Chemistry Question (SN2)?

Question

2,2-Dimethyl-1- bromopropane and bromoethane, both primary alkyl halides undergo SN2. Which one of them would react slower in the reaction and why?

I know that the stronger the nucleophile, the faster the rate of the SN2 reaction, but could someone please explain how to find if one is stronger than another? I know that bromoethane has a simpler structure, but that have anything to do with this question?

Thanks for any help. :-)

Answer 1

The bromopropane will react slower due to steric hinderence. Since the propane group is larger/bulkier than the ethane group, the nucleophile will have a harder time attacking the bromopropane only because there is more "stuff" in the way.

Answer 2

2,2-Dimethyl-1- bromopropane

The side group is very bulky and will not have a planar config although the C from which Br leaves will. This bulk will then hinder the approach of any nucleophile.