THE CHEMISTRY OF CHLOROPHYLL 441 



rhodophyllin (which will be described below). It could be freed 

 from magnesium by treatment with oxalic acid, and yielded, not 

 phaeophytin, but a product from which no phytol was obtainable by 

 alkaline hydrolysis, and which was designated phceophorbin. This 

 substance reacts in the cold with neither acids nor bases, but is a 

 neutral product. On warming with methyl-alcoholic potassium 

 hydroxide, it yielded, however, phytochlorins and phytorhodins. 



Rhodophyllin and Alloporphyrin. — The more vigorous action of 

 alkalis on chlorophyllin was also investigated by Willstatter. 

 By the action of alcoholic potassium hydroxide at 140 — 200 in 

 an autoclave (with the reaction mixture in a silver beaker) a 

 product still containing magnesium was obtained, the composi- 

 tion of which corresponded with the formula CssHsiOi^Mg. 

 This product, which was called rhodophyllin, is of great interest, 

 in that its chemical composition corresponds very closely with 

 that of the blood-pigment haematin, to which Zaleski has assigned 

 the formula C 3 4H330 5 N 4 Fe. The analysis will agree quite closely, 

 however, with the formula C.^H330 5 N 4 Fe. As will be evident 

 from considerations advanced below, the correspondence between 

 the haematin and rhodophyllin can hardly be accidental. 



Rhodophyllin crystallised in beautiful shining prisms, with a 

 deep blue surface colour ; it was readily soluble in alcohol, but 

 with difficulty soluble in ether, and formed easily crystallisable 

 salts. It was readily decomposed by acids, with elimination of 

 magnesium. In this way a new product, designated alloporphyrin, 

 was obtained, which possessed exactly the same chemical 

 composition as a product obtained by Nencki and Zaleski by 

 the reduction of phylloporphyrin, which they called mesoporphyrin 

 and which differed from the latter only in its oxygen content (see 

 below on " relation of chlorophyll to blood-pigment "). Allopor- 

 phyrin is insoluble even in hot alcohol, and in most other organic 

 solvents. It is easily soluble, however, in pyridine. It is insoluble 

 in very dilute hydrochloric acid, and in this respect differs from 

 the isomeric mesoporphyrin, which is readily soluble. It forms 

 an insoluble sodium salt, and in this respect also differs from its 

 isomer. On treatment with acetic anhydride it yields an anhydride. 



The above forms a short account of the various derivatives 

 of the two chlorophylls (crystalline and non-crystalline), which 

 have been described by Willstatter up to the time of writing. 

 The genetic relationship of the various substances to one 

 another can be schematically represented as follows : 



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