436 ALDEHY DES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP (c) All the aldehydes yield chiral alcohols on reaction with methylmagnesium iodide. Thus CHaMgl CAHg CH 2 HO* C4Hg CCH3 OH A stereogenic center is introduced in each case. None of the ketones yield chiral alcohols. L CH,Mgl 2-Pentanone 2-Methyl-2-pentanol L CH, Mgl OH 3-Pentanone 3-Methyl-3-pentanol OH CHaMgl 3-Methyl-2-butanone 2,3-Dimethyl-2-butanol 17. 20(a) Chloral is the trichloro derivative of ethanal(acetaldehyde CH3CH CI -CH Ethanal Trichloroethanol (b) Pivaldehyde has two methyl groups attached to C-2 of propanal H3 o CH CHCH CH2C—CH 2, 2-Dimethylpropanal (pivaldehyde) (c) Acrolein has a double bond between C-2 and C-3 of a three-carbon aldehyde H,C=CHCH Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(c) All the aldehydes yield chiral alcohols on reaction with methylmagnesium iodide. Thus, A stereogenic center is introduced in each case. None of the ketones yield chiral alcohols. 17.20 (a) Chloral is the trichloro derivative of ethanal (acetaldehyde). (b) Pivaldehyde has two methyl groups attached to C-2 of propanal. (c) Acrolein has a double bond between C-2 and C-3 of a three-carbon aldehyde. O H2C CHCH 2-Propenal (acrolein) CH3 O CH3C CH3 CH 2,2-Dimethylpropanal (pivaldehyde) O CH3CH2CH Propanal O CH3CH Cl O Cl C Cl CH Trichloroethanal (chloral) Ethanal O 3-Methyl-2-butanone 1. CH3MgI 2. H3O 2,3-Dimethyl-2-butanol (achiral) OH O 3-Pentanone 1. CH3MgI 2. H3O 3-Methyl-3-pentanol (achiral) OH O 2-Pentanone 2-Methyl-2-pentanol (achiral) 1. CH3MgI 2. H3O OH H OH C4H9CCH3 O C4H9CH 1. CH3MgI 2. H3O 436 ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 437 (d) Crotonaldehyde has a trans double bond between C-2 and C-3 of a four-carbon aldehy CH (e) Citral has two double bonds: one between C-2 and C-3 and the other between C-6 and C-7 The one at C-2 has the E configuration. There are methyl substituents at C-3 and C-7. (E)-3,7-Dimethyl-2, 6-octadienal Cf) diacetone alcohol is CH; CCH,C(CH3)2 (g) The parent ketone is 2-cyclohexenone. Carvone has an isopropenyl group at C-5 and a methyl group at C-2 CH3 CH (h) Biacetyl is 2, 3-butanedione. It has a four-carbon chain that incorporates ketone carbonyls as C-2 and C-3 CH CCCH 2.3-Butanedione Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(d) Crotonaldehyde has a trans double bond between C-2 and C-3 of a four-carbon aldehyde. (e) Citral has two double bonds: one between C-2 and C-3 and the other between C-6 and C-7. The one at C-2 has the E configuration. There are methyl substituents at C-3 and C-7. ( f ) Diacetone alcohol is (g) The parent ketone is 2-cyclohexenone. Carvone has an isopropenyl group at C-5 and a methyl group at C-2. (h) Biacetyl is 2,3-butanedione. It has a four-carbon chain that incorporates ketone carbonyls as C-2 and C-3. 2,3-Butanedione (biacetyl) CH3CCCH3 OO 5-Isopropenyl-2-methyl-2- cyclohexenone (carvone) O CH3 CH3 H2C C 2-Cyclohexenone O 6 5 2 1 3 4 O OH O CH3CCH2C(CH3)2 OH 4-Hydroxy-4-methyl- 2-pentanone H CH O 8 7 6 5 4 2 3 1 (E)-3,7-Dimethyl-2,6-octadienal (citral) C C H H3C CH H O (E)-2-Butenal (crotonaldehyde) ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 437 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
438 ALDEHYDESANDKETONES:NUCLEOPHIUIC ADDITION TO THE CARBONYL GROUP 1721(a)Lithium aluminum hydride reduces aldehydes to primary alcohols. 1. LiAIH, CHa CH,CH CH;CH,CH,OH (b) Sodium borohydride reduces aldehydes to primary alcohols. NaB CH CH,CH CHa CHCH,OH (c) Aldehydes can be reduced to primary alcohols by catalytic hydrogenation CH CHCH CHa CH,CH,OH (a) Aldehydes react with Grignard reagents to form secondary alcohols 1. CH, Mgl CH CHCH diethyl ether CHCH CHCH 2-Butanol (e) Sodium acetylide adds to the carbonyl group of propanal to give an acetylenic alcohol HC≡CNa CHCHCH CH2CH,CHC≡CH 2. O (f) Alkyl-or aryllithium reagents react with aldehydes in much the same way that Grignard CH CHCH CHa CH,CHCSH (g) Aldehydes are converted to acetals on reaction with alcohols in the presence of an acid CH,CH,CH 2CHOH CH,CH,CH(OCH3) 2 Propanal Methanol Propanal dimethyl acetal Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
17.21 (a) Lithium aluminum hydride reduces aldehydes to primary alcohols. (b) Sodium borohydride reduces aldehydes to primary alcohols. (c) Aldehydes can be reduced to primary alcohols by catalytic hydrogenation. (d) Aldehydes react with Grignard reagents to form secondary alcohols. (e) Sodium acetylide adds to the carbonyl group of propanal to give an acetylenic alcohol. ( f ) Alkyl- or aryllithium reagents react with aldehydes in much the same way that Grignard reagents do. (g) Aldehydes are converted to acetals on reaction with alcohols in the presence of an acid catalyst. O CH3CH2CH Propanal 2CH3OH Methanol CH3CH2CH(OCH3)2 Propanal dimethyl acetal HCl O CH3CH2CH Propanal OH CH3CH2CHC6H5 1-Phenyl-1-propanol 1. C6H5Li, diethyl ether 2. H3O CH3CH2CH O 2. H3O 1. HC CNa, liquid ammonia CH3CH2CHC CH OH Propanal 1-Pentyn-3-ol O CH3CH2CH Propanal OH CH3CH2CHCH3 2-Butanol 1. CH3MgI, diethyl ether 2. H3O O CH3CH2CH Propanal CH3CH2CH2OH 1-Propanol H2 Ni O CH3CH2CH Propanal CH3CH2CH2OH 1-Propanol NaBH4 CH3OH O CH3CH2CH Propanal CH3CH2CH2OH 1-Propanol 1. LiAlH4 2. H2O 438 ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 39 (h) Cyclic acetal formation occurs when aldehydes react with ethylene glycol CHSCHCH+ lOCH,CH,OH、o H CHCH Ethylene glycol (i) Aldehydes react with primary amines to yield imines. CH CH, CH+ CHsNH? CHaCH CHENC6H Aniline N-Propylideneaniline ( Secondary amines combine with aldehydes to yield enamines N(CH duenesulfonic acid CHaCH,CH +(CH)2NH CHaCH=CH Dimethylamine k) Oximes are formed on reaction of hydroxylamine with aldehydes HNOH CH CHCH CH,CHOCHENOH ( Hydrazine reacts with aldehydes to form hydrazones. H, NNH, CHaCHLCH CHa CH,CHENNH? Propanal hydrazone (m) Hydrazone formation is the first step in the wolff-Kishner reduction( Section 12.8). CH3CH,CH=NH2m时时 CH,, CH,CH+N2 Propanal hydrazone (n) The reaction of an aldehyde with p-nitrophenylhydrazine is analogous to that with hydrazine. CH, CH,CH O,N NINH CHCHCHENNH- NO,+ H,O p-Nitropheny hydrazine p-nitrophenylhydrazone Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(h) Cyclic acetal formation occurs when aldehydes react with ethylene glycol. (i) Aldehydes react with primary amines to yield imines. ( j) Secondary amines combine with aldehydes to yield enamines. (k) Oximes are formed on reaction of hydroxylamine with aldehydes. (l) Hydrazine reacts with aldehydes to form hydrazones. (m) Hydrazone formation is the first step in the Wolff–Kishner reduction (Section 12.8). (n) The reaction of an aldehyde with p-nitrophenylhydrazine is analogous to that with hydrazine. H2O Propanal Propanal p-nitrophenylhydrazone CH3CH2CH CH3CH2CH NNH NO2 O p-Nitrophenylhydrazine O2N NHNH2 CH3CH2CH NNH2 Propanal hydrazone CH3CH2CH3 N2 Propane NaOH triethylene glycol, heat CH3CH2CH O Propanal CH3CH2CH NNH2 Propanal hydrazone H2NNH2 CH3CH2CH O Propanal CH3CH2CH NOH Propanal oxime H2NOH (CH3)2NH Dimethylamine 1-(Dimethylamino)propene CH3CH CH N(CH3) O 2 CH3CH2CH Propanal p-toluenesulfonic acid benzene H2O C6H5NH2 Aniline N-Propylideneaniline CH3CH2CH NC6H5 O CH3CH2CH Propanal p-toluenesulfonic acid HOCH2 benzene CH2OH Ethylene glycol O CH3CH2CH Propanal 2-Ethyl-1,3-dioxolane H CH2CH3 O O ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 439 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
440 ALDEHY DES AND KETONES: NUCLEOPHI ON TO THE CARBONYL GROUP (o) Semicarbazide converts aldehydes to the corresponding semicarbazone CH,,CH H,NNHCNH CHaCH,CH=NNHCNH, H,O (p) Phosphorus ylides convert aldehydes to alkenes by a wittig reaction CHCH,CH +(C HS)3P--CHC CH,CH,CH=CHCH3 +(CHs)3P- Ethylidenetriphenyl Triphenylphosphine (q) Acidification of solutions of sodium cyanide generates HCN, which reacts with aldehydes to form cyanohydrins CH CHCH+ HCN CHCHCHCN Propanal Hydrogen (r) Chromic acid oxidizes aldehydes to carboxylic acids. H,CrO, CHCH.CH CH CH,CO,H Propan 17.22(a) Lithium aluminum hydride reduces ketones to secondary alcohols H OH Cyclopentanone Cyclopentanol b) Sodium borohydride converts ketones to secondary alcohols CH, O Cyclopentanone (c) Catalytic hydrogenation of ketones yields secondary alcohols. OH Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(o) Semicarbazide converts aldehydes to the corresponding semicarbazone. (p) Phosphorus ylides convert aldehydes to alkenes by a Wittig reaction. (q) Acidification of solutions of sodium cyanide generates HCN, which reacts with aldehydes to form cyanohydrins. (r) Chromic acid oxidizes aldehydes to carboxylic acids. 17.22 (a) Lithium aluminum hydride reduces ketones to secondary alcohols. (b) Sodium borohydride converts ketones to secondary alcohols. (c) Catalytic hydrogenation of ketones yields secondary alcohols. O Cyclopentanone H OH Cyclopentanol H2 Ni O Cyclopentanone H OH Cyclopentanol NaBH4 CH3OH 1. LiAlH4 2. H2O O Cyclopentanone H OH Cyclopentanol Propanoic acid CH3CH2CO2H Propanal CH3CH2CH O H2CrO4 Hydrogen Propanal cyanohydrin cyanide HCN Propanal CH3CH2CH O CH3CH2CHCN OH Propanal CH3CH2CH O 2-Pentene CH3CH2CH CHCH3 Ethylidenetriphenylphosphorane (C6H5)3P CHCH3 Triphenylphosphine oxide (C6H5)3P O H2O Propanal CH3CH2CH O Semicarbazide H2NNHCNH2 O Propanal semicarbazone CH3CH2CH NNHCNH2 O 440 ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website