$C H_{3} C H_{2} O H + H C l \overset{Z n C l_{2}}{\to} C H_{3} C H_{2} C l + H_{2} O$
In the above SN² reaction, the leaving group is:

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$H O^{Θ}$

$H_{3} O^{\oplus}$

$HO \overset{Θ}{Zn} {Cl}_{2}$

$H_{2} O$

answer is C.

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Detailed Solution

Reaction Overview

This chemical reaction illustrates the zinc chloride (ZnCl2) catalyzed cleavage of an ether. The reaction proceeds through a Lewis acid-catalyzed mechanism where zinc chloride acts as a catalyst to facilitate the breaking of the carbon-oxygen bond in the ether.

Starting Material: CH3-CH2-O-H (Ethanol or an ether derivative)

Catalyst: ZnCl2 (Zinc chloride - acts as a Lewis acid)

Final Products: CH3-CH2-Cl (Ethyl chloride/Chloroethane) + HOZnCl2 (Hydroxyzinc chloride complex)

Step-by-Step Mechanism

Step 1: Coordination with Lewis Acid

The ether oxygen atom donates a lone pair of electrons to the zinc chloride (ZnCl2), which acts as a Lewis acid. This forms a coordination complex between the ether and zinc chloride, making the C-O bond more susceptible to cleavage.

Step 2: Formation of Intermediate Complex

The intermediate shows the ether coordinated to ZnCl2, forming a cyclic-like structure. This weakens the C-O bond and activates it for nucleophilic attack by chloride ion.

Step 3: Cleavage and Product Formation (c+⊖)

The notation "c+⊖" indicates the generation of charged species (carbocation and anion). A chloride ion from ZnCl2 attacks the carbon, cleaving the C-O bond. This results in the formation of:

CH3-CH2-Cl (Ethyl chloride)
HOZnCl2 (Hydroxyzinc chloride complex)

Important Note: This reaction demonstrates the utility of Lewis acids like zinc chloride in activating ethers for nucleophilic substitution reactions. The curved arrows (⌢ and ⌣) in the original equation represent electron movement and bond formation/breaking during the reaction mechanism.

Key Concepts

Lewis Acid Catalysis: ZnCl2 accepts electron pairs, activating the substrate
Ether Cleavage: Breaking of C-O bonds in ether functional groups
Nucleophilic Substitution: Chloride ion acts as nucleophile replacing the -OH group
Coordination Chemistry: Formation of metal-oxygen coordination complexes