LECTURE XIV.] HISTORY OF CHEMISTRY. 285 



the one of Skraup 78 which has become so important for the 

 whole group. This latter synthesis depends upon the carrying 

 out of one of the ideas indicated by Grabe. 74 



Quinoline, also, is the starting-point for a large number of 

 compounds, which are formed from it and can be converted 

 into it just as benzene passes into aromatic compounds and 

 can be obtained from them. 



The relations between pyridine and quinoline, which are 

 quite analogous to those between benzene and naphthalene, 

 are also worthy of mention. In the same way that the latter 

 is converted by oxidation into benzene-ortho-dicarbonic acid 

 (phthalic acid 75 ), so quinoline, according to Hoogewerff and 

 Van Dorp, 70 is converted by oxidation into an ortho- (a/?-) 

 pyridine-dicarbonic acid. 



But what is of the greatest significance is the fact that the 

 most important alkaloids are derivatives of pyridine and of 

 quinoline (or of their hydrogenised derivatives) in the same 

 way that the aromatic oils are derivatives of benzene. The 

 first fact bearing upon this relationship was found out by 

 Gerhardt in 1842, when he discovered quinoline as a product 

 of the decomposition of quinine, of cinchonine, and of strych- 

 nine. 77 Huber obtained in 1867, by the. oxidation of nicotine, 78 

 an acid C (; H 5 NO., which he recognised, three years later, as 

 pyridine-carbonic acid ~ 9 a fact which was at first disputed and 

 then confirmed. 80 Piperidine, which was discovered by Wert- 

 heim and Rochleder by the decomposition of piperine, 81 and the 

 correct formula of which was established by Cahours 8 ' 2 and by 

 Anderson, 83 was regarded by Hofmann as a hydrogen addition 

 product of pyridine, 84 a view which was proved to be correct 

 by Konigs and others. 85 



73 Monatshefte. I, 317 ; 2, 141. 74 Annalen. 201, 333. 73 Laurent, 

 ibid. 19, 38; 41, 98. 76 Berichte. 12, 747. 77 Annalen. 42, 310; 

 44, 279. 78 Ibid. 141, 271. 79 Berichte. 3, 849. 80 Weidel, Annalen. 

 145, 328; and Laiblin, ibid. 196, 129. 81 Ibid. 54, 254 ; 70, 58. 8 ' 2 Ibid. 

 84, 342. 83 Ibid. 84, 345. 84 Berichte. 12, 984. 8r ' Ibid. 12, 2341; 

 Schotlen, ibid. 15, 421; Hofmann, ibid. 16, 586; Ladenburg, ibid. 17, 

 156, 388; Ladenburg and Roth, 17, 513. 



