BENZENE SERIES. AROMATIC COMPOUNDS. 593 



CH 3 .H C 6 H 6 .H C 6 H 4 N.H 



Methane. Benzene. Pyridine. 



CH 3 .C0 2 H C 6 H 5 .C0 2 H C 5 H 4 N.CO 2 H. 



Acetic acid. Benzoic acid. Nicotinic acid. 



Pyridine is also obtained together with another basic substance, 

 termed quinoline, C 9 H 7 N, by distilling quinine or cinchonine with 

 potash. These observations, showing an intimate relationship between 

 alkaloids and the pyridine and quinoline bases, have led to numerous 

 experiments made with the view of either solving the problem of 

 making alkaloids synthetically, or of obtaining substances which 

 might have physiological actions similar to those of the alkaloids. 

 The result of these efforts has been the introduction into the materia 

 medica of quite a number of new remedies. 



Pyridine is a colorless liquid, having a sharp, characteristic odor, 

 strongly basic properties, and a boiling-point of 116 C. (241 F.). 



Quinoline, C 9 H 7 N ( Chinoline), has been mentioned above as a product of the 

 distillation of quinine with potash ; it may also be obtained by the action of 

 sulphuric acid upon a mixture of aniline, nitro-benzene, and glycerin. It is, 

 like pyridine, a colorless liquid, but its aromatic odor is less pleasant and its 

 basic properties are less marked than those of pyridine. Boiling-point 237 C. 

 (458 F.). 



The constitution of pyridine and quinoline is supposed to correspond to 

 benzene and naphthalene respectively, one of the groups CH having been re- 

 placed by an atom of nitrogen, thus : 



H H H H H 



! 



C X /Cx //CH HQ, /(\ 



^/ ^^ ^c x x 



HC\ /CH H 



\N/ 



H H H 



Pyridine. Quinoline. Isoquinoline. 



Isoquinoline is very similar to quinoline, but differs slightly in its proper- 

 ties. Like quinoline it is closely related to a number of alkaloids, especially 

 those of the opium group. It is found together with quinoline among the bases 

 of coal-tar and bone-oil. 



Kairine, C 10 H 13 .NO.HC1. The name kairine has been given to the hydro- 

 chloride of methyl-oxychinoline hydride. It is a white, crystalline, odorless 

 powder, soluble in 6 parts of water or in 20 parts of alcohol. 



Thalline, C 10 H n NO (Tetra-hydro-paramethyt-oxy quinoline). Quinoline serves 



in the manufacture of thalline, a white, crystalline substance, which has an 



aromatic odor, fuses at 40 C. (104 F.) and is soluble in water, alcohol, and 



ether. The most characteristic feature of the substance is that it is colored 



38 



