2.4- Dinitrotoluene-3-sulphonic acid

Gomall and R. Robinson [28] suggested reducing sodium dinitrotoluene sulphate (e.g. the sodium salt of 2,4-dinitrotoluene-3-sulphonic acid) to yield m- toluene-diamine-3-sulphonic acid which could serve as an intermediate for obtaining azo dyes. Oxidation of sodium 2,4-dinitrotoluene-3-sulphonic acid with potassium permanganate in alkaline medium gave 2,4-dinitro-3-sulphobenzoic acid, also an intermediate for azo dyes. 

As Muraour [103] found, the reaction of sodium sulphite was not confined to unsymmetrical trinitro derivatives of toluene, a- Trinitrotoluene also reacted with Na2S03 to form dinitrotoluene sulphonic acid, the difference lying in the fact that the reaction proceeds much more slowly than with unsymmetrical isomers. A 3% solution of Na2S03, acting for 1 hr, dissolves at room temperature about 1% of a- trinitrotoluene. 

Substitution of SOjH with chlorine by reacting with POCI3 and then removing chlorine with copper. The method was described for 2,4,6-lrinitrobenzene 1106) and 2.4-dinilrobenzenesulphonic (107) acids but it does not give the desired results with dinitrotoluene sulphonic acids (98). 

The theory that sulphonation takes place before the nitration can be accomplished may be the key to the question as to why some mono- and dinitrotoluenes are easily nitrated, and some are difficultly nitrated. The sulphonic group follows the laws of orientation perhaps more closely than almost any other group, and this explains why (assuming the sulphonation theory) dilute nitric acid will not nitrate direct, but will merely replace a sulphonic group. Therefore, if the sulphonic group is not already in place, the nitro-group cannot enter the molecule. So, if the previous... 

The first step in the third stage is the sulphonation of the, dinitrotoluene. Oleum (fruning sulphuric acid) is used for this purpose in the majority of plants. The acid may be added very rapidly in the third stage, since the temperature is 90 to 100°. The acid analysis shows 50 per cent each sulphuric and nitric. When the addition is complete, the temperature is raised to 120° and the charge is cooked for one and one-half hours. The nitration is then supposedly complete, and the TNT is separated from the acid, and is ready for washing. The yield of TNT per kilo toluene is... 

The second stage of the German process is very much like the American. The mononitrotoluene (500 kilograms) is placed in the nitrator and sulphonated with 1400 kilos sulphuric acid at a temperature of 60 to 70°. Then a mixture of 700 kilos of 100 per cent sulphuric acid and 700 kilos 48° B6. nitric acid, is run in. The mixture is agitated until a sudden drop of the temperatme indicates the end of the reaction of nitrating the mononitrotoluene to dinitrotoluene. The... 

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