Process for separating mixtures of 3- and 4-nitrophthalic acid

Details Process for separating mixtures of 3- and 4-nitrophthalic acid Process for separating mixtures of 3- and 4-nitrophthalic acid

1979-05-31

1981-08-18

Gerstl, Robert

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acids and salts thereof

C07C 7946

Patent

active

042847974

ABSTRACT:
A novel improved process for separating mixtures of 3- and 4-nitrophthalic acid is described. The said process comprises treating a mixture of 3- and 4-nitrophthalic acid, which mixture is free from inorganic acid residues, in an aqueous-organic medium containing 1-20 percent by volume of water, at a temperature of between 20.degree. and 100.degree. C., stepwise with a base capable of forming salts of 3- and 4-nitrophthalic acid, which salts are essentially insoluble in the reaction medium, the treatment being carried out by adding base until a pH value of about 2.8 is obtained, separating the precipitating product consisting mainly of a 3-nitrophthalic acid mono-salt, subsequently precipitating, by the addition of further base, a product consisting principally of a 4-nitrophthalic acid salt, and finally converting the resulting nitrophthalic acid salts separately into the corresponding free acids, and optionally purifying these. The 3- and 4-nitrophthalic acid can be obtained by the process according to the invention in a simple manner in an isomer-free form and in good to very good yields.

REFERENCES:
patent: 1549885 (1925-08-01), Littmann
Hine, Physical Organic Chemistry, pp. 81-103 (1962).

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