HEMATINS 



171 



of pyridine {885,1122) or from acetylhemin crystals by hj'drolysis {1122) 

 are readily reconverted into hemins, e.g., into formylhemin or acetylhemin 



CO2H 



H20Fe+ O2C 



CO, +Fe.0H2 



HO,C 



Fig. 3. Hydroxyhemin. In this projection diagram the lines with the iron in the 

 middle represent the porphyrin molecule lying perpendicularly to the plane of the 

 paper. The serrated lines between the carhoxylic acid groups and the porphyrin 

 nucleus represent the — CH2CH2 — group of the propionic acid side chains, one 

 attached to a pyrrole ring above, the other to one below the plane of the paper. 



in concentrated formic or acetic acid, or into chlorohemin. They have the 

 composition of hydroxyhemin and are soluble in sodium bicarbonate solution, 

 alcohol, and pyridine. 



If the hematin precipitate is left standing in the mother liquor or if heat 

 is used in the preparation, the hematin becomes insoluble in sodium bicar- 

 bonate solution and alcohol, less soluble in pyridine, and no longer convertible 

 into crystalline hemins. These /3-hematins {cf. 1601,2507) have the com- 

 position of half or full anhydrides of hydroxyhemin {1122). The facts that 

 they are insoluble in sodium bicarbonate solution, that a-hematin esters are 

 not transformed into /3-hematin compounds on standing, and thatjS-hematins 

 are reconvertible into a-hemin esters by esterification {3087) indicate that 

 the carboxylic acid groups of hematin are involved in /3-hematin formation. 

 "Hj^droxyhemin" itself is probably a dimeric substance of the formula shown 

 in Figure 3. Here the iron is bound to the propionic acid groups by electro- 



H20Fe+ O2C, CO2 Fe+ O.C CO.H 



X/ 



/\ 



\y 



,/\ 



HO2C CO2 Fe+ 0,C CO. Fe+OHj 



Fig. 4. iS-Hematin (half-anhydride) 



