郑州大学 有机化学8卤代烃 金属有机化合物
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试剂的亲核性对SN1的反应速率影响很小，对SN2影响很大
1)Nucleophilicity and basicity
Basicity(碱性): the affinity of a base for a proton (与质子的结合能力) Nucleophilicity(亲核性): the affinity of a Lewis base for a carbon atom (与碳 原子的结合能力) 亲核性除与碱性有关外，还与可极化度 (Polarizability) 有关
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
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
B- +
Reduction (还原)
H C C X
[H] RH
C C + HB + X-
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)
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 仲(2º )卤代烃 叔(3º )卤代烃
RCH2X
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
TsO– 60,000 ×
I– 30,000
Br– 10,000
Cl– 200 √
F– 1
HO–, H2N–, RO– ~0
离去基团的离去顺序： -N+≡N > -O+R2 > -OSO2C6H4NO2-p > -OSO2Ph > -OSO2C6H4CH3-p > -OSO2CH3 > -I > -O+H2 > -Br > -Cl
(CH3)2CHOH 12
SN2反应速度: PhCH2X, CH2=CHCH2X > CH3X > 1º RX > 2º RX > 3º RX >> CH2=CHX, PhX
SN1反应速度: PhCH2X , CH2=CHCH2X > 3º RX > 2º RX > 1º RX > CH3X >> CH2=CHX, PhX
8.2.1.2.2 Leaving groups
离去基团对SN2和SN1具有类似的影响，但对SN1影响程度更大
Good L (好的离去基团)
Stable (稳定) Weakly basic (碱性弱)
HL Strong acid (强酸)
离去能力
-I > -Br > -Cl >> -F
其它常见的离去基团
Stereochemistry
Nu C back side attack
Nu-
C+
Nu-
front side attack
C
Nu
H3CH2CH2C H3C H3CH2C C
H2O H3CH2CH2C Br C H3C acetone H3CH2C
O H
+ H
O
CH2CH2CH3 + HBr C CH3 CH2CH3
E2
SN1 Kinetics v= k[t-BuCl]
unimolecular nucleophilic substitution (单分子亲核取代)
Mechanism
1)
C L
slow
C
+
:L
Multistep reaction (多步反应)
carbocation
2) C + :Nu fast C Nu
RX
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
SN2
CH3Br + OH-
80%C2H5OH 55℃
CH3OH + Br-
Kinetics
质子溶剂中亲核性 I->F-：1)可极化度; 2)溶剂化效应
Nucleophilicity
a. In a group of nucleophiles in which the nucleophilic atom is the same, nucleophilicities parallel basicities (试剂中亲核原子相同时，亲核性与碱性一致). RO- > HO- > ArO- > RCOO- > ROH > H2O b. Nucleophilicity decrease to the right in an row of the peridoic table (同一周期 中亲核性自左向右逐渐降低，与碱性一致). NH2- > OH- > FR3C- > R2N- > RO- > Fc. Nucleophilicity usually increases in going down a column of the periodic table (同一主族自上而下亲核性增强，与碱性相反)(在质子溶剂中). F- < Cl- < Br- < IHO- < HSRO- < RS-
NuNu
+ CH3Br
HS– CN–
NuCH3 + BrI– CH3O–
SN2 HO– 16,000 Cl– 1,000 NH3 700 H2 O 1
Relative 125,000 125,000 100,000 25,000 reactivity In aqueous ethanol
Polar aprotic solvents(偶极溶剂, 极性非质子溶剂)
60% S (inversion)
Ion-pair Mechanism(离子对机理)
RL
R+LClose ion-pair (紧密离子对)
R+‖ Lloose ion-pair (松散离子对)
R+ + Lfree ions (自由离子)
Energy Diagram
R3CX
Side Reaction
CH3O(CH3)3CO-
very easy very difficult
8.2.1.2.4 The solvent effects(溶剂效应)
O H C N CH3 CH3
O CH3 S CH3
DMF
DMSO “Naked” anions are highly reactive both as bases and nucleophiles (裸露的负离子具有很强的亲核 性和碱性).
在偶极溶剂中亲核性顺序: F- > Cl- > Br- > I(与碱性顺序一致)
Stability of the carbocations SN1 Alkyl halide Type Product Relative rate
CH3Br
CH3CH2Br (CH3)2CHBr (CH3)3CBr
Methyl
1° 2° 3°
CH3OH
CH3CH2OH (CH3)3COH
1.0
1.0 1,200,000
-OTs -OMs -ONs -OSO2OR
N N
O OS O O OSCH3 O O OS O
O O S O O R
CH3
对甲基苯磺酸酯基 -OSO2C6H4CH3-p
甲基磺酸酯基
NO2
对硝基苯磺酸酯基 -OSO2C6H4NO2-p 烷基硫酸酯基
NR3
OH2
OR2
Leaving group Relative reactivity
2)Nucleophilicity affected by solvents (亲核性受溶剂影响)
Protic Solvents(质子溶剂) H2O ROH
亲核性顺序：RS– ArS– HS– > CN– > I– >NH3 NR3 > RO- HO– > N3– > Br– > ArO– > CH3COO– > Cl– >> H2O > F–
Polarizability (可极化度): the ease with which the electron distribution around an atom is distorted by a nearby electric field(核外电子分布受外界电场影响而 发生扭曲变形)
Larger atoms are more polarizable. I > Br > Cl > F S>O
Racemization
H3C C2H5 Cl H3C C2H5 OH 40% R (retention) + HO C2H5 CH3
Βιβλιοθήκη Baidu
H2O
C2H5OH (CH2)3CH(CH3)2 (R)-6-Chloro2,6-dimethyloctane
(CH2)3CH(CH3)2
+ HCl (CH2)3CH(CH3)2
O ROH H3C OSOCH3 碱 O
CH3OR
硫酸二甲酯是个很好的甲基化试剂， 常用于和醇反应得到甲基醚
O R OS O
CNCH3 RCN
OSO2
G C2H5OH
OC2H5
SN1
G = OCH3 CH3 H Cl NO2 速率 1.0 1.6 3.1 8.4 55
8.2.1.2.3 The nucleophile
v= k[CH3Br][OH-] second order
bimolecular nucleophilic substitution (双分子亲核取代)
Mechanism
≠ Nu: + C L
Nu C L
Nu C
+
:L
Stereochemistry
single-step reaction(一步反应)
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) Propgarpyl halides (炔丙型卤代烃) Benzylic halides (苄型卤代烃, 苄基卤)
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)
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) (CH3)3CCH2Cl为何既难以发生SN2又难以发生SN1?
Br + CH3ONa
×
OCH3
?
SN2 ONa + CH3Br
对SN2反应，偶极溶剂比质子溶剂有利
N3 + CH3CH2CH2CH2Br
Solvent Relative reactivity HMPA
Solvent
CH3CN
CH3CH2CH2CH2N3 +
DMF 2,800 DMSO 1,300 H2O 6.6
Br
200,000 5,000
3) Sterically hindered nucleophiles are poor ones (位阻大的试剂亲核性差) 亲核性顺序：CH3O- > CH3CH2O- > (CH3)2CHO- > (CH3)3CO(与碱性顺序相反) SN2
The nucleophile attacks the carbon bearing the leaving group from the BACK SIDE.
Inversion of configuration(构型翻转): Walden inversion
Energy Diagram
Side Reaction
1)Nucleophilicity and basicity
Basicity(碱性): the affinity of a base for a proton (与质子的结合能力) Nucleophilicity(亲核性): the affinity of a Lewis base for a carbon atom (与碳 原子的结合能力) 亲核性除与碱性有关外，还与可极化度 (Polarizability) 有关
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
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
B- +
Reduction (还原)
H C C X
[H] RH
C C + HB + X-
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)
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 仲(2º )卤代烃 叔(3º )卤代烃
RCH2X
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
TsO– 60,000 ×
I– 30,000
Br– 10,000
Cl– 200 √
F– 1
HO–, H2N–, RO– ~0
离去基团的离去顺序： -N+≡N > -O+R2 > -OSO2C6H4NO2-p > -OSO2Ph > -OSO2C6H4CH3-p > -OSO2CH3 > -I > -O+H2 > -Br > -Cl
(CH3)2CHOH 12
SN2反应速度: PhCH2X, CH2=CHCH2X > CH3X > 1º RX > 2º RX > 3º RX >> CH2=CHX, PhX
SN1反应速度: PhCH2X , CH2=CHCH2X > 3º RX > 2º RX > 1º RX > CH3X >> CH2=CHX, PhX
8.2.1.2.2 Leaving groups
离去基团对SN2和SN1具有类似的影响，但对SN1影响程度更大
Good L (好的离去基团)
Stable (稳定) Weakly basic (碱性弱)
HL Strong acid (强酸)
离去能力
-I > -Br > -Cl >> -F
其它常见的离去基团
Stereochemistry
Nu C back side attack
Nu-
C+
Nu-
front side attack
C
Nu
H3CH2CH2C H3C H3CH2C C
H2O H3CH2CH2C Br C H3C acetone H3CH2C
O H
+ H
O
CH2CH2CH3 + HBr C CH3 CH2CH3
E2
SN1 Kinetics v= k[t-BuCl]
unimolecular nucleophilic substitution (单分子亲核取代)
Mechanism
1)
C L
slow
C
+
:L
Multistep reaction (多步反应)
carbocation
2) C + :Nu fast C Nu
RX
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
SN2
CH3Br + OH-
80%C2H5OH 55℃
CH3OH + Br-
Kinetics
质子溶剂中亲核性 I->F-：1)可极化度; 2)溶剂化效应
Nucleophilicity
a. In a group of nucleophiles in which the nucleophilic atom is the same, nucleophilicities parallel basicities (试剂中亲核原子相同时，亲核性与碱性一致). RO- > HO- > ArO- > RCOO- > ROH > H2O b. Nucleophilicity decrease to the right in an row of the peridoic table (同一周期 中亲核性自左向右逐渐降低，与碱性一致). NH2- > OH- > FR3C- > R2N- > RO- > Fc. Nucleophilicity usually increases in going down a column of the periodic table (同一主族自上而下亲核性增强，与碱性相反)(在质子溶剂中). F- < Cl- < Br- < IHO- < HSRO- < RS-
NuNu
+ CH3Br
HS– CN–
NuCH3 + BrI– CH3O–
SN2 HO– 16,000 Cl– 1,000 NH3 700 H2 O 1
Relative 125,000 125,000 100,000 25,000 reactivity In aqueous ethanol
Polar aprotic solvents(偶极溶剂, 极性非质子溶剂)
60% S (inversion)
Ion-pair Mechanism(离子对机理)
RL
R+LClose ion-pair (紧密离子对)
R+‖ Lloose ion-pair (松散离子对)
R+ + Lfree ions (自由离子)
Energy Diagram
R3CX
Side Reaction
CH3O(CH3)3CO-
very easy very difficult
8.2.1.2.4 The solvent effects(溶剂效应)
O H C N CH3 CH3
O CH3 S CH3
DMF
DMSO “Naked” anions are highly reactive both as bases and nucleophiles (裸露的负离子具有很强的亲核 性和碱性).
在偶极溶剂中亲核性顺序: F- > Cl- > Br- > I(与碱性顺序一致)
Stability of the carbocations SN1 Alkyl halide Type Product Relative rate
CH3Br
CH3CH2Br (CH3)2CHBr (CH3)3CBr
Methyl
1° 2° 3°
CH3OH
CH3CH2OH (CH3)3COH
1.0
1.0 1,200,000
-OTs -OMs -ONs -OSO2OR
N N
O OS O O OSCH3 O O OS O
O O S O O R
CH3
对甲基苯磺酸酯基 -OSO2C6H4CH3-p
甲基磺酸酯基
NO2
对硝基苯磺酸酯基 -OSO2C6H4NO2-p 烷基硫酸酯基
NR3
OH2
OR2
Leaving group Relative reactivity
2)Nucleophilicity affected by solvents (亲核性受溶剂影响)
Protic Solvents(质子溶剂) H2O ROH
亲核性顺序：RS– ArS– HS– > CN– > I– >NH3 NR3 > RO- HO– > N3– > Br– > ArO– > CH3COO– > Cl– >> H2O > F–
Polarizability (可极化度): the ease with which the electron distribution around an atom is distorted by a nearby electric field(核外电子分布受外界电场影响而 发生扭曲变形)
Larger atoms are more polarizable. I > Br > Cl > F S>O
Racemization
H3C C2H5 Cl H3C C2H5 OH 40% R (retention) + HO C2H5 CH3
Βιβλιοθήκη Baidu
H2O
C2H5OH (CH2)3CH(CH3)2 (R)-6-Chloro2,6-dimethyloctane
(CH2)3CH(CH3)2
+ HCl (CH2)3CH(CH3)2
O ROH H3C OSOCH3 碱 O
CH3OR
硫酸二甲酯是个很好的甲基化试剂， 常用于和醇反应得到甲基醚
O R OS O
CNCH3 RCN
OSO2
G C2H5OH
OC2H5
SN1
G = OCH3 CH3 H Cl NO2 速率 1.0 1.6 3.1 8.4 55
8.2.1.2.3 The nucleophile
v= k[CH3Br][OH-] second order
bimolecular nucleophilic substitution (双分子亲核取代)
Mechanism
≠ Nu: + C L
Nu C L
Nu C
+
:L
Stereochemistry
single-step reaction(一步反应)
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) Propgarpyl halides (炔丙型卤代烃) Benzylic halides (苄型卤代烃, 苄基卤)
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)
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) (CH3)3CCH2Cl为何既难以发生SN2又难以发生SN1?
Br + CH3ONa
×
OCH3
?
SN2 ONa + CH3Br
对SN2反应，偶极溶剂比质子溶剂有利
N3 + CH3CH2CH2CH2Br
Solvent Relative reactivity HMPA
Solvent
CH3CN
CH3CH2CH2CH2N3 +
DMF 2,800 DMSO 1,300 H2O 6.6
Br
200,000 5,000
3) Sterically hindered nucleophiles are poor ones (位阻大的试剂亲核性差) 亲核性顺序：CH3O- > CH3CH2O- > (CH3)2CHO- > (CH3)3CO(与碱性顺序相反) SN2
The nucleophile attacks the carbon bearing the leaving group from the BACK SIDE.
Inversion of configuration(构型翻转): Walden inversion
Energy Diagram
Side Reaction