Dehydration of alcohol requires cleavage of a C–-O bond with loss of a proton from the beta position. The result of dehydration is either an alkene or a mixture of the alkenes and the order of dehydration is first tertiary, then secondary, and finally primary.
What is Dehydration of Alcohols? Alcohol upon reaction with protic acids tends to lose a molecule of water to form alkenes. These reactions are known as dehydrogenation or dehydration of alcohols. It is an example of an elimination reaction.
The acid-catalyzed dehydration of secondary and tertiary alcohols proceeds via an E1 mechanism. First, the hydroxyl group in the alcohol is protonated in a fast step to form an alkyloxonium ion. Next, a molecule of water is lost from the alkyloxonium ion in the slow, rate-determining step, leaving behind a carbocation.
Ethanol can be dehydrated to give ethene by heating it with an excess of concentrated sulphuric acid at about 170°C.