O-Azobenzoic acid

The zinc-dust treatment serves to reduce and remove small amounts of azo compounds (notably o-azobenzoic acid) which always discolor the crude product. Attempts to purify the crude product by crystallization from 33 per cent alcohol invariably led to a darker colored product with the same melting point as the crude. The decolorizing carbon is not intended to decolorize the solution but to clarify the filtrate before the precipitation of the diphenic acid. 

Azobenzoic Acid Azodibenzoic Acid or Azobenzenedicarboxylic Acid, HOOC -C(H4-N N-C,H4-C00H, mw 270.24, N 10.37%. Three isomers o,o -, m,m - and p,p - are described in Beil 16, 228,232,233,236 (287). Of these only the para-isomer is of interest because its nitro- and dinitro- derivs form ejqj] salts see below)... 

Other Names C.I. Acid Red 2 2-Carboxy-4 -(dimethylamino)azobenzene 2-[(/ -Dimethylamino)-phenyl]azobenzoic acid 2-[[4-(Dimethylamino)-phenyl]azo]benzoic acid 4 -(Dimethylamino)-azobenzene-2-carboxylic acid 4-(2-Carboxyphenylazo)-A,A-dimethylaniline Acid Red 2 C.I. 13020 Methyl red Methyl red C.I. 13020 NSC 215212 NSC 34729 NSC 9597 o-Methyl red o-[[p-(Dimethylamino)-phenyl]azo]-benzoic acid p-(Dimethylamino)-azobenzene-o-carboxylic acid... 

Reduction of methylated desulfated dermatan sulfate with sodium boro-hydride transformed the L-iduronic acid moiety into an L-idose moiety. Hydrolysis, followed by adsorption of the hexosamine fraction, gave a neutral fraction consisting of sirupy i,6-anhydro-2,3-di-0-methyl-/ -L-ido-pyranose (XXIX), identical with a synthetic sample, and of a mixture of 2,3-di-O-methyl, 2-0-methyl and 3-O-methyl-D-glucose. The yield of XXIX was low, because of the volatility of the substance, which was further characterized as a crystalline mono- -azobenzoate. No other methylidoses were observed . 

---