364 Mr Fenton, Oxidation in Presence of Iron. 



Synthesis of Hexoses. 



[Trans. Chem. Soc. 1897. 375.] 



When glycollic aldehyde is heated in a vacuum to about 100° 

 it partly vaporizes unchanged, as previously mentioned ; the 

 remainder is found on cooling as a solid transparent gum which is 

 somewhat brittle and has a sweet taste. Analyses and molecular 

 weight determinations by the freezing-point method shew that 

 this product has the formula C 6 H 12 6 . Its aqueous solution 

 reduces Feh ling's solution and gives various colour reactions 

 characteristic of sugars, and when heated with water to 140° it 

 yields furfural. After purification by treatment with alcohol it 

 gives with phenylhydrazine acetate a normal hexosazone 



If the product obtained from condensation of glycollic alde- 

 hyde by heat, and puiifi cation with alcohol as above described, be 

 further heated for several hours in a vacuum to 100 — 106°, it 

 becomes more brittle and its composition then approximates to 

 the formula C 6 Hi O 5 . 



The synthetical formation of sugars in the manner here 

 described is of especial interest as tending to throw light on the 

 natural formation of carbohydrates, more particularly when the 

 following facts are considered. 



When tartaric acid or its salts are exposed to sunlight and air 

 in presence of small quantities of ferrous salts, a notable quantity 

 of dioxymaleic acid is produced. For this experiment to succeed 

 the three conditions presence of iron, oxygen and sunlight are 

 absolutely necessary ; in absence of any one of these conditions 

 the change does not occur. Since dioxymaleic acid spontaneously 

 decomposes, even at ordinary temperatures, in aqueous solution 

 giving glycollic aldehyde, and the latter readily undergoes con- 

 densation to hexose (and probably to hexose ' anhydrides' also) it 

 is evident that a theory as to the natural formation of carbo- 

 hydrates may be formulated which perhaps compares favourably 

 in some respects with the popular 'formaldehyde hypothesis' of 

 Baeyer. [Compare Fenton, B. A. Report, 1895.] 



With regard to the chemical nature of the sugar obtained in 

 the manner here described it may be remarked that it closely 

 resembles the condensation products obtained by Loew and by 

 Fischer from formaldehyde and by Fischer and Tafel from 

 ' glycerose.' In order to throw further light upon the matter 

 glycollic aldehyde was afterwards condensed in presence of dilute 

 alkalis instead of by heat, and from this product a hexosazone 

 was obtained which corresponds exactly in melting point and 



