MHTCET 11 Apr 2026 Shift 2 Paper

Concept:Dehydration of alcohols to ethers occurs through bimolecular nucleophilic substitution ($S_N2$).Explanation:In this reaction, two alcohol molecules participate.For example, ethanol forms ethoxyethane with concentrated sulphuric acid at $413\,K$:$$2\mathrm{C_2H_5OH} \xrightarrow[\mathrm{413\,K}]{\mathrm{conc.\ H_2SO_4}} \mathrm{C_2H_5OC_2H_5} + \mathrm{H_2O}$$First, one alcohol molecule is protonated to form a good leaving group:$$\mathrm{C_2H_5OH} + \mathrm{H^+} \rightarrow \mathrm{C_2H_5OH_2^+}$$Then, the second alcohol molecule attacks the protonated alcohol.Water is displaced in this step.Since both the attacking alcohol and the substrate participate in the slow rate-determining step, the mechanism is bimolecular nucleophilic substitution ($S_N2$).Answer:Option B: Nucleophilic substitution bimolecular reaction.