Before You Begin

Question #44672

Difficulty: 8/10 | 🟢 Free

The Question

An organic compound $X$ has the empirical formula \ce{C5H11O} and a molar mass of $174 \text{ g/mol}$ . The $^1\text{H}$ NMR spectrum of $X$ exhibits exactly three singlet signals with an integration ratio of 6:3:2. A chemist attempts to synthesize $X$ via the Williamson ether synthesis by reacting the corresponding symmetrical dibromide $A$ with excess sodium methoxide in methanol at $330 \text{ K}$ . However, due to mechanistic constraints, the expected substitution fails completely. Instead, a highly stable conjugated hydrocarbon $Y$ is isolated as the major product. What is the IUPAC name of $Y$ ?

Options

A.
2,5-dimethylhexa-1,5-diene
B.
2,5-dimethylhexa-2,4-diene
C.
2,5-dimethoxy-2,5-dimethylhexane
D.
2-methoxy-2,5-dimethylhex-4-ene

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

Empirical vs Molecular Formula|Williamson Ether Synthesis Constraints

Why This Question Is Tricky

Common Mistakes

This question tests the fundamental steric limitations of the Williamson ether synthesis.

Students must first deduce the structure of the target diether from its empirical formula and NMR data, identifying it as having tertiary ether linkages.

The primary trap is assuming the textbook 'alkoxide + alkyl halide' stoichiometry will blindly yield the ether.

Instead, reacting a tertiary halide with a strong base (\ce{CH3O^-}) forces an E2 elimination.

Furthermore, students must differentiate between the possible elimination products, recognizing that the thermodynamic driving force of forming a conjugated diene dictates the Zaitsev product (2,5-dimethylhexa-2,4-diene) over the Hofmann product.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Some Basic Concepts of Chemistry - Class 11 Part 1
Concept	Empirical vs Molecular Formula
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free