308 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



This reaction may be used as a test for pyridine : 



If a few drops of pyridine be heated with a few drops of methyl 

 iodide, a violent reaction takes place and pyridine methiodide is formed 

 On adding a small quantity of solid potash and again heating, the com- 

 pound is decomposed and the disagreeable smell of methyl pyridine 

 hydroxide will be noticed. 



Pyridine is not oxidised by nitric acid, or chromic acid, and it is only 

 slowly attacked by the halogens and sulphuric acid forming substitution 

 products. 



Piperidine. C 5 H 10 NH. 



Piperidine is a constituent of the alkaloid piperine from which it is 

 obtained by hydrolysis with alkali. 



It is formed by the reduction of pyridine with sodium and alcohol, 

 and it is converted into pyridine by heating with concentrated sulphuric 



acid at 300 : 



CH 2 



_ H 2 c/\CH a 



NH. 



Piperidine is also formed by the distillation of pentamethylene 

 tliamine : 



^CHg-CH, 

 HN 2 . CH a . CH 2 . CH a . CH 2 . CH 2 . NH 2 NH 8 + CH a "/NH. 



\CH a CH a 

 Preparation. 



Powdered pepper is extracted with alcohol , the extract is evaporated to 

 dryness and the residue is distilled with soda. The alkaline distillate is 

 neutralised with hydrochloric acid and evaporated to dryness. The residue 

 which consists of ammonium chloride and piperidine hydrochloride is treated 

 with hot alcohol. The solution containing the piperidine hydrochloride is 

 evaporated and distilled with soda and the oil which passes over is purified 

 by distillation. 



Properties. 



Piperidine is a colourless liquid which boils at 106. It has the 

 pungent smell of pepper and mixes with water. It is a strong base 

 -and a secondary amine, forming nitrosopiperidine with nitrous acid. 





