (Henkel, Huls, Akzo, BASF) having patents in the field from 1988 onwards [49-51]. Here, the carbohydrate is suspended in the alcohol as very fine particles and, in some cases, crystal water is removed to minimise side reactions. 

Henkel [24] used the novel 3-A, A (dhnethylamino)-isocyanoacrylate-wang resin (xxvi) for the synthesis of imidazole-4-carboxylic acids (xxvii) in a microwave reaction condition. 

Henkel has developed a continuous countercurrent esterification using a doubleplate reaction column. The technology is based on the principle of an esterification reaction with the simultaneous absorption of the superheated methanol vapor and desorption of the methanol-water mixture (15). 

Figure 6 shows the Henkel continuous process of fatty acid esterification. The reaction is carried out at a pressure of approximately 1000 kPa and a temperature of 240°C. One advantage of this process is the excess methanol can be kept significantly lower at 1.5 1 molar ratio of methanohfatty acid versus the batch process at 3—. 1 molar ratio. The methyl ester, having undergone distillation, does not require further refining. The excess methanol is rectified and reused (15). 

Alkyl phosphates, also coco based, are formed by the reaction of fatty alcohol with phosphorous pentoxide. The product is a mixture of monoesters and diesters. Its sodium salt (MAP) is reportedly mild and is used in facial wash, such as Kao s Biore. Other uses are as antistatics in textile auxiliaries, corrosion inhibitors, surfactant additives for extreme pressure (EP) lubricants, and surfactant components in alkali and acid cleaners. Coco-based alkyl polyglycosides (APG) have been successfully produced and marketed by Henkel in the United States. The alkyl polyglycoside fuUy satisfies the demand for a mild surfactant and is completely biodegradable. 

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