[Copaiba]

Could someone please explain why hydroxide group #3 (URL below) is the most acidic? I get that it's neither 1 nor 2 since the double bond and carbonyl group are electron withdrawing, but I can't seem to figure out why 3 would be more acidic than 4, especially since 4 is closer to the carbonyl. Many thanks.

http://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/questions/problems/Images1/struct6.gif

[discodermolide]

Could someone please explain why hydroxide group #3 (URL below) is the most acidic? I get that it's neither 1 nor 2 since the double bond and carbonyl group are electron withdrawing, but I can't seem to figure out why 3 would be more acidic than 4, especially since 4 is closer to the carbonyl. Many thanks.

http://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/questions/problems/Images1/struct6.gif

Have a read of this page
http://en.wikipedia.org/wiki/Ascorbic_acid
about half-way down it explains the acidity of this compound.

[Copaiba]

Have a read of this page
http://en.wikipedia.org/wiki/Ascorbic_acid
about half-way down it explains the acidity of this compound.

Holy cow, I completely overlooked the effects of conjugation  . THANK YOU!