MELVIN CALVIN 



325 



smaller than that loi the tianslonnatioii in the other direction, but 

 it involvctl, 1 bclie\c, a storage ol c hemic al energy. 



The reaction does not generally stop at the dihydro- stage but gcjes 

 on into the tetrahydro- and hexahydroporphyrin stages, llie various 

 relationshijjs ol these porphyrins are shown in Fig. 7, which illus- 



Photoroductlon of Zinc Tetraphenylporphln 

 by Benzoin In Benzene 



Run XI of Table VIII 



Wave length 



3. after 17| minutes Illumination 



4. after 87| minutes Illumination 



. 6SQ 



Fig. 6. Spectra showing photoreduction of zinc tetraphenylpoipliin by benzoin. 



trates the hydrogen transfer reactions that have been demonstrated 

 for this particular porphyrin. The first of these reactions was the 

 transformation of chlorin by light into porphyrin using quinones as 

 the acceptor. The reverse reaction, that is, the transformation of 

 porphyrin into chlorin using ene-diols, is a variable one, depending 

 on the ene-diol and also on the conditions of the reaction. The chlorin 



