Question

why would a pair of bicyclic diastereomers differ in reaction time? what does it have to do with the rate determining step for each ?

Answer 1

Let’s have an example of diastereomers of 2-Norbornyltosylates viz. exo- and endo-

The ionization rate of exo-2-norbornyl tosylate is 350 times faster than endo-2—norbornyltosylate.

The reason is that, In exo isomer C-C bond gives anchimeric assistance (neighboring group participation) to the expulsion of leaving group OTs and an intermediate bridged ion is formed opening of this ion by acetic acid, followed by deprotonation gives exo-2-norbornyl acetate.

Interestingly both exo and endo tosylate gives single diastereomer exo-2-norbornyl acetate.