MHT CET · Chemistry · Hydrocarbons

Identify major product \(\mathrm{A}\) in following reaction. 3-Bromo-2-methylpentane \(\stackrel{\text { ak } \mathrm{KoH}}{\longrightarrow} \mathrm{A}\)

A 2-Methylpentan-3-ol
B 2-Methylpent-2-ene
C 4-Methylpent-3-ene
D 4-Methylpentan-3-ol

Verified Solution

Answer & Solution

Correct Answer

(B) 2-Methylpent-2-ene

Step-by-step Solution

Detailed explanation

When alkyl halide having at least one \(\beta\)-hydrogen is boiled with alcoholic solution of potassium hydroxide, it undergoes elimination of hydrogen atom from \(\beta\)-carbon and halogen atom from \(\alpha\)-carbon resulting in the formation of an alkene. This reaction is known as dehydrohalogenation reaction or \(\beta\)-elimination. The preferred product is that alkene which has greater number of alkyl groups attached to doubly bonded carbon atoms according to Saytzeff rule.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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