320 PIGMENTS 



to crystallize which at first sight would appear to be in contra- 

 diction with the well-known fact first observed by Borodin * 

 that when green leaves are moistened with alcohol, and allowed 

 to evaporate slowly under a coverslip, crystals of chlorophyll 

 may be observed under the microscope. Willstatter and 

 Benz f described a method of obtaining this substance in 

 quantity from Galeopsis tetrahit, and later Willstatter and 

 Stoll $ showed that this so-called crystalline chlorophyll was 

 not present as such in the plant, but was a secondary product 

 produced by the action of the alcohol upon the chlorophyll 

 under the action of an enzyme chlorophyllase. The phytyl 

 group is thereby replaced by the ethyl group as illustrated 

 by the equation — • 



yCOOCHg /COOCH3 



)CO 



>CO 



NH NH 



Amorphous chlorophyll a Crystalline chlorophyll a 



For the monomethyl ester of chlorophyllin a Willstatter has 

 proposed the name chlorophyllide a — 



/COOCH3 

 C3iH29N3Mg^COOH 

 yCO 

 NH 



and adopting this nomenclature, amorphous chlorophyll would 

 be termed phytylchlorophyllide, while crystaUine chlorophyll 

 would be ethylchlorophyllide. 



On the other hand, working with methyl alcohol and 

 chlorophyllase, it has been found possible to replace the phytyl 

 group by methyl, forming methylchlorophyllides, a and h — 

 C32H3oON4Mg(COOCH3)2 and C32H,802N4Mg(COOCH3)2 



which are the methyl analogues of ethylchlorophyllide or 

 crystalline chlorophyll ; they are best obtained by treating 

 fresh leaves with 66 per cent methyl alcohol, and extracting 

 the mixture of methylchlorophyllides formed both from the 

 solution and the leaf residue. 



* Borodin : " Bot. Ztg.," 1882, 40, 608. 



t Willstatter and Benz : " Annalen," 1907, 358, 267. 



+ Willstatter and Stoll : id., 1910, 378, 18. 



