Intro To Organic Powerpoint.ppt

What is Organic Chemistry? 1 1

New Way Chemistry for Hong Kong A-Level Book 3A

Organic Chemistry

2 2

•

Chemistry of the compounds present in living organisms.

•

They all contain carbon.

•

Organic Chemistry is the Chemistry of Carbon.

New Way Chemistry for Hong Kong A-Level Book 3A

Natural Sources of Organic Compounds Living things

Carbohydrates / Proteins / Fats / Vitamins / Antibiotics

A variety of organic products obtained from living things 3 3

New Way Chemistry for Hong Kong A-Level Book 3A

Natural Sources of Organic Compounds Fractional distillation / oil destructive distillation

Crude or coal

Alkanes / Alkenes / Alkynes / Aromatic hydrocarbons

A variety of useful products derived from crude oil and coal 4 4

New Way Chemistry for Hong Kong A-Level Book 3A

Development of Organic Chemistry as a Science In the past …, Chemistry

Organic compounds obtained from living organisms 5 5

Inorganic compounds obtained from non-living sources

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Development of Organic Chemistry as a Science

(Inorganic compound) 6 6

(Organic compound)

New Way Chemistry for Hong Kong A-Level Book 3A

Development of Organic Chemistry as a Science Organic chemistry is the study of carbon compounds (except CO, CO2, carbonates, hydrogencarbonates, carbides and cyanides) obtained from natural sources or synthesized in the laboratories.

7 7

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The Unique Nature of Carbon

8 8

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Ability to form four strong covalent bonds

• Electronic configuration of carbon (ground state) : 1s22s22p2

Carbon (ground state)

9 9

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Ability to form four strong covalent bonds

• Each carbon atom has four unpaired electrons when excited • Tend to form four strong covalent bonds

Carbon (excited state) 10 10

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Ability to Catenate • Carbon atoms link together to form chains of varying length, branched chains and rings of different sizes • Catenation:  Ability of atoms in forming stable bonds with itself, hence joining up into chains or rings 11 11

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Ability to Form Multiple Bonds sp3 sp2 sp

4 bonds 1 bond, 3 bonds

2 bonds, 2 bonds

Carbon (excited state) 12 12

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Single bond

Double bond

Triple bond

* X = halogens

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Classification of Organic Compounds 14 14

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Functional Groups •

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Organic compounds are classified by the the presence of characteristic functional groups.

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Functional Groups A functional group is defined as an atom or a group of atoms that effectively determines the chemical properties of an organic compound.

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Functional Groups

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Functional Groups

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•

Propane does not react with sodium

•

Ethanol and propan-1-ol react with sodium to give hydrogen gas

New Way Chemistry for Hong Kong A-Level Book 3A

Functional Groups

and

• have similar chemical properties

 they contain the same functional group –OH  they are classified into the same homologous series — alcohols 19 19

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Homologous Series A homologous series is a series of compounds that have the same functional group, and each member differs from the next member by a – CH2 – unit in their formulae.

CH4

C2H6 CH2

20 20

C3H8 CH2

C4H10 CH2

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Number of carbon atom(s)

IUPAC name

Molecular formula

Condensed structural formula

1

Methane

CH4

CH4

2

Ethane

C2H6

CH3CH3

3

Propane

C3H8

CH3CH2CH3

4

Butane

C4H10

CH3CH2CH2CH3

21 21

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Structural formula

The first four members of straight-chain alkanes

Number of carbon atom(s)

IUPAC name

Molecular formula

Condensed structural formula

1

Methanol

CH3OH

CH3OH

2

Ethanol

C2H5OH

CH3CH2OH

3

Propan-1ol

C3H7OH

CH3CH2CH2OH

4

Butan-1ol

C4H9OH

CH3CH2CH2CH2OH

22 22

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Structural formula

The first four members of straight-chain alcohols

Homologous Series • Members in the same series can be represented by a general formula. e.g. alkanes: CnH2n+2 alkenes: CnH2n alkynes: CnH2n-2

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Homologous Series • Members in the same series can be represented by a general formula. e.g. alkanols: CnH2n+1OH alkanals: CnH2n+1CHO

alkanoic acids: CnH2n+1COOH

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Homologous Series Functional group of an organic compound

Chemical properties

Members of a homologous series have similar chemical properties

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Homologous Series • The physical properties change gradually along the homologous series • e.g. the longer the carbon chain in the molecule ( or the greater the molecular mass)  the greater the attractive force between molecules  the higher the melting point, boiling point and density 26 26

New Way Chemistry for Hong Kong A-Level Book 3A

Some physical properties of the first 20 members of straight-chain alkanes State (at Number room Density of of Molecular Melting Boiling temperature solid / liquid at point (°C) point (°C) carbon formula 20°C (g cm–3) and atom(s) pressure) 1 CH4 Gas –183 –161 – 2 C 2H 6 Gas –172 –89 – 3 C 3H 8 Gas –188 –42 – 4 C4H10 Gas –135 0 – 5 C5H12 Liquid –130 36 0.626 6 C6H14 Liquid –95 69 0.657 7 C7H16 Liquid –91 98 0.684 8 C8H18 Liquid –57 126 0.703 9 C9H20 Liquid –54 151 0.718 27 10 C10H22 –30 174 0.730 NewLiquid Way Chemistry for Hong Kong A-Level 3A 27

New Way Chemistry for Hong Kong A-Level Book 3A

Some physical properties of the first 20 members of straight-chain alkanes State (at Number room Density of of Molecular Melting Boiling temperature solid / liquid at point (°C) point (°C) carbon formula 20°C (g cm–3) and atom(s) pressure) 11 C11H24 Liquid –26 196 0.740 12 C12H26 Liquid –10 216 0.749 13 C13H28 Liquid –7 233 0.753 14 C14H30 Liquid –3 260 0.761 15 C15H32 Liquid 10 271 0.769 16 C16H34 Liquid 18 287 0.773 17 C17H36 Liquid 22 302 0.778 18 C18H38 Solid 28 316 0.777 19 C19H40 Solid 32 330 0.777 28 20 C20H42 37Kong A-Level 344 0.785 NewSolid Way Chemistry for Hong 3A

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Factors Affecting the Physical Properties of Organic Compounds 29 29

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Main Factors Affecting the Physical Properties of Organic Compounds 1. Structure of the functional group 1.1 Dipole moment of the molecule

1.2 Formation of hydrogen bonding 2. Length of carbon chains (London dispersion forces) 30 30

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Structure of Functional Group • Molecules having a polar functional group have a higher b.p. than others with a non-polar functional group of similar molecular masses  Stronger intermolecular attraction among molecules

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Structure of Functional Group Molecule

Molecules with polar functional groups

Molecules with nonpolar functional groups 32 32

Relative molecular mass

Boiling point (oC)

CH3CH2CH2OH

60

97.2

CH3CH2CH2NH2

59

48.6

64.5

12.5

CH3CH2COOH

60

141

CH3CH2CH2CH3

58

-0.5

CH3CH2CH=CH2

56

-6.2

CH3CH2CCH

54

8.1

CH3CH2Cl

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Dipole Moment of Molecule • Tetrachloromethane has 4 polar bonds in the molecule • M.p. and b.p. are very low  the molecule is non-polar

 the molecule is tetrahedrally symmetrical  the dipole moments of the C  Cl bond cancel each other 33 33

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Examples of Polar Molecules with Net Dipole Moment

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Solubility of Organic Molecules • Depends on the polarity of organic molecules and the solvent • Non-polar or weakly polar compounds dissolve readily in non-polar or weakly polar solvents • Highly polar compounds dissolve readily in highly polar solvents • “Like dissolves like” 35 35

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Solubility of Organic Molecules

Hexane in tetrachloromethane 36 36

Hexane in water

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Why does Hexane Dissolve Readily in Tetrachloromethane?

Intermolecular forces among hexane molecules and those  among tetrachloromethane molecules 37 37

Intermolecular forces between hexane and tetrachloromethane molecules

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Why is Hexane Insoluble in Water?

38 38

New Way Chemistry for Hong Kong A-Level Book 3A

Formation of Hydrogen Bonding • Molecules having OH or  NH2 groups are able to form hydrogen bonds • Hydrogen bonds affect the physical properties of alcohols and amines with low molecular masses

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Why does Propan-1-ol have a Higher Boiling Point?

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Formation of Hydrogen Bonding • Also affect the solubility of a molecule • Molecules with OH groups are able to form hydrogen bonds with surrounding water molecules  Soluble in water

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New Way Chemistry for Hong Kong A-Level Book 3A

Length of Carbon Chains • Molecules with higher molecular masses have higher m.p., b.p. and density  Higher molecular masses  Large molecular sizes  Stronger London dispersion forces among molecules

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New Way Chemistry for Hong Kong A-Level Book 3A

Length of Carbon Chains • Molecules with branched chains

 b.p. and density lower than its straight-chain isomer  Straight-chain isomers have greater surface area in contact with each other  Greater attractive force among the molecules 43 43

New Way Chemistry for Hong Kong A-Level Book 3A

Length of Carbon Chains • Molecules with branched chains  m.p. higher than its straight-chain isomer  Branched-chain isomers are more spherical  Packed more efficiently in solid state  Extra energy is needed to break down the efficient packing 44 44

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Family

General formula

Functional group

Alkane

RH

(Nil)

Alkene

RCH = CH2 RCH = CHR R2C = CHR R2C = CR2

Alkyne

RC  CH RC  CR

Aromatic hydrocarbon

ArH

45 45

R = CnH2n+1 –

Carboncarbon double bond –CC– Carboncarbon triple bond

Example Formula IUPAC name CH3CH3 Ethane

CH2 = CH2

Ethene

HC  CH

Ethyne

Benzene

Phenyl group

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Example Formula IUPAC name

Family

General formula

Functional group

Haloalkane

RX

X halo group

CH3Cl

Chloromethane

Alcohol

ROH

 OH hydroxyl group

CH3OH

Methanol

Ether

RO  R

O oxy group

CH3  O  Methoxymethane CH3

Aldehyde

Methanal

R = CnH2n+1 – 46 46

carbonyl group

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Family

General formula

Functional group

Example Formula IUPAC name

Ketone

Propanone carbonyl group

Carboxylic acid

Ethanoic acid carboxyl group

Amine

Nitrile

RNH2 R2NH R 3N RCN

CH3NH2

Methylamine

CH3CN

Ethanenitrile

amino group CN nitrile group

R = CnH2n+1 –New Way Chemistry for Hong Kong A-Level Book 3A

47 47

Family

General formula

Functional group

Example Formula IUPAC name Methyl ethanoate

Ester

ester group

Ethanoyl chloride

Acyl halide

acyl halide group

Amide

Ethanamide amide group

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R = CnH2n+1 –

Family

Acid anhydride

49 49

General formula

Functional group

Example Formula IUPAC name

acid anhydride group

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Ethanoic anhydride

R = CnH2n+1 –