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New Way Chemistry for Hong Kong A-Level Book 3A11
Introduction to Introduction to Organic ChemistryOrganic Chemistry
21.121.1 What is Organic Chemistry?What is Organic Chemistry?21.221.2 The Unique Nature of CarbonThe Unique Nature of Carbon21.321.3 Classification of Organic CompoundsClassification of Organic Compounds21.421.4 Factors Affecting the Physical Properties of Factors Affecting the Physical Properties of
Organic CompoundsOrganic Compounds
2211
New Way Chemistry for Hong Kong A-Level Book 3A2New Way Chemistry for Hong Kong A-Level
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21.21.11 What is What is
Organic Organic Chemistry?Chemistry?
New Way Chemistry for Hong Kong A-Level Book 3A3New Way Chemistry for Hong Kong A-Level
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21.1 What is Organic Chemistry (SB p.2)
Organic ChemistryOrganic Chemistry• 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 3A4New Way Chemistry for Hong Kong A-Level
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Living things
Carbohydrates / Proteins / Fats / Vitamins / Antibiotics
21.1 What is Organic Chemistry (SB p.4)Natural Sources of Organic Natural Sources of Organic CompoundsCompounds
A variety of organic products
obtained from living things
New Way Chemistry for Hong Kong A-Level Book 3A5New Way Chemistry for Hong Kong A-Level
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Crude oil or coal
Fractional distillation / destructive distillation
Alkanes / Alkenes / Alkynes / Aromatic hydrocarbons
21.1 What is Organic Chemistry (SB p.4)Natural Sources of Organic Natural Sources of Organic CompoundsCompounds
A variety of useful products
derived from crude oil and
coal
Check Point 21-1Check Point 21-1
New Way Chemistry for Hong Kong A-Level Book 3A6New Way Chemistry for Hong Kong A-Level
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In the past …,
Chemistry
Organic compound
sobtained from living
organisms
Inorganic compound
sobtained from non-living sources
21.1 What is Organic Chemistry (SB p.3)
Development of Organic Development of Organic Chemistry as a ScienceChemistry as a Science
New Way Chemistry for Hong Kong A-Level Book 3A7New Way Chemistry for Hong Kong A-Level
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(Inorganic compound)
(Organic compound)
In 1828, Wohler (a German chemist)
21.1 What is Organic Chemistry (SB p.3)
Development of Organic Development of Organic Chemistry as a ScienceChemistry as a Science
New Way Chemistry for Hong Kong A-Level Book 3A8New Way Chemistry for Hong Kong A-Level
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Redefining … ...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 Development of Organic Chemistry as a ScienceChemistry as a Science
21.1 What is Organic Chemistry (SB p.3)
New Way Chemistry for Hong Kong A-Level Book 3A9New Way Chemistry for Hong Kong A-Level
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21.21.22 The Unique The Unique
Nature of Nature of CarbonCarbon
New Way Chemistry for Hong Kong A-Level Book 3A10New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.5)
Ability to form four Ability to form four strongstrong covalent bonds covalent bonds
Carbon (ground state)
• Electronic configuration of carbon (ground state) : 1s22s22p2
New Way Chemistry for Hong Kong A-Level Book 3A11New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.5)
• Each carbon atom has four unpaired electrons when excited
• Tend to form four strong covalent bonds
Carbon (excited state)
Ability to form four Ability to form four strongstrong covalent bonds covalent bonds
New Way Chemistry for Hong Kong A-Level Book 3A12New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.5)
• 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
Ability to Ability to CatenateCatenate
New Way Chemistry for Hong Kong A-Level Book 3A13New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.5)
Ability to Ability to CatenateCatenateC – C > Si – Si > Ge – Ge > Sn – SnBond strength as bond length
New Way Chemistry for Hong Kong A-Level Book 3A14New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.5)
Ability to Ability to CatenateCatenateC – C > N – N > O – O
Bond strength as the number of lone pairs
New Way Chemistry for Hong Kong A-Level Book 3A15New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.5)
Ability to Ability to CatenateCatenateCnH2n+2 n = 1,2,3,…(no limit for n)SinH2n+2 n = 1 to 6 only silanesGenH2n+2 n = 1 to 3 only germanesSnnH2n+2 Only SnH4 (stannane) exists
New Way Chemistry for Hong Kong A-Level Book 3A16New Way Chemistry for Hong Kong A-Level
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Carbon (excited state)
21.2 The Unique Nature of Carbon (SB p.5)
Ability to Form Multiple Ability to Form Multiple BondsBonds
sp2 bonds, 2 bonds
sp2
1 bond, 3 bonds
sp3
4 bonds
New Way Chemistry for Hong Kong A-Level Book 3A17New Way Chemistry for Hong Kong A-Level
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Single bond Double bond Triple bond
21.2 The Unique Nature of Carbon (SB p.6)
* X = halogens
New Way Chemistry for Hong Kong A-Level Book 3A18New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.6)
Example 21-2Example 21-2 Check Point 21-2Check Point 21-2
New Way Chemistry for Hong Kong A-Level Book 3A19New Way Chemistry for Hong Kong A-Level
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21.21.33Classification Classification
of Organic of Organic CompoundsCompounds
New Way Chemistry for Hong Kong A-Level Book 3A20New Way Chemistry for Hong Kong A-Level
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• Organic compounds are classified by the the presence of characteristic functional groups.
21.3 Classification of Organic Compounds (SB p.7)
Functional Functional GroupsGroups
New Way Chemistry for Hong Kong A-Level Book 3A21New Way Chemistry for Hong Kong A-Level
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A functional group is defined as an atom or a group of atoms that effectively determines the chemical properties of an organic compound.
21.3 Classification of Organic Compounds (SB p.7)
Functional Functional GroupsGroups
New Way Chemistry for Hong Kong A-Level Book 3A22New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.7)
Functional Functional GroupsGroups
New Way Chemistry for Hong Kong A-Level Book 3A23New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.7)
Functional Functional GroupsGroups• 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 3A24New Way Chemistry for Hong Kong A-Level
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• have similar chemical properties they contain the same functional group –OH they are classified into the same homologous series — alcohols
and
21.3 Classification of Organic Compounds (SB p.7)
Functional Functional GroupsGroups
New Way Chemistry for Hong Kong A-Level Book 3A25New Way Chemistry for Hong Kong A-Level
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Homologous SeriesHomologous Series21.3 Classification of Organic Compounds (SB p.12)
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
New Way Chemistry for Hong Kong A-Level Book 3A26New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.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
New Way Chemistry for Hong Kong A-Level Book 3A27New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.12)
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
New Way Chemistry for Hong Kong A-Level Book 3A28New Way Chemistry for Hong Kong A-Level
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• Members in the same series can be represented by a general formula.
e.g. alkanes: CnH2n+2
alkenes: CnH2n
alkynes: CnH2n-2
21.3 Classification of Organic Compounds (SB p.13)
Homologous SeriesHomologous Series
New Way Chemistry for Hong Kong A-Level Book 3A29New Way Chemistry for Hong Kong A-Level
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• Members in the same series can be represented by a general formula.
21.3 Classification of Organic Compounds (SB p.13)
Homologous SeriesHomologous Series
e.g. alkanols: CnH2n+1OH
alkanals: CnH2n+1CHO
alkanoic acids: CnH2n+1COOH
New Way Chemistry for Hong Kong A-Level Book 3A30New Way Chemistry for Hong Kong A-Level
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Functional group of an
organic compound
Chemical properties
Members of a homologous series have similar chemical
properties
21.3 Classification of Organic Compounds (SB p.13)
Homologous SeriesHomologous Series
New Way Chemistry for Hong Kong A-Level Book 3A31New Way Chemistry for Hong Kong A-Level
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• 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
21.3 Classification of Organic Compounds (SB p.13)
Homologous SeriesHomologous Series
New Way Chemistry for Hong Kong A-Level Book 3A32New Way Chemistry for Hong Kong A-Level
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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)
123456789
10
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
GasGasGasGas
LiquidLiquidLiquidLiquid Liquid Liquid
–183–172–188–135–130
–95–91–57–54–30
–161–89–42
0366998
126151174
––––
0.6260.6570.6840.7030.7180.730
Some physical properties of the first 20 members of straight-chain alkanes
21.3 Classification of Organic Compounds (SB p.13)
New Way Chemistry for Hong Kong A-Level Book 3A33New Way Chemistry for Hong Kong A-Level
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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)
11121314151617181920
C11H24
C12H26
C13H28
C14H30
C15H32
C16H34
C17H36
C18H38
C19H40
C20H42
LiquidLiquidLiquidLiquidLiquidLiquidLiquid SolidSolidSolid
–26–10
–7–3101822283237
196216233260271287302316330344
0.7400.7490.7530.7610.7690.7730.7780.7770.7770.785
Some physical properties of the first 20 members of straight-chain alkanes
21.3 Classification of Organic Compounds (SB p.13)
New Way Chemistry for Hong Kong A-Level Book 3A34New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.13)
Example 21-3AExample 21-3A Example 21-3BExample 21-3B
Example 21-3CExample 21-3C Check Point 21-3Check Point 21-3
New Way Chemistry for Hong Kong A-Level Book 3A35New Way Chemistry for Hong Kong A-Level
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21.21.44Factors Affecting Factors Affecting the Physical the Physical Properties of Properties of
Organic Organic CompoundsCompounds
Refer to notes on ‘Bonding and Structure’ pp.77-92 – intermolecular forces
New Way Chemistry for Hong Kong A-Level Book 3A36New Way Chemistry for Hong Kong A-Level
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1. Structure of the functional group1.1 Dipole moment of the molecule1.2 Formation of hydrogen bonding
2. Length of carbon chains (London dispersion forces)
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.17)
Main Factors Affecting the Main Factors Affecting the Physical Properties of Physical Properties of Organic CompoundsOrganic Compounds
New Way Chemistry for Hong Kong A-Level Book 3A37New Way Chemistry for Hong Kong A-Level
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• 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
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.17)
Structure of Functional Structure of Functional GroupGroup
New Way Chemistry for Hong Kong A-Level Book 3A38New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.17)Structure of Functional Structure of Functional
GroupGroupMolecule 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
New Way Chemistry for Hong Kong A-Level Book 3A39New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18)
Dipole Moment of MoleculeDipole 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
New Way Chemistry for Hong Kong A-Level Book 3A40New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18)
Examples of Polar Molecules Examples of Polar Molecules with Net Dipole Momentwith Net Dipole Moment
New Way Chemistry for Hong Kong A-Level Book 3A41New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18)
Examples of Non-polar Examples of Non-polar Molecules with No Net Dipole Molecules with No Net Dipole MomentMoment
New Way Chemistry for Hong Kong A-Level Book 3A42New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18)Solubility of Organic Solubility of Organic
MoleculesMolecules• 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”
New Way Chemistry for Hong Kong A-Level Book 3A43New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18)Solubility of Organic Solubility of Organic
MoleculesMolecules
Hexane in tetrachloromethane
Hexane in water
New Way Chemistry for Hong Kong A-Level Book 3A44New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.19)
Why does Hexane Dissolve Readily Why does Hexane Dissolve Readily in Tetrachloromethane?in Tetrachloromethane?
Intermolecular forces among hexane molecules and those among tetrachloromethane
molecules
Intermolecular forces between hexane and tetrachloromethane
molecules
New Way Chemistry for Hong Kong A-Level Book 3A45New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.19)
Why is Hexane Insoluble in Why is Hexane Insoluble in Water?Water?
New Way Chemistry for Hong Kong A-Level Book 3A46New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.19)Formation of Hydrogen Formation of Hydrogen
BondingBonding• 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
New Way Chemistry for Hong Kong A-Level Book 3A47New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20)
Why does Propan-1-ol have Why does Propan-1-ol have a Higher Boiling Point?a Higher Boiling Point?
New Way Chemistry for Hong Kong A-Level Book 3A48New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20)
Formation of Hydrogen Formation of Hydrogen BondingBonding• Also affect the solubility of a
molecule• Molecules with OH groups are able
to form hydrogen bonds with surrounding water molecules Soluble in water
New Way Chemistry for Hong Kong A-Level Book 3A49New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20)
Example 21-4AExample 21-4A
Example 21-4BExample 21-4B
New Way Chemistry for Hong Kong A-Level Book 3A50New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21)
Length of Carbon Length of Carbon ChainsChains• 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
New Way Chemistry for Hong Kong A-Level Book 3A51New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21)
Length of Carbon Length of Carbon ChainsChains• 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
New Way Chemistry for Hong Kong A-Level Book 3A52New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21)Length of Carbon Length of Carbon
ChainsChains• 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
New Way Chemistry for Hong Kong A-Level Book 3A53New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21)
Example 21-4CExample 21-4C
Check Point 21-4Check Point 21-4
New Way Chemistry for Hong Kong A-Level Book 3A54New Way Chemistry for Hong Kong A-Level
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Family General formula
Functional group
Example
Formula IUPAC name
Alkane RH (Nil) CH3CH3 Ethane
Alkene
RCH = CH2
RCH = CHRR2C = CHR
R2C = CR2
Carbon-carbon
double bond
CH2 = CH2 Ethene
AlkyneRC CHRC CR
– C C –Carbon-
carbon triple bond
HC CH Ethyne
Aromatic hydrocarbon ArH
Phenyl group
Benzene
21.3 Classification of Organic Compounds (SB p.8)
R = CnH2n+1 –
New Way Chemistry for Hong Kong A-Level Book 3A55New Way Chemistry for Hong Kong A-Level
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Family General formula
Functional group
Example
Formula IUPAC name
Haloalkane RX X
halo groupCH3Cl Chloromethane
Alcohol ROH OHhydroxyl group
CH3OH Methanol
Ether RO R O oxy group
CH3 O CH3
Methoxymethane
Aldehyde
carbonyl group
Methanal
R = CnH2n+1 –
21.3 Classification of Organic Compounds (SB p.8)
New Way Chemistry for Hong Kong A-Level Book 3A56New Way Chemistry for Hong Kong A-Level
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Family General formula
Functional group
Example
Formula IUPAC name
Ketone
carbonyl group
Propanone
Carboxylic acid
carboxyl group
Ethanoic acid
AmineRNH2
R2NHR3N amino group
CH3NH2 Methylamine
Nitrile RCN C Nnitrile group
CH3CN EthanenitrileR = CnH2n+1 –
21.3 Classification of Organic Compounds (SB p.8)
New Way Chemistry for Hong Kong A-Level Book 3A57New Way Chemistry for Hong Kong A-Level
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Family General formula
Functional group
Example
Formula IUPAC name
Ester
ester group
Methyl ethanoate
Acyl halideacyl halide
group
Ethanoyl chloride
Amide
amide group
Ethanamide
R = CnH2n+1 –
21.3 Classification of Organic Compounds (SB p.8)
New Way Chemistry for Hong Kong A-Level Book 3A58New Way Chemistry for Hong Kong A-Level
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Family General formula
Functional group
Example
Formula IUPAC name
Acid anhydride
acid anhydride group
Ethanoic anhydride
R = CnH2n+1 –
21.3 Classification of Organic Compounds (SB p.9)
New Way Chemistry for Hong Kong A-Level Book 3A59New Way Chemistry for Hong Kong A-Level
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The END
New Way Chemistry for Hong Kong A-Level Book 3A60New Way Chemistry for Hong Kong A-Level
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21.1 What is Organic Chemistry (SB p.4)
(a)How was organic chemistry defined before 1800s? Answer
(a) The knowledge of organic and inorganic compounds was raised during the 1780s. Scientists defined organic chemistry as the study of compounds that could be obtained from living organisms. They believed that the synthesis of organic compounds took place in living organisms only.
New Way Chemistry for Hong Kong A-Level Book 3A61New Way Chemistry for Hong Kong A-Level
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21.1 What is Organic Chemistry (SB p.4)
(b) How is organic chemistry defined nowadays?
Back
Answer(b) Nowadays, scientists have discovered that
many organic compounds can be synthesized from inorganic substances. The updated definition of organic chemistry is the study of carbon compounds, except for carbon monoxide, carbon dioxide, carbonates, hydrogencarbonates, carbides and cyanides. These compounds have been traditionally classified under inorganic chemistry.
New Way Chemistry for Hong Kong A-Level Book 3A62New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.5)
Why is carbon able to catenate?
Back
AnswerThe ability to catenate of carbon is chiefly due to the high strength of the CC single bond (bond enthalpy of C C single bond is 356 kJ mol-1).
New Way Chemistry for Hong Kong A-Level Book 3A63New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.6)
Would you expect silicon, which is just below carbon in the Periodic Table, to catenate to form diverse molecular structures? Explain your answer. Answer
Silicon, unlike carbon, does not catenate to form diverse molecular structures. Carbon is able to catenate because carbon atoms have a relatively small atomic size. This enables a carbon atom to form strong covalent bonds with other carbon atoms. However, due to the greater atomic size of silicon, its ability to catenate is much lower than that of carbon.
Back
New Way Chemistry for Hong Kong A-Level Book 3A64New Way Chemistry for Hong Kong A-Level
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21.2 The Unique Nature of Carbon (SB p.7)
Would you expect sulphur, which has an electronegativity value very close to carbon, to catenate? Why?
Back
AnswerThe electronic configuration of sulphur is 1s22s22p63s23p4. It has only two unpaired electrons. Its atomic size is larger than that of carbon. So it has a much lower tendency to catenate than carbon.
New Way Chemistry for Hong Kong A-Level Book 3A65New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.14)
Identify the functional group(s) in the following compounds:(a)
Answer(a) Carbon-carbon double bond ( ) and
chloro group (Cl)
New Way Chemistry for Hong Kong A-Level Book 3A66New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.14)
Identify the functional group(s) in the following compounds:(b)
Answer(b) Carbonyl group ( )
New Way Chemistry for Hong Kong A-Level Book 3A67New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.14)
Identify the functional group(s) in the following compounds:(c)
Answer(c) Amino group ( ) and carboxyl group
( )
Back
New Way Chemistry for Hong Kong A-Level Book 3A68New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.15)
To which homologous series does each of the following compounds belong?(a)
Answer
(a) Ester
New Way Chemistry for Hong Kong A-Level Book 3A69New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.15)
To which homologous series does each of the following compounds belong?(b)
Answer
(b) Amide
New Way Chemistry for Hong Kong A-Level Book 3A70New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.15)
To which homologous series does each of the following compounds belong?(c)
Answer
(c) Acid anhydride
Back
New Way Chemistry for Hong Kong A-Level Book 3A71New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.15)
State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answer.(a)
Answer(a) No, the first one is a carboxylic acid and the
second one is an ester.
New Way Chemistry for Hong Kong A-Level Book 3A72New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.15)
State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answer.(b)
Answer(b) Yes, both of them are alcohols.
New Way Chemistry for Hong Kong A-Level Book 3A73New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.15)
State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answer.(c)
Answer(c) No, the first one is an amide and
the second one is an amine.
Back
New Way Chemistry for Hong Kong A-Level Book 3A74New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.16)
(a) Name the homologous series of organic compounds that contain oxygen atoms in their functional groups. Answer(a) Alcohol, ether, aldehyde, ketone,
carboxylic acid, ester, acyl halide, amide and acid anhydride
New Way Chemistry for Hong Kong A-Level Book 3A75New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.16)
(b) Identify and name the functional groups in glucose which has the following structure.
Answer
(b) OH (hydroxyl group) and O (oxy group)
New Way Chemistry for Hong Kong A-Level Book 3A76New Way Chemistry for Hong Kong A-Level
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21.3 Classification of Organic Compounds (SB p.16)
(c) Identify and name the functional groups in the following compounds:
Answer
Back
(c) Br (bromo),
(aldehyde),
(acyl chloride),
(carbon-carbon double bond) groups
New Way Chemistry for Hong Kong A-Level Book 3A77New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18)
Why is oil immiscible with water?Answer
Oil molecules do not have free OH groups, so they cannot form hydrogen bonds with water molecules.
Back
New Way Chemistry for Hong Kong A-Level Book 3A78New Way Chemistry for Hong Kong A-Level
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21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20)
The relative molecular mass of glucose is 180.0, but it is soluble in water. Why?
AnswerGlucose molecules have OH groups, so they are able to form hydrogen bonds with water molecules. Therefore, glucose is soluble in water despite it has a high molecular mass. Back
New Way Chemistry for Hong Kong A-Level Book 3A79New Way Chemistry for Hong Kong A-Level
3A79
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20)
Despite the fact that butan-1-ol and ethoxyethane have the same relative molecular mass, they have very different boiling points. The boiling points of butan-1-ol and ethoxyethane are 117oC and 35oC respectively. Explain the difference. Answer
New Way Chemistry for Hong Kong A-Level Book 3A80New Way Chemistry for Hong Kong A-Level
3A80
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20)
There is an OH group in butan-1-ol. Thus, butan-1-ol molecules are able to form hydrogen bonds with one another and the energy required to separate butan-1-ol molecules would be much greater. Whereas for ethoxyethane, the attraction among the molecules is weak van der Waals’ forces only. The amount of energy required to break the forces would not be great. Therefore, the boiling point of ethoxyethane is lower than that of butan-1-ol.
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New Way Chemistry for Hong Kong A-Level Book 3A81New Way Chemistry for Hong Kong A-Level
3A81
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21)
Explain why propan-1-ol is soluble in water but
1-chloropropane is insoluble in water.
AnswerThe OH group of propan-1-ol molecules enables it to form hydrogen bonds with water molecules. Thus it is soluble in water. Although 1-chloropropane is a polar molecule, it does not form hydrogen bonds with water molecules. So it is insoluble in water.
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New Way Chemistry for Hong Kong A-Level Book 3A82New Way Chemistry for Hong Kong A-Level
3A82
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21)
Which molecule would have a higher boiling point, 1-bromobutane or 2-bromobutane? Why?
Answer1-bromobutane would have a higher boiling point. 1-bromobutane is a straight-chain molecule while 2-bromobutane is a branched-chain molecule. Straight-chain molecules have a greater surface area in contact with each other, so greater intermolecular forces exist among the molecules. Higher energy is required to break down the intermolecular forces among the molecules of 1-bromobutane.
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New Way Chemistry for Hong Kong A-Level Book 3A83New Way Chemistry for Hong Kong A-Level
3A83
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.22)
1-Chlorobutane and 2-chloro-2-methylpropane have the same molecular mass, yet their melting points differ. The melting point of 1-chlorobutane is –123oC while that of 2-chloro-2-methylpropane is –27.1oC. Explain the difference.
Answer
New Way Chemistry for Hong Kong A-Level Book 3A84New Way Chemistry for Hong Kong A-Level
3A84
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.22)
Melting point is a measure of how efficient the molecules are packed together in the solid state instead of just comparing the van der Waals’ forces among molecules. Hence melting point is a function of the efficient packing of molecules but not the contact surface area. 1-Chlorobutane is a straight-chain molecule while 2-chloro-2-methylpropane is a branched-chain molecule. As 2-chloro-2-methylpropane is more spherical and symmetrical, its molecules are packed more efficiently in the solid state. 1-Chlorobutane is linear in shape and flattened, its packing in the solid state is not so efficient. Hence, it has a lower melting point than 2-chloro-2-methylpropane.
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New Way Chemistry for Hong Kong A-Level Book 3A85New Way Chemistry for Hong Kong A-Level
3A85
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24)
(a) What are the major factors that affect the physical properties of organic compounds?
Answer(a) The physical properties of organic compounds
are mainly affected by the structure of the functional groups, dipole moment of the molecule, the formation of hydrogen bonding between molecules, and the length of carbon chains of the molecule.
New Way Chemistry for Hong Kong A-Level Book 3A86New Way Chemistry for Hong Kong A-Level
3A86
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24)
(b) The melting point and boiling point of pentane are –130oC and 36.3oC respectively while the melting point and boiling point of 2,2-dimethylpropane are –15.9oC and 9.5oC respectively. Account for the difference in melting point and boiling point between the two isomers.
Answer
New Way Chemistry for Hong Kong A-Level Book 3A87New Way Chemistry for Hong Kong A-Level
3A87
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24)
(b) Pentane is a straight-chain molecule, while 2,2-dimethylpropane is a branched-chain molecule. Straight-chain molecules have a greater surface area in contact with each other than branched-chain molecules. Straight-chain molecules are held together by stronger intermolecular forces. Therefore, pentane has a higher boiling point than 2,2-dimethylpropane. Molecules of 2,2-dimethylpropane are more spherical in shape and are packed more efficiently in the solid state. Molecules of pentane are linear in shape and flattened, so their packing in the solid state is not efficient. Since extra energy is required to break down the efficient packing of 2,2-dimethylpropane, 2,2-dimethylpropane has a higher melting point than pentane.
New Way Chemistry for Hong Kong A-Level Book 3A88New Way Chemistry for Hong Kong A-Level
3A88
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24)
(c) Which molecule, hexane or cyclohexane, would have a higher melting point? Explain your answer.
Answer
New Way Chemistry for Hong Kong A-Level Book 3A89New Way Chemistry for Hong Kong A-Level
3A89
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24)
(c) Cyclohexane has a higher melting point than hexane. Molecules of cyclohexane are more spherical in shape and are packed more eff iciently in the solid state. Molecules of hexane are linear in shape and flattened, so their packing in the solid state is not efficient. Since extra energy is required to break down the efficient packing of cyclohexane, cyclohexane has a higher melting point than hexane.
New Way Chemistry for Hong Kong A-Level Book 3A90New Way Chemistry for Hong Kong A-Level
3A90
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24)
(d) Arrange the following molecules in increasing order of boiling points. Explain your answer.
Answer
New Way Chemistry for Hong Kong A-Level Book 3A91New Way Chemistry for Hong Kong A-Level
3A91
21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24)
(d) The boiling points increase in the order:butane < propanal < propan-1-olMolecules of butane are non-polar. Their molecules are held together by weak instantaneous dipole-induced dipole interactions. A relatively small amount of energy is required to separate the molecules in the process of boiling. Both propanal and propan-1-ol are polar molecules. Molecules of propanal are held together by relatively weak dipole-dipole interactions, while molecules of propan-1-ol are held together by intermolecular hydrogen bonds. Since the intermolecular forces present in molecules of propan-1-ol are stronger than those present in molecules of propanal, a larger amount of energy is required to separate the propan-1-ol molecules in the process of boiling.
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