MEASUREMENTS OF ABSORPTION SPECTRA OF PIGMENTS 



1813 



(a) 



(b) 



17 16 15 

 FREQUENCY CM"' 



Fig. 37C.14. Infrared absorption spectra: (a) of chlorophyll a and pheophytin a, 

 in ecu and CsHsN; (b) of chloropliyll b, in CCI4 and CHC'U, and of pheophytin b in 

 ecu (after Holt and Jacobs 1954). Note (1) additional "aldehyde" C=0 band in b- 

 compound; (2) bands of "chelated" C=0 in chlorophylls a and 6 in CCU* (absent in 

 CsHjN and CHCI3!); (3) absence of "chelated" C=0 band in plieophytins; (4) presence 

 of OH band— indicating enolization— in chlorophyll a and pheophytin a in pyridine, and 

 its practical absence in CCU; (5) presence of OH band in chlorophyll b in CCU, and its 

 absence in pheophytin b in the same solvent. * 



* Experiments with fresh chlorophyll b prei)arations showed no evidence of chelation 

 in ecu. Also, the OH— band seen before in chlorophyll b in CCU was weakened by 

 prolonged evacuation, indicating that it may be due to traces of water. 



