QuestionOrganic / neighbouring group participation
The relative order of the rate of acetolysis among the following norbornyl derivatives is:
- (a) 1 > 2 > 3
- (b) 1 > 3 > 2
- (c) 3 > 2 > 1
- (d) 3 > 1 > 2
Answer: (b) 1 > 3 > 2
1 = anti-7-norbornenyl tosylate: C=C π electrons sit directly behind the C–OTs bond and assist ionisation → ~10¹¹ times faster than saturated 2. 3 (syn) cannot use the π bond from the back, but is still faster than 2. 1 > 3 > 2 → (b).