Process for production of lower alkanoic acids
AssigneeWyckoff Chemical Company, Inc.
InventorAndrew G. Zeiler
Life of this patent
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Abstract
A process for production of lower alkanoic acids. A reaction mixture comprising a substituted malonic acid, an acid catalyst, and a limited amount of water is heated to a temperature sufficient to hydrolyze and decarboxylate the ester. The reaction mixture is maintained at the temperature by periodic addition of limited amounts of water, and the reaction is continued for a period of time sufficient to remove substantially all of the alcohol and carbon dioxide generated by the hydrolysis reaction, thereby converting substantially all of the ester to alkanoic acid. The process is particularly useful for the production of valproic acid.
Claims28
A process for production of alkanoic acids of the formula ##STR5## wherein R.sup.1 is an alkyl group containing from about 2 to 10 carbon atoms, or a branched alkyl, cycloalkyl or aryl group containing from about 3 to 10 carbon atoms and R.sup.2 is H or an alkyl group containing from about 1to 10 carbon atoms, or a branched alkyl, cycloalkyl or aryl group containing from about 3 to 10 carbon atoms, the process comprising:
- heating a reaction mixture comprising (1) a substituted malonic ester of the formula ##STR6## wherein R.sup.1 and R.sup.2 represent alkyl, branched alkyl, aryl or cycloalkyl groups as described above, and R.sup.3 and R.sup.4 represent lower alkyl groups, (2) water, and (3) an acid catalyst to a temperature sufficient to hydrolyze and decarboxylate the ester, said acid catalyst being at least partially soluble in the ester at temperatures above about 100.degree. C. and being selected from the group consisting of arylsulfonic acids, alkylsulfonic acids and mixtures thereof, said water being limited to an amount insufficient for complete extraction of the acid catalyst from the ester to the water;
- removing substantially all of the alcohol and carbon dioxide generated by the hydrolysis and decarboxylation from the reaction mixture including alkanoic acid and the catalyst by maintaining the reaction mixture at said temperature for a period of time sufficient to drive the hydrolysis reaction substantially to completion;
- and
- separating the catalyst from the alkanoic acid.
A process for production of alkanoic acids of the formula ##STR7## wherein R.sup.1 is an alkyl group containing from about 2 to 10 carbon atoms, or a branched alkyl, cycloalkyl or aryl group containing from about 3 to 10 carbon atoms and R.sup.2 is H or an alkyl group containing from about 1 to 10 carbon atoms, or a branched alkyl, cycloalkyl or aryl group containing from about 3 to 10 carbon atoms, and wherein the sum of the carbon atoms in R.sup.1 and R.sup.2 does not exceed about 16, comprising:
- preparing a reaction mixture consisting essentially of a substituted malonic acid of the formula ##STR8## wherein R.sup.1 and R.sup.2 represent alkyl, branched alkyl, aryl or cycloalkyl groups as described above, and R.sup.3 and R.sup.4 represent lower alkyl groups;
- an acid catalyst, said acid catalyst being at least partially soluble in the ester at temperatures above 100.degree. C. and comprising an arylsulfonic acid, an alkylsulfonic acid or a mixture thereof;
- and water, the water in the reaction mixture being limited to an amount insufficient for complete extraction of the acid catalyst from the ester to the water;
- heating the reaction mixture to a temperature sufficient to hydrolyze and decarboxylate the ester;
- maintaining the reaction mixture at said temperature by periodic addition of water in said limited amount to the reaction mixture, and continuing to heat the reaction mixture at said temperature for a period of time sufficient to remove substantially all of the alcohol and carbon dioxide generated by the hydrolysis reaction, thereby converting substantially all of the ester to alkanoic acid;
- and
- separating the catalyst from the alkanoic acid.
A process for preparing valproic acid comprising:
- preparing a reaction solution in a reflux flask equipped with a distillation column, said reaction solution consisting essentially of a substituted malonic ester selected from the group consisting of diethyl dipropylmalonate and dimethyl dipropylmalonate, an acid catalyst selected from the group consisting of an arylsulfonic acid, an alkylsulfonic acid and mixtures thereof, and water, the acid catalyst being at least partially soluble in the ester at temperatures above 100.degree. C., and the water being limited to an amount insufficient for complete extraction of the acid catalyst from the ester to the water;
- heating the reaction mixture to a temperature sufficient to hydrolyze and decarboxylate the ester, said temperature being between about 100.degree.-155.degree. C.;
- maintaining the reaction mixture at said temperature by periodic addition of water in said limited amount to the flask, and continuing to heat the reaction mixture at said temperature for a period of time sufficient to remove substantially all of the ethanol and carbon dioxide generated by the hydrolysis and decarboxylation of the ester, thereby converting substantially all of the ester to valproic acid;
- separating the catalyst from the valproic acid;
- and
- purifying the valproic acid.
Dependencies are inferred from the claim text.