Abstract: A manganese dioxide catalyst for hydrolysing organic nitrites which bear readily oxidizable groups such as thiol or thioether groups to the corresponding carboxamides, and to a process for preparing the catalyst and to its use for hydrolysing organic nitrites.

Abstract: A process for preparing 2-hydroxy-4-methylthiobutyric acid ammonium salt involves reacting 3-methylthiopropionaldehyde with hydrogen cyanide to form 2-hydroxy-4-methylthiobutyronitrile, and subsequently hydrolyzing the 2-hydroxy-4-methylthiobutyronitrile by catalytic hydrolysis to form the ammonium salt of the 2-hydroxy-4-methylthiobutyric acid in a single process step. One catalyst may be used in the hydrolysis for the whole reaction. The catalyst is preferably a solid containing a titanium compound such as, e.g., titanium nitride, titanium sulfide or titanium dioxide. The 2-hydroxy-4-methylthiobutyric acid ammonium salt produced by this process is nutritional and can be used as an additive in feedstuffs.

Abstract: A manganese dioxide catalyst for hydrolysing organic nitrites which bear readily oxidizable groups such as thiol or thioether groups to the corresponding carboxamides, and to a process for preparing the catalyst and to its use for hydrolysing organic nitrites.

Abstract: The invention relates to a process for the production of 2-hydroxy-4-methylthiobutyric acid ammonium salt from 2-hydroxy-4-methylthiobutyronitrile, and to the use of the 2-hydroxy-4-methylthiobutyric acid ammonium salt produced by this process.

Abstract: A process for the preparation of &agr;-amino acids by hydrolysis of hydantoins in the presence of water and at least one metallic oxide under conditions such that all the starting materials are completely dissolved in the water as a result of high pressure and high temperature and only one further phase is present in the reactor in addition to the metallic oxide phase.

Abstract: A process for the preparation of &agr;-amino acids by hydrolysis of hydantoins in the presence of water and at least one metallic oxide under conditions such that all the starting materials are completely dissolved in the water as a result of high pressure and high temperature and only one further phase is present in the reactor in addition to the metallic oxide phase.

Abstract: A process for the preparation of racemic amino acids, characterized in that an acylamino acid of the formula R1—CH(NH—CO—R2)COOH wherein R1 is hydrogen, a linear, branched or cyclic alkyl that has from 1 to 7 carbon atoms and that may contain substituents such as a hydroxyl, alkyloxy or alkylthio group; and R2 is a hydrogen atom or an alkyl having from 1 to 3 carbon atoms; is heated in the presence of water, in a pressure-resistant vessel, to a temperature in the range from 110° C. to 220° C. and is hydrolyzed.

Abstract: A process for the preparation of racemic amino acids, characterized in that an acylamino acid of the formula

Abstract: A process for preparing esterified chroman compounds from 2,6,6-trimethylcylohex-2-ene-1,4-dione, wherein the esterified intermediates are reacted directly to give the desired chroman derivatives without an additional purification step.

Abstract: A process for the production of 2,3,5-trimethylhydroquinone diesters by aromatization of 2,6,6-trimethyl-2-cyclohexene-1,4-dione (4-oxoisophorone, ketoisophorone, KIP) with an acylating agent and an acidic soluble or insoluble catalyst, which process may be operated alternatively continuously or discontinuously. The process includes the following steps: a) a carboxylic anhydride having a C1 to C4 alkyl residue is used as the acylating agent, b) after the reaction, a proportion of the resultant carboxylic acid is optionally removed by distillation, c) the reaction solution is cooled, d) the product which has crystallized out is separated and washed, and e) the filtrate is returned to step a).

Abstract: Aliphatic alkanals with a water content of greater than 300 ppm which are stable in storage, and a method of improving the storage stability of these aliphatic alkanals, especially of substituted, sulfur-containing alkanals. The formation of oligomers, polymers and condensation products from elimination reactions and oxidation and the subsequent reactions of the products formed results in undesired impurities that are largely prevented by the addition of an organic acid that forms metal complexes and, optionally, alkanolamines or trialkanolamines.

Abstract: Preparation of 2,3,5-trimethylhydroquinone diesters by rearrangement of 2,6,6-trimethylcyclohex-2-ene-1,4-dione (4-oxo-isophorone, ketoisophorone) in the presence of a solid, acid catalyst and an acylating agent, for example carboxylic acid anhydrides or carboxylic acid halides. The 2,3,5-trimethylhydroquinone diester may then optionally be saponified to the free 2,3,5-trimethylhydroquinone, which is a valuable building block in the synthesis of vitamin E.

Abstract: A process for the production of .alpha.-tocopherol esters, derivatives or homologs thereof of the general formula ##STR1## in which the mono- or diester of a hydroquinone is reacted with an allyl alcohol derivative or an allyl alcohol in the presence of zinc halides and proton-liberating acids at a temperature of 25.degree. to 100.degree. C.

Abstract: An improved process for the production of 2,3,5-trimethylhydroquinone by rearrangement of 4-oxoisophorone (ketoisophorone, 3,5,5-trimethyl-2-cyclohexen-1,4-dione) to yield a trimethylhydroquinone diester and the subsequent saponification thereof. Trimethylhydroquinone is in turn an important starting material for the production of vitamin E.

Abstract: The direct saponification of methionine nitrile obtained from methylmercaptopropionaldehyde, prussic acid and ammonia gives low yields, catalyst and educt losses and unwanted side-products. The aim of the invention is therefore to provide a method which can be carried out without isolating the intermediate products, in particular continuously, and with low losses. The ketone used is recovered in high yields after amide saponification since this liberates the ketone from side-products. In order to recover the ammonia, it is necessary for the ammonia to be substantially freed of ketone, the mixture of ammonia, ketone and water obtained being separated under pressure in a separation column. When the amide is saponified at .gtoreq.160.degree. C., amide concentrations of less than 25% by wt. are preferred. Methionine nitrile is produced by treatment with at least 4 equivalents of .gtoreq.50% by wt. ammonia at between 40.degree. and 80.degree. C./or between 5 and 60 min.

Abstract: Aqueous solutions of free, neutral .alpha.-amino acids are recovered from aqueous solutions of their alkali-metal salts. Two equally large rectifying columns filled with a strongly acidic cation exchanger in the H.sup.+ form are used, the discharge of the first column being connected to the head of the second column. The solution of the alkali-metal salt is at first delivered to the head of the first column, then the residual solution, reduced by the alkali-metal cations adsorbed in the exchanger, is displaced to the second column by means of the addition of water. A product-free forerun is first separated at the discharge of the second column and, when free .alpha.-amino acid begins to exit in the flow-off from the second column, the receiver is changed and the delivery of water to the head of the first column continues further until a mixed pH between 5 and 7 has been achieved in the receiver.

Abstract: Pure L-leucine is obtained from an aminoacid mixture which contains at least 45 weight percent L-leucine, at most 40 weight percent L-isoleucine and at most 25 weight percent of other aminoacids by acetylating the mixture, precipitating the acetylation product by acidification, subjecting the acetylation product to a saponification by an L-aminoacid acylate until 30 to 95% of the N-acetyl-L-leucine employed is saponified and isolating the L-leucine from the saponification mixture.

Abstract: The separation of L-leucine and L-isoleucine in aminoacid mixtures containing at least 30 weight percent L-leucine, at most 70 weight percent L-isoleucine and at most 40 weight percent of other aminoacids is accomplished by acetylating the mixture, precipitating the acetylation product by acidification, subjecting the aqueous solution to a saponification by an L-aminoacid acylase until 25 to 95% of the N-acetyl-L-leucine is saponified, crystallizing pure L-leucine from the saponification mixture and separating it off, isolating N-acetyl-L-isoleucine from the mother liquor and saponifying it in known manner to the free aminoacid and isolating the free aminoacid.

Abstract: The subject matter of the invention is a process for the recovery of S-(carboxymethyl)-(R)-cysteine and S-(carboxymethyl)-(S)-cysteine from a mixture of the two enantiomers. The mixture to be separated is dissolved in water in the presence of sufficient ammonia that the ammonium salt solution formed has a pH between 6 and 9. Then there is brought about in the solution of ammonium salt a state of supersaturation by the addition of seeding crystals of the ammonium salt of one of the two enantiomers, insofar as the starting material contains one of the two enantiomers in excess, the ammonium salt of this enantiomer, the ammonium salt of one of the two enantiomers is brought to crystallization and separated off. Subsequently by addition of seeding crystals of the ammonium salt of the other enantiomers to the remaining mother liquor the ammonium salt of this enantiomer is likewise brought to crystallization and separated off.

Abstract: There are prepared specific .alpha.-aminocarboxylic acids or their methyl, ethyl, or benzyl esters in which the .alpha.-amino group is substituted by a 3-cyanopropanoyl group. The compounds are useful for producing the corresponding derivatives of 4-aminobutyramide ("Gabamide") by catalytic hydrogenation of the cyano group.