ENOLS AND ENOLATES 477 compounds are noncyclic). There are a total of five isomers: HC=CHCH.CH 3-Butenal (Er-2-Butenal (Z)-2-Butenal H, C=CCH H,C=CHCCH 2-Methy propenal 3-Buten-2-one b) The E and Z isomers of 2-butenal are stereoisomers. (c) None of the ChO aldehydes and ketones is chiral (d) The aB-unsaturated aldehydes are(E)-and(2)-CH3CH=CHCHO; and H,C=CCHO CH There is one a B-unsaturated ketone in the H,C=CHCCH (e) The E and z isomers of 2-butenal are formed by the aldol condensation of acetaldehyde 18.19 The main flavor component of the hazelnut has the structure shown. H C CHCH 18.20 The characteristic reaction of an alcohol on being heated with KHsO is acid-catalyzed dehydration Secondary alcohols dehydrate faster than primary alcohols, and so a reasonable first step is HOCHCHCHOH HOCHCHECHOH OH The product of this dehydration is an enol, which tautomerizes to an aldehyde. The aldehyde then undergoes dehydration to form acrolein HOCHCHECHOH HOCH. CHCH KHso→H2C= 3-Hydroxypropanal Acrolein Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Websitecompounds are noncyclic). There are a total of five isomers: (b) The E and Z isomers of 2-butenal are stereoisomers. (c) None of the C4H6O aldehydes and ketones is chiral. (d) The ,-unsaturated aldehydes are (E)- and ; and . There is one ,-unsaturated ketone in the group: . (e) The E and Z isomers of 2-butenal are formed by the aldol condensation of acetaldehyde. 18.19 The main flavor component of the hazelnut has the structure shown. 18.20 The characteristic reaction of an alcohol on being heated with KHSO4 is acid-catalyzed dehydration. Secondary alcohols dehydrate faster than primary alcohols, and so a reasonable first step is The product of this dehydration is an enol, which tautomerizes to an aldehyde. The aldehyde then undergoes dehydration to form acrolein. KHSO4 heat (H2O) HOCH2CH CHOH Propene-1,3-diol 3-Hydroxypropanal HOCH2CH2CH O Acrolein H2C CHCH O KHSO4 heat HOCH2CHCH2OH OH 1,2,3-Propanetriol HOCH2CH CHOH Propene-1,3-diol C C H H3C H C C O H CH3 CH2CH3 (2E,5S)-5-Methyl-2-hepten-4-one H2C O CHCCH3 H2C CH3 (Z)-CH3CH CHCHO CCHO O H2C CH3 CCH 2-Methylpropenal O H2C CHCCH3 3-Buten-2-one (methyl vinyl ketone) O O H2C CHCH2CH 3-Butenal C C H3C H H CH (E)-2-Butenal C C H3C H H CH (Z)-2-Butenal O ENOLS AND ENOLATES 477 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website