Question

What's the difference between a nucleophile and a lewis base? Don't they both donate electrons?

Answer 1

Not a lot. All nucleophiles are Lewis bases. I suppose in a reaction in which a Lewis base forms a bond just to H+, e.g.

H2O(l) + H+(aq) -> H3O+(aq)

You might not consider the Lewis base (H2O) a "nucleophile," since the bond that's being formed is just to H, and usually in an organic addition reaction you think of a new bond being formed to carbon or some heteroatom.

Answer 2

Well I guess that makes sense, it seems like that happens a lot in SN1 reactions so thanks.