Reactions of alcohols 1

Elimination:
Alcohols are converted to alkenes by reaction with concentrated sulfuric acid, a strong dehydrating agent. 
 
conc H2SO4

or H3PO4
CH3CH2CH=CH2
 
Primary, secondary and tertiary alcohols may react in this way.  Alcohols that have different adjacent carbons bearing hydrogen may give rise to more than one alkene.  The major product is the alkene having the fewest hydrogen atoms on the double bond.
 
Substitution:
Alcohols react by substitution with various halogen-containing reagents to give haloalkanes.  Primary, secondary and tertiary alcohols react to give primary, secondary and tertiary halides respectively. 
SOCl2

(or PCl3 or conc HCl)
 
HBr

Alcohols react with carboxylic acids and acyl chlorides to give esters.  The reaction with carboxylic acids is slow and is catalysed by aqueous acid.
+ H3O+
+ H2O
HCl

 
Dr Sheila Woodgate
© The University of Auckland 2002