Question

the mechanism of dehydration of an alcohol to give an alkene involves formation of​

Answer 1

it involves the formation of water.

Let's take an example,

C2H5OH — C2H4 + H2O.

here, ethyl alcohol is dehydrated in presence of sulphuric acid.

Answer 2

Answer:

The mechanism of dehydration of an alcohol to give an alkene involves three steps:

1. Protonation of alcohol
2. Formation of carbocation
3. Deprotonation

Explanation:

• First step: The formation of protonated alcohol from the simple alcohol. The alcohol acts as a weak base because it has two lone pairs on the oxygen atom of (-OH) group. The alcohol reacts with strong acids such as HCl to form oxonium salt.

        CH₃CH₂-OH   +   H⁺   ⇄    CH₃CH₂-O⁺H₂

• Second step: Protonated alcohol removes a water molecule from it, which leads to formation of a carbocation.

        CH₃CH₂-O⁺H₂       ⇄      CH₃CH₂⁺          +          H₂O

     Protonated alcohol              Primary carbocation

• Third step: Ethylene carbocation is very reactive species. it easily removed proton and formed ethene molecule.

       H-CH₂-CH₂⁺    ⇄    CH₂=CH₂   +   H⁺

                                       alkene

Hence, the formation of alkene from the alcohol by dehydration.