(完整版)郑州大学有机化学8卤代烃金属有机化合物

SN2
CH3Br + OH- 80%C2H5OH 55℃
CH3OH + Br-
Kinetics v= k[CH3Br][OH-] bimolecular nucleophilic substitution
second order
(双分子亲核取代)
Mechanism Nu: + C L Stereochemistry
SN1
Stability of the carbocations
Alkyl halide Type Product
Relative rate
CH3Br CH3CH2Br (CH3)2CHBr (CH3)3CBr
Methyl 1° 2° 3°
CH3OH CH3CH2OH (CH3)2CHOH (CH3)3COH
B- +
H CC
X
Reduction (还原)
[H]
RX
RH
C C + HB + X-
Formation of Organomatelic Compounds (形成金属有机化合物)
8.2.1 Nucleophilic Substitution (亲核取代)
8.2.1.1 SN1 and SN2
Nu C L


≠ Nu C + :L
single-step reaction(一步反应)
The nucleophile attacks the carbon bearing the leaving group from the BACK SIDE.
Inversion of configuration(构型翻转): Walden inversion
8.2.1.2.1 The structures of alkyl groups
SN2 Substituent Methyl 1° 2°
Neopentyl 3°
Steric effect
Compound CH3X CH3CH2X (CH3)2CHX (CH3)3CCH2X (CH3)3CX
Relative Rate 30 1 0.02 0.00001 ~0
对于苄基卤、烯丙基卤， SN1和SN2均容易发生；对于乙烯型卤、芳基卤，SN1 和SN2均难以发生；使用非常强的碱，如NaNH2，将使其发生消除反应，分别 得到炔烃、苯炔(会进一步发生加成)
C2H5 CH3 + HCl (CH2)3CH(CH3)2
60% S (inversion)
Ion-pair Mechanism(离子对机理)
RL
R+L-
Close ion-pair (紧密离子对)
R+‖ L-
loose ion-pair (松散离子对)
R+ + L-
free ions (自由离子)
Energy Diagram
R3CX
Side Reaction Rearrangement and E1
8.2.1.2 Factors affecting SN1 and SN2 • The structures of alkyl groups (烃基的结构) • Leaving groups (离去基团) • The nucleophile (亲核试剂) • The solvent (溶剂)
按卤素所连接的烃基的结构分类
Saturated halohydrocarbons (饱和卤代烃) Unsaturated halohydrocarbons (不饱和卤代烃) Aromatic halohydrocarbons (芳香卤代烃)
Allylic halides (烯丙型卤代烃, 烯丙基卤)
Energy Diagram
Side Reaction
E2
SN1
Kinetics v= k[t-BuCl] Mechanism
unimolecular nucleophilic substitution (单分子亲核取代)
1) CL
slow
2) C
+ :Nu
C + :L carbocation
Propgarpyl halides (炔丙型卤代烃)
Benzylic halides (苄型卤代烃, 苄基卤)
Vinylic halides (乙烯型卤代烃, 乙烯基卤)
Aryl halides (芳型卤代烃, 芳基卤)
按与卤素相连的碳原子的级数分类
伯(1º)卤代烃
RCH2X
仲(2º)卤代烃 叔(3º)卤代烃
1.0 1.0 12 1,200,000
SN2反应速度: PhCH2X, CH2=CHCH2X > CH3X > 1ºRX > 2ºRX > 3ºRX >> CH2=CHX, PhX SN1反应速度: PhCH2X , CH2=CHCH2X > 3ºRX > 2ºRX > 1ºRX > CH3X >> CH2=CHX, PhX
Chapter 8 Halohydrocarbons (卤代烃) Organometallic Compounds (有机金属 化合物)
8.1 Classification (分类), Nomenclature (命名), Structure (结构) and Physical Properties (物理性质)
R2CHX R3CX
按分子中卤素的数目分类
一卤代烷 多卤代烷（邻二卤代烷 偕二卤代烷）
CH2Cl2 二氯甲烷
8.2 Reactions
Nucleophilic Substitution (亲核取代)：SN1/SN2)
Nu -+ R X
Nu R + X-
Elimination Reactions (消除反应): E1/E2
+O
H3CH2C
HH
源自文库
Racemization
CH2CH2CH3 C CH3 + HBr
CH2CH3
H3C C2H5
H2O
Cl
C2H5OH
(CH2)3CH(CH3)2
(R)-6-Chloro2,6-dimethyloctane
H3C C2H5 OH + HO
(CH2)3CH(CH3)2
40% R (retention)
fast
C Nu
Multistep reaction (多步反应)
Stereochemistry
Nu C back side Nu-
attack
C+
Nu- front side
C Nu
attack
H3CH2CH2C H3C C
H3CH2C
H2O H3CH2CH2C Br acetone H3C C O