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.
In C6H5CH2Cl C6H5 CH2 + Cl , the benzyl carbocation is stabilised by resonance, the positive charge being spread over the ortho and para carbons of the ring.
In CH3CH2Cl CH3 CH2 + Cl , the ethyl carbocation is stabilised only by hyperconjugation with three α-C–H bonds, which is much weaker.
Thus the ethyl carbocation (hyperconjugation) is less stabilised than the benzyl carbocation (resonance), so Statement II is true.
Hence benzyl chloride ionises faster and reacts faster by SN1 than ethyl chloride, so Statement I is also true.
Answer: (1)