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NEET CHEMISTRYAlcohols, Phenols and EthersMedium

Question

Which of the following methods is incorrect for the synthesis of alkenes?

A

Treatment of alkynes with Na in liquid NH3\text{NH}_3

B

Heating alkyl halides with alcoholic KOH\text{KOH}

C

Treating alkyl halides in aqueous KOH\text{KOH} solution

D

Treating vicinal dihalides with Zn metal

Step-by-Step Solution

Treating alkyl halides with aqueous KOH\text{KOH} leads to a nucleophilic substitution reaction, forming alcohols as the major product rather than alkenes . In contrast, heating alkyl halides with alcoholic KOH\text{KOH} causes a β\beta-elimination (dehydrohalogenation) reaction, which successfully forms alkenes . Additionally, the reduction of alkynes with sodium in liquid NH3\text{NH}_3 produces trans-alkenes , and the treatment of vicinal dihalides with zinc metal undergoes dehalogenation to form alkenes . Therefore, the use of aqueous KOH\text{KOH} is the incorrect method for alkene synthesis.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Alcohols, Phenols and Ethers. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYAlcohols, Phenols and Ethersfollowingmethodsincorrectsynthesisalkenes

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