ORGANIC CHEMISTRY 3 



By introducing one atom of oxygen so that its two valencies 

 are united one with carbon and the other with hydrogen, 

 the hydroxyl group ( O H or OH) is formed. This 

 converts the paraffins into alcohols, of which there are three 

 varieties depending on the number of hydrogens attached to 

 the carbon atom, to which the hydroxyl group is attached. 



A primary alcohol retains two hydrogen atoms, a secondary 

 alcohol one, and a tertiary alcohol has no hydrogen united 

 directly to the carbon atom to which the hydroxyl group is 

 attached. The introduction of a second atom of oxygen should 

 lead to the presence of two hydroxyls but water (H 2 O) is split 

 off and one oxygen atom is left united to the carbon by its 

 two bonds. By oxidation a primary alcohol is converted into 

 an aldehyde, and a secondary alcohol into a ketone : a tertiary 

 alcohol is decomposed on oxidation, because a valency must 

 be set free in order to furnish the two valencies required by 

 oxygen. Further oxidation of the aldehyde produces an 

 acid, whilst a ketone like a tertiary alcohol cannot be 

 oxidised further without decomposition. 



R 2 H Rg 



i 



R, C OH RJ C OH Rj C OH 



I T? 



I or g>CHOH __ or R CH 2 OH or R \ C OH 



K R/ 



Secondary Alcohol. Primary Alcohol. Tertiary Alcohol, 



4- oxygen water I + oxygen water 



I 4- 



R 2 H H 



| oxygen O 



Rj C=O R! C=0 



org> CO orRCHO R l C=O 



R^ C or RCOOH 



Ketone Aldehyde (Acid 



The groups RJ, R 2 and R 3 may also contain other alcohol, 

 aldehyde, ketone or acid groups. 



CARBOHYDRATES ' 



A substance in which several alcohol groups occur is known 

 as a polyhydroxy alcohol. One of these, containing three 

 alcohol hydroxyl groups, is the substance glycerine in which 

 two primary and one secondary alcohol groups occur. By 

 oxidising one of the primary alcohol groups to an aldehyde, 

 or the secondary alcohol group to a ketone, simple sugars are 

 formed, and these belong to our first group : the carbohydrates 



