- Process for producing pyromellitic acid
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A process for producing pyromellitic acid which comprises oxidizing 2,4,5-trimethylbenzealdehyde and/or its oxidized derivative in the presence of a catalyst containing iron, manganese and bromine, or additionally containing zirconium or cerium continuously or semi-continuously using aqueous acetic acid solvent and 0.05-2% by weight of bromide ion. The catalyst used in the present invention has high activity, and the catalyst solution has low corrosive because the reaction is performed at low bromide concentration by using a solvent of aqueous acetic acid. So pyromellitic acid is produced industrially advantageously in high yield continuously or semi-continuously which has been a major difficulty up to now.
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- Process for preparing alkyl- and arylmalonic acids
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Alkyl- and arylmalonic acids of the formula I STR1 where R1 =H, C1 -C12 -alkyl, phenyl, C1 -C4 -alkylphenyl, C2 -C4 -dialkylphenyl, R2 =C1 -C12 -alkyl, phenyl, C1 -C4 -alkylphenyl, C2 -C4 -dialkylphenyl or R1 +R2 =--CH2 --CH2 --, are prepared by alkaline saponification by hydrolyzing the corresponding C1 -C4 -alkyl esters of the malonic acid of formula I, with alkali metal hydroxide dissolved in an aqueous alkali metal salt solution containing salt at 90-100% of saturation, acidifying the hydrolysis product with a mineral acid, removing the precipitated alkali metal salt which forms upon acidification, and extracting the alkyl- and arylmalonic acid formed from the aqueous solution with the aid of an organic solvent.
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- Preparation of N-substituted maleimides by use of tin catalysts
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A process for the preparation of N-substituted maleimides by conducting heat-dehydration and dehydrating imidization of N-substituted maleamic acids under azeotropic distillation of generated water in a solvent mixture containing a solvent capable of forming water azeotrope and an organic aproptic polar solvent, in the presence as catalyst of metallic tin, tin oxide, a tin salt of a maleamic acid or a tin compound which forms a thin salt of the N-substituted maleamic acid in the reaction system.
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- Nucleophilic cleavage of the Si-C bond in organotrifluorosilanes and diorganodifluorosilanes
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The Si-C bond in aryltrifluorosilanes, 4-XC6H4SiF3 (X = H, CH3, Cl, Br or NO2), is readily cleaved by mercury(II) salts HgY2 (Y = Cl, Br, I, CN or OCOCH3) or HgO to form organomercurials of the type 4-XC6H4HgY or (4-XC6H4)2Hg, respectively.Electron-donating substituent X facilitate the reaction, whereas electron-withdrawing substituents make it more difficult.Mercury(II) salts and mercury(II) oxide also cleave the Si-C bond in chloromethyltrifluorosilanes, F3Si(CH3-nCln) (n = 1-3) to produce the corresponding organic mercurials containing an Hg(CH3-nCln) group.The substitution of the fluorine atom in organotrifluorosilanes by an alkyl group hinders the bond cleavage between the silicon atom and the electronegative organic substituent.The reactions studied are believed to follow a nucleophilic mechanism involving asynchronous formation of a four-centered transition state with a pentacoordinate silicon atom.
- Voronkov, M. G.,Chermov, N. F.,Perlova, E. M.
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p. 225 - 230
(2007/10/02)
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