Which process involves removing water from an alcohol to form an alkene?

• A. Hydration
• B. Elimination
• C. Addition
• D. Substitution

Answer: (B)

Dehydration of an alcohol to form an alkene is an elimination reaction. In acid-catalyzed dehydration, the -OH group is converted into a good leaving group (water) and departs, creating a carbocation. A neighboring hydrogen is then removed by a base, and the electrons rearrange to form a carbon–carbon double bond, yielding the alkene and releasing water. Hydration would add water to form an alcohol, not remove it. Addition would add atoms across a double or triple bond, not generate one from an alcohol. Substitution would swap the hydroxyl-bearing carbon for another group without creating an alkene.