introduction to organic chemistry - zakład biochemii · new way chemistry for hong kong a-level...

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

1

Introduction to

Organic Chemistry

What is Organic Chemistry?

The Unique Nature of Carbon

Classification of Organic Compounds

Factors Affecting the Physical Properties of

Organic Compounds


2

Organic Chemistry

• Chemistry of the compounds present in living organisms.

• They all contain carbon.

• Organic Chemistry is the Chemistry of Carbon.


3

NH4NCO heat

2HN C NH2

O

In 1828, Professor Wohler who was at the time finishing up his post-doctoral work as a student, succeeded in synthesizing in the laboratory an organic compound previously observed in living tissue as Urea. Student Wohler made this organic compound from non-living chemical substance, Ammonium Cyanate. He evaporated a solution of Ammonium Cyanate to produce Urea.


4

Organic Chemistry has undergone a substantial change since then. There are well over a 40 millions synthetic organic compounds. Organic Chemistry is defined as the Chemistry of Carbon and its compounds.

• Organic compound: • hydrobarbons • one functional compounds • many functional compounds • heterocyclic compounds

Development of Organic Chemistry as a Science


5

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.

Development of Organic Chemistry as a Science


6

Classification of Organic

Compounds


7

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

Functional Groups


8

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

Functional Groups


9

Functional Groups


10

Functional Groups

• Propane does not react with sodium

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


11

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 C3H8 C4H10

CH2 CH2 CH2


12 New Way Chemistry for Hong Kong A-Level 3A 12

Number

of carbon

atom(s)

IUPAC

name

Molecular

formula

Condensed

structural

formula

Structural

formula

1 Methane CH4 CH4

2 Ethane C2H6 CH3CH3

3 Propane C3H8 CH3CH2CH3

4 Butane C4H10 CH3CH2CH2CH3

The first four members of straight-chain alkanes



Number

of carbon

atom(s)

IUPAC

name

Molecular

formula

Condensed

structural

formula

Structural

formula

1 Methanol CH3OH CH3OH

2 Ethanol C2H5OH CH3CH2OH

3 Propan-1-

ol

C3H7OH CH3CH2CH2OH

4 Butan-1-

ol

C4H9OH CH3CH2CH2CH2OH

The first four members of straight-chain alcohols


14

• Members in the same series can be represented by a general formula.

e.g. alkanes: CnH2n+2

alkenes: CnH2n

alkynes: CnH2n-2

Homologous Series


15

• Members in the same series can be represented by a general formula.

Homologous Series

e.g. alkanols: CnH2n+1OH

alkanals: CnH2n+1CHO

alkanoic acids: CnH2n+1COOH


16

Functional group of an organic

compound

Chemical properties

Members of a homologous series have similar chemical properties

Homologous Series


17

• 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

Homologous Series



Number

of

carbon

atom(s)

Molecular

formula

State (at

room

temperature

and

pressure)

Melting

point (°C)

Boiling

point (°C)

Density of

solid / liquid at

20°C (g cm–3)

1

2

3

4

5

6

7

8

9

10

CH4

C2H6

C3H8

C4H10

C5H12

C6H14

C7H16

C8H18

C9H20

C10H22

Gas

Gas

Gas

Gas

Liquid

Liquid

Liquid

Liquid

Liquid

Liquid

–183

–172

–188

–135

–130

–95

–91

–57

–54

–30

–161

–89

–42

0

36

69

98

126

151

174

–

–

–

–

0.626

0.657

0.684

0.703

0.718

0.730

Some physical properties of the first 20 members of straight-chain alkanes



Number

of

carbon

atom(s)

Molecular

formula

State (at

room

temperature

and

pressure)

Melting

point (°C)

Boiling

point (°C)

Density of

solid / liquid at

20°C (g cm–3)

11

12

13

14

15

16

17

18

19

20

C11H24

C12H26

C13H28

C14H30

C15H32

C16H34

C17H36

C18H38

C19H40

C20H42

Liquid

Liquid

Liquid

Liquid

Liquid

Liquid

Liquid

Solid

Solid

Solid

–26

–10

–7

–3

10

18

22

28

32

37

196

216

233

260

271

287

302

316

330

344

0.740

0.749

0.753

0.761

0.769

0.773

0.778

0.777

0.777

0.785

Some physical properties of the first 20 members of straight-chain alkanes


20

Factors Affecting the Physical Properties of Organic Compounds


21

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)

Main Factors Affecting the Physical Properties of Organic Compounds


22

• 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

Structure of Functional Group


23

23

Structure of Functional Group Molecule Relative

molecular

mass

Boiling point

(oC)

Molecules

with polar

functional

groups

CH3CH2CH2OH 60 97.2

CH3CH2CH2NH2 59 48.6

CH3CH2Cl 64.5 12.5

CH3CH2COOH 60 141

Molecules

with non-

polar

functional

groups

CH3CH2CH2CH3 58 -0.5

CH3CH2CH=CH2 56 -6.2

CH3CH2CCH 54 8.1


24

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


25

Examples of Polar Molecules with Net Dipole Moment


26

Examples of Non-polar Molecules with No Net Dipole Moment


27

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”


28

Solubility of Organic Molecules

Hexane in tetrachloromethane

Hexane in water


29

Why is Hexane Insoluble in Water?


30

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


31

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


32

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


33

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


34

Classification of Organic

Compounds



Family General

formula

Functional

group

Example

Formula IUPAC name

Alkane RH (Nil) CH3CH3 Ethane

Alkene

RCH = CH2

RCH = CHR

R2C = CHR

R2C = CR2

Carbon-

carbon

double bond

CH2 = CH2 Ethene

Alkyne RC CH

RC CR

– C C –

Carbon-

carbon triple

bond

HC CH Ethyne

Aromatic

hydrocarbon ArH

Phenyl group

Benzene

R = CnH2n+1 –


36

Family General

formula

Functional

group

Example

Formula IUPAC name

Haloalkane RX X

halo group CH3Cl Chloromethane

Alcohol ROH OH

hydroxyl group CH3OH Methanol

Ether RO R O

oxy group

CH3 O

CH3

Methoxymethane

Aldehyde

carbonyl group

Methanal

R = CnH2n+1 –



Family General

formula

Functional

group

Example

Formula IUPAC name

Ketone

carbonyl group

Propanone

Carboxylic

acid

carboxyl group

Ethanoic acid

Amine

RNH2

R2NH

R3N

amino group

CH3NH2 Methylamine

Nitrile RCN C N

nitrile group CH3CN Ethanenitrile

R = CnH2n+1 –



Family General

formula

Functional

group

Example

Formula IUPAC name

Ester

ester group

Methyl

ethanoate

Acyl halide

acyl halide

group

Ethanoyl

chloride

Amide

amide group

Ethanamide

R = CnH2n+1 –


39

Family General

formula

Functional

group

Example

Formula IUPAC name

Acid

anhydride

acid anhydride

group

Ethanoic

anhydride

R = CnH2n+1 –


40

The END

introduction to organic chemistry - zakład biochemii · new way chemistry for hong kong a-level...

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