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Question #43994

Difficulty: 8/10 | 🟢 Free

The Question

Which of the following reaction sequences is the most appropriate for the high-yield synthesis of 2-methyloxirane starting from propanoic acid?

Options

A.
(i) $Br_2$ , red $P$ , then $H_2O$ (ii) $LiAlH_4$ , dry ether, then $H_3O^+$ (iii) $NaH$ , $THF$
B.
(i) $Br_2$ , red $P$ , then $H_2O$ (ii) $BH_3 \cdot THF$ , then $H_3O^+$ (iii) $NaH$ , $THF$
C.
(i) $Br_2$ , red $P$ , then $H_2O$ (ii) $Sn / HCl$ , then $H_3O^+$ (iii) $NaH$ , $THF$
D.
(i) $Br_2$ , red $P$ , then $H_2O$ (ii) $NaBH_4$ , $EtOH$ (iii) $aq.\ NaOH$ , $\Delta$

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Hunsdiecker/Hell-Volhard-Zelinsky|Reduction Selectivity (Sn/HCl vs LiAlH4)|Nucleophilic Acyl Substitution

Why This Question Is Tricky

Common Mistakes

This question tests the student's mastery of chemoselectivity in reduction reactions, specifically targeting the 'hidden variable' of reductive dehalogenation.

Students often memorize $LiAlH_4$ as the standard reagent for reducing carboxylic acids to primary alcohols.

However, they overlook its strong nucleophilic nature, which leads to the unwanted $S_N2$ displacement of the $\alpha$ -halogen.

The problem requires recognizing that $BH_3$ , an electrophilic reducing agent, operates via Lewis acid-base coordination with the carbonyl oxygen, thereby selectively reducing the carboxylic acid without cleaving the sensitive $C-Br$ bond required for the final intramolecular epoxidation.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Aldehydes, Ketones, and Carboxylic Acids - Class 12
Concept	Hunsdiecker/Hell-Volhard-Zelinsky
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free