Explain the mechanism of acid catalysed dehydration of ethanol
Answers
The mechanism involved in acid catalysed dehydration of ethanol to ethene is elimination reaction mechanism. The mechanism involved is called beta elimination. The hydrogen from the beta carbon is removed and reacts with hydroxyl group to form water. And the beta carbon forms the double bond.
As u can see from the above image that the hydrogen is removed from beta carbon and a double bond gets attached there. However if the hydroxyl group is on the secondary carbon like the example below and we have two beta carbon atoms then the hydrogen would be extracted from that carbon atom which has less number of hydrogen atom. This is called Markonikov's rule. Apart from that the major product in the second example is but-2-ene because it has 6 hyperconjugating structures whereas but-1-ene has 2 hyperconjugating structures. Hence greater the hyperconjugating structures greater is the stability of the product.
The concentrated sulphuric acid acts as a dehydrating agent which removes water from ethanol.