Identify the given compound

The compound is: $\mathrm{CH_2=CH-CH_2-Cl}$

This is allyl chloride.

In an allylic halide, the halogen is attached to the carbon atom adjacent to a carbon-carbon double bond.

Check Assertion (A)

Assertion says: $\mathrm{CH_2=CH-CH_2-Cl}$ is an example of allyl halide.

This is true, because the chlorine is attached to the carbon next to the double bond.

Check Reason (R)

Reason says: Allyl halides are compounds in which the halogen atom is attached to an $sp^2$ hybridised carbon atom.

This is false.

In allyl halides, the halogen is attached to an allylic carbon, which is typically $sp^3$ hybridised, not $sp^2$.

For example, in $\mathrm{CH_2=CH-CH_2-Cl}$ the carbon bearing Cl is the $\mathrm{CH_2}$ carbon, and it is $sp^3$ hybridised.

Conclusion

• Assertion (A): True
• Reason (R): False

Therefore, the correct option is: A: (A) is true but (R) is false