Before You Begin

Question #45049

Difficulty: 8/10 | 🟢 Free

The Question

Consider the solvolysis reactions of the following three alkyl chlorides in $80\%$ aqueous ethanol at $298\text{ K}$ :

(I) \ce{CH3-O-CH2-CH2-CH2-CH2-Cl} (II) \ce{CH3-CH2-CH2-CH2-CH2-Cl} (III) \ce{CH3-O-CH2-CH2-Cl}

Let $k_1$ , $k_2$ , and $k_3$ be their respective first-order rate constants. Let \textbf{X} be the major organic product (containing $\ge 4$ carbon atoms) formed from the solvolysis of (I). Which of the following correctly represents the order of reaction rates and the identity of \textbf{X}?

Options

A.
$k_1 > k_2 > k_3$ ; \textbf{X} = Tetrahydrofuran
B.
$k_1 > k_2 > k_3$ ; \textbf{X} = 4-methoxybutan-1-ol
C.
$k_2 > k_1 > k_3$ ; \textbf{X} = 4-methoxybutan-1-ol
D.
$k_3 > k_1 > k_2$ ; \textbf{X} = Tetrahydrofuran

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

Inductive Effect (I-Effect)|SN1 Carbocation Rearrangement

Why This Question Is Tricky

Common Mistakes

This problem tests two elite-level traps.

Trap 1 (Kinetic): Students typically rely on the Inductive Effect ( $-I$ ) to predict transition state stability, which would incorrectly predict the unsubstituted halide (II) to be the fastest.

The hidden variable is Neighboring Group Participation (NGP), where the kinetic favorability of forming a 5-membered ring makes (I) exceptionally fast, while the $-I$ effect dominates in (III) due to the strain of a 3-membered oxonium ring.

Trap 2 (Regioselectivity): Even if students recognize NGP, they often assume the solvent will attack the ring carbon to restore the linear chain (yielding 4-methoxybutan-1-ol).

However, regioselectivity in cyclic oxonium ions dictates $S_N2$ attack at the least hindered carbon (the methyl group), leading to ring retention and the formation of Tetrahydrofuran.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2
Concept	Inductive Effect (I-Effect)
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free