358 PHOTOSYNTHESIS 



The decomposition of the phyllins in the manner just mentioned is of 

 considerable importance in interpreting the behavior of chlorophyll toward 

 acids. When chlorophyll is treated with an organic acid such as oxalic 

 acid, the green color changes to an olive, the solution is only slightly 

 fluorescent and magnesium is split out of the chlorophyll molecule. The 

 compound formed when chlorophyll, in alcohol solution, is treated with 

 oxalic acid in the cold, is called phaeophytin. It contains no magnesium, 

 is a dark waxy substance ; in ether it is not very soluble, easily soluble 

 in benzol and chloroform. It has no acid properties but is slightly basic. 

 A remarkable property of this substance is that, while in solution it 

 has a dark brown color, some metals can be introduced into the molecule, 

 which results in the formation of brightly colored compounds. Thus 

 copper and zinc in acetic acid solution react with alcoholic solutions of 

 phaeophytin. Especially interesting is the fact that when phcTophytin is 

 heated in a silver test tube with alcoholic potassium hydroxide and mag- 

 nesium oxide a series of phyllins are formed. When these solutions are 

 acidified very carefully and extracted with ether the brilliant green, blue 

 and red fluorescent phyllins pass into the ether extract. On account of 

 the alkali present the reformation of chlorophyll is prevented, however. 

 Magnesivmi can also be introduced into the phaeophytin molecule by 

 means of the Grignard reagent, methylmagnesiumiodide : 



acid 

 CaiHssN^CCOOH) ±^ CsxHssN.Mg . COOH 



MgCH3l 

 Phylloporphyrin Phyllophytin 



On saponification with alkalies phaeophytin yields, besides complex 

 nitrogen compounds with 34 carbon atoms, a nitrogen-free alcohol with 

 20 carbon atoms. This comiX)und which Willstatter called phytol, is an un- 

 saturated, primary alcohol of open chain structure. It has the empirical 

 formula C20H39OH with the possible following structure : 



CH3 — CH — CH — CH — CH — CH — CH — CH — C = C — CHoOH 



I I I i I I I I I 



CH3 CHs CH3 CH3 CH3 CH3 CH3 CH3 CH3 



Phytol is a colorless, thick oil soluble in most organic solvents, boil- 

 ing at 145° under 0.03-0.04 mm. pressure. It is easily oxidized, adds 

 one molecule of bromine or of iodine. The capacity of phytol to take 

 up oxygen may account for the reducing power of chlorophyll. The 

 determination of the amount of phytol in a chlorophyll preparation, by 

 treating this first with acid and then with alkali, has served as a method 

 of determining the purity of the preparation. 



The study of the products formed by the action of acids on chloro- 

 phyll has shown also what the action is of alkalies on the chlorophyll 

 molecule ; this is chiefly a saponification of the phytol ester. Besides 

 the saponification of the phytol ester, the alkali attacks a COOCH3 group 



