.346 Contents of enols at equilibrium (%h,COCH, CH,(CO, C,Hh NCCH,CO, CH 0.00015 0.0077 0.25 CH3COCH, CO2C2H5 CH2COCHCHsCOCH CH3COCH2COC6H5 76.4 89.2
Contents of enols at equilibrium （%） p.346 CH3COCH3 CH2 (CO2C2H5 )2 NCCH2CO2C2H5 CH3COCH2CO2C2H5 0.00015 0.0077 0.25 8 CH3COCHC6H5CO2C2H O O CH3COCH2COC6H5 1.2 30 76.4 89.2 O
Acid-catalyzed ketone-enol tautomerism →+OH OH H H u H Base-catalyzed ketone-enol tautomerism 0 BH 一BH OH B H H
B H O O - O - －BH H + OH BH －B Acid-catalyzed ketone-enol tautomerism H O H + H OH H OH + + －H + OH H + －H + Base-catalyzed ketone-enol tautomerism
C=0 C-0 CC0H→CC=0H hs attached to heteroatoms. as in the enol form are more acidic than c-h's as in the ketone form
* H’s attached to heteroatoms , as in the enol form, are more acidic than C-H’s, as in the ketone form * C O C + O - C C O H C - C O + H
11.2 Reactivity of Enols: The Mechanism of Alpha-Substitution Reactions oH +Oh +OH H E E E H OH E OH E
11.2 Reactivity of Enols: The Mechanism of Alpha-Substitution Reactions . .OH OH - + H O OH . . E + OH E －H + O E + OH OH + E . . E + －H +
11.3 Alpha Halogenation of Aldehydes and Ketones p.348 Aldehydes and ketones can be halogenated at their -positions by reaction with cl. Br, or h in acidic solution H H+x x +HX
11.3 Alpha Halogenation of Aldehydes and Ketones • Aldehydes and ketones can be halogenated at their a -positions by reaction with Cl2 , Br2 , or I2 in acidic solution p.348 H O + X2 X HX O + H +