| 摘要 |
<p>1,222,778. Pyridine carboxylic acids. LONZA Ltd. 7 Nov., 1969 [8 Nov., 1968; 24 Feb., 1969; 6 June, 1969; 1 Aug., 1969; 19 Sept., 1969], No. 54683/69. Heading C2C. Pyridine carboxylic acids are made by a continuous process comprising (a) oxidizing a heterocyclic base having a pyridine nucleus substituted in at least one position, the oxidation being effected with an excess of aqueous nitric acid at a temperature up to about 370‹ C. and a pressure up to about 500 atm., (b) adjusting the nitric acid concentration to 10-28% by weight and cooling to 0-20‹ C. to crystallize the pyridine carboxylic acid in the form of its nitrate, which is then separated from the acid mother-liquor, (c) dissolving the acid nitrate in water and adding to the solution the heterocyclic base used as starting material until the isoelectric point of the pyridine carboxylic acid to be produced is reached, (d) separating the crystallized free pyridine carboxylic acid from the mother-liquor and (e) combining the two mother-liquors for re-use in the process, after replenishment. Specified starting materials include picolines, collidines, lutidines, ethylpyridines, quinoline, isoquinoline and acridine and substitution products of any of the last three compounds. Specified products are nicotinic, isonicotinic, picolinic, cinchomeronic and isocinchomeronic acids. Examples are given of the manufacture of nicotinic acid from 2- methyl - 5 - ethylpyridine, # - picoline and quinoline.</p> |
