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Question #44504

Difficulty: 8/10 | 🟢 Free

The Question

An organic chemist aims to synthesize 5-bromo-2-methylpentan-1-ol starting from ethyl 2-methylpent-4-enoate. Which of the following reaction sequences will successfully yield the desired target molecule as the major product?

Options

A.
1. $\ce{HBr}$ , $\ce{(PhCOO)2}$ , $h\nu$ ; 2. $\ce{LiAlH4}$ (excess), THF, $\Delta$ ; 3. $\ce{H3O+}$
B.
1. $\ce{HBr}$ , $\ce{(PhCOO)2}$ , $h\nu$ ; 2. $\ce{NaBH4}$ , $\ce{EtOH}$
C.
1. $\ce{LiAlH4}$ (excess), THF, $\Delta$ ; 2. $\ce{H3O+}$ ; 3. $\ce{HBr}$ , $\ce{(PhCOO)2}$ , $h\nu$
D.
1. $\ce{NaBH4}$ , $\ce{EtOH}$ ; 2. $\ce{H3O+}$ ; 3. $\ce{HBr}$ , $\ce{(PhCOO)2}$ , $h\nu$

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

Peroxide Effect (Kharasch)|Reduction Selectivity (Hydrides)|Aldehydes, Ketones, and Carboxylic Acids

Why This Question Is Tricky

Common Mistakes

This question tests the student's understanding of functional group compatibility and the chemoselectivity of hydride reducing agents.

The 'Hidden Variable' is the dual reactivity of $\ce{LiAlH4}$ .

Students often memorize that $\ce{LiAlH4}$ reduces esters to alcohols, but forget that it also readily reduces primary and secondary alkyl halides to alkanes.

By forcing the student to plan a multi-step synthesis, they must recognize that the order of operations is critical: the ester must be reduced before the alkyl bromide is introduced to prevent the lethal collision of the halide with $\ce{LiAlH4}$ .

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Hydrocarbons - Class 11 Part 2
Concept	Peroxide Effect (Kharasch)
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free