646 



ABSORPTION SPECTRA OF PIGMENTS IN VITRO 



CHAP. 21 



Characteristic changes apparently occur in the "doublet structure" of 

 the blue-violet band. In chlorophyll a in alcohols, the two components of 

 this band are well separated and almost equal in prominence. (This sepa- 

 ration of the band into two almost equal components may be the cause 

 for the fact that the blue-violet peak is in this case not much higher than 

 the red peak.) In dioxane, on the other hand, the violet component is a 

 "satellite" only half as high as the main blue peak (the latter being in this 

 case almost 50% higher than the peak of the red band). It was mentioned 



o 



o 

 o 



CL 

 CE 

 O 



cn 

 m 

 < 



UJ 



> 



UJ 



ir 



TT 

 I 1 



A 



Dry benzene 



Benzylamine 



Benzyl alcohol 



Benzene activated with benzylamine 

 or benzyl alcohol 



450 



550 

 WAVE LENGTH, m/i 



650 



Fig. 21.26A. Absorption spectra of chlorophyll a in pure hydrocarbon and hydro- 

 carbon containing an alcohol or amine (after Livingston et al. 1949). 



on page 607 that these differences may perhaps be indicative of tautomeric 

 eciuilibria; but this is merely a conjecture. 



It w^ould be interesting to evaluate the total areas under the different 

 curves to find whether the transition probabilities are changed by the sol- 

 vent, or whether the latter merely affects the shapes of the bands, without 

 changing their total areas. 



An as yet httle investigated subject is the absorption spectrum of dye- 

 stuffs in general, and of chlorophyll in particular, in mixed solvents. Ob- 

 servations of this type could give information about the occurrence, and 



