48 PLANT PHYSIOLOGY 



a methyl alcohol and the other to the phytol. The third or ineffec- 

 tive one is in the lactam ring of chlorophyll A, while in chlorophyll 

 B it is absent entirely. 



When chlorophyll is heated with alkalies at a high temperature, 

 the carboxyl groups are broken off leaving a substance called 

 etiophyllin (C3iH 3 4N 4 Mg) with the following proposed structural 

 formula (Fischer and Klarer) : 



CH 3 — C — C — CH 2 — CH 3 



II II 



c c 



\ / 



— [Mg] - y-jtN \ 



O-H 



A/ 



c c 



I I 



C — C — CH2 — CH3 CH3 — CH2 — C — C — CHj 



Here we see that magnesium is the heart of the etiophyllin molecule 

 and that in this acid part of chlorophyll, Mg plays the central role. 

 No iron or other metals enter at all into the chlorophyll molecule. 



Two Series of Decomposition Products. — The preceding para- 

 graph has shown what happens when chlorophyll is treated with 

 alkalies. The carboxyl groups are driven off successively giving 

 products known as phyllins, which contain magnesium. The green 

 color of the chlorophyll, as previously hinted, is connected with 

 the presence of the magnesium, and it is not surprising that these 

 decomposition products retain their green color. The final phyllin, 

 when all the carboxyl groups have been driven off, is the etiophyllin 

 mentioned above. 



If chlorophyll, on the other hand, is treated with acids, the 

 magnesium is replaced by hydrogen and a series of products re- 

 sults which are called phytins. Thus chlorophylls A and B give 

 phdeophytins A and B, the former of which has the formula: 



.COOCH3 



(C 32 H320N 4 ) 



\COOC 20 H 3 9 



If a phyllin is treated with an acid one gets magnesium-free sub- 

 stances to which have been given the name of porphyrins. 



