4-NITRO-5-METHYL-2-SULPHOBENZOIC ACID 
175 
THE 4-NITR0-5-METHYL-2-SULPH0BENZ01C 
ACID AND SOME OF ITS DERIVATIVES. 
WILLIAM J. KARSLAKE and PERRY A. BOND. 
The 4-nitro-5-methyl-2-sulphobeiizoie acid has been investi- 
gated to a limited extent as one of the products formed when 
the 6-nitro-l, 3-dimethyl-4-sulphonic acid is oxidized by potas- 
sium permanganate in dilute alkaline solution. Previous to this 
research^ the only record of its preparation was by Limpricht,^ 
in which case only a small amount of the neutral potassium 
salt was isolated. He gives this as occurring with one-half a 
molecule of water of crystallization, but does not state which 
of the two methyl groups of the original acid had been oxidized. 
The neutral potassium salt does not seem to contain any water 
of crystallization, however, and some doubt is cast upon the 
pwalue of, the observation as made by him. 
Since the preparation of our acid is intimately associated 
with the work of Karslake and Bond upon the oxidation of the 
6-nitro-l, 3-dimethyl-4-sulphonic acid, it seems best to outline 
the work already done. This is the more necessary, as since the 
publication of the results of that work it has been found that 
the materials were not absolutely pure, and that certain irregu- 
larities occurring as a result of this fact may be explained and 
corrected in the new work. It may be said here, however, that 
in no case does this error affect the final conclusions which 
were drawn at that time. 
Wl\en 6-nitro-l, 3-dimethyl-4-sulphonic acid is oxidized in 
very dilute potassium hydroxide solution, three main products 
are formed. These are the salts of the 6-nitro-3-methyl-4-sul- 
phobenzoic acid (I), the 4-nitro-5-methyl-2-sulphobenzoic acid 
(II), and the 6-nitro'-4-sulphoisophthalic acid (HI). 
COOH (I) CH3 (II) COOH (III) 
NOs 
NO2 
CH3 
COOK 
COOH 
X/SOsH \/ \/ 
SO3H SO3H 
^Karslake and Bond, J. Am. Chem. Soc., 31, 405, 1909. 
2Limpricht, Ber., 18, 2191, 1885. 
