HYDROXY-, KETO- AND DIBASIC ACIDS. 



In the previous sections compounds having only a single function 

 of either alcohol, aldehyde, or acid have been considered. In com- 

 pounds of carbon containing two or more atoms of carbon in their 

 molecule the replacement of hydrogen atoms by other atoms or groups 

 can occur in several of the atoms, and compounds, will result which 

 have multiple functions. They may be alcohol and acid, ketone and 

 acid, etc., at the same time. The properties of such compounds are 

 the sum of the properties possessed by the particular groups contained 

 in the molecule. Numerous natural compounds are included amongst 

 the large number of compounds which are theoretically possible : most, 

 if not all, of these have been prepared in the laboratory. 



COMPOUNDS CONTAINING TWO CARBON ATOMS. 



The variety of the compounds is most easily seen in the series of 

 compounds which are derived from ethane : 



Glycollic Aldehyde. 



Glycollic aldehyde is prepared by oxidising glycol with hydrogen 

 peroxide in the presence of ferrous sulphate, or by hydrolysing bromacet- 

 aldehyde with baryta. 



It is a sweet crystalline substance having the properties of an alde- 

 hyde. It is the first representative of the group of carbohydrates. 



T 06 





