274 PHOTOSYNTHESIS 



A. Euler report finding dioxyaceton in a mixture of formaldehyde treated 

 with calcium carbonate. 



The tremendous complexity of the reactions which occur when a solu- 

 tion of formaldehyde is treated with an alkali is made evident by the ex- 

 tensive investigations of Nef on the action of alkalies on various hexose 

 and pentose sugars. In such a reaction Nef calculates there may take 

 part no less than 116 different substances. These include (1) the 32 

 theoretically possible normal aldoses with one to six carbon atoms; (2) the 

 32 methylenenols which are formed from these as : 



CHoOH CHoOH — CHOH 



> CHOH, > C < , > C < , etc. ; 



OH OH 



(3) all 26 ketoses with three to six carbon atoms in a straight chain and 



(4) the 26 endiols which may be formed from the dififerent aldoses and 

 ketoses. As a matter of experience Nef found the number of substances 

 reacting is no more than 93. The endiols may undergo rearrangement, 

 thus bringing about a transformation of aldoses into ketoses and vice versa 

 as was first made evident by the discovery of Lobry de Bruyn and van 

 Ekenstein that d-glucose, d-mannose, d-fructose, d-pseudo-fructose and a 

 and (3 d-glutose are all interconvertible. Also the endiols may undergo 

 a splitting at the double bond yielding aldoses with fewer carbon atoms. 

 Thus, for example, d-glucose in alkaline solution may yield the following 

 endiols : 



H H OH 



1. CH.OH — C — C — C— COH = CHOH, a-1, 2-d-Glucose endiol. 



1 I I 

 OH OH H 



H H 



2. CH2OH — C — C — COH = COH . CH.OH, 2, 3-d-Glucose endiol. 



I I 

 OH OH 



H H H 



3. CH2OH — C — C — C — COH = CHOH, |3-1, 2-d-Glucose endiol. 



I 1 I 

 OH OH OH 



H 



4. CH2OH — C — COH = COH — * CHOH . CH^OH, 3, 4-d-Glucose 



I endiol (2 forms) 



OH 



