HEMATINS 



169 



without tension. He overlooks the fact that the iron, pyrrole ring, 

 and the methylene group bound to it lie in one plane, and that the 

 oxygen atom lies perpendicularly above the iron.* 



Harasik (1118,1120, cf. also 2035,2903) obtained evidence that 

 acetone can be bound to chlorohemin by dipole or covalent linkage. 

 The absorption spectrum of alcoholic hematin solutions suggests 

 combination with alcohol {536, cf. also 501), but Richter could find 

 no evidence for a compound of alcohol with solid hematin. 



The hemins of some other porphyrins have also been obtained 

 crystalline, among them spirographis hemin, C32H32O5N4CI (932,933, 

 2957). 



3.3. Hematins 



If we write only the central iron atom and the two carboxylic 

 groups present in hemin, the reaction which occurs when hemin is 

 dissolved in excess alkali can be formulated as follows if 



-,+ 



COoH 



H,0 • Fe • 0H> 



CO2H 



+ 3 OH" 



-i2- 



CO, 



H,0 • Fe OH 



CO, 



+ 3 H2O 



It gives rise to a divalent anion of ferriporphyrin hydroxide (1116, 

 1120,1990). The presence of the hydroxy 1 group in this complex can 

 be shown by methylation with dimethyl sulfate (1157), which gives 

 a trimethylated product, or by formation of tripotassium salt with 

 potassium raethylate (3087). The dimethyl ester of ferrimesopor- 



* It is interesting to compare this formula with that of the cysteine adduct of 

 protohenie {-3167), in which such a ring occurs, containing, however, one more atom: 



CO.H 



,CH CHj 



-CH, 



t .\dditional water molecules, to maintain a coordination number of 6 (in aqueous 

 solution) were postulated by Haurowitz and Clark {^5^^,1175). 



