- METHOD FOR PRODUCING HEXANEDIOL
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A process for preparing 1,6-hexanediol from a carboxylic acid mixture comprising adipic acid, 6-hydroxycaproic acid and small amounts of 1,4-cyclohexanediols which is obtained as by-product in the oxidation of cyclohexane to cyclohexanone/cyclohexanol after water extraction of the reaction mixture followed by extraction with aqueous sodium hydroxide solution, by esterification of the acids and hydrogenation comprisesa) liberating the carboxylic acids from the alkaline extract by addition of a mineral acid,b) fractionating the organic phase comprising carboxylic acids to give a distillate comprising the low molecular weight monocarboxylic acids and a residue comprising adipic acid and 6-hydroxycaproic acid,c) reacting the monocarboxylic an dicarboxylic acids present in the aqueous dicarboxylic acid mixture with a low molecular weight alcohol to give the corresponding carboxylic esters,d) freeing the esterification mixture obtained of excess alcohol and low boilers in a first distillation step,e) fractionating the bottom product in a second distillation step to give an ester fraction essentially free of 1,4-cyclohexanediols and a fraction comprising at least the major part of the 1,4-cyclohexanediols,f) catalytically hydrogenating the ester fraction which is essentially free of 1,4-cyclohexanediols andg) isolating 1,6-hexanediol from the hydrogenation product in a manner known per se in a final distillation step.
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- The products of hydrolysis of cyclic orthoesters as a function of pH and the theory of stereoelectronic control
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The acid hydrolysis of cyclic orthoesters 1, 3-6 (R=Me), and 2 (R=Me and Et) as a function of pH was studied.The bicyclic orthoester 5 yields mainly the hydroxy-ester (less than 5percent lactone), and this result is essentially independent of pH.For the other orthoesters, the relative percentage of products differs for each case and varies with pH.At pH3.These results are explained on the basis of the stereoelectronic theory for the cleavage of tetrahedral intermediates.
- Deslongchamps, Pierre,Lessard, Jean,Nadeau, Yves
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p. 2485 - 2492
(2007/10/02)
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- STEREOCHEMICAL INVESTIGATION ON ASYMMETRICALLY MODIFIED RANEY NICKEL CATALYST. MODE OF INTERACTION BETWEEN MODIFYING REAGENT AND SUBSTRATE IN THE ENANTIOFACE-DIFFERENTIATING PROCESS.
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This paper considers details on the mode of enantioface-differentiation process and the validity of a proposed sterochemical model, based on the following two series of investigations: 1) The hydrogenation of methyl acetoacetate over Raney nickel modified with NaBr and a compound whose structure is analogous to tartaric acid, and 2) the hydrogenation of various prochiral ketones over tartaric acid-NaBr- modified Raney nickel.
- Tai,Harada,Hiraki,Murakami
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p. 1414 - 1419
(2007/10/02)
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