4-NITRO-5-METHYL-2-SULPHOBENZOIC ACID 
205 
Ethyl Benzoic Ester of the Sulphonic Acid. 
NO, . CHs . CgH, . Cobc.Hg . SO,OH 
This was made in the same manner as the methyl ester acid, 
and the free acid was not isolated, its presence being proven 
by the making and analysis of the barium salt. The salt crys- 
tallized in tufts of soft needles from the hot solution of the 
acid, to which barium chloride had been added. It was purified 
by recrystallizing from dilute alcohol. 
.2244 g. substance gave .0742 g. barium sulphate. 
Theory for CioHioOTNS.Ba Pound 
Barium, 19.26 per cent. 19.45 per cent. 
The Dimethyl Ester. 
NO, . CHs • CgH, . CobcHs • SoIoCH.^ 
The dimethyl ester cannot be made by the direct action of 
the acid chlorides on alcohol. The method which seems to have 
been most commonly used (see Remsen and Bird,^^ or Gobb®°) 
is the use of sodium methylate either dry or in absolute alcO“ 
hoi solution, with an absolute ether solution of tlie acid chloride. 
Cobb reports that the best yields are found when dry sodium 
methylate is added to the ether solution, but notes that in any 
case there is a tendency to pass over to the sodium salt of the 
ester acid, which is, of course, dissolved in the washing of the 
ether solution. This naturally affects the yield which can be 
obtained. This method was tried on both the symmetrical and 
unsymmetrical acid chlorides of our acid. It produced no sat- 
isfactory results. The pure acid chloride which melts at 134'" 
gave no action which could be followed, when it was treated 
with dry sodium methylate in ether solution, though a pinkish 
color appeared as each portion of the methylate was added to 
the solution. The melting point of the substance recovered from 
the ether after treatment was 132°, and on analysis it gave 
22.9 per cent chlorine as compared with the theoretical 23.5 
per cent for the acid chloride. This indicates that in the main 
the acid chloride was unchanged. 
The pure acid chloride which melts at 83° gave what was 
apparently a mixture of the unchanged acid chloride and the 
methyl ester chloride. The melting point of the product ranged 
2«Am. Chem. J., 30, 262, 1903. 
30 Am. Chem. J., 35, 488, 1908. 
