MEASUREMENTS OF ABSORPTION SPECTRA OF PIGMENTS 



1801 



180 



380 400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 



Fig. 37C.6. Absorption spectrum of ethyl pheophorbide h in ether (after Holt and 



Jacobs 1954). 



change. A similar spectral shift is caused by dissolving chloroi)liyll in 

 parabcnzoylamine (Livingston, Watson and McArdle 1949). 



The observations of Freed and Sancier (1951), concerning the irre- 

 versible transformation of spectra of chlorophyll solutions in secondary 

 amines, belong to the same category. All these results were mentioned 

 in chapter 37B (section 4) as evidence of irreversible aminolysis of the 

 cyclopentanone ring in chlorophyll, which proceeds faster the more basic 

 the amine. 



Freed and Sancier (1951-54) studied the absorption spectra of the 

 chlorophylls and their derivatives at low temperatures. As stated in 

 chapter 37B (section 4), they first attributed the observed changes to a 

 reversible isomerization of the pigment; later (1954) it was suggested 

 that they are caused by a reversible formation of solvates. (That the 

 two phenomena may be coupled was also mentioned in chapter 37B.) 



Freed and Sancier (1951) measured the spectra of the chlorophylls 

 a, b, and b' in a mixture of w-propyl ether (20 p.), propane (60 p.) and 

 propene (60 p.), from —198° to —63° C; and in a mixture of n-propyl 

 ether (20 p.) and n-hexane (80 p.) from —63° C. to room temperature. 

 Figs. 37C.7 and 8 show the observed transformations. They indicate 



