532203 Organic 532203 Organic Chemistry Chemistry

for Engineeringfor Engineering

Semester 2/2012Semester 2/2012

Ref.

Yanisa Laoong-u-thai, Ph.D. 2012

SyllabusSyllabus

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Introduction to Organic Chemistry, Review, Molecular Structure

Structure, reactivity and organic reaction

Resonance and Stereochemistry Alkanes

Alkenes Alkynes

Alkyl halides •

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Benzene and aromatic compounds

Alcohols and phenols

Carbonyl compounds

Biomolecules

Introduction of petrochemistry • Petrochemical process

A. NomenclatureB. Properties C. Reactivity

1.Synthesis of alkyl halides

2. Reaction of alkyl halides

D. Used

Alkyl halidesAlkyl halides

Yanisa Laoong-u-thai, Ph.D. 2012

Alkyl Halides(Haloalkanes or halogenoalkanes)

R-X (X = F, Cl, Br, I)

Classification of alkyl halides according to the class of the carbon that the halogen is attached to.

RCH2-X R2CH-X R3C-X

1o 2o 3o

Yanisa Laoong-u-thai, Ph.D. 2012

A : Nomenclature

common names: “alkyl halide”

(fluoride, chloride, bromide, iodide)

IUPAC names: use rules for alkanes

halogen = halo (fluoro, chloro, bromo, iodo)

Cl

CH3CH2CH2CH2-Br CH3CHCH3

n-butyl bromide isopropyl chloride

1-bromobutane 2-chloropropane

1o 2o

CH3 CH3

CH3CHCH2CHCH3 CH3CCH3

Br I2-bromo-4-methylpentane tert-butyl iodide

2-iodo-2-methylpropane 2o 3o

CH3

Cl-CHCH2CH3

sec-butyl chloride2-chlorobutane 2o

Dichloromethane (or methylene chloride) is an important solvent, once used to decaffeinate coffee.

Halothane is a safe general anesthetic

Occurrence of Selected RX

Chloromethane: is produced by giant kelp and algae and also found in emissions of volcanoes such as Hawaii’s Kilauea.

http://www.sudipan.net/phpBB2/viewtopic.php?t=5866&sid=95a10981c8e146cfefc36f313c103514

B: Physical properties

polar + no hydrogen bonding

=> moderate boiling/melting points

water insoluble

Uses: pesticides, refrigerants (freons), solvents, synthetic intermediates.

CH3Br CClF3 CCl4

The C-X bond is polar.

C. ReactivityC. Reactivity

1.Synthesis of alkyl halides 1.Synthesis of alkyl halides

2. Reaction of alkyl halides2. Reaction of alkyl halides

C1. Synthesis of alkyl halides:

1. Free-radical halogenation of alkanes

2. Addition to alkenes and alkynes

3. Electrophilic aromatic substitution

4.Reaction of alcohols with hydrogen halides

5. Reaction of alcohols with thionyl chloride

6. Reaction of alcohols with phosphorus trihalide

1. Free-radical halogenation of alkanes1. Free-radical halogenation of alkanes

R H + Cl2 R Cl + HCllight

CH3CH3 + Br2 CH3CH2Br + HBrlight

2. Addition to alkenes and alkynes2. Addition to alkenes and alkynes

When EA is Cl2, Br2, I2, HCl, HBr or HI

C C

E A

C C + EA

C CC C + EAEA

C C

E

A

A

EE A

CCl4/peroxide

+ X2(X = Cl, Br)

FeX3 X + HX

3. Electrophilic aromatic substitution

CH2CH3

+ Br2

CH2CH3

+

Br

FeBr3CH2CH3

Br

o-bromoethylbenzene

p-bromoethylbenzene

ethylbenzene

4. Reaction of alcohols with hydrogen halides

R OH + HX R X + H O2

O + H XR

H

O H + XR

H

alkyl oxonium ionalcohol

+

R OH + HX R X + H O2

X + RCH2 OH2CX

H

R

OH2

H

X CH2R + H2O+

transition state

+...... ......

O + H X

RCH2

H

O H + X

RCH2

H

alkyl oxonium ionalcohol

+

Mechanism For 10 alcohol

O + H X

R2CH

H

O H + X

R2CH

H

alkyl oxonium ionalcohol

+

Mechanism For 20 และ 30 alcohol

R2CH OH2R2CH + H2OR2CH OH2

transition state carbocation

+ + +.....

R2CH + X R2CH Xfast+

5. Reaction of alcohols with thionyl chloride

R OH + SOCl2R Cl + SO2 + HCl

pyridine

Homework:

What is the mechanism of this

reaction?

6. Reaction of alcohols with phosphorus trihalide

R OH + PCl3 R Cl + P(OH)33 3

CH3CH2OH + PBr3 CH3CH2 Br + H3PO33 3

C2. Reactions of alkyl halides:

1. Nucleophilic substitution Best with 1o or CH3!!!!!!

R-X + :Z- R-Z + :X-

2. Elimination

3. Preparation of Grignard Reagent

R-X + Mg RMgX

4. Reduction

R-X + Mg RMgX + H2O R-H

R-X + Sn, HCl R-H

5. Coupling of alkyl halide with organometallic compound5. Coupling of alkyl halide with organometallic compound

1. 1. Nucleophilic substitutionNucleophilic substitution

R X + OH R OH + XH O2

R X + R O Na R O R + NaX+ alcohol

R X + Nu R Nu + X

R X + CN R CN + Xalcohol

(KCN)

R X + SH R SH + Xalcohol

(KSH)

(nitrile)

(thioalcohol)

R X + SR R S R + Xalcohol

(NaSR) (thioether)

(KCN = potassium cyanide)

(KSH = potassium hydrogen sulfide)

(KSR = potassium mercaptide)

R X + NH2 R NH2 + XNH3(l)

(NaNH2)

R X + I R I + Xacetone

(NaI)

(amine)

(NaNH2 = sodamide)

(NaI = sodium iodide)

R X + Na C CR R C CR + XNH3(l)

(sodium acetylide)

R X + NH3 R NH3 + XNH3(l)

(alkyl ammonium salt)

(alkyne)

+

+

R X + Nu R Nu + X

Mechanism of substitution reaction

Substitution reaction of SN1

CX

R

R

C + X

R R

R

R

slow +

Nu

C

R R

R NuCNu

R

R

R

C NuR

R

R

retention

inversion

fast

fast

+

R X + Nu R Nu + X

Mechanism of substitution reaction

Substitution reaction of SN2

+ Nu CX

R

R

Nu

R

CX

R

R

R

C Nu + X

R

R

R

transition state

(leaving group)

....... .......

2. Elimination2. Elimination

Saytzeff theory

C C

H

KOH / C2H5OH

X

C C + HX

C C

X

KOH(alc)

X

C C

X

HNaNH2

C C

In chemistry, Zaitsev's rule, Saytzeff's rule or Saytsev's rule named after Alexander Mikhailovich Zaitsev (number of different spellings due to the name being transliterated from Russian) is a rule that states that if more than one alkene can be formed during dehalogenation by an elimination reaction, the more stable alkene is the major product.

Mechanism of elimination reaction

Type E1

C C

H

X C C + X

H

+

C C + NuHC C

H

Nu

+

Type E2

C C + NuH + XC C

HNu

X

C C

HNu

X

..

.

..

.

transition state

........

....

Mechanism of elimination reaction

Competitive of Substitution and Elimination reaction

CH3 C CH3 + NaOCH3

substitution product

CH3

Cl CH3 C CH3

CH3

OCH3

CH3 C CH2

CH3

Elimination product(predominates)

ter-butylchloride

sodium methoxide

CH3 C O Na + CH3Cl

CH3

CH3

CH3 C CH3

CH3

OCH3

sodium ter-butoxide

+

2-methoxy-2-methylpropane

3. Preparation of Grignard reagent3. Preparation of Grignard reagent

Grignard reagent use for synthesis of many organic compound

R X + Mg R MgXdry ether

R H + MgXOHR MgX + H2O

alkaneGrignard reagent

4. Reduction of metal and acid4. Reduction of metal and acid

R X + LiAlH4 R H(alkane)

R X + Zn + H R H + Zn + X(alkane)

2++

5. Coupling of alkyl halide with 5. Coupling of alkyl halide with organometallic compound organometallic compound

R X + Li RLi

alkyl lithium

dry ether CuIR2CuLi

lithium dialkylcopperalkyl halide

2 2 2

R2CuLi + R X R R + RCu + LiX

10 alkyl halide

CH3CH2Brdry ether

CuICuLi

bromoethane

LiCH3CH2Li

CH3CH2

CH3CH2

lithium diethylcopperethyl lithium

CuLi

CH3CH2

CH3CH2

lithium diethylcopper

CH3CH2

propane

+ CH3Br CH3

D. UsedD. Used

They are used as They are used as

- - flame retardantsflame retardants - fire fire extinguishantsextinguishants - refrigerantsrefrigerants - propellantspropellants - SolventsSolvents- pharmaceuticalspharmaceuticals

Many halocarbons have also been Many halocarbons have also been shown to be serious shown to be serious pollutantspollutants and and toxins.toxins.

Chlorofluorocarbons have been shown Chlorofluorocarbons have been shown to lead to ozone depletion. to lead to ozone depletion.

Methyl bromide is a controversial Methyl bromide is a controversial fumigant. fumigant.

Only haloalkanes which contain Only haloalkanes which contain chlorine, bromine, and iodine are a chlorine, bromine, and iodine are a threat to the ozone layer, but threat to the ozone layer, but fluorinated volatile haloalkanes in fluorinated volatile haloalkanes in theory may have activity as theory may have activity as greenhouse gases. greenhouse gases.