360 PHOTOSYNTHESIS 



Starting with the chlorophylHd. it has also been possible to synthesize 

 chlorophyll with phytol and chlorophyllase, according to : 



(C32H3oON4Mg) (CO2CH3) (CO,H) + Q0H39OH 



(Cs^HsoON^Mg) (CO2CH3) (CO2C20H39) + H2O. 



The discovery of the nature of the action of chlorophyllase and the chem- 

 ical composition of the chlorophyllids and methyl- and ethylchlorophyllids 

 aided greatly in determination of the constitution of chlorophyll. 



It has already been mentioned that the saponification of phseophytin 

 yields, besides phytol, a number of complex carboxylic acids containing 

 nitrogen. The latter constitute a complicated mixture of substances the 

 separation of which offered many severe obstacles. Willstatter and Mieg 

 finally devised a method of separation which utilizes the basic nature of 

 these substances. The chlorophyll derivative is dififerentiated by its 

 "hydrochloric acid number," i.e.. the concentration of hydrochloric acid 

 which is necessary to extract it from an ether solution. Thus, an ether 

 solution, containing a mixture of these carboxylic acids, can be fraction- 

 ated by extraction with dilute hydrochloric acid of different concentra- 

 tions. In this manner there were obtained two substances which were of 

 much importance in the development of the chemistry of chlorophyll, viz., 



Phytochlorin e C3iH3oN4(CO) (COOH), 

 Phytorhodin g CsoHsiN^CCO) (CO()H)3. 



Phytochlorin ^ is a tricarboxylic acid with two free carboxylic groups and 

 one lactam ; phytorhodin (/ is a tetracarboxylic acid in which two or three 

 of the carboxyl groups may be free. 



The hydrolysis of chlorophyll, first with acid and then with alkali thus 

 leads to two products, the one green, the other red. This fact led to 

 the conclusion that phseophytin as well as chlorophyll are both a mix- 

 ture of two components each; one of these components yields phyto- 

 chlorin e, the other phytorhodin g. This was finally established by separat- 

 ing chlorophyll by the method already described, into the two compo- 

 nents, chlorophyll a and chlorophyll h, from which phytochlorin e and 

 phytorhodin g respectively were obtained. The two chlorophyll compo- 

 nents and the products derived from them by acid and alkali hydrolysis 

 are very similar in chemical composition ; they contain the same quantity 

 of magnesium and of phytol ; the basic nuclei of the two components, 

 phytochlorin and phytorhodin, have vei-y nearly the same composition. 

 This relationship between the derivatives of the two components is main- 

 tained in parallel steps of the disintegration of the chlorophyll molecules. 

 From analyses it would appear that the difference between the two series 

 of derivatives from the a and h components lies chiefly in one oxygen 

 atom, two atoms of hydrogen of chlorophyll a being replaced by one 

 atom of oxygen in chlorophyll b, corresponding to the following probable 

 formulae : 



