chap_enols - Chap 22 Enols and Enolate 1. O base H C O E+...

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1 Chap 22 Enols and Enolate 1. major- most substituted base used is LDA lithium diisopropyl amine- good base but poor nucleophile condensation with ketones and aldehydes C O H α base C O - C O- E + enolate C O E α C O - enolate O O O - ROH O OH C O H C OH enol less stable keto :N Li + -
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2 ketones in the presence of acid. 2. alpha halogenation Rxn of methyl ketones 1. Basic conditions- Use I 2 to identify methyl ketones. O CH 3 H R H 3 O + O CH 3 H H + O CH 3 H H + H 2 O CH 3 OH enol O H CH 3 racemic mixture O H H Cl 2 (can be X) OH - , H 2 O O Cl H + Cl- + H 2 O O Cl Cl can get further halogenation R CH 3 O + 3X 2 + 3 OH - R CX 3 O + 3X- + 3H 2 O R CX 3 O + OH - R O- CX 3 OH R OH O + -CX 3 R O- O + HCX 3
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3 2. Acidic conditions- O CH 3 CH 3 COOH use as solvent O CH 3 H + O CH 2 H Br-Br O CH 3 H + O CH 3 H + + Br- O CH 2 Br Mono halogenation Stops here 3. alpha bromination of acids- HVZ rxn. O CH 3 + Br 2 CH 3 COOH use as solvent O CH 2 Br + HBr H 2 O OH O R Br 2 /PBr 3 Br O R Br OH O R Br + HBr R OH O H H Br 2 /PBr 3 R Br O H H R Br OH H H Br-Br R Br O H Br H + Br-
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Alkylation of enolate ions- Ex. Milder way to complete the same rxn. Enamine Rxn. C O C - C C - O R C H 2 X two possisble places of attack C O C R C C O R small yield 1. Use LDA as the base. 2. Need to have only one type of alpha proton or get complex mixture. O
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chap_enols - Chap 22 Enols and Enolate 1. O base H C O E+...

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