HEMICHROMES 



181 



For several other hematin compounds hepta, or even oeta coordination, 

 has also been assumed, e.q., for carhon monoxide carbylamine hemoglobin, 

 hydrogen peroxide azide catalase, carl)on monoxide hydrogen peroxide azide 

 catalase and related hydrogen peroxide compounds of hem/globin, as well 

 as ethanol hem/'globin hydroxide {■'>()1) {rf. Chapters \1 and IX), but there 

 is no satisfactory evidence for the existence of tliese compounds. 



The data of Clark and Perkins make it necessary to reject an explanation 

 of the structure of hem/cliroines based oidy on the ecjuilibrium of the com- 

 pounds Fe''"'" Bo and Fe''+ OH with base and liydroxyl ions. The possibility 

 that a further species Fe''+ B OH may exist, introducing the additional 

 equilibrium: 



[IV+B.] + + OH ^ [Fe'!+ BOH] + B 



is, however, not discussed.* 



Whatever view is taken of the foregoing possibilities, the analytical data 

 for the imiilazole hem/chromes still re((uire interpretation. Hamsik's com- 



ImFe-Im 



HO,C CO2HI1 



CV 



-lO 



Im-FeCl 



IMHO2C COoHIr 



ImFe+ O2C CO, 



O2C CO2 +Felm 



r.+ 



k: 



-|0 



ImFe+ O2C COoHIm 



ImHOjC CO. +Felr 



Fig. 7. Imidazole hematin compounds. 



pounds containing tlirec molecules of base [)er atom of iron can only be 

 exi)lained by the assumption of salt formation with one or two of the side 

 chain carboxylic acid grou[)s of the liemin (.( or /i. Fig. 7). This may also 



* In their recent paper. Shack and ("lark (-i't-iSa) come to the conclu.sion that 

 pyridine ferriprotoporphyrin hydroxide has this composition, but that, in contrast to 

 dipyridine ferriprotoporphyrin, it is dimeric. 



