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Question #44494

Difficulty: 8/10 | 🟢 Free

The Question

Consider the reaction of 2-methylbut-1-en-3-yne with one equivalent of disiamylborane (\ce{Sia2BH}) in THF at 273 K, followed by treatment with alkaline hydrogen peroxide (\ce{H2O2} / \ce{NaOH}) at 298 K. What is the major organic product isolated at the end of the reaction?

Options

A.
3-methylbut-2-enal
B.
3-methylbut-3-enal
C.
3-methylbut-3-en-2-one
D.
2-methylbut-3-yn-1-ol

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

Hydroboration-Oxidation Logic|Tautomerism Conditions

Why This Question Is Tricky

Common Mistakes

The problem tests the student's ability to track a reaction through multiple stages of selectivity and thermodynamic equilibration.

The 'Hidden Variable' is the base-catalyzed isomerization.

Students often mechanically apply the hydroboration-oxidation rules to form the initial tautomer (3-methylbut-3-enal) but fail to recognize that the basic conditions of the oxidation step (\ce{OH-}) will drive the $\beta,\gamma$ -unsaturated system to the thermodynamically more stable $\alpha,\beta$ -conjugated system (3-methylbut-2-enal).

Distractors include the kinetic tautomer, the Markovnikov hydration product, and the alkene-hydroboration product.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Hydrocarbons - Class 11 Part 2
Concept	Hydroboration-Oxidation Logic
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free