1559T_ch18_323-34311/3/0511:12Page332 EQA 332.Chapter 18 ENOLS,ENOLATES,AND THE ALDOL CONDENSATION:B-UNSATURATED ALDEHYDES AND KETONES wSae+a8○ No a hydrogens in-inC o a hydroge Major product OH O OH O :-CH2-C-CHCHa CH:CH2-C-CH-C-CH acetaldehyde for illustration). :OH :OH CH CH-CH-CH-C product (b) (c) 44. Because enolates are not feasible intermediates, consider an alternative—a neutral enol, which should be a nucleophile somewhat similar to an enamine. Compare with How can acid play a role? You already know (Section 17-5) that acid can catalyze carbonyl addition reactions by attachment to the carbonyl oxygen, thereby generating a better electrophile. So (using acetaldehyde for illustration), OH CH3 CH CH2 OH C H H  product O OH CH3 C H CH2 CH OH CH3 C H H  NR2 NR2  C C C C OH   C C OH C C  , O CH2 C CH2CH3 O CH3 C CH2CH3 CH3 CH OH Very little of these (ketone  ketone) Major product O C H  No
hydrogens

O C CH3 CH CH OH O CH2 C CH2CH3 CH3 C OH CH3CH2 CH3 C OH CH3CH2 CH3 O CH C CH3 C O CH3 C CH2 OH C O (CH3)3C CH CH2 OH Very minor (ketone  ketone) Major product C O (CH3)3CCHO CH3

 No
hydrogens 332 • Chapter 18 ENOLS, ENOLATES, AND THE ALDOL CONDENSATION:
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