[Zairair]

Say there's a solution of bromocyclopentane and bromocyclohexane and each were reacted with a solution of NaI in acetone, which one display higher SN2 reactivity?

I did this in a lab recently and bromocyclopentane formed it's precipitate and bromocyclohexane failed to within a certain time period. It's kind of hard visualizing the structure, but the best explanation I could come up with is that since there's most likely axial hydrogens in the chair formation, it's harder to get into the ring of a cyclohexane to have a backside attack whereas bromocyclopentane has a less rigid chair and the angles of the hydrogens allow an easier entrance into the ring structure.

And then also for say an SN1 reaction with silver nitrate in acetone, how could the carbocation of one be more stable than the other if they both have 2 other carbons attached to them?