306 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Pyrroline and Pyrrolidine. 



Pyrrole is easily reduced by zinc and acetic acid, or by electrolysis, 

 to pyrroline ; it is converted into pyrrolidine by hydriodic acid, or 

 by passing pyrrole and hydrogen over nickel dust heated to 190. 



Pyrrole is a liquid boiling at 91 and has an ammoniacal smell. 

 It is a strong base and forms stable salts with acids. 



Pyrrolidine is a liquid which has a smell resembling pepper. It 

 boils at 87 and like pyrroline is a strong base. 



Proline and Hydroxyproline. 



These compounds are constituents of proteins. They result from 

 the hydrolysis of proteins by acids or alkalies. A complex process 

 of separation is required to isolate them from proteins (see " Chemical 

 Constitution of the Proteins "). They differ from other units of the 

 protein molecule by being easily soluble in alcohol (cf. glycine, p. 1 39). 



Alkyl Derivatives of Pyrrole. 



Derivatives of pyrrole are easily prepared from potassium pyrrole. 

 Potassium pyrrole reacts with alkyl halides, acid chlorides, etc., to form 

 derivatives in which the substituting group is attached to the nitrogen 

 atom : 



CH=CH V CH=CH. 



>NK + CHJ = I >N . CH 3 + KI. 



CH=^CH/ CH=CH/ 



On heating, these compounds undergo rearrangement; the sub- 

 stituting group changes its position and attaches itself to a carbon 

 atom. 



Isohaemopyrrole, kryptopyrrole, phyllopyrrole and other alkyl 

 pyrroles are formed by the reduction of haemin, chlorophyll and bile 

 pigments. A mixture is obtained from which the individual compounds 

 are separated. 



