93醛酮的反应 Reactions of Aldehydes and Ketones
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 9.3 醛酮的反应 Reactions of Aldehydes and Ketones
醛酮的反应概貌 O∠氧化 C-C-H 亲核加成还原 活泼a-H的反应
Organic Chemistry Organic Chemistry Xiamen Xiamen University University C H C O H 亲核加成 还原 氧化 活泼α− H的反应 醛酮的反应概貌
931羰基的亲核加成( Nucleophilic Addition To The Carbon-Oxygen Double bond) g The most characteristic reaction of aldehydes and ketones is nucleophilic addition to the carbon-oxygen double bond LC=O H-Nu C-OH N Nucleophilic addition to the carbon-oXygen double bond occurs in either of two general ways
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 9.3.1 羰基的亲核加成(Nucleophilic Addition To The Carbon-Oxygen Double Bond) The most characteristic reaction of aldehydes and ketones is nucleophilic addition to the carbon-oxygen double bond. C O + C OH Nu H Nu Nucleophilic addition to the carbon-oxygen double bond occurs in either of two general ways
反应机理 1)无催化剂或碱性条件下的加成机理 Addition of a Strong nucleophile to an Aldehyde or Ketone R,δ+8 R C=0=R R O、HMR R C-OH Ni Nua Nu ①D The important aspect of this step is the ability of the carbonyl oxygen atom to accommodate the electron pair of the carbon-oxygen double bond
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 反应机理 1) 无催化剂或碱性条件下的加成机理 C O R' R δ − δ + Nu C O R' R Nu H Nu C OH R' R Nu Addition of a Strong Nucleophile to an Aldehyde or Ketone The important aspect of this step is the ability of the carbonyl oxygen atom to accommodate the electron pair of the carbon-oxygen double bond
2)酸催化下的反应机理 Acid-Catalyzed Nucleophilic Addition to an Aldehyde or Ketone + C O=C=OH← C--ouI: Nu-H Slow H C-OH =--C-OH ①D +NuH Nu
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 2) 酸催化下的反应机理 Acid-Catalyzed Nucleophilic Addition to an Aldehyde or Ketone C O H + C OH C OH C OH Nu Nu H Sl o w H H + C OH Nu
3)反应活性: 醛>脂肪酮>芳香酮 环酮>脂肪酮 a In general, aldehyde are more reactive in nucleophilic addition than are ketones C R H R R Aldehyde Ketone Carbonyl carbon is Carbonyl carbon is more positive less positive
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 3) 反应活性 醛 > 脂肪酮 > 芳香酮; 环酮 > 脂肪酮 In general, aldehyde are more reactive in nucleophilic addition than are ketones. R C H O δ + δ − R C R O δ + δ − Ald ehyd e Ke t o n e Carbony l c a rbon i s m ore p o sitive Carbony l c arbon i s less p o sitiv e
4)亲核试剂的分类 g■含碳的亲核试剂RMgX,HCN,C 含氮的亲核试剂RNH2,R2NH,H2NG 含氧的亲核试剂H2O.ROH g·含硫的亲核试剂 Naso3,RSH
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 4) 亲核试剂的分类 含碳的亲核试剂 RMg X , HCN , C RNH 2 , R 2NH , H 2 N − G H 2O . ROH NaHS O 3 , RS H 含氮的亲核试剂 含氧的亲核试剂 含硫的亲核试剂
1.羰基与含碳亲核试剂的加成 (1The Addition of Gringard Reagents (1)Et2O CH3h2CH-C-CH(CH3)2 CH3 CH,MgBr (2)H3O OH X(CH3)2CH-C-CH(CH3)2 80 CH2CH 空间位阻增大时,加成的产率降低
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 1. 羰基与含碳亲核试剂的加成 (1)The Addition of Gringard Reagents (C H 3 ) 2CH C CH(CH 3 ) 2 O + CH 3CH 2MgBr (1) E t 2 O (2) H 3 O + (C H 3 ) 2CH C CH(CH 3 ) 2 OH CH 2CH 3 80% 空间位阻增大时 加成的产率降低
加成反应的立体化学 当羰基与手性中心相连时 加成存在立体选择性问题 CH3CH2 CH 3-C—C H R g Cram规则1:当C上结合L,MS三个基团 的不对称醛酮进行亲核加成反应时,应当取 如下稳定构象:
Organic Chemistry Organic Chemistry Xiamen Xiamen University University 加成反应的立体化学 当羰基与手性中心相连时 加成存在立体选择性问题 C O R C H CH 3 CH 3CH 2 Cram 规则 1 当 α − C上结合L, M, S三个基团 的不对称醛酮进行亲核加成反应时 应当取 如下稳定构象
M N RL RL 重叠构象 Nu S S R R 全交叉构象
Organic Chemistry Organic Chemistry Xiamen Xiamen University University M L S O R S L M O R Nu S L M O R S L M O R Nu 重叠构象 全交叉构象
