76 3-Methylbutanal 2-Propenal (2E)-3,7-Dimethyl-2,6-octadienal 6 5 trans-3-enyl-2-propenal yclopentanecarbaldehyde trans-4-ydroxycyclohexanecarbaldehy

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1 75 hap 16 Aldehydes and Ketones 16.1 Structure and bonding 16.2 omenclature 16.3 ysical properties 16.4 eactions 16.5 Addition of carbon nucleophiles 16.6 The Wittig reaction 16.7 Addition of oxygen nucleophiles 16.8 Addition of nitrogen nucleophiles 16.9 Keto-enol tautomerism xidation eductions eactions at an α-carbon 16.1 Structure and Bonding Aldehyde() : 카보닐 (=) 기에수소및탄소원자가결합된구조 Ketone(') : 카보닐 (=) 기에두탄소원자가결합된구조 Methanal Ethanal Propanone (Formaldehyde) (Acetaldehyde) (Acetone) 16.2 omenclature A. IUPA omenclature Aldehyde의명명 : i) 가장긴탄소사슬을모체로선정하고, alkane의어미 -e -al 로변환. ii) Unsaturated aldehyde의경우에는삽입어 en- 혹은 -yn-을사용하여이중결합혹은삼중결합의위치를표시함. iii) -가고리에직접결합된경우는고리명칭에 carbaldehyde를붙여줌

2 76 3-Methylbutanal 2-Propenal (2E)-3,7-Dimethyl-2,6-octadienal 6 5 trans-3-enyl-2-propenal yclopentanecarbaldehyde trans-4-ydroxycyclohexanecarbaldehyde (innamaldehyde) Ketone의명명 : 카보닐기를포함하는가장긴모체탄소사슬을선정하고, alkane 의어미 -e -one로변환 Propanone 1-enyl-1-pentanone B. 관용명 Aldehyde : 카복실산의 -ic acid 혹은 -oic acid -aldehyde 로변환 Ketone : 2 개의 alkyl 혹은 aryl ketone 으로명명 Formaldehyde Benzaldehyde Ethyl isoproryl ketone Dicyclohexyl ketone Acetophenone. IUPA ames for More omplex Aldehydes and Ketones 작용기의우선순위 (Table 16.1) : arboxylic acid > Aldehyde > Ketone > Alcohol > Amine > Thiol 3-xopropanoic acid 3-xobutanoic acid 4-ydroxybutanoic acid 2 3-Aminobutanoic acid S 2-Mercaptoethanol

3 ysical Properties arbonyl(=) : 탄소와산소의전기음성도차이로인하여극성을띰 = 작용기사이의 dipole-dipole interaction Table 16.2 : Boiling point of some compounds of similar molecular wight Bp : arboxylic acid > Alcohol > Aldehyde, Ketone > Ether, Alkane Table 16.3 : ysical properties of some aldehydes and ketones 16.4 eactions 친전자성을띠는 carbonyl carbon 에친핵체가첨가반응을일으켜정사면체의중간 체생성 - ucleophilic addition( 친핵성첨가반응 ) 1) Basic condition u u u ' ' ' aq l ' ' u Tetrahedral intermediate (acemic) u acemic alcohol 2) Acidic condition B fast u u B 1st step : Protonation of carbonyl by - Activation of = arbonyl 의 electrophilicity 증가 2nd step : ucleophilic addition of u - - Formation of racemic alcohols

4 Addition of arbon ucleophiles 탄소를포함하는친핵체 : -Li > -MgX > - - > - A. Addition of Grignard eagents arbonyl 화합물에 MgX 시약을첨가하면친핵성첨가에의하여 tetrahedral alkoxide 의중간체가생성되고, aq l 로산성화하면 alcohol 이생성된다. 3 2 MgBr Et MgBr Propanol (1 o ) eaction of acetaldehyde and acetone with Grignard reagent MgBr MgBr Et o MgBr TF MgBr 3 3 o 예제 16.4 : Synthesis of 2-phenyl-2-butanol

5 79 B. Addition of rganolithium ompounds Li : More reactive than MgBr arbonyl 화합물과친핵성첨가반응하여 alcohol 을생성함 Li Li 3 lithium alkoxide. Addition of Anions of Terminal Alkynes 말단 alkyne의음이온은알데하이드나케톤의 carbonyl기에친핵성첨가하여삼중결합을가진 alcohol을생성한다. a 3 a D. Addition of ydrogen yanide 알데하이드나케톤에 K(or a)/ 을첨가하면친핵성첨가에의하여 cyanohydrin( 동일한탄소에 - 기와 - 기가결합된화합물 ) 을생성한다. K K * Utility of cyanohydrin compound 2 2 2, i Acrylonitrile

6 The Wittig eaction osphonium ylide( 3 P=) 가알데하이드나케톤과반응하여 alkene 을생성하는반응 3 P P yclohexanone osphonium ylide 1) Formation of phosphonium ylide Methylenecyclohexene Triphenylphisphineoxide 3 P 3 I S 2 3 P 3 I n-buli 3 P LiI 3 P 2 2) Wittig reaction 3 P 2 P 3 P3 Betaine xaphosphetane 2 3 P ontrol of cis-/trans-alkene by Wittig reaction osphonium ylide 의구조가주로 alkene 의 configuration 을결정함 3 P : = Alkyl ( 3, Et etc) cis-alkene 이주생성물로얻어짐 = - 3, -Et etc trans-alkene 이주생성물로얻어짐 3 P 3 P cis-1-phenyl-2-butene trans-1-phenyl-2-butene 87% 13% Et Et 3 P 3 P Ethyl trans-4-phenyl-2-butenoate (major product) osphonium ylide 가공명안정화되면반응성이감소하게되어평형상태가반응을 지배하게된다. trans-alkene 은 cis-alkene 보다안정하므로 trans- 가주생성물로 얻어진다.

7 81 orner-emmons-wadsworth reaction 염기하에서 α-phosphonoester or α-phosphonoketone 과 aldehyde or ketone 을 반응시켜 alkene 을합성하는반응 1) Preparation of α-phosphonoester or α-phosphonoketone Br 2 Et α-bromoester (Me) 2 P 2 Et MeBr α-osphonoester (Me) 3 P Br 2 Trimethylphosphite α-bromoketone (Me) 2 P 2 MeBr α-osphonoketone α-osphonoester or α-phosphonoketone 의유용성 : α- 이 acidic 하므로염기에의하여쉽게제거되어 stabilized anion 을생성함. osphonate 로안정화된 anion 은 Wittig 반응에서거의대부분 trans-alkene 을생성함 2) Wittig reaction (Me) 2 P 2 a Et (Me) 2 P Et P (Me) 2 P Me P (Me) 2 Et Me Et only E-isomer Dimethylphosphate anion Et 예제 16.5 : 3 Br

8 Addition of xygen ucleophiles A. Addition of Water: Formation of arbonyl ydrates Aldehyde나 ketone에 2 를첨가하면 nucleophilic addition ( 친핵성첨가 ) 에의하여 geminal diol이생성된다. K 2 hydrate (geminal diol) ' ' eversible reaction Geminal diol - 일반적으로 unstable, easy dehydration 반응물보다생성물의 steric repulsion이증가함 K의크기 :,'=, >,'= 3, >,'= 3, 3 (K=0.002) B. Addition of Alcohols: Formation of Acetals ' ' ' aldehyde hemiacetal ' ' acetal emiacetal : 일반적으로 unstable 5 원자혹은 6 원자고리의 hemiacetal 은상대적으로 angle strain 이 작으므로안정하게존재함 2 아노머탄소 2 D-Glucose (open chain form) β-anomer of D-glucose (cyclic hemiactal) α-anomer of D-glucose (cyclic hemiacetal) 1) Acid-catalyzed formation of hemiacetal ' ' - ' hemiacetal : catalyst, eversible reaction, Warming 조건, 1 eq alcohol 의사용

9 83 2) Acid-catalyzed formation of acetal ' 2 ' - 2 ' ' ' ' ' - ' acetal : catalyst, 가열조건, Aldehyde에 2 eq 알코올의사용 eversible reaction : Dean-Stark trap을이용하여반응을완결시킴 Figure 16.1 : Dean-Stark trap for removing water by azeotrope( 공비혼합물 ) Acetal : stable to basic reagent (LiAl 4, ab 4, MgBr) Protecting group of carbonyl (=) unstable to acidic reagent Formation of cyclic acetal 2-3. Acetals as arbonyl-protecting Groups M?? 5-ydroxy-5-phenylpentanal Synthesis of 5-hydroxy-5-phenylpentanal from 4-bromobutanal : Br Mg Br BrMg TF -MgBr l, 2 5-ydroxy-5-phenylpentanal

10 84 D. Tetrahydropyranyl Ethers: Protecting an Alcohol as an Acetal Protection of : Use of dihydropyran (DP) Tetrahydropyranyl (TP) ether 2 Dihydropyran 2 Tetrahydropyranyl ether : Stable to basic reagent (ab 4, MgBr) 예제 16.7 : Mechanism of TP ether formation 16.8 Addition of itrogen ucleophiles A. Ammonia and Its Derivatives 1) 3, 2 (1차아민 ) 과 aldehyde 혹은 ketone과의반응친핵성을갖는 3, 2 는산성조건에서 aldehyde or ketone의카보닐기와반응하여 imine( 이민 ) 또는다른말로 Schiff base(schiff 염기 ) 를생성함 Imine (Schiff base) Mechanism : 1단계 : 단계 : Imine (Schiff base) 1 단계 : ucleophilic addition of aniline to acetaldehyde Formation of tetrahedral carbonyl addition compound 2단계 : Tetrahedral 화합물의 의 protonation 및 dehydration - catalyst

11 85 Imine 화합물의유용성 ydrogenation에의하여 =이 -으로환원됨 eduction amination ( 환원적아민화 ) : 2 2 / i 2) 2 (2 차아민 ) 과 aldehyde 혹은 ketone 과의반응 친핵성을갖는 2 는산성조건에서 aldehyde or ketone 의카보닐기와반응하여 enamine( 엔아민 ) 을생성함 2 yclohexanone Piperidine Enamine B. ydrazine and elated ompounds Aldehyde 나 ketone 이 hydrazine( 2 2 ) 과반응하면 Schiff base 의일종인 hydrazone( 하이드라존 ) 을생성함 ydrazine ydrazone Table 16.4 : Derivatives of ammonia and hydrazine used for forming imines

20 A. Mechanism 1) Base-catalyzed aldol reaction a 3 2 new bond 3-ydroxybutanal ( -hydroxyaldehyde, racemic mixture) 2 + a + pk a 20 arbanion En

20 A. Mechanism 1) Base-catalyzed aldol reaction a 3 2 new bond 3-ydroxybutanal ( -hydroxyaldehyde, racemic mixture) 2 + a + pk a 20 arbanion En 19 hap 19 : Enolate Anions and Enamines 19.1 Formation and eactions of Enolate Anions : An verview α- of aldehydes or ketones : acidic (pk a = 20) 2 : Alkylation by S2 substitution Br a + 2 + a + 2 arbanion