The Chemistry of Chlorophyll. 1 3 



from the phyllins by the action of acids are called porphyrins. 

 Thus aetiophyllin gives £etioporphyrin, Ca^HgeN^. 



While the action of alkalis on chlorophyll produces no change 

 in the optical properties of the chlorophyll derivatives, with acids 

 the colour becomes olive-green and the fluorescence becomes less. 

 It is another group of the chlorophyll that is attacked, but the 

 resulting substance is incapable of forming salts : no saponification 

 has taken place. 



For instance, the action of oxalic acid or dilute alcoholic 

 hydrochloric acid on an alcoholic extract of leaves is to produce a 

 wax-like chlorophyll derivative called phaeophytin. It contains no 

 magnesium, and the replacement of that metal by hydrogen is the 

 only change which takes place. The substance is not easily soluble 

 in alcohol and so is precipitated easily. Its solution differs from 

 that of chlorophyll in colour, but if a metal is introduced into the 

 molecule again, it regains the chlorophyll colour. This may easily 

 be effected with copper and zinc by adding their acetates to 

 phseophytin. Magnesium is not so easily replaced, but Willstatter 

 has succeeded in doing this by treating pheeophytin with magnesium 

 methyl iodide. 



If phaeophytin is saponified with alkali, nitrogen-containing 

 acids are produced and a nitrogen-free alcohol called phytol of the 

 formula CjoHjgOH. Willstatter has also shown that a— COOCHj 

 group is broken up by this hydrolysis. 



Prom the results of the treatment of chlorophyll with alkalis 

 and acids Willstatter has thus been able to write the formula of 

 chlorophyll a as (CjaHgoON^lVIg) (COOCH3) (COOC20H39), 

 thatofchlorophyllbas(C3aH2802N^Mg)(COOCH3)(COOC3oH3g). 



When a mixture of chlorophyll a and b is saponified with alkali 



the green colour changes first to a deep brown (chlorophyll a 



changes to yellow, chlorophyll b to red). After a few minutes 



the colour changes back to the original green. Willstatter 



explains this as possibly due to the presence of a lactam ring 



CO — NH which is opened when the brown phase is produced. 



I I 



The reappearance of the green colour is supposed to be due to the 



formation of another lactam ring which is more alkali-stable. 



During the production of the brown phase the complex 



combination of the magnesium is affected. On the reproduction of 



the green colour the carboxyl group might combine with the same 



nitrogen group or with a different nitrogen group, or the nitrogen 



