Question

# In the dehydration of alcohols to alkenes by heating with concentrated sulphuric acid, the initiation step is :a.) formation of carbocationb.) formation of an esterc.) protonation of alcohol moleculed.) elimination of water

Hint: In the first step of dehydration of alcohol to an alkene, the atom with lone pair i.e. the oxygen atom will attack the proton abstracting it. The sulphuric acid can donate two protons which are attached with two oxygen atoms.

${H_2}S{O_4} \rightleftharpoons {H^ + } + HSO_4^ -$
In the first step, the oxygen atom of alcohol attacks the ${H^ + }$ ion of sulphuric acid. This results in the formation of alkyloxonium ion which has a positive charge on oxygen and oxygen are bonded to three atoms.