THE CHEMICAL CONSTITUTION OF H^MIN 

 AND H^MATOPORPHYRIN. 



Haemin and haematoporphyrin contain pyrrole nuclei in their molecule, 

 as has been shown by (i) dry distillation ; pyrrole is formed; (2) oxidation; 

 the imide of haematinic acid, 



CH 3 .CH CO 



HOOC . CH 2 . CH 2 . CH CO, 



is formed (Kiister) ; (3) reduction ; haemopyrrole is formed (Nencki and 

 Zaleski). Mesoporphyrin, which resembles phylloporphyrin from chlorophyll, is 

 obtained by milder reducing action. Haemopyrrole has been proved to be a 

 mixture of phyllopyrrole, isohaemopyrrole and kryptopyrrole (p. 304). At 

 least three pyrrole nuclei are thus present in these compounds ; from the 

 yield of haematinic acid it seemed most probable that four pyrrole nuclei were 

 contained in these compounds. Both Nencki and Kiister suggested formulae 

 for these compounds containing four pyrrole nuclei. 



Willstatter and his pupils have carried out experiments upon haemin 

 as well as upon chlorophyll and they have proved that the compound 

 aetioporphyrin is the parent substance from which both chlorophyll and 

 haemin are derived. 



The empirical formulae of haemin, haematoporphyrin and mesoporphyrin 

 according to Willstatter are 



C,,H a 4 N 4 FcCl f C n H K OJ* 4 and C 33 H 38 O 4 N 4 , 

 instead of those previously adopted containing 34 atoms of carbon. 



Haemin contains iron in organic combination, haematoporphyrin does not 

 contain iron. The conversion of haemin into haematoporphyrin is a complex 

 reaction and has been supposed to take place by the addition of hydrobromic 

 acid followed by its removal. This has been proved by Willstatter who has 

 isolated the following addition products, 



C 33 H 34 O 4 N 4 FeBr a 



C 33 H 39 4 N 4 Br B , 



which give haematoporphyrin on hydrolysis. Haematoporphyrin was known 

 only as an amorphous compound, but Willstatter has prepared it in a crystal- 

 line state (p. 496). 



Two other compounds very similar to haematoporphyrin are obtained by 

 the hydrolysis of the hydrochloric acid addition compounds of haemin, namely, 

 haemino- and haemidoporphyrin. 



By heating haematoporphyrin with pyridine and methyl alcoholic potash in 

 an autoclave it loses carbon dioxide and is converted into haemoporphyrin 

 C33H 36 O 4 N 4 . If haemin be heated in a similar way it yields mesohaemin, from 

 which on removal of the iron, mesoporphyrin is formed, identical with the meso- 

 porphyrin obtained by Nencki and Zaleski from haemin by reduction with 

 hydriodic acid. Haemoporphyrin is converted into aetioporphyrin by heating 

 with soda lime. 



Willstatter and M. Fischer point out that haemin is a dicarboxylic acid as 

 was first shown by Nencki and Zaleski and confirmed by Kiister ; in its iron- 

 free form it has the formula 



x 

 COOH 



516 



