THE CHEMISTRY OF PHOTOSYNTHESIS 



283 



lated a theory of the reduction of carbonic acid which, though not entirely 

 novel, has several original features. The theory pertains more especially 

 to the mode of "deoxidation" of carbonic acid. The fact is accepted that 

 in photosynthesis the reduction of carbonic acid attains the level of for- 

 maldehyde, in fact, the formaldehyde theory so far as it postulates the in- 

 termediate formation of this substance is accepted. Willstatter and Stoll 

 consider that carbonic acid is added to the magnesium complex of the 

 chlorophyll, and the carbonic acid or a carbonic acid derivative thus be- 

 comes a component of the pigment. They believe the chlorophyll to be in 

 a colloidal solution in the leaf and that the colloidal state and the optical 

 properties of the chlorophyll are not altered by the addition of the car- 

 bonic acid. Chemical change is accomplished in the chlorophyll mole- 

 cule itself by means of the absorbed light energy. The vi^hole theory is 

 thus based upon the supposed property of chlorophyll to form an addi- 

 tion compound with carbonic acid. 



The result of light absorption by the chlorophyll-carbonic acid 

 complex is a rearrangement of the molecule of carbonic acid : "eine 

 Verschiebung der A'alenzen im Kohlensauremolekiil, eine Umgruppierung 

 der Atome, welche durch die zugefiihrte Energie bewirkt wird." This re- 

 arrangement of the carbonic acid molecule leads to the formation of a 

 peroxide and two possible structures are proposed, namely: 



H 

 / 



c==o 



\ 



O — OH 



Performic acid 



H 



/ 



C 

 l\ 



o— o 



OH 



Formaldehyde peroxide 



The performic acid is known and some evidence is presented for the 

 possible existence of the formaldehyde peroxide. The possibility is also 

 suggested that the addition to chlorophyll may not be of carbonic acid 

 itself but of some carbonic acid derivative. The addition product may 

 be written as follows : 



\ 



N O 



/ \ // 



::MMg — o — c 

 \ \ 



NH OH 



/ 



Chlorophyll-carbonic acid 

 compound 



\ 



N 



\ 



rMg - O 



NH 



O 



/ 

 -C 



l\ 

 H O 



/ 



Chlorophyll-formaldehyde 

 peroxide 



The further rearrangement of the chlorophyll- formaldehyde-peroxide 

 results in the splitting out of oxygen which may take place in two stages, 



