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Given below are two statements labeled as Assertion (A) and Reason (R)

Assertion (A): Halogens are ortho and para-directing groups

Reason (R): Halogens are electron-withdrawing groups

Select the most appropriate answer from the options given below:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A.

(c) A is true but R is false.

(d) A is false but R is true.

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Best answer

Correct option is (b) Both A and R are true but R is not the correct explanation of A.

Halogens withdraw electrons through an inductive effect (–I) and release electrons through resonance (+R). Through inductive effect, halogens destabilize the intermediate carbocation formed during the electrophilic substitution. Through resonance, halogen tends to stabilize the carbocation and the effect is more pronounced at ortho- and para-positions. Reactivity is thus controlled by the stronger inductive effect and orientation is controlled by resonance effect. 

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