JEE Chemistry 2024 Question with Solution

Given: Assertion (A) states that $\text{CH}_2=\text{CH}-\text{CH}_2-\text{Cl}$ is an allyl halide. Reason (R) states that in allyl halides, the halogen is attached to an $\text{sp}^2$ hybridised carbon atom.

Find: Which option correctly describes the truth value of (A) and (R).

An allyl halide has the general structure $\text{CH}_2=\text{CH}-\text{CH}_2-\text{X}$, where the halogen is attached to the carbon adjacent to the double bond.

In $\text{CH}_2=\text{CH}-\text{CH}_2-\text{Cl}$, the chlorine atom is attached to the $\text{CH}_2$ carbon next to the double bond. This carbon is $\text{sp}^3$ hybridised, so the compound is indeed an allyl halide.

Therefore, Assertion (A) is true.

The reason says that the halogen in allyl halides is attached to an $\text{sp}^2$ hybridised carbon atom. This is incorrect because in allyl halides the halogen is attached to an $\text{sp}^3$ hybridised carbon atom adjacent to the $\text{C=C}$ bond.

Therefore, Reason (R) is false.

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

Given: The compound $\text{CH}_2=\text{CH}-\text{CH}_2-\text{Cl}$ and a statement about allyl halides.

Find: Whether the assertion and reason are true or false.

1. Understanding allyl halide: An allyl halide is a compound in which the halogen is bonded to the carbon atom next to a carbon-carbon double bond.
2. The structure $\text{CH}_2=\text{CH}-\text{CH}_2-\text{Cl}$ matches the allylic pattern, so the assertion is correct.
3. The carbon bearing $\text{Cl}$ is the terminal $\text{CH}_2$ carbon, and it is $\text{sp}^3$ hybridised.
4. Hence the reason is incorrect because it says the halogen is attached to an $\text{sp}^2$ hybridised carbon.

Therefore, the final answer is A.