Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :
- Both Statement I and Statement II are true
- Both Statement I and Statement II are false
- Statement I is true but Statement II is false
- Statement I is false but Statement II is true
Answer
(1) Both Statement I and Statement II are true
Solution
In SN1, the slow step is ionisation to a carbocation, so the more stable the carbocation, the faster the reaction.
C6H5CH2Cl C6H5 CH2 + Cl : the benzyl carbocation is stabilised by resonance — the positive charge is spread over the ortho and para carbons of the ring.
CH3CH2Cl CH3 CH2 + Cl : the ethyl carbocation is stabilised only by hyperconjugation with three α-C–H bonds, which is much weaker.
⇒ Ethyl carbocation is less stabilised (by hyperconjugation) than the benzyl carbocation (by resonance) ∴ Statement II is true.
⇒ Benzyl chloride ionises faster, so it reacts faster by SN1 than ethyl chloride ∴ Statement I is true.
Answer: (1)