2007-01-17 05:03:46 · 3 answers · asked by manuelkuhs 1 in Science & Mathematics ➔ Chemistry
Remember resonance. A ketone with its double bonded oxygen really can’t resonate. So a nuclophile attacks the carbon with the double bonded oxygen, forms a new bond and the oxygen pulls a hydrogen from somewhere and become an alcohol. In this example nothing was substituted, a nucleophile was just pasted on.
Where an ester there that second oxygen in the line of the molecule (R-O). That second Oxygen has a Pi bond that can resonate with the double bonded oxygen. You form that unstable intermediate the enol. In that intermediate state a nucleophile can approach the carbocation and bond, ejecting the R-O group to go off and form an alcohol someplace else. And you’ve substituted your nucleophile with your R-O group.
2007-01-17 06:47:27 · answer #1 · answered by James H 5 · 0⤊ 0⤋
The alcohol is a reasonable leaving group, that's why. There's no suitable leaving group in a ketone.
2007-01-17 05:09:04 · answer #2 · answered by Gervald F 7 · 4⤊ 0⤋
Just adding my support to James H answer, I'm a carbohydrate chemist (grad student anyway) and that's about right
2007-01-24 17:13:47 · answer #3 · answered by Cara 2 · 0⤊ 0⤋