510,638. Butane polycarboxylic acids. JOHNSON, G. W. (I.G. Farbenindustrie Akt.- Ges.) July 20, 1938, No. 21573. [Class 2 (iii)] Butane polycarboxylic acids are produced by oxidising with nitric acid #<;4>; cyclohexenes which are substituted in at least one of the positions 1 and 2 of the hexene nucleus by carboxylic, carboxylic anhydride, cyano or keto groups. An oxidation catalyst, e.g. an alkali molybdate or vanadate, may be used. The #<;4>; cyclohexenes are prepared by condensing butadiene or other hydrocarbons of the butadiene series, 'e.g. isoprene, cyclohexadiene, with olefine compounds in which the carbon double linkage is in the alpha position to at least one carboxyl, cyano or keto group, e.g. crotonic acid, maleic acid, maleic anhydride, cinnamic acid, acrylic nitrile, cinnamic acid nitrile, maleic acid dinitrile, vinylalkyl ketones or vinyl benzoyl ketone. In examples (1) #<;4>;-cyclohexene-1-2 dicarboxylic anhydride is oxidised to butane- 1.2.3.4-tetracarboxylic acid and by boiling this with acetic anhydride the dianhydride is obtained ; (2) 2 - phenyl - #<;4>; - cyclohexene-1- carboxylic acid is oxidised to 2-phenylbutane- 1.3.4-tricarboxylic acid; (3) #<;4>;-cyclohexene-1- methyl ketone is oxidised to butane-1.2.4- tricarboxylic acid; (4) #<;4>;-cyclohexene-1-nitrile is oxidised to a mixture of butane-1.2.4- tricarboxylic acid and 2-cyanbutane-1.4-dicarboxylic acid.;4>;4>;4>;4>;4>;4>