PORPHINS, CHLORINS, PHORBINS, PHYTINS, PHYLLINS 



447 



dihydroporphin, and haderiochlorophyll from tetrahydroporphin, com- 

 pounds in which one or both of the semi-isolated double bonds, present in 

 porphin, are hydrogenated, while the conjugated bond system is left intact. 

 Fischer designates dihydroporphin derivatives as chlorins if they do 

 not contain the cyclopentanone ring V, and phorhins if they do. The 

 presence of magnesium is indicated by the term phyllin, the presence of 

 phytol by the term phytin. The accompanying scheme may help to 

 retain the meaning of these terms. 



Compounds with an ethyl instead of a vinyl group in nucleus I are 

 indicated by the prefix meso; compounds of the 6-series are sometimes 

 referred to as rhodins (instead of chlorins). 



Specific compounds of each of these groups are designated by prefixes. 

 The compounds which have the same substituents as chlorophyll are 

 designated by the prefix pheo — e. g., pheophytin (a or b), and pheophorhide 

 (a or 6). The following scheme illustrates the relationship between 

 these compounds, the chlorophylls, and the chlorophyllides. 



Pheophorbin 



pheophytin 

 (methyl-phytyl 

 pheophorhide) 

 Mg introduced 

 (Grignard) 



methyl pheophorhide 



Mg removed 

 (acid) 



■^ + methanol 



chlorophyll > 



(methyl-phytyl (.MoTophyiiase) 

 chlorophymde) ' + phytol 



methyl ch 



Mg introduced 

 (Grignard) 



orophyllide 



chlorophylUn 



alkali 



alkali chlorophyllide 



