Unsymmetrical isomers of trinitrotoluenes

The action of some inorganic substances on unsymmetrical isomers of trinitrotoluene is mentioned on p. 331, Vol. I. 

UNSYMMETRICAL ISOMERS OF TRINITROTOLUENE The following unsymmetrical trinitro derivatives of toluene are known ... 

The physical properties of the unsymmetrical isomers of trinitrotoluene are similar to those of a- trinitrotoluene. They are crystalline substances of a pale yellow colour, soluble in most organic solvents, insoluble in water and non-hygroscopic. 

HEATS OF COMBUSTION AND FORMATION OF UNSYMMETRICAL ISOMERS OF TRINITROTOLUENE... 

The unsymmetrical isomers of trinitrotoluene readily react with aqueous solutions of sodium or potasium hydroxide, forming salts of dinitrocresol (Will [37]) ... 

Sodium hydroxide gives the following colour reactions with the unsymmetrical isomers of trinitrotoluene (Table 79). 

The unsymmetrical isomers of trinitrotoluene also give specific reactions with sodium carbonate and with lead oxide. The former also affects the ignition temperatures of the isomers. The corresponding data are tabulated below, in Table 80 (after Brunswig [141]). 

SPECIFIC REACTIONS OF THE UNSYMMETRICAL ISOMERS OF TRINITROTOLUENE WITH... 

The unsymmetrical isomers of trinitrotoluene are affected by light in an apparently similar way, as in the instance of a- isomer, turning brown on exposure to sun. However, the chemical nature of the process has not been investigated. 

Apart from the unsymmetrical isomers of trinitrotoluene, other by-products are formed in the nitration process, owing to oxidation or decomposition processes. 

Seliwanoff s test analy chem A color test helpful in the identification of ketoses, which develop a red color with resorcinol in hydrochloric acid. s3 liv3,nofs, test sellite liNORG chem A solution of sodium sulfite (Na2S03) used in the purification of 2,4,6-trinitrotoluene to remove unsymmetrical isomers. se,lTt ... 

The reaction occurs with more difficulty than the corresponding one with the unsymmetrical trinitrotoluenes and requires a higher temperature or more concentrated solutions of sodium sulphite. The reaction of sulphitation of dinitro-toluene may be used in practice for removing m-nitrotoluene derivatives from mixtures of dinitro-isomers. Thus the sulphitation of trinitrotoluene becomes unnecessary. 

At higher temperatures, however, the a- trinitrotoluene undergoes a more drastic transformation. This is the result of both the action of Na2S03 and of the high pH of the solutions one N02 group is substituted by an S03Na group. Thus the reaction proceeds in essentially the same way as in the case of the unsymmetrical isomers. 

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. 

According to the British literature of World War I, the optimum temperature of sulphitation is 40-45°C. At higher temperatures a- trinitrotoluene reacts too vigorously, which results in a certain loss of the product. On the other hand, the action of sulphite on the unsymmetrical isomers at lower temperatures is too slow. 

In industrial practice, losses of crude TNT in the sulphitation process amount from 6 to 8%. Out of this 2%-3. 5% is ascribed to the loss of a- trinitrotoluene and 3.5-4.5% to that of unsymmetrical isomers and other impurities, such as tetrani-tromethane (p. 339) and trinitrobenzene which is easily soluble in sodium sulphite, forming addition products. 

Crude TNT contains isomers and nitrated phenolic compounds resulting from side reactions. The usual method of purification is to treat crude TNT with 4% sodium sulfite solution at pH 8-9, which converts the unsymmetrical trinitro compounds to sulfonic acid derivatives. These by-products are then removed by washing with an alkaline solution. Pure TNT is then washed with hot water, flaked and packed. It is important to remove the waste acid and unsymmetrical trinitrotoluenes together with any by-products of nitration as they will degrade the TNT, reduce its shelf life, increase its sensitivity and reduce its compatibility with metals and other materials. Trace amounts of unsymmetrical trinitrotoluenes and by-products will also lower the melting point of TNT. TNT can be further recrystallized from organic solvents or 62% nitric acid. 

---