ORGANIC CHEMISTRY 



29 



When the compound reacts in the second form, iodine or hy- 

 droxyl is added, giving (ix), which again loses acetic acid to give 

 pyridine. 



I : i'-Dibenzyltetrahydro-4 : 4'-dipyridyI has long been 

 known, but it is only recently that Emmert {Ber., 1920, 

 53, 370) has shown that it undergoes dissociation in solution. 

 Weitz and Nelken {Ann., 1921, 425, 187) have now succeeded in 

 isolating i -benzylpyridinium as a deep red crystalline com- 

 pound dissolving in alcohol to a deep blue solution. 



The Nitration of Toluene. — ^The extensive use of trinitro- 

 toluene as a filling for high explosive shell during the war 

 resulted in a large amount of research on the various isomeric 

 nitro-compounds of toluene and a general study of the nitration 

 of this body. Some of this work is now being published. The 

 state of our knowledge in 1914 of the nitration of toluene was 

 summarised by Will {Ber., 191 4, 47, 704). At this time but 

 three of the six possible isomeric trinitrotoluenes were known, 

 all three being formed in the nitration of toluene. The main 

 product of this reaction consists of 2:4: 6-trinitrotoluene, 

 the 2:3:4- and 3:4: 6-trinitro-compounds totalling but 

 approximately 4 per cent, resulting from the nitration of that 

 amount of m-nitrotoluene formed in the first stage. Since 

 that date Korner and Contardi {Atti. R. Accad. Lincei, 1914, 

 [v], 23, ii. 464 ; 191 5, [v], 24, i. 888 ; 1916, [v], 25, ii. 339) have 

 prepared the remaining isomerides by the following series of 

 reactions : 



Me 







-> 



NO 



NHAc 



NO, 

 NHAc 



-> 



Me 



NO. 



N0„ 



NO, 



Me 







OMe 



-> 



Me 



NO, 



OMe 



NO, "^ NO,l^ 



Me 



NO, 



-> 



Me 

 /^NO, 



noxJno, 



Me 

 NO,<^NNO, 



a 



NO, 



-^ 



Me 

 NO.^NO, 



NH. 



-^ 



Me 

 NOa-^^NOa 



UBr 

 NH, 



-> 



Me 

 NO,p.NO, 



-^ 



Me 

 NO.j^NO, 



-> 



Me 

 NO.^NO, 



