Question

Which of the following is the major product of the reaction between 1-bromobutane and potassium hydroxide in ethanol?

• A. Butan-1-ol
• B. But-2-ene
• C. Butan-2-ol
• D. Butane

Hint:

In a reaction with KOH in ethanol, the elimination (E2) mechanism typically leads to the formation of an alkene.

Answer 1

The Correct Option is B

The reaction involves 1-bromobutane (an alkyl halide) with potassium hydroxide (KOH) in ethanol. This is a typical example of an elimination reaction (E2 mechanism), where the hydroxide ion (OH⁻) removes a proton from the carbon adjacent to the carbon that is bonded to the leaving group (Br⁻), leading to the formation of a double bond. Step 1: Identify the type of reaction Since the reaction is occurring in ethanol, which is a polar protic solvent, the elimination occurs via the E2 mechanism. Step 2: Identify the product - The E2 mechanism will lead to the formation of an alkene. - The hydrogen is removed from the carbon next to the carbon bearing the bromine (the β-carbon), leading to the formation of But-2-ene. Answer: The major product of the reaction is But-2-ene, and thus the correct answer is option (2).