Chapter 16 

 CHLOROPHYLL 



A. Molecular Structure* 



1. Historical Remarks 



The part played by chlorophyll in the pigment system of plants has 

 been described in chapter 15. The gradual unveihng of the structure of 

 this compound, one of the most important in nature, is an admirable 

 example of patient systematic work in organic chemistry. The versatile 

 genius of Berzelius, who in his long life analyzed, or tried to analyze, 

 every compound which came into his hands, stands at the beginning of 

 this development, a little over a century ago (1838). The ease with 

 which chlorophyll decomposes and the difficulty of its purification, have 

 led to many initial errors in its analysis. An important step forward 

 was the realization of the similarity between chlorophyll and hemin, the 

 red blood pigment, first suspected by Verdeil in 1851, and later confirmed 

 by Hoppe-Seyler (1879, 1880, 1881), who transformed chlorophyll into 

 a red "porphyrin" similar to those obtainable from hemin. However, 

 further progress in the elucidation of the chemical structure of both 

 chlorophyll and hemin remained slow, until the subject was taken up by 

 Willstatter in 1905. His fundamental work has been developed further 

 by StoU in Switzerland, Conant in America and, most persistently and 

 successfully, by Hans Fischer in Germany. 



The investigations of Willstatter and his coworkers (published in twenty separate 

 papers between 1905 and 1913), were summarized by Willstatter and Stoll in their 

 well-known book, Untersuchungen iiber Chlorophyll (1913, American edition 1928). A 

 second book by the same authors, Untersuchungen iiber die Assbnilation der Kohlensaure, 

 appeared in 1918; it described the work carried out during the war years of 1914 to 

 1918 and not pubUshed elsewhere, and dealt with the state of the pigments in nature 

 and their participation in photosynthesis. It has been repeatedly quoted in the pre- 

 ceding chapters. 



The fourteen Studies in the Chlorophyll Series of Conant and coworkers appeared 

 in 1929-1934. The results of Fischer and coworkers were presented in a series of 

 papers, Zur Kenntnis des Chlorophylls, the first published in 1928 and the hundredth in 

 1940; closely related to this series is another one, Die Synthese der Porphyrine. Short 

 summaries were given by Fischer in 1936, 1937, and 1940. A complete review by 



* Bibliography, page 467. 



438 



