Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the correct answer from the options given below:
- A is true but R is false
- A is false but R is true
- Both A and R are true and R is the correct explanation of A
- Both A and R are true but R is not the correct explanation of A
Answer
(3) Both A and R are true and R is the correct explanation of A
Solution
In an SN2 reaction the C–X bond breaks in the rate-determining step.
The C–I bond is longer and weaker than the C–Cl bond; the large iodide ion stabilises the negative charge better, so I- is a better leaving group.
Hence 1-iodobutane reacts faster than 1-chlorobutane (reactivity RI > RBr > RCl).
Both A and R are true and R explains A.
Answer: (3)