296 HISTORY OF CHEMISTRY. [LECTURE XIV. 



reactions of this very kind, how the ortho-compounds may be 

 distinguished from their isomers ; and he was the first to point 

 out that the formation of the above-mentioned substances 

 depends upon " ortho-condensation." Baeyer then turned his 

 attention to this subject, and the syntheses of quinoline and of 

 oxindol, already referred to, constitute the valuable fruits of 

 his studies. 



Closely related to this internal condensation, is internal 

 oxidation. Reactions involving the latter change are those in 

 which oxygen atoms already present in the molecule, and 

 generally belonging to NO. 2 groups, oxidise, by the dissolution 

 of existing unions, other groups belonging to the same molecule. 

 The first reaction of this kind was observed by Wachendorff, 173 

 but Greiff 1T4 was the first to explain it. The matter involved 

 was the action of bromine on ortho-nitrotoluene, which the 

 latter of the above-named chemists represented in the following 

 manner : 



This reaction furnishes the explanation of the important method, 

 discovered by Baeyer, 175 for preparing isatine from ortho-nitro- 

 phenylpropiolic acid, by boiling this acid with alkalies : 



/CO CO 



= C 6 H 4 <^ / 



The formation of indigo from ortho-nitro-phenylpropiolic 

 acid, depends upon similar rearrangements. 



" 3 Berichte. 9, 1345. 174 Ibid. 13, 288. 175 Ibid. 13, 2259. 



