Unformatted text preview: 16-48 (e) u
E F continued GH H+ catalyst catalyst
+ H+ () d HO � base --- V phenol ·0 o . .1)- . :0
. Dehydration of that anstable aromaticproduct from is moreeaction product produces r thanproduces a more stable product the that usually happen faster under will milder conditions becausethat product the transition state leading to to a lower will be stabilized, activation energy. leading
F E. A Resonance the negative the phenoxide anionthe onestabilization ofchargecarbons. over shows para and two ortho distributed
:0 HO R umbelliferone of only the stabilization ofesonance forms gives not the anion same but as the phenoxide anion,threein addition,(-gives an extra resonance form most significanton a carbon, andcontributor, )another form the with charge resonance- charge on with the (oxygen. Thisthe other carbonyl ) stable than phenoxide anion is much moreinterpret as enhanced which of aciditywe the starting material, of umbelliferone.isIn fact,hile phenol is umbelliferone w the pKa about
Angiosperms: Fabaceae, Asteraceae, Apiaceae, and Rutaceae.) (Umbelliferone is one of about coumarins isolated from plants, primarily the families of umbelliferone base --1000 . . :0 10. 7.7 3 63 ...
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