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)
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)
+O
H3CH2C
HH
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)
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
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
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
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
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)
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
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
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
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
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)
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)
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
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