Question

A set of compounds in which the reactivity of halogen atom is in ascending order is:

• A. chlorobenzene, vinyl chloride, chloroethane
• B. chloroethane, chlorobenzene, vinyl chloride
• C. vinyl chloride, chlorobenzene, chloroethane
• D. vinyl chloride, chloroethane, chlorobenzene

Hint:

Reactivity order: aryl halide < vinyl halide < alkyl halide.

Answer 1

The Correct Option is A

Concept: Reactivity of halogen in substitution depends on:
• Bond strength (C–Cl)
• Hybridization of carbon
• Resonance stabilization

Step 1: Chlorobenzene (least reactive).
\[ C_6H_5-Cl \] Strong resonance gives partial double bond character → very stable → least reactive.

Step 2: Vinyl chloride.
\[ CH_2=CH-Cl \] Attached to \(sp^2\) carbon → stronger bond than alkyl halide → low reactivity.

Step 3: Chloroethane (most reactive).
\[ CH_3CH_2-Cl \] \(sp^3\) carbon, no resonance → weakest bond → most reactive.

Step 4: Ascending order.
\[ \text{chlorobenzene}<\text{vinyl chloride}<\text{chloroethane} \]