282 



PHOTOSYNTHESIS 



C< 



H 



OH 



H 



C< 



CHO 



I 

 CH2OH 



IV 



OH 



Fincke pictures that in the first stage the oxygen of the moloxide to- 

 gether with the carbonyl oxygen of the carbonic acid are spHt out by the 

 action of Hght, thus an equal volume of oxygen is emitted for that of 

 carbon dioxide absorbed. The second step is a rearrangement of com- 

 pound I and splitting of compound H with the formation of the un- 

 saturated alcohol HI. The third stage is a rearrangement of this alcohol 

 into glycollic aldehyde. 



The intermediate substance H contains two asymmetric carbon atoms. 

 If R is also asymmetric, and being a plant product this can be assumed, 

 asymmetry can thus be induced in the further condensation products. 

 Fincke thus pictures a stepwise condensation : 



H 



H 



R 



/ 



O — C< 



OH / 



O — C< 



R 



H 



O — C< 



\ 



OH / 



O 



R 



OH 



O — C — OH 



I 

 HO — C — H 



H 



+ C< 



o 



OH 



CHO - 



I 



CH2OH 



CHO 



I 

 CH2OH 



H — C — OH 



I 

 H — C — OH 



HX — OH 



C — OH 



I 



HO — C — H 



I 

 H — C — OH 



I 

 H — C — OH 



I 



HoC — OH 



CHO 



I 

 H — C — OH 



I 

 OH — C — H 



— > 1 



H — C — OH 



I 

 H — C — OH 



I 



HoC — OH 



It will be observed that the third from the left of the above formulae 

 represents the endiol of glucose, mannose and fructose so that all three of 

 these sugars could be derived in the same manner. 



Fincke's theory is perhaps somewhat fanciful in its present form, but 

 it possesses some advantages over the formaldehyde theory. In another 

 paper Fincke ^^ does not include the moloxide ; this does, however, not 

 make for much greater simplicity. 



£. The Theory of Willstatter and Stoll. 



Willstatter and Stoll ^^ on the basis of their extensive researches on 

 chlorophyll and the mechanism of the photosynthetic process have formu- 



'^ Fincke, Zeit. Nahrung. Genussm., 27, 8 (1914). 



"' Willstatter and Stoll, "Untersuchungen uber die Assimilation der Kohlensaure," 

 Berlin, 1918, pp. 236, 415. 



