hoaÙ hoÏc hÖÕu cÔ organic chemistry chÖÔng 6 alkanes

HOAÙ HOÏC HÖÕU CÔHOAÙ HOÏC HÖÕU CÔOrganic ChemistryOrganic Chemistry

CHÖÔNG 6Alkanes

GIÔÙI THIEÄU MOÂN HOÏC1.: HOÙA HOÏC HÖÕU CÔ

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Unbranched AlkanesUnbranched Alkanes

““Straight-chain” alkanes have a zig-zag Straight-chain” alkanes have a zig-zag orientation when they are in their most orientation when they are in their most straight orientationstraight orientation

Branched AlkanesBranched Alkanes

Branched Branched alkanes have alkanes have at least one at least one carbon which carbon which is attached to is attached to more than more than two other two other carbonscarbons

Physical PropertiesPhysical Properties

Boiling points of unbranched alkanes Boiling points of unbranched alkanes increase smoothly with number of carbonsincrease smoothly with number of carbons• CHCH44-C-C44HH1010: gazes: gazes

Melting points roughly increase with Melting points roughly increase with number of carbonsnumber of carbons• CC55HH1212-C-C1717HH3636: liquids: liquids

Low polarityLow polarity• Insoluble in waterInsoluble in water• Soluble in non-polar solventsSoluble in non-polar solvents

Physical PropertiesPhysical Properties

The boiling point increases The boiling point increases with the length of the chainwith the length of the chain

Structural IsomersStructural Isomers

Constitutional isomers have the same molecular Constitutional isomers have the same molecular formula but different connectivity of atomsformula but different connectivity of atoms

IUPAC Rules for Alkanes and IUPAC Rules for Alkanes and Alkyl HalidesAlkyl Halides

1.1. Select the longest continuous chainSelect the longest continuous chainBasic nameBasic name

2.2. Number the carbons form the end nearest the first branchNumber the carbons form the end nearest the first branchNumberingNumbering

3.3. Locate substituents on the main chainLocate substituents on the main chainLocationLocationIf two substituents on the same carbon, use the number If two substituents on the same carbon, use the number

twicetwice4.4. Identify substituents Identify substituents

IdentificationIdentificationif more than one use “di”, “tri”, “tetra”,…if more than one use “di”, “tri”, “tetra”,…

5.5. Put substituents in alphabetical orderPut substituents in alphabetical order6.6. Separate numbers from letters using dashes and place the Separate numbers from letters using dashes and place the

basic name at the end.basic name at the end.

DANH PHAÙPhttp://www.acdlabs.com/iupac/nomenclature/

RadicalsRadicals

CHCH33- - methyl (Me)methyl (Me) CHCH33-CH-CH22-- ethyl (Et)ethyl (Et) CHCH33-CH-CH22-CH-CH22-- n-propyl (n-propyl (nnPr)Pr) (CH(CH33))22-CH--CH- iso-propyl (iso-propyl (iiPr)Pr) CHCH33-CH-CH22-CH-CH22-CH-CH22-- n-butyl (n-butyl (nnBu)Bu) (CH(CH33))22-CH-CH-CH-CH22-- iso-butyl (iso-butyl (iiBu)Bu) (CH(CH33))33-C--C- tert-butyl (tert-butyl (ttBu)Bu) CC66HH55-- phenyl (Ph)phenyl (Ph)

DANH PHAÙP

AlkanesAlkanes

DANH PHAÙP

LAI HOÁ sp3

Nobel prize 1969Nobel prize 1969

Sir Derek Barton (UK, 1918-1998)Sir Derek Barton (UK, 1918-1998) Odd Hassel (Norway, 1897-1981)Odd Hassel (Norway, 1897-1981) for their contributions to the development of the for their contributions to the development of the

concept of conformation and its application in concept of conformation and its application in chemistry"chemistry"

Sir Derek BartonSir Derek Barton

Nobel Lecture starting with this citation:Nobel Lecture starting with this citation:

StereoisomersStereoisomers ConformersConformers

• Isomers resulting from the free rotation of a single bondIsomers resulting from the free rotation of a single bond Ethane: Ethane: staggered conformationstaggered conformation (C-H bonds on (C-H bonds on

adjacent carbons as far apart from each other as adjacent carbons as far apart from each other as possible)possible)

The drawing to the right is called a Newman The drawing to the right is called a Newman projectionprojection

eclipsed conformation:eclipsed conformation: all C-H bonds on adjacent all C-H bonds on adjacent carbons directly on top of each othercarbons directly on top of each other

The Newman RepresentationThe Newman Representation

The Newman RepresentationThe Newman Representation

Staggered and eclipsedStaggered and eclipsed

Staggered

Eclipsed

3D Formulas3D Formulas

H

H H

HH

H

The Torsional StrainsThe Torsional Strains

Staggered: most stable

Eclipsed: least stable

Ethane conformationEthane conformation the staggered conformation is more stable the staggered conformation is more stable

than eclipsed by 12 kJ molthan eclipsed by 12 kJ mol-1-1

ÑOÀNG PHAÂN CAÁU DAÏNG

ButaneButane

Anti most stableAnti most stable

Fully eclipsed most unstableFully eclipsed most unstable

H H

H3C

H H

H3C

CH3

H3C

H

H

H

H

H

H

CH3

H H

H3C H3C CH3

HHH H

ButaneButane

Gauche less stable than antiGauche less stable than anti

Eclipsed less unstable than fully eclipsedEclipsed less unstable than fully eclipsed

H CH3

H

H H

H3C

H

H3C

H

CH3

H

H

H

CH3

H

H H

H3C H3C H

CH3HH H

ButaneButane

H H

H3C

H H

H3C

H

CH3

H

H H

H3C

H

H CH3

H H

H3C

H

H

CH3

H H

H3C

H

HH3C

H H

H3C

H

H3C

H

H H

CH3

H H

H3C

H H

H3C

ButaneButane

ÑOÀNG PHAÂN CAÁU DAÏNG

Preparation of AlkanesPreparation of Alkanes

Catalytic hydrogenation of alkenes Catalytic hydrogenation of alkenes and alkynesand alkynes

Preparation of AlkanesPreparation of Alkanes The Kolbe reactionThe Kolbe reaction is the electrosynthesis of is the electrosynthesis of

hydrocarbons via electrooxidation of carboxylic hydrocarbons via electrooxidation of carboxylic acids.acids.

Reduction/OxidationReduction/Oxidation ReductionReduction: gain of hydrogen, loss of oxygen, …: gain of hydrogen, loss of oxygen, …

• Level of oxidation decreasesLevel of oxidation decreases OxidationOxidation: gain of oxygen, loss of hydrogen, …: gain of oxygen, loss of hydrogen, …

• Level of oxidation increasesLevel of oxidation increases Hydrogenation: reduction of alkenes and alkynesHydrogenation: reduction of alkenes and alkynes

Syn Addition in Heterogeneous Syn Addition in Heterogeneous CatalysisCatalysis

hydrogen and alkene adsorbed to hydrogen and alkene adsorbed to the catalyst surfacethe catalyst surface

Syn AdditionSyn Addition

Both hydrogens add to the same Both hydrogens add to the same face of the alkene (syn addition)face of the alkene (syn addition)

ExamplesExamples

1,2-dimethylcyclohexene1,2-dimethylcyclohexene

Reduction of Alkyl HalidesReduction of Alkyl Halides

With metalsWith metals

Paul Sabatier (1854-1941)Paul Sabatier (1854-1941)

Nobel Prize 1912Nobel Prize 1912 "for his method of "for his method of

hydrogenating organic hydrogenating organic compounds in the presence of compounds in the presence of finely disintegrated metals finely disintegrated metals whereby the progress of whereby the progress of organic chemistry has been organic chemistry has been greatly advanced in recent greatly advanced in recent years"years"

University of Toulouse, University of Toulouse, FranceFrance

Victor GrignardVictor Grignard Nobel prize 1912Nobel prize 1912 "for the discovery of the so-"for the discovery of the so-

called Grignard reagent, which called Grignard reagent, which in recent years has greatly in recent years has greatly advanced the progress of advanced the progress of organic chemistry" organic chemistry"

University of Nancy, FranceUniversity of Nancy, France

Ph. Barbier, University of Ph. Barbier, University of Lyon, FranceLyon, France

Barbier reactionBarbier reaction

Grignard ReagentsGrignard Reagents

Grignard reagent preparationGrignard reagent preparation Reaction of organic halides with Reaction of organic halides with

magnesium turnings in ether (DRY magnesium turnings in ether (DRY ether)ether)

Killed with water: form alkanesKilled with water: form alkanes


Strongly react with waterStrongly react with water Grignard reagents behave as if they were Grignard reagents behave as if they were

carbanions and they are therefore very carbanions and they are therefore very strong basesstrong bases

R rich in electronR rich in electron


Formally: conversion of halides to Formally: conversion of halides to hydrogenhydrogen

The Grignard reaction: addition of The Grignard reaction: addition of Grignard reagents to carbonylsGrignard reagents to carbonyls

Elias J. CoreyElias J. Corey Nobel Prize 1990Nobel Prize 1990 "for his development of the theory "for his development of the theory

and methodology of organic and methodology of organic synthesis" synthesis"

Harvard University, USAHarvard University, USA

Many Corey reactions…Many Corey reactions…• (Corey-Winter, Corey-Chakovsky, (Corey-Winter, Corey-Chakovsky,

Corey-Bakshi-Shibata, Corey-Corey-Bakshi-Shibata, Corey-Fuchs, Corey-Kim, …)Fuchs, Corey-Kim, …)

… … and reagentsand reagents• PDC, PCC, …PDC, PCC, …

OrganometallicsOrganometallics

Organolithium reagentsOrganolithium reagents

Organocuprate reagents (Gilman Organocuprate reagents (Gilman reagents)reagents)

Corey-Posner, Whitesides-Corey-Posner, Whitesides-HouseHouse

Coupling of two alkyl halides Coupling of two alkyl halides Organocuprate reagentsOrganocuprate reagents

Henry GilmanHenry Gilman Henry Gilman (1893-1986), Iowa Henry Gilman (1893-1986), Iowa

State UniversityState University Talking about his research as a Talking about his research as a

student: 'A sheer delight. Here I student: 'A sheer delight. Here I was, just a senior. We'd work at was, just a senior. We'd work at night until 11 or 12 o'clock, night until 11 or 12 o'clock, without any compulsion--just for without any compulsion--just for the joy of it.'the joy of it.'

Post doc at Harvard with Kohler Post doc at Harvard with Kohler who is credited with having who is credited with having introduced the use of the introduced the use of the Grignard reagent to the U.S.A.Grignard reagent to the U.S.A.

Lithium dialkylcuprate are called Lithium dialkylcuprate are called Gilman ReagentsGilman Reagents

Posner, Whitesides and HousePosner, Whitesides and House

Georges M. Whitesides, Georges M. Whitesides, Harvard UniversityHarvard University• Material ScienceMaterial Science

Gary H. Posner, Johns Gary H. Posner, Johns Hopkins UniversityHopkins University• Organic ChemistryOrganic Chemistry

H O. House, Georgia H O. House, Georgia Institute of technologyInstitute of technology

ExamplesExamples

hoaÙ hoÏc hÖÕu cÔ organic chemistry chÖÔng 6 alkanes

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