Bayer Aktiengesellschaft

Karl Heinz Neumann

Helmut Fiege

Reinhard Langer

Lars Rodefeld

Wolfram Kissener

Dieter Heitkamp

The present invention relates to the preparation of nitrobenzoic acids by oxidizing particular nitrotoluenes, nitrobenzyl alcohols, esters and/or ethers in the presence of nitric acid at elevated temperature and elevated pressure. It has been found that the particular nitrotoluenes, nitrobenzyl alcohols, esters and/or ethers may be oxidized particularly reliably and in high yields using nitric acid to the benzoic acid derivatives when they are metered into the nitric acid.

Method for producing substituted nitro benzoic acids by oxidation of corresponding nitro toluenes, nitro benzyl alcohols, esters and/or ethers

Method for producing substituted nitro benzoic acids by oxidation of corresponding nitro toluenes, nitrol benzyl alcohols, esters and/or ethers

Hydroxypivalic acid is obtained from aqueous solutions by removal of the water by azeotropic distillation and subsequent crystallization from a solvent mixture which is composed of a polar and a non-polar component. The distillation is carried out under reduced pressure and at a maximum bottom temperature of 90.degree. C., until a residual water content of at least 0.1% of the total weight of the resulting solution is achieved.

Process for isolating hydroxypivalic acid from aqueous solution

2,3-dichloro-nitrobenzene can be prepared by nitration of 1,2-dichlorobenzene using an anhydrous mixture of phosphoric acid, sulphuric acid and nitric acid. The conditions according to the invention displace the ratio of 2,3,-dichloro-nitrobenzene and 3,4-dichloro-nitrobenzene in favor of the 2,3-isomer.

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Augustin, Germany

Karl Heinz Neumann