Is the book mistaken or am I just not getting it? Sn2 reactions. 1-bromo-2 phenylethane vs 1-iodo-2 phenylethane

[frankenstein18]

I'm studying Sn2 reactions and I know that Iodine is a weaker base and therefore a better leaving group than Br

In an exercise in my book (essential organic chem 3rd edition by paula yurkanis bruice) it asks to see which is more reactive between 1-bromo-2 phenylethane and 1-iodo-2 phenylethane

1-bromo-2 phenylethane and 1-iodo-2 phenylethane look pretty much the same except that one has Br and the other has Iodine

I thought it was 1-iodo-2 phenylethane because it has a better leaving group but the back of the book says its 1-bromo-2 phenylethane

Does the book have an error or am I just not understanding?

[hypervalent_iodine]

Does it offer an explanation? Could you post the question as it appears in the book? I would have picked the iodo compound as well.

[John Cuthber]

I would also have picked the iodinated version as more reactive.

And, for what it is worth, Hypervalent Iodine and I are both chemists.

Edited November 15, 2015 by John Cuthber