有机化学2-卤代烷

Chapter

6Alkyl

Halides§

6.1 Classification,

Nomenclature

andIsomerization§

6.2 Spectrum

Data

&

Physical

Properties§

6.3 Chemical

Reactions§

6.4 Mechanism

of

Nucleophilic

Substitution§

6.5 Elimination

Reaction§

6.6 Preparation

of

Alkyl

Halides§

6.1 Classification,

Nomenclature

andIsomerizationClassificationNomenclatureIsomerizationCC

CH2CH2

CH3H3CHH3CBrH(2R,3S)-3-甲基-2-溴己烷§

6.2 Spectrum

Data

&

Physical

Properties1H-NMR13C-NMR-碳、-碳化移向低场方向移动XCH2

CH2

CH22.16-4.41.25-1.551.03-1.08IRC-F1350-1100cm-1(s)C-Cl750-700cm-1(m)C-Br700-500cm-1(m)C-I610-485cm-1(m)§

6.3 Chemical

Reactions6.3.1 Structure

&

Inductive

Effect(A)

Structure

of

alkyl

halidesC-IC-F

139

pmC-Cl

176

pmC-Br

194

pm214

pmPolar

bond(B)

Inductive

EffectCH2CH2CH3

CH2CH3ClElectronegativity:C:

2.5特点

表示法静态与动态Cl:

2.8H:2.2分类

强度CH2CH3(C)

Polarizability含义与反应性关系影响因素CH2CCXHHHHX吸电子，易断裂，X被取而代之诱导效应，易断裂，“消除”带部分正电荷，易被带负电荷或带孤对电子的分子进攻6.3.2 Nucleophilic

SubstitutionH2ONaOHHOC2H5NaOC2H5NaSHNaSR'NaOCOR'NH3

NaONO2R-OHR-OHR-OC2H5

R-OC2H5R-SHR-SR'R-OCOR'R-+NH3R-ONO2醇醇醚

醚硫醇硫醚腈酯铵盐硝酸酯R-X中溶剂解广泛应用于鉴别6.3.3 Elimination

ReactionCH3CH

CH3BrEtONa

/

EtOHH3C

CHCH2一般地：30

RX

> 20

RX

> 10

RX消除方向：选择性：反式共平面区域选择性：Saytzeff规则6.3.4 Reactions

with

MetalsWith

MgWith

NaWith

Li6.3.5

ReductionRX

H

R

HH:LiAlH4

（氢化铝锂），强氧化剂。以醚为溶剂。遇水立即分解：LiAlH4

+

4H2O

LiOH

+

Al(OH)3

+

4H2NaBH4（硼氢化钠），以

二甲醚为溶剂。Na

+

NH3(l)Zn

+

HClHIH2

/

Pd§

6.4 Mechanism

of

Nucleophilic

Substitution6.4.1 Two

Mechanism1st-order2nd-orderSN2Walden

InversionSN1碳正离子Rate-determinedstepCarbocationStructureStabilityRearrangementCRR'R"6e-p hyper

conjugationCCR'R"RearrangementCCHCCH+CCH负氢迁移烷基迁移CCRCCR+CCR动力：由不稳定的碳正离子变为稳定的碳正离子化学CR1R2R3BrR1CR2

R3HOR1R2CR1R2R3HOab+a

构型转化C

OHR3b

构型保持Experimental

Result多少R-XRX溶剂分子对R

+

XR

X紧密离子对Winstein

S.Ion

Pair

Theory>保型＝保型RearrangementCH3CH3C

H

O-CH32C CH

Br2

5CH3CH3C2H5OHCH3C

CH2OC2H5CH3CH3CH3CH3C2H5OH

CHCCH3CH2

CH33OC2H5SN1重排C

CH2CH31°C+CCH2

CH33°

C+少6.4.2 Factors

Which

Effect

the

Two

MechanismRate-determiningStep:SN2SN1(A)

Effects

of

Alkyl

GroupsSN2SN1电子效应（超共轭效应）空间效应（空助效应）C

CHClHHClOther

Alkyl

Groups既不易发生SN1反应又不易发生SN2反应HO

+CH2

ClCHCH2HO

…C

…

ClCHCH2δδHHCH2

ClCHCH2+

Cl既容易发生SN1反应又容易发生SN2反应CSN1SN2既不易发生SN1反应又不易发生SN2反应Xsp3SN1sp2rigid

structureSN2XSterichindranceconfiguration

inversion:Nu(B)

Effects

of

Leaving

GroupsSN2SN1均有影响离去基的离去能力越强，反应越易进行。I-Result:

>

Br-

>

Cl-

>

F-Reasons:

1)

Dissociation

Energy

(kJ/mol)C-Cl:

355.9>

HClC-I:

238.6

C-Br:

197.32)

Acidity

of

HX:

HI >

HBrStability:

I-

>

Br-

>

ClApplication:

1)

IdentificationRI+AgONO2

/

EtOH

迅速RBr+AgONO2

/

EtOH

片刻RCl+AgONO2

/

EtOH

加热Application:

2)

SynthesisRCH2Cl

+

H2O

RCH2Cl

+

I-

RCH2I

+

H2O

RCH2OH

+

HClRCH2I

+

Cl-RCH2OH

+

HI(C)

Effects

of

NucleophilicityNo

EffectNucleophilicity

of

the

Reagents进攻原子相同时：带负电荷基团>中性基团HO-

>

H2O

-NH2

>

NH3

RO-

>ROH进攻原子相同时：一般地，碱性

亲核性RO-

> HO-

> ArO-

>

RCOO-（酸性：

ROH

<

H2O

<

ArOH

<

RCOOH）同族元素，原子序数

亲核性原因：可极化性4

空间因素（CH3)3CO-大体积碱(D)

Effects

ofSolvents稳定带电荷反应物种Protic

Solvents极性很强，含－OH，－NH2等基团如：

H2O，

ROH, NH3

等Aprotic

Polar

Solvents极性很强，但不含－OH，－NH2等基团如：Dimethylformamide(

DMF

)Dimethylsulfoxide（DMSO）等OH

C

NCH3CH3SOH3CCH3SN1极性溶剂极性增大对反应有利SN2极性溶剂极性增大对反应不利极性非质子溶剂不溶剂化负离子，使亲核试剂不受溶剂分子包围，有利于SN2反应：Summary一般地：30

RX10

RX20

RXRX发生SN1反应发生SN2反应受试剂影响较大原因：+AgA夺gO电N子O能2

/力Et强OH

RONO2

+

AgX

SN15）

R－Br

＋

NaI /

无水

－ClR－I

＋

NaBr

NaCl

均为SN2反应原因：*：I-亲核性强*：溶剂弱极性§

6.5 Elimination

Reaction6.5.1 Two

MechanismsE1CH3H3CCCH3BrslowCH3H3CCCH3+Br-3H

CCCH3+HOC2H5fastCH2H3C

CCH32+ C2H5OH

+-H+C2H5OHH2C

HCH3CBrCH3C2H5O-+HH2CCCH32H

CCH3HBrC2H5OH2CCH3C

CH3E2反式共平面E1

vs

E2碱的强度与浓度增加，有利于E