HOAÙ HOÏC HÖÕU CÔ Organic Chemistry CHÖÔNG 6 Alkanes

GIÔÙI THIEÄU MOÂN HOÏC 1.: HOÙA HOÏC HÖÕU CÔ (ORGANIC CHEMISTRY) 1.Soá tín chæ: 3 (3.1.6) 2.Maõ soá moân hoïc: Noäi dung toùm taét moân hoïc: Lieân keát- Caáu taïo-caáu truùc hôïp chaát höõu cô Phaûn öùng vaø cô cheá phaûn öùng höõu cô Caùc phöông phaùp cô baûn toång hôïp caùc hôïp chaát höõu cô Tính chaát lyù hoùa caùc hôïp chaát höõu cô ÖÙng duïng: Hôïp chaát maøu, hôùp chaát coù höông, chaát hoaït ñoäng beà maët, chaát noå, chaát dieät khuaån-coân truøng, chaát kích thích taêng tröôûng….

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

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

Physical Properties Boiling points of unbranched alkanes increase smoothly with number of carbons Boiling points of unbranched alkanes increase smoothly with number of carbons CH 4 -C 4 H 10 : gazesCH 4 -C 4 H 10 : gazes Melting points roughly increase with number of carbons Melting points roughly increase with number of carbons C 5 H 12 -C 17 H 36 : liquidsC 5 H 12 -C 17 H 36 : liquids Low polarity Low polarity Insoluble in waterInsoluble in water Soluble in non-polar solventsSoluble in non-polar solvents

Physical Properties The boiling point increases with the length of the chain The boiling point increases with the length of the chain

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

IUPAC Rules for Alkanes and Alkyl Halides 1. Select the longest continuous chain Basic name 2. Number the carbons form the end nearest the first branch Numbering 3. Locate substituents on the main chain Location If two substituents on the same carbon, use the number twice 4. Identify substituents Identification if more than one use “di”, “tri”, “tetra”,… 5. Put substituents in alphabetical order 6. Separate numbers from letters using dashes and place the basic name at the end.

DANH PHAÙP

Radicals CH 3 - methyl (Me) CH 3 - methyl (Me) CH 3 -CH 2 -ethyl (Et) CH 3 -CH 2 -ethyl (Et) CH 3 -CH 2 -CH 2 -n-propyl (nPr) CH 3 -CH 2 -CH 2 -n-propyl (nPr) (CH 3 ) 2 -CH-iso-propyl (iPr) (CH 3 ) 2 -CH-iso-propyl (iPr) CH 3 -CH 2 -CH 2 -CH 2 -n-butyl (nBu) CH 3 -CH 2 -CH 2 -CH 2 -n-butyl (nBu) (CH 3 ) 2 -CH-CH 2 -iso-butyl (iBu) (CH 3 ) 2 -CH-CH 2 -iso-butyl (iBu) (CH 3 ) 3 -C-tert-butyl (tBu) (CH 3 ) 3 -C-tert-butyl (tBu) C 6 H 5 -phenyl (Ph) C 6 H 5 -phenyl (Ph)

DANH PHAÙP

Alkanes

LAI HOÁ sp 3

Nobel prize 1969 Sir Derek Barton (UK, ) Sir Derek Barton (UK, ) Odd Hassel (Norway, ) Odd Hassel (Norway, ) for their contributions to the development of the concept of conformation and its application in chemistry" for their contributions to the development of the concept of conformation and its application in chemistry"

Sir Derek Barton Nobel Lecture starting with this citation: Nobel Lecture starting with this citation:

Stereoisomers Conformers Conformers Isomers resulting from the free rotation of a single bondIsomers resulting from the free rotation of a single bond Ethane: staggered conformation (C-H bonds on adjacent carbons as far apart from each other as possible) Ethane: staggered conformation (C-H bonds on adjacent carbons as far apart from each other as possible) The drawing to the right is called a Newman projection eclipsed conformation: all C-H bonds on adjacent carbons directly on top of each other eclipsed conformation: all C-H bonds on adjacent carbons directly on top of each other

The Newman Representation

Staggered and eclipsed Staggered and eclipsed Staggered Eclipsed

3D Formulas

The Torsional Strains Staggered: most stable Eclipsed: least stable

Ethane conformation the staggered conformation is more stable than eclipsed by 12 kJ mol -1 the staggered conformation is more stable than eclipsed by 12 kJ mol -1

ÑOÀNG PHAÂN CAÁU DAÏNG

Butane Anti most stable Anti most stable Fully eclipsed most unstable Fully eclipsed most unstable

Butane Gauche less stable than anti Gauche less stable than anti Eclipsed less unstable than fully eclipsed Eclipsed less unstable than fully eclipsed

Butane

Butane

ÑOÀNG PHAÂN CAÁU DAÏNG

Preparation of Alkanes Catalytic hydrogenation of alkenes and alkynes Catalytic hydrogenation of alkenes and alkynes

Preparation of Alkanes

The Kolbe reaction is the electrosynthesis of hydrocarbons via electrooxidation of carboxylic acids. The Kolbe reaction is the electrosynthesis of hydrocarbons via electrooxidation of carboxylic acids.

Preparation of Alkanes

Reduction/Oxidation Reduction: gain of hydrogen, loss of oxygen, … Reduction: gain of hydrogen, loss of oxygen, … Level of oxidation decreasesLevel of oxidation decreases Oxidation: gain of oxygen, loss of hydrogen, … Oxidation: gain of oxygen, loss of hydrogen, … Level of oxidation increasesLevel of oxidation increases Hydrogenation: reduction of alkenes and alkynes Hydrogenation: reduction of alkenes and alkynes

Syn Addition in Heterogeneous Catalysis hydrogen and alkene adsorbed to the catalyst surface hydrogen and alkene adsorbed to the catalyst surface

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

Examples 1,2-dimethylcyclohexene 1,2-dimethylcyclohexene

Reduction of Alkyl Halides With metals With metals

Paul Sabatier ( ) Nobel Prize 1912 Nobel Prize 1912 "for his method of hydrogenating organic compounds in the presence of finely disintegrated metals whereby the progress of organic chemistry has been greatly advanced in recent years" "for his method of hydrogenating organic compounds in the presence of finely disintegrated metals whereby the progress of organic chemistry has been greatly advanced in recent years" University of Toulouse, France University of Toulouse, France

Victor Grignard Nobel prize 1912 Nobel prize 1912 "for the discovery of the so- called Grignard reagent, which in recent years has greatly advanced the progress of organic chemistry" "for the discovery of the so- called Grignard reagent, which in recent years has greatly advanced the progress of organic chemistry" University of Nancy, France University of Nancy, France Ph. Barbier, University of Lyon, France Ph. Barbier, University of Lyon, France Barbier reaction Barbier reaction

Grignard Reagents Grignard reagent preparation Grignard reagent preparation Reaction of organic halides with magnesium turnings in ether (DRY ether) Reaction of organic halides with magnesium turnings in ether (DRY ether) Killed with water: form alkanes Killed with water: form alkanes

Grignard Reagents Strongly react with water Strongly react with water Grignard reagents behave as if they were carbanions and they are therefore very strong bases Grignard reagents behave as if they were carbanions and they are therefore very strong bases R rich in electron R rich in electron

Grignard Reagents Formally: conversion of halides to hydrogen Formally: conversion of halides to hydrogen The Grignard reaction: addition of Grignard reagents to carbonyls The Grignard reaction: addition of Grignard reagents to carbonyls

Elias J. Corey Nobel Prize 1990 Nobel Prize 1990 "for his development of the theory and methodology of organic synthesis" "for his development of the theory and methodology of organic synthesis" Harvard University, USA Harvard University, USA Many Corey reactions… Many Corey reactions… (Corey-Winter, Corey-Chakovsky, Corey-Bakshi-Shibata, Corey- Fuchs, Corey-Kim, …)(Corey-Winter, Corey-Chakovsky, Corey-Bakshi-Shibata, Corey- Fuchs, Corey-Kim, …) … and reagents … and reagents PDC, PCC, …PDC, PCC, …

Organometallics Organolithium reagents Organolithium reagents Organocuprate reagents (Gilman reagents) Organocuprate reagents (Gilman reagents)

Corey-Posner, Whitesides- House Coupling of two alkyl halides Organocuprate reagents Coupling of two alkyl halides Organocuprate reagents

Henry Gilman Henry Gilman ( ), Iowa State University Henry Gilman ( ), Iowa State University Talking about his research as a student: 'A sheer delight. Here I was, just a senior. We'd work at night until 11 or 12 o'clock, without any compulsion--just for the joy of it.' Talking about his research as a student: 'A sheer delight. Here I was, just a senior. We'd work at night until 11 or 12 o'clock, without any compulsion--just for the joy of it.' Post doc at Harvard with Kohler who is credited with having introduced the use of the Grignard reagent to the U.S.A. Post doc at Harvard with Kohler who is credited with having introduced the use of the Grignard reagent to the U.S.A. Lithium dialkylcuprate are called Gilman Reagents Lithium dialkylcuprate are called Gilman Reagents

Posner, Whitesides and House Georges M. Whitesides, Harvard University Georges M. Whitesides, Harvard University Material ScienceMaterial Science Gary H. Posner, Johns Hopkins University Gary H. Posner, Johns Hopkins University Organic ChemistryOrganic Chemistry H O. House, Georgia Institute of technology H O. House, Georgia Institute of technology

Examples