Name the reagent used for the dehydrohalogenation of alkyl halides.a) aqueous KOHb) alcoholic KOHc) Dry A{g_2}O d) Zn

The correct answer is: b) alcoholic KOH.

Explanation:
Dehydrohalogenation of alkyl halides is a type of elimination reaction (commonly referred to as E2 reaction) where a hydrogen atom and a halogen atom are removed, forming a double bond (alkene).

Aqueous KOH (option a) typically promotes substitution reactions (nucleophilic substitution) because the hydroxide ions act as nucleophiles in a polar medium, leading to the formation of alcohols.

Alcoholic KOH (option b) is used as a reagent for dehydrohalogenation. In the alcoholic solution, the hydroxide ions are more basic, and under these conditions, elimination reactions are favored over substitution. This results in the removal of a hydrogen atom and a halide ion (usually forming an alkene).

Dry Ag₂O (option c) is used for the conversion of alkyl halides into alcohols via substitution, not dehydrohalogenation.

Zn (option d) is used in dehalogenation reactions, where halogens are removed but it is not involved in dehydrohalogenation reactions.

Thus, alcoholic KOH is the reagent used for dehydrohalogenation of alkyl halides to form alkenes.