ABSORPTION SPECTRA OF THE CHLOROPHYLLS 309 



tion of chlorophyll in living cells, magnesium is the only metallic constituent 

 of the chlorophyll molecule. Chlorophyll contains 2.7 per cent of magnesium. 

 From the results of the intensive study of the chemistry of the degradation 

 products of chlorophyll the probable structural formulas of both chlorophyll a 

 and chlorophyll b (Fig. 80) have been determined (Fischer and Breitner, 



1936). 



As shown in Fig. 80 the nucleus of a molecule of chlorophyll a consists 

 of a complex ring structure composed principally of four pyrrol or modified 



■HC=0; 



H3C- 



H3C- 



COOCH3 



COOC20H39 



Fig. 80. Structural formula of chlorophyll a. The formula of chlorophyll b is 

 supposed to be the same except that a CHO group occurs in place of the CH3 group 

 enclosed in the dotted circle. 



pyrrol rings linked together by intermediate atomic groupings. Each such ring 

 bears side chains, the most prominent of which is the phytyl (CooHogO — ) 

 grouping which upon hydrolysis gives rise to phytol. The position of the Mg 

 atom in the chlorophyll molecule is not known with certainty and its location 

 as shown in this figure is hypothetical. 



Absorption Spectra of the Chlorophylls. — When a colored solution such 

 as an ether solution of a chlorophyll is interposed between a source of "white 

 light" and a spectroscope it can readily be shown that certain wave lengths of 



