- Process for the separation, by countercurrentwise liquid-liquid extraction, of a glyoxal diacetal from a crude mixture comprising it
-
The invention relates to a method for separating a diacetal of the glyoxal of a raw mixture comprising said diacetal of the glyoxal and a monoacetal of the glyoxal, by means of counter-current liquid-liquid extraction.
- -
-
Page/Page column 4
(2008/06/13)
-
- METHOD FOR PROCESSING COMPOSITIONS CONTAINING 1,1,2,2-TETRAMETHOXYETHANE AND GLYOXAL DIMETHYL ACETAL
-
Disclosed is a method for processing an aqueous composition containing 1,1,2,2-tetramethoxyethane, glyoxal dimethyl acetal, and methanol by means of distillation. Said method is characterized in that the composition is processed in a partition column so as to form low-boiling, medium-boiling, and high-boiling fractions. A partition is disposed in the longitudinal direction of the partition column such that a common top column area, a common bottom column area, a feeding zone comprising a rectification section and a stripping section, and a removing zone encompassing a stripping section and a rectification section are created. The aqueous composition is delivered to the central area of the feeding zone.
- -
-
Page/Page column 17-23, chart 1/2; 2/2
(2008/06/13)
-
- Process for the continuous preparation of acetals of alpha,beta-dicarbonyl compounds
-
The production of linear and cyclic acetals of formulae (I) and (Ia) respectively comprises reacting alpha ,beta -dicarbonyl compounds (II) of the type R-CO-CO-R' with alcohols (III) of the type ROH or HO-X-OH continuously in countercurrent apparatus: (RO)2CRCR'(OR)2 (I). The production of linear acetals (I) and cyclic acetals (Ia) comprises reacting alpha ,beta -dicarbonyl compounds, selected from glyoxal and higher dialdehydes, diketones and ketoaldehydes with 1-8 carbon (C) alkyl, 3-8 C cycloalkyl, 2-8 C alkenyl, 2-8 C alkynyl and/or 6-18 C aryl groups, with 1-8 C alkanols, 3-8 C cycloalkanols, 2-8 C alkenols, 2-8 C alkynols or diols with a 2-12 C alk(en)ylene chain continuously in a countercurrent apparatus. [Image] R and R' : H, 1-8 C alkyl, 3-8 C cycloalkyl, 2-8 C alkenyl, 2-8 C alkynyl or 6-18 C aryl R : 1-8 C alkyl, 3-8 C cycloalkyl, 2-8 C alkenyl or 2-8 C alkynyl or a chain X; and X : 2-12 C alkylene or 2-12 C alkenylene linking both O atoms of the alpha -C atom and/or both O atoms of the beta -C atom.
- -
-
-
- Process for continuously preparing acetals of alpha, beta-dicarbonyl compounds
-
The present invention relates to a process for preparing acetals of α,β-dicarbonyl compounds of the general formula (R″O)2CRCR′(OR″)2 which are obtained by continuous reaction of α,β-dicarbonyl compounds R—CO—CO—R′ with alcohols R″OH or HO—X—OH in countercurrent.
- -
-
-
- Preparation of diacetals of glyoxal
-
A process is described for preparing diacetals of glyoxal by reacting from 40 to 75% by weight aqueous glyoxal with monohydric alcohols in the presence of an acid catalyst, which comprises leaving a liquid mixture which, at the beginning of the reaction, comprises alcohol and glyoxal in a molar ratio of at least 15:1 and also water in a concentration of not more than 8% by weight in contact with the acid catalyst until concentration in the reaction mixture of the diacetal formed reaches at least 70% of the equilibrium concentration without more than 5% by weight of the alcohol used having already been distilled off.
- -
-
-
- Ozonolyse von Olefinen, III: Saeurekatalysierte Ozonolyse von 3-Hexen-1,6- und 2-Penten-1,5-dicarbonylderivaten
-
The ozonolysis of mono-unsaturated compounds containing the structural element =CH-CH2-R was investigated.Reductive ozonolysis of (E)-3-hexene-1,6-dioic acid gives methyl 3,3-dimethoxypropanoate (2), whereas ozonolysis of dimethyl (E)-3-hexene-1,6-dioate (1a) and (Z)-1,1,6,6-tetramethoxy-3-hexene (1b) in a methanolic solution of HCl leads to a mixture of 2, dimethyl malonate (3a) and 1,1,3,3-tetramethoxypropane (3b).The homologuos derivatives, dimethyl glutaconate (4a) and 1,1,5,5-tetramethoxy-2-pentene (4b), were ozonized to give mixtures of 2, 3, dimethyl oxalate (5), methyl 2,2-dimethoxyacetate (6a), and 1,1,2,2-tetramethoxyethane (6b).The ratios of the various reaction products were determined by gas chromatography.In each case the formation of the bifunctional derivatives 2 and 6a was favoured.
- Poklukar, Norbert,Mittelbach, Martin
-
p. 203 - 207
(2007/10/02)
-
- THE MONOACETALIZATION OF GLYOXAL: A DIRECT SYNTHESIS OF 2,2-DIMETHOXY AND DIETHOXY ETHANALS
-
Direct monoacetalization of glyoxal by methanol or ethanol is described.Yields of 50 to 70percent are obtained.
- Sangsari, Farid Hamedi,Chastrette, Francine,Chastrette, Maurice
-
p. 1343 - 1348
(2007/10/02)
-
- Les dialkoxy-2,2 ethanals, synthons difonctionnels a deux carbones : preparation par acetalisation du glyoxal et quelques applications en synthese
-
Known for a long time, 2,2-dialkoxy ethanals had to be prepare by rather tedious indirect pathways since monoacetalization of glyoxal was unknown.We discovered that it is possible to acetalize only one of the glyoxal functions using a great excess of alcohol, in the presence of an active enough catalyst.With careful monitoring of the reaction, 50 to 70 percent yield of monoacetals is obtained.The monoacetal is formed much quicker than the diacetal and the maximum yield is rather quickly obtained; with further elimination of water, diacetalization proceeds at the expense of the monoacetal.Depending on azeotropic compositions and boiling points, one of the following methods is used: 1.General method: 40 percent aqueous glyoxal (1 mol), alcohol (10 mol), catalyst (0.01 to 0.1 equivalent) and solvent are refluxed with azeotropic water extraction.The monitored (GC) reaction is stopped at the most favourable moment. 2.Method without solvent, convenient for unreactive alcohols, such as i-butanol: water is evaporated from glyoxal solution (1 mol); the residue, alcohol (10 mol) and catalyst are refluxed with water azeotropic extraction. 3.Method without solvent and without water azeotropic extraction: dehydrated glyoxal (1 mol) is refluxed with alcohol (10 mol) and catalyst.This method is the most convenient for methanol and ethanol.This sample and inexpensive preparation of 2,2-dialkoxy ethanals prompted us to perform syntheses of difunctional molecules otherwise only tediously accessible, since easily obtained functionalized acetals can be hydrolysed to functionalized aldehydes which constitute interesting synthons.Hydride or catalytic reduction as well as organometallic reactions lead to alcohols, further hydrolysed into 2-hydroxy aldehydes or oxidized to give way finally to α-ketoaldehydes for which this method provides a general synthetic pathway.From the oximes, prepared by classical methods, nitriles and amines can be obtained.Starting directly from the aldahydes, amines may be prepared by hydrogenation in the presence of ammonia or amines.The reaction of 2,2-dialkoxy ethanals with amides provides hydroxy and alkoxy acetal amides.The Cannizzaro reaction was also investigated; the same reactivity is displayed by formaldehyde and glyoxal monoacetals.Other reactions, among which Wittig and Wittig-Horner, are presently being studied in our laboratory.
- Stambouli, Abdelhamid,Hamedi-Sangsari, Farid,Amouroux, Roger,Chastrette, Francine,Blanc, Alain,Mattioda, Georges
-
-
- DIISOPROPOXY- AND DI-tert-BUTOXYETHYNE STABLE ACETYLENE DIETHERS
-
The rather stable acetylene diethers diisopropoxy- and di-t-butoxyethyne are prepared either from glyoxal or dioxane.Catalytic hydrogenation, acid-catalyzed hydration and formation of the corresponding hexacarbonyl dicobalt complexes are reported.
- Bou, Anna,Pericas,Miquel A.,Serratosa, Felix
-
p. 1441 - 1449
(2007/10/02)
-