[specialk08]

When (S)-2-bromopropanoic acid [(S)-CH3CHBrCO2H] reacts with concentrated
sodium hydroxide, the product formed (after acidification) is (R)-2-hydroxypropanoic acid [(R)-CH3CHOHCO2H, commonly known as (R)-lactic acid]. This
is, of course, the normal stereochemical result for an SN2 reaction. However, when
the same reaction is carried out with a low concentration of hydroxide ion in the
presence of Ag2O (where Ag

acts as a Lewis acid), it takes place with overall retention of configuration to produce (S)-2-hydroxypropanoic acid. The mechanism
of this reaction involves a phenomenon called neighboring-group participation.
Write a detailed mechanism for this reaction that accounts for the net retention of
configuration when Ag

and a low concentration of hydroxide are used.


Help? This is so much harder than anything we've done in class and I have no idea..

[Honclbrif]

Basically it means an internal nucleophile displaces the leaving group to make some sort of cyclic intermediate. Then an external nucleophile attacks that intermediate, opening the ring and producing the final product. Think about which side an internal nucleophile would attack from, and what that would mean for the stereochem of the intermediate, and how the intermediate could then be attacked to yield the product.

[specialk08]

I GOT IT! So excited about this!!! lol im not going to post it all here because it is so hard to draw but i think  i got it thanks