304 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



THIOPHENE AND ITS DERIVATIVES. 



Thiophene, G 4 H 4 S, was discovered in the benzene from coal tar from which 

 it was obtained by extraction with concentrated sulphuric acid. Its constitu- 

 tion has been shown to be 



HC CH 



HC CH 



a heterocyclic compound containing 4 carbon atoms and a sulphur atom. 



Thiophene resembles benzene in its reactions more closely than furfurane 

 and pyrrole, but as yet neither thiophene nor its derivatives have been obtained 

 from natural substances. 



PYRROLE AND ITS DERIVATIVES. 



Pyrrole and its derivatives are closely connected with the proteins 

 and with the two respiratory pigments, chlorophyll and haemoglobin. 

 A pyrrole derivative is also present in the molecule of nicotine, and 

 cocaine contains a pyrrole nucleus. The heterocyclic ring in pyrrole 

 consists of 4 carbon atoms and I nitrogen atom. We have to con- 

 sider the following compounds in order to understand the constitution 

 of the proteins and the complex chlorophyll and haemoglobin mole- 

 cules : 



HX CH 



HC CH 



II II 

 HC CH 



Yn 



Pyrrole. 



CH 3 . C C . C 2 H 5 



II II 

 CH a .C C.H 



3 2 C CH 



\/ 



NH 

 Pyrrol inc. 



H 2 C CH a 

 H 2 C CH a 



NH 

 Pyrrolidine. 



CH 3 .C C.C 2 H 6 

 H . C C . CH 8 



NH 



Isohaemopyrrole 

 a, 0-dimethyl, 

 0-ethyl-pyrrole. 



NH 

 Kryptopyrrole 



a-methyl, 



j3-methyl-)8-ethyl 



pyrrole. 



CH 3 .C C.C 2 H 5 



II H 

 CH,.C C.CH 3 



Y* 



Phyllopyrrole 



or 



a, a-dimethyl, 



methyl-/8-ethyl 



pyrrole. 



H 2 C CH 2 



H 2 C CH.COOH 



\/ 



NH 



a-pyrrolidine- 

 carboxylic acid 



or 

 proline. 



CH 3 .C C CH 2 .CH 2 .COOH HO . CH CH 2 



II II 

 CH 3 .C CH H 2 C CH.COOH 



Y* Yn 



Isophonopyrrole- Hydroxyproline 



carboxylic acid 

 a-methyl-0-ethyl- 



pyrrole- 

 j3-propionic acid. 



or 



j8-hydroxy-a-pyrrolidine 

 carboxylic acid. 



