SUBJECT: PHYSICAL SCIENCES
TOPIC:
TEACHER AND LEARNER CONTENT MANUAL
AUTUMN CLASSES
Nomenclature &
Structure
Physical Properties
Reactions
JENN TRAINING: SETTLEMENT GEOGRAPHY CONTENT MANUAL TERM 2 TEACHER/LEARNERS:
CONTENTS
PAGE
Examination Guidelines
3-6
Important Terms and Definitions
7-10
Nomenclature and Structure
11-24
Physical Properties
25-44
Reactions
45-53
ICON DESCRIPTION
MIND MAP
BIBLIOGRAPHY
EXAMINATION
GUIDELINE
TERMINOLOGY
CONTENTS
ACTIVITIES
WORKED EXAMPLES STEPS
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
2
EXAMINATION GUIDELINES
➢ Define organic molecules as molecules containing carbon atoms.
Organic molecular structures – functional groups, saturated and unsaturated
structures, isomers
➢ Write down condensed structural formulae, structural formulae, molecular
formulae, and IUPAC names (up to 8 carbon atoms) for:
1. Alkanes (no ring structures)
2. Alkenes (no ring structures)
3. Alkynes
4. Halo-alkanes (primary, secondary and tertiary haloalkanes; no ring structures)
5. Alcohols (primary, secondary and tertiary alcohols)
6. Carboxylic acids
7. Esters
8. Aldehydes
9. Ketones
➢ Know the following definitions/terms:
1. Molecular formula: A chemical formula that indicates the element and
numbers of each of the atoms in a molecule. Example: C 4H8O
2. Structural formula: A structural formula of a compound shows which atoms
are attached to which within the molecule. Atoms are represented by their
chemical symbols and lines are used to represent ALL the bonds that hold the
atoms together. Example:
3. Condensed structural formula: This notation shows the way in which atoms
are bonded together in the molecule but DOES NOT SHOW ALL bond lines.
Example:
4. Hydrocarbon: Organic compounds that consist of hydrogen and carbon only.
5. Homologous series: A series of organic compounds that can be described by
the same general formula OR in which one member differs from the next with a
CH2 group.
6. Saturated compounds: Compounds in which there are no multiple bonds
between C atoms in their hydrocarbon chains
7. Unsaturated compounds: Compounds with one or more multiple bonds
between C atoms in their hydrocarbon chains
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
3
8. Functional group: A bond or an atom or a group of atoms that determine(s)
the physical and chemical properties of a group of organic compounds.
9. Structural isomer: Organic molecules with the same molecular formula, but
different structural formulae.
➢ Identify compounds (up to 8 carbon atoms) that are saturated, unsaturated and
are structural isomers.
➢ Restrict structural isomers to chain isomers, positional isomers and functional
isomers.
1. Chain isomers: Same molecular formula, but different types of chains, e.g.,
butane and 2-methylpropane
2. Positional isomers: Same molecular formula, but different positions of the
side chain, substituents, or functional groups on the parent chain, e.g., 1chloropropane and 2-chloropropane or but-2-ene and but-1-ene.
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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3. Functional isomers: Same molecular formula, but different functional groups,
e.g., methyl methanoate and ethanoic acid.
IUPAC naming and formulae for compounds in the homologous series above
➢ Write down the IUPAC name when given the structural formula or condensed
structural formula.
➢ Write down the structural formula when given the IUPAC name or molecular
formula.
➢ Compounds must be restricted to one functional group per compound (except
haloalkanes).
➢ Haloalkanes restricted to two functional groups per compound.
➢ Alkyl substituents (methyl- and ethyl- only) restricted to a maximum of THREE on
the parent chain.
➢ When naming haloalkanes:
1. Halogen substituents do not get preference over alkyl groups.
2. Numbering should start from the end nearest to the first substituent.
3. When substituents, e.g., Br and Cℓ or Cℓ and methyl, have the same number
when numbered from different ends of chain, preference is given to alphabetical
order, e.g., bromo- over chloro-; chloro- over methyl-.
➢ When writing IUPAC names, substituents are written alphabetically namely bromo,
chloro, ethyl, methyl. Ignore prefixes di and tri.
Structure and physical properties (boiling point, melting point, vapour pressure)
relationships
➢ For a given example (from the above functional groups), explain the relationship
between physical properties and:
1. Strength of intermolecular forces (Van der Waal's forces), i.e., hydrogen bonds,
dipole-dipole forces, induced dipole forces
2. Type of functional groups.
3. Chain length.
4. Branched chains.
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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Oxidation of alkanes
➢ State the use of alkanes as fuels.
➢ Write down an equation for the combustion of an alkane in excess oxygen.
Esterification
➢ Write down an equation, using structural formulae or condensed structural
formulae, for the formation of an ester.
➢ Name the alcohol and carboxylic acid used and the ester formed.
➢ Write down reaction conditions for esterification.
Substitution, addition, and elimination reactions
➢ Identify reactions as elimination, substitution, or addition.
➢ Write down, using structural formulae or condensed structural formulae, equations
and reaction conditions for the following addition reactions of alkenes:
1. Hydrohalogenation: The addition of a hydrogen halide to an alkene
2. Halogenation: The reaction of a halogen (Br2, Cℓ2) with a compound
3. Hydration: The addition of water to a compound
4. Hydrogenation: The addition of hydrogen to an alkene
➢ Identify major and minor products in the above addition reactions.
➢ Write down, using structural formulae or condensed structural formulae, equations
and reaction conditions for the following elimination reactions:
1. Dehydrohalogenation of haloalkanes: The elimination of hydrogen and a
halogen from a haloalkane
2. Dehydration of alcohols: Elimination of water from an alcohol
3. Cracking of alkanes: The chemical process in which longer chain hydrocarbon
molecules are broken down to shorter more useful molecules.
➢ Identify major and minor products in the above elimination reactions. • Write down,
using structural formulae or condensed structural formulae, equations, and reaction
conditions for the following substitution reactions:
1. Hydrolysis of haloalkanes Hydrolysis: The reaction of a compound with water
2. Reactions of HX (X = Cℓ, Br) with alcohols to produce haloalkanes
3. Halogenation of alkanes The reaction of a halogen (Br2, Cℓ2) with a compound
➢ Distinguish between saturated and unsaturated hydrocarbons using bromine water
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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IMPORTANT TERMS AND DEFINITIONS
MATTER AND MATERIALS: ORGANIC MOLECULES
A reaction in which a double bond in the starting material is broken and
Addition reaction
elements are added to it.
An organic compound in which H atoms in an alkane have been
Alcohol
substituted with hydroxyl groups (-OH groups).
General formula: CnH2n + 1OH
Organic compounds having the general structure RCHO where R = H or
Aldehydes
alkyl. General formula: RCHO (R = alkyl group)
An organic compound containing only C-H and C-C single bonds.
Alkane
General formula: CnH2n + 2
A compound of carbon and hydrogen that contains a carbon-carbon double
Alkene
bond. General formula: CnH2n
Alkyl group
A group formed by removing one H atom from an alkane.
A compound of carbon and hydrogen that contains a carbon-carbon triple
Alkyne
bond.
The temperature at which the vapour pressure of a liquid equals
Boiling point
atmospheric pressure.
Carbonyl group
Functional group of ketones (>C=O)
Carboxyl group
Functional group of carboxylic acids (-COOH)
An organic compound containing a carboxyl group (-COOH group).
Carboxylic acid
General formula: CnH2n + 1COOH (or RCOOH)
Chain isomers
Compounds with the same molecular formula, but different types of chains.
Condensed structural A formula that shows the way in which atoms are bonded together in the
formula
molecule but DOES NOT SHOW ALL bond lines.
The chemical process in which longer chain hydrocarbon molecules are
Cracking
broken down to shorter more useful molecules.
Dehydration
Elimination of water from a compound usually such as an alcohol.
Dehydrohalogenation The elimination of hydrogen and a halogen from a haloalkane.
Intermolecular forces found between polar molecules i.e. molecules in
Dipole-dipole force
which there is an uneven distribution of charge so that the molecule has a
positive and a negative side.
A reaction in which elements of the starting material are “lost” and a double
Elimination reaction
bond is formed.
The preparation of an ester from the reaction of a carboxylic acid with an
Esterification
alcohol.
A bond or an atom or a group of atoms that determine(s) the physical and
Functional group
chemical properties of a group of organic compounds.
Compounds with the same molecular formula, but different functional
Functional isomers
groups.
An organic compound in which one or more H atoms in an alkane have
Haloalkane
been replaced with halogen atoms.
(Alkyl halide)
General formula: CnH2n + 1X (X = F, Cℓ, Br or I)
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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The reaction of a halogen (Br2, Cℓ2) with a compound.
Halogenation
Homologous series
Hydration
Hydrocarbon
Hydrogenation
Hydrogen bond
Hydrohalogenation
Hydrolysis
Intermolecular force
IUPAC name
London force
Melting point
Molecular formula
Organic chemistry
Positional isomer
A series of organic compounds that can be described by the same general
formula and that have the same functional group.
OR A series of organic compounds in which one member differs from the
next with a CH2 group.
The addition of water to a compound.
Organic compounds that consist of hydrogen and carbon only.
The addition of hydrogen to an alkene
A strong intermolecular force found between molecules in which an H atom
is covalently bonded to wither an N, O or F atom.
The addition of a hydrogen halide to an alkene.
The reaction of a compound with water.
Forces between molecules that determine physical properties of
compounds.
A chemical nomenclature (set of rules) created and developed by the
International Union of Pure and Applied Chemistry (IUPAC) to generate
systematic names for chemical compounds.
A weak intermolecular force between non-polar molecules.
The temperature at which the solid and liquid phases of a substance are at
equilibrium.
A chemical formula that indicates the type of atoms and the correct number
of each in a molecule, e.g., CH4.
Chemistry of carbon compounds.
Compounds with the same molecular formula, but different positions of the
side chain, substituents or functional groups on the parent chain.
The C atom bonded to the hydroxyl group is bonded to ONE other C atom.
Example:
Primary alcohol
The C atom bonded to the halogen is bonded to ONE other C atom.
Example:
Primary haloalkane
Saturated
compounds
Compounds in which there are no multiple bonds between C atoms in their
hydrocarbon chains.
OR Compounds with only single bonds between C atoms in their
hydrocarbon chains.
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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The C atom bonded to hydroxyl group is bonded to TWO other C atoms.
Example:
H
Secondary alcohol
H
H
C
C
H
O
H
H
C
H
H
The C atom bonded to the halogen is bonded to ONE other C atom.
Example:
Secondary
haloalkane
H
H
H
C
C
Br
H
H
C
H
H
Structural formula
Structural isomer
Substituent (branch)
Substitution reaction
A structural formula of a compound shows which atoms are attached to
which within the molecule. Atoms are represented by their chemical
symbols and lines are used to represent ALL the bonds that hold the atoms
together.
Organic molecules with the same molecular formula, but different structural
formulae.
A group or branch attached to the longest continuous chain of C atoms in
an organic compound.
A reaction in which an atom or a group of atoms in a molecule is replaced
by another atom or group of atoms.
The C atom bonded to the hydroxyl group is bonded to THREE other C
atoms. Example:
H
H
C
H
H
Tertiary alcohol
H
C
C
O
H
H
H
C
H
H
The C atom bonded to the halogen is bonded to THREE other C atoms.
Example:
H
H
C
H
H
Tertiary haloalkane
H
C
C
Br
H
H
C
H
H
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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Unsaturated
compounds
Van der Waals
forces
Vapour pressure
Compounds in which there are multiple bonds (double or triple bonds)
between C atoms in their hydrocarbon chains.
A combined name used for the different types of intermolecular forces.
The pressure exerted by a vapour at equilibrium with its liquid in a closed
system.
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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ACTIVITY 1
1.1
[36 MARKS; 36 min]
Write down the IUPAC names of the compounds below:
A
B
…………………………………………. (2)
…………………………………………. (2)
D
C
…………………………………………. (2)
E
…………………………………………. (2)
F
…………………………………………. (2)
…………………………………………. (2)
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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The letters A to E in the table below represent six organic compounds.
1.2
1.3
A
Butane
B
4,4-dimethylpent-2-yne
C
2,2,4-trimethylhexane
D
2,2-dimethylpropane
E
Pent-1-yne
F
CH3CH2CHCH2
Write down the STRUCTURAL FORMULA of the following compounds:
1.2.1
B
Answer:
(2)
1.2.2
C
Answer:
(2)
1.2.3
D
Answer:
(2)
Compound A is a gas used in cigarette lighters.
1.3.1
To which homologous series does compound A belong?
Answer:
(1)
1.3.2
Is compound A, a hydrocarbon compound? YES or NO.
Give a reason for the answer.
(2)
Is compound A SATURATED or UNSATURATED compound?
Give a reason for the answer.
(2)
Answer:
1.3.3
Answer:
1.3.4
STRUCTURAL FORMULA of a structural isomer of compound A.
Answer:
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
(2)
12
Structural isomers can be further divided into chain isomers, positional isomers and
functional isomers.
1.3.5
Is the isomer in QUESTION 1.3.4 a CHAIN, POSITIONAL or FUNCTIONAL
isomer? Give a reason for your answer.
(2)
Answer:
Compound A undergoes combustion in excess oxygen.
1.3.6
Balanced equation, using molecular formulae, for the combustion of
compound A in excess oxygen
(3)
Answer:
1.4
Consider Compound F:
1.4.1
Is compound F, SATURATED or UNSATURATED compound?
Give a reason for the answer.
(2)
Answer:
Write down the:
1.4.2
GENERAL FORMULA of the homologous series to which compound F
belongs.
(1)
Answer:
1.4.3
STRUCTURAL FORMULA of the functional group for compound F.
Answer:
(1)
1.4.4
The IUPAC NAME of a POSITIONAL isomer of compound F.
Answer:
(2)
1.4.5
STRUCTURAL FORMULA of a CHAIN isomer of compound F.
Answer:
(2)
[36]
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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ACTIVITY 2
2.1
[30 MARKS; 30 min]
Write down the IUPAC names of the compounds below:
A
B
…………………………………………. (2)
…………………………………………. (2)
D
C
…………………………………………. (2)
…………………………………………. (2)
F
E
H
H
H
H
H
H
H
H
C
C
C
C
C
H
H
O
H
C
H
H
C
H
H
C
C
H
H
H
H
H
C
H
H
…………………………………………. (2)
…………………………………………. (2)
………………………………………….
(2)
JENN TRAINING & CONSULTANCY: ORGANIC
MOLECULES
14
The letters A to E in the table below represent six organic compounds.
2.2
2.3
A
2,3-dibromo-3-methylpentane
B
2-chlorobutane
C
Pentan-1-ol
D
3-chloro-4-methylhexane
E
3,6-dimethyloctan-4-ol
F
C3 H8 O
Write down the STRUCTURAL FORMULA of the following compounds:
2.2.1
A
Answer:
(2)
2.2.2
D
Answer:
(2)
2.2.3
E
Answer:
(2)
Consider compound C.
2.3.1
To which homologous series does compound C belong?
Answer:
(1)
Write down the:
2.3.3
GENERAL FORMULA of the homologous series to which compound C
belongs.
(1)
Answer:
2.3.4 Name of the functional group of compound C.
Answer:
(1)
2.3.5
STRUCTURAL FORMULA of the functional group for compound C.
Answer:
(1)
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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2.3.6
STRUCTURAL FORMULA of a secondary alcohol that is a structural
isomer of compound C.
(2)
The IUPAC name of a tertiary alcohol that is a structural isomer of
compound C.
(2)
Answer:
2.3.7
Answer:
2.4
Consider Compound B:
2.4.1
Is this a PRIMARY, SECONDARY or TERTIARY haloalkane Give a
reason for the answer
(2)
STRUCTURAL FORMULA of a secondary alcohol that is a structural
isomer of compound B.
(2)
Answer:
2.4.2
Answer:
[30]
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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ACTIVITY 3
3.1
[27 MARKS; 27 min]
Write down the IUPAC names of the compounds below:
A
B
…………………………………………. (2)
C
…………………………………………. (2)
H
H
H
H
C
C
C
H
H
H
O
H
H
C
C
C
C
H
H
H
H
H
H
C
H
H
D
H
C
C
H
C
H
…………………………………………. (2)
E
O
H
H
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
…………………………………………. (2)
…………………………………………. (2)
F
H
H
H
H
H
C
C
C
H
H
H
C
H
C
H
H
C
H
H
H
H
O
C
C
C
C
H
H
H
H
…………………………………………. (2)
H
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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The letters A to E in the table below represent six organic compounds.
A
Pentan-2-one
B
C
3,5-dimethylheptan-2-one.
D
E
3.2
3.3
F
2-ethyl-4-methylhexanal.
Write down the STRUCTURAL FORMULA of the following compounds:
3.2.1
C
Answer:
(2)
3.2.2
Answer:
D
(2)
3.2.3
Answer:
F
(2)
Consider compound A.
3.3.1
Answer:
To which homologous series does compound A belong?
(1)
Write down the:
3.3.2
GENERAL FORMULA of the homologous series to which compound A
belongs.
(1)
Answer:
3.3.3 Name of the functional group of compound A.
Answer:
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
(1)
18
3.3.4
Answer:
STRUCTURAL FORMULA of the functional group for compound A.
(1)
Study the condensed structural formulae for compounds D and E.
3.3.5
Give a reason why compounds A and B are said to be positional
isomers.
(2)
Write down the compound STRUCTURAL FORMULA of another
positional isomer of compounds D and E.
(1)
Answer:
3.3.6
Answer:
3.4
Consider Compound B:
3.4.1
Answer:
The IUPAC NAME of a CHAIN isomer of compound B.
(2)
[27]
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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ACTIVITY 4
4.1
[32 MARKS; 32 min]
Write down the IUPAC names of the compounds below:
A
B
…………………………………………. (2)
…………………………………………. (2)
C
D
…………………………………………. (2)
E
…………………………………………. (2)
F
H
H
C
H
H
…………………………………………. (2)
H
H
H
H
H
C
H
HO
C
C
C
C
C
C
C
H
H
H
H
H
C
H
H
H
C
H
O
H
H
…………………………………………. (2)
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
20
The letters A to E in the table below represent six organic compounds.
A
4.2
B
Pentyl butanoate
C
Pentanoic acid
D
3-ethyl-5-methylheptanoic acid
E
Ethyl propanoate
F
2-methylpentanoic acid
Write down the STRUCTURAL FORMULA of the following compounds:
4.2.1
B
Answer:
(2)
4.2.2
D
Answer:
4.3
(2)
Consider compound C.
4.3.1
To which homologous series does compound C belong?
Answer:
(1)
Write down the:
4.3.2
GENERAL FORMULA of the homologous series to which compound C belongs.
Answer:
(1)
4.3.3 Name of the functional group of compound C.
Answer:
(1)
4.3.4
STRUCTURAL FORMULA of the functional group for compound C.
Answer:
(1)
4.3.5
STRUCTURAL FORMULA of the FUNCTIONAL isomer of compound C.
Answer:
(2)
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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4.3.6
The IUPAC NAME of a CHAIN isomer of compound C.
Answer:
4.4
(2)
Consider Compound E:
4.4.1
NAME of the catalyst used for the preparation of compound E
(1)
4.4.2
The IUPAC name of the organic acid used in its preparation
(2)
4.4.3
STRUCTURAL FORMULA of the alcohol used in its preparation
(2)
4.4.4
Write down the FORMULA of the inorganic product formed.
(2)
4.4.5
Type of reaction which takes place to prepare compound E
(1)
Answer:
Answer:
Answer:
Answer:
Answer:
[32]
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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Activity 5
18 Marks; 18 min
The letters A to F in the table below represent six organic compounds.
Use the information in the table to answer the questions that follow.
5.1
5.2
Write down the letter(s) that represent(s):
5.1.1 A compound with the general formula CnH2n+2
Answer:
5.1.2 A ketone
Answer:
(1)
5.1.3 An aldehyde
Answer:
(1)
5.1.4 An unsaturated hydrocarbon
Answer:
(1)
For compound F, write down the:
5.2.1 Structure of the functional group to which it belongs
Answer:
5.2.2 IUPAC name of the acid and an alcohol needed to prepare F
Answer:
5.3
(1)
Write down the IUPAC name of:
5.3.1 Compound C
Answer:
5.3.2 Compound D
Answer:
(2)
(2)
(2)
(2)
Write down the condensed structural formula for C.
Answer:
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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5.4
Write down the structural formula of:
5.4.1 A chain isomer of compound E
Answer:
5.4.2 Compound F
Answer:
(2)
(2)
[18]
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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ACTIVITY 1
29 Marks; 29 minutes
Three compounds are used to investigate one of the factors that influences boiling point. The results
obtained are shown in the table below.
1.1
In one investigation the boiling points of compound B and compound C, are compared.
1.1.1
Is this a fair investigation? Write down YES or NO. Refer to the data
in the table and give a reason for the answer.
(2)
Answer:
1.1.2
Write down the independent variable for this investigation.
Answer:
(1)
1.2
Which ONE of the compounds (A, B or C) has the highest vapour pressure?
Give a reason for the answer.
Answer:
(2)
1.3
Refer to the intermolecular forces present in each compound and FULLY explain the trend in
boiling points, as shown in the above table.
Answer:
(5)
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
28
An experiment is conducted to determine the boiling point of organic compounds with three different
homologous series, indicated with letters A to C, determined under the same conditions. The results
are given in the table below:
1.4
Write the name of the homologous series to which A, B and C belong to.
Answer:
(3)
1.5
Formulate an investigative question for this practical investigation.
Answer:
(2)
1.6
Identify the:
1.6.1
DEPENDENT variable for this investigation.
Answer:
(1)
1.6.2
INDEPENDENT variable for this investigation.
Answer:
(1)
1.7
Fully explain the difference between the boiling points of compound B and C.
Answer:
(4)
1.8
Fully explain the difference between the boiling points of compound A and B.
Answer:
(4)
1.9
Which one of the above-mentioned compounds will have the highest VAPOUR PRESSURE?
Explain your answer.
Answer:
(2)
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
29
1.10
Explain why this investigation can be regarded as a fair test.
Answer:
(1)
Four compounds of comparable molecular mass are used to investigate the effect of functional
groups on vapour pressure. The results obtained are shown in the table below.
1.11
Which ONE of the compounds (A, B, C or D) in the table has the: Highest boiling point
(Refer to the vapour pressures in the table to give a reason for the
answer.)
Answer:
(1)
[29]
JENN TRAINING & CONSULTANCY: ORGANIC MOLECULES
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Surface area – chain length
Methane, ethane, propane, butane, pentane, hexane, heptane, octane
➢For compounds with the same functional group
➢The longer the carbon chain, the larger the surface area and the higher the
boiling point/melting point and the lower the vapour pressure. .
➢Carbon chain length increases and therefore molecular mass increases from
methane to octane.
➢Intermolecular forces increase with an increase in molecular mass/ carbon chain
length.
➢The stronger the intermolecular forces, the more energy will be needed to
overcome them (London/ dispersion/ induced dipole force).
EXAMPLE 1
Learners investigate factors that influence the boiling points. In their
investigations they determine the boiling points of the first three alkanes.
1. Fully explain why the boiling point increases from methane to propane.
STRUCTURE
ANSWER
STRENGTH OF
INTERMOLECULAR
FORCES
ENERGY
• The chain length / surface area
increases from methane to
propane.
• Strength of intermolecular
forces/ London forces increases
• More energy is needed to
overcome the intermolecular
forces
Increasing chain length, increasing surface area, increasing strength of
intermolecular forces, increasing boiling point, increasing melting point
and decreasing vapour pressure
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ACTIVITY 2
Learners use compounds A to C, shown in the table below, to investigate a factor which influences the
boiling point of organic compounds.
2.1
Which ONE of the compounds (A, B or C) has the highest boiling point?
Answer:
2.2
For this investigation, write down the:
2.2.1
Independent variable
Answer:
2.3
(1)
(1)
2.2.2
Dependent variable
Answer:
(1)
Write down the name of the type of Van der Waals force that occurs between the
molecules of compound B.
Answer:
(1)
The table below shows the results obtained from experiments to determine the boiling point of
some alkanes and alcohols of comparable molecular masses.
2.4
Define the term boiling point
Answer:
2.5
Consider the boiling points of the four alkanes in the above table.
2.5.1
Describe the trend in their boiling points.
Answer:
(2)
(1)
2.5.2
Fully explain the trend in QUESTION 2.5.1
Answer:
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The boiling points of some organic compounds are given in the table below. Y represents an
unknown boiling point.
2.6
For the compounds listed above, write down the:
2.6.1
Structural formula of compound F.
(3)
LETTER that represents a POSITIONAL isomer of compound E.
(1)
Answer:
2.6.2
Answer:
2.6.3
LETTER that represents a CHAIN isomer of compound E.
Answer:
2.7
(1)
The boiling points increase from compound A to compound D.
2.7.1
Give a reason for this increase in terms of the molecular structure.
(1)
Name the intermolecular force in these compounds responsible for
this increase.
(1)
Answer:
2.7.2
Answer:
A group of learners investigated the effect of intermolecular forces on the boiling points of
compounds. They tabulated their results below:
2.8
Which compound (A, B or C) will have the highest vapour pressure at a given temperature?
Answer:
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(2)
Refer to the data in the table to explain the answer.
For this investigation, write down the:
2.9
Independent variable
Answer:
(1)
2.10 Controlled variable
Answer:
(1)
2.11 Explain the trend in boiling point in the table above by referring to the MOLECULAR
STRUCTURE, INTERMOLECULAR FORCES and ENERGY involved.
(4)
The boiling points of five organic compounds (P, Q, R, S and T) are studied.
2.12 Write down the:
2.12.1
Name of the FUNCTIONAL GROUP of these compounds
Answer:
(1)
2.12.2
IUPAC name of compound C
Answer:
(1)
2.12.3
Structural formula of the FUNCTIONAL isomer of compound B
Answer:
(2)
2.13 Which ONE of the compounds, A or B or C, has the highest vapour pressure? Refer to the
data in the table to give a reason for the answer.
Answer:
(2)
Learners investigate factors which influence the boiling points of alcohols.
They use equal volumes of each of the alcohols and heat them separately in a water bath. The
temperature at which each boils is measured. The results obtained are shown in the table below.
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2.14 What property of alcohols requires them to be heated in a water bath?
Answer:
(1)
2.15 The boiling points of the alcohols are compared with each other.
2.15.1
What structural requirements must the alcohols meet to make it a fair
comparison?
(2)
Answer:
2.15.2
Fully explain the trend in the boiling points
Answer:
(3)
2.16 How will the boiling point of hexan-1-ol be affected if the volume of hexan-1-ol used is
doubled? Choose from INCREASES, DECREASES or REMAINS THE SAME
Answer:
(1)
The boiling points of five (5) organic compounds (A to E) are determined and the results are
shown in the table below.
2.17 Write down the homologous series to which compounds A to E belong.
(1)
Answer:
2.18 Compound B has a higher boiling point than compound A.
2.18.1
Name the intermolecular force responsible for this difference.
(1)
Fully explain this difference in boiling point.
(3)
Answer:
2.18.2
Answer:
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2.19 Compounds B and C are structural isomers. Name the type of structural
isomer of which they are an example.
(1)
Answer:
The table below shows the vapour pressure values of three alkanes.
2.20 Fully explain why the vapour pressure DECREASES from ethane to butane.
Answer:
(3)
2.21 Which of the alkanes will be the most difficult to ignite at room temperature?
Answer:
(1)
2.22 Predict whether ethanol will have a HIGHER or a LOWER vapour pressure than ethane.
Answer:
(1)
2.23 Fully explain the answer to QUESTION 1.22
Answer:
(2)
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Surface area – branching
COMPOUND
A
Pentane
(Mr=72)
BOILING POINT
( C)
36
The boiling points of compounds
A, B and C are compared.
Give a reason why this is a fair
comparison.
2-methylbutane
(Mr =72)
B
27,7
2,2-dimethylpropane
(Mr=72).
C
9,5
COMPOUND
Pentane
A
2-methylbutane
(A, B and C) have same molecular
mass/formulae/number of carbon
and hydrogen atoms/are (chain)
isomers.
The compounds are all alkanes /
belong to the same homologous
series/ have the same number of
carbon and hydrogen atoms.
The compounds are all alkanes /belong to same homologous
series/have the same functional group.
A, B & C have same
1. molecular mass/formulae
2. number of carbon and hydrogen atoms
Therefore, they are chain isomers.
COMPARE THE STRUCTURE OF COMPOUND B
WITH THE STRUCTURE OF COMPOUND A
B
❑ Compound B has a smaller surface area than Compound A or
❑ Compound B is branched and Compound A is a straight chain.
2,2-dimethylpropane.
COMPARE THE STRUCTURE OF COMPOUND B
WITH THE STRUCTURE OF COMPOUND C
C
❑ Compound B has a larger surface area than Compound C or
❑ Compound B is less branched than Compound C.
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Link the shape/structure of the molecule to the strength of the
intermolecular forces, and then the energy needed to overcome the
intermolecular forces.
COMPOUND
Compound with straight carbon chain have greater surface area over
which intermolecular forces can act.
Pentane
A
2-methylbutane
Compound
with larger
surface
area/Straigh
t Chain
Have strong
intermolecul
ar forces.
More
energy is
needed to
overcome
intermolecul
ar forces
Higher
Boiling
point/Meltin
g point.
Low Vapour
Pressure.
B
Compound with branched carbon chain have less surface area over
which intermolecular forces can act.
2,2-dimethylpropane.
Compound
with smaller
surface
area/ More
Branched.
C
•
•
•
•
Lower
Boiling
point/Meltin
g point
High
Vapour
Pressure
Branching increases from A to C
The intermolecular forces decrease from A to C.
Intermolecular forces decrease with an increase in branching.
The weaker the intermolecular forces, the less the amount of energy required to overcome the
intermolecular forces (London / dispersion/ induced dipole force).
COMPOUND
A
Have weak
intermolecul
ar forces.
Less
energy is
needed to
overcome
intermolecul
ar forces
Pentane
(Mr=72)
BOILING POINT (°C)
1. What is the Controlled Variable?
36
2-methylbutane
(Mr =72)
B
Link the three chain isomers to the boiling
points
27,7
Molecular Mass/ Number of carbon
and hydrogen atoms are the same.
2. What is the Independent variable?
From A to C,
More branched (Increasing
branching, decreasing surface area).
3. What is the dependent variable?
Boiling point
2,2-dimethylpropane
(Mr=72).
4. What is the investigative question?
C
9,5
How does increase in branching influence the
boiling point? or
What is the relationship between branching
and the boiling point?
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For compounds with the same functional group and same molecular mass, increase in
branching, results in a decrease in surface area, weaker intermolecular forces and thus a
decrease in boiling point.
COMPOUND
BOILING POINT (°C)
VAPOUR PRESSURE
(kPa at 20℃)
36
57,9
Pentane
A
Vapour Pressure increase
with an increase in
branching (of carbon chain).
OR
2-methylbutane
B
27,7
77
2,2-dimethylpropane.
C
9,5
147
Vapour Pressure increases
with a decrease in the
exposed surface area.
Vapour pressure increases
as the strength of
intermolecular forces
decreases
EXAMPLE 1
Explain the trend in the boiling points from compound A to compound C.
The boiling point increases from compound A to compound C
ISOMERS
A
2,2dimethylpropane
BOILING
POINT ( C)
9
B 2-methylbutane
28
C pentane
36
STRUCTURE
STRENGTH OF
INTERMOLECULAR
FORCES
ENERGY
• From A to C
• Less branched / larger
surface area over which
intermolecular forces act
• Strength of intermolecular
forces/ London forces
increases from A to C
• More energy is needed to
overcome the intermolecular
forces from A to C
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Activity 3
40 Marks: 40 Minutes
The boiling points of three isomers are given in the table below.
3.1
What type of isomers (POSITIONAL, CHAIN or FUNCTIONAL) are these three compounds?
Answer:
(1)
3.2
Explain the trend in the boiling points from compound A to compound C.
Answer:
(3)
3.3
Which ONE of the three compounds (A, B or C) has the highest vapour pressure? Refer to
the data in the table to give a reason for the answer
Answer:
(2)
The boiling points of some organic compounds are given in the table below.
Y represents an unknown boiling point.
Consider the boiling points given below.
3.4
From these boiling points, choose the boiling point represented by Y in the table above.
Answer:
(1)
3.5
Fully explain how you arrived at the answer to QUESTION 3.4
Answer:
(1)
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Learners use compounds A to C, shown in the table below, to investigate a factor which influences
the boiling point of organic compounds.
3.6
How will the vapour pressure of 2-methylpentane compare to that of compound C? Write
down only HIGHER THAN, LOWER THAN or EQUAL TO.
Answer:
(1)
Compounds A to E, shown in the table below, are used during two investigations to determine
factors which influence boiling point. The compounds are of similar molecular mass and therefore it
is considered as a controlled variable.
3.7
Compounds A, B and C are structural isomers. Write down the:
3.7.1
Name of the homologous series to which they belong
Answer:
(1)
3.7.2
Type of structural isomerism shown by these compounds
Answer:
3.8
(1)
Consider the boiling points of the compounds in investigation I.
3.8.1
Write down the independent variable for this investigation.
Answer:
(1)
3.8.2
Fully explain why boiling point increases from compound A to
compound C.
(3)
Which ONE of compounds B or C will have the higher vapour pressure at
a given temperature? Refer to the data in the table to give a reason for
the answer.
(2)
Answer:
3.8.3
Answer:
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The boiling points of five (5) organic compounds (A to E) are determined and the results are shown
in the table below.
3.9
Compound D has an unknown boiling point indicated as N.
3.9.1
Predict the boiling point of compound D. Choose from the boiling points listed
below.
(1)
Answer:
3.9.2
Fully explain how you arrived at the answer to QUESTION 3.9.1.
Answer:
(4)
During a practical investigation the boiling points of the three structural isomers (A, Band C) of an
alkane with five carbon atoms were determined. The results obtained were recorded in the table
below.
3.10 Write down the conclusion that can be drawn from the above results.
Answer:
(2)
3.11 Which alkane (A, B or C) is a liquid at 30 °C?
Answer:
(1)
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3.12 What type of structural isomers are compounds A, B and C? Choose from POSITIONAL,
CHAIN or FUNCTIONAL isomers. Give a reason for the answer.
Answer:
(2)
Compounds A, B and C are used to investigate a factor which influences the boiling points of
organic compounds. The results of the investigation are given in the table below.
3.13 Is this a fair investigation? Choose from YES or NO.
Answer:
(1)
3.14 Give a reason for the answer to QUESTION 3.13
Answer:
(1)
3.15 Fully explain the difference in the boiling points of compounds B and C.
Answer:
(3)
3.16 From compounds A, B and C, choose the letter(s) that represent(s) EACH of the following:
3.16.1 Positional isomers
Answer:
(1)
3.16.2 A tertiary alcohol. Give a reason for the answer.
Answer:
(2)
The boiling points of five organic compounds (P, Q, R, S and T) are studied.
The boiling points of compounds Q, R and S are compared.
3.17
Give a reason why this is a fair comparison.
Answer:
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The boiling points of Q, R and S are given below (NOT necessarily in the correct order).
3.18
Which ONE of the three boiling points is most likely the boiling point of compound
R? Explain the answer
(4)
Answer:
[26]
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ACTIVITY 1
15 MARKS; 15 MIN
The flow diagram below shows how prop-1-ene can be used to prepare other organic
compounds.
propane
A
compoundX
(major product
)
C
D
prop-1-ene
B
HBr
alcohol
(major product
)
E
1.1
1.2
F
Write down the type of reaction represented by:
1.1.1 A
Answer:
(1)
1.1.2 D
Answer:
(1)
1.1.3 F
Answer:
(1)
Write down the:
1.2.1 NAME or FORMULA of the catalyst needed for reaction A
Answer:
(1)
1.2.2 NAME or FORMULA of the inorganic reagent needed for reaction B
Answer:
(1)
1.2.3 Type of addition reaction represented by reaction C
Answer:
(1)
1.2.4 IUPAC name of compound X
Answer:
(2)
(5)
1.3 Use structural formulae to write down a balanced equation for reaction B.
Answer:
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1.4 Both reactions D and E take place in the presence of a strong base. State TWO
conditions that will favour reaction D over reaction E.
(2)
Answer:
[15]
ACTIVITY 2
9 Marks: 9 Min
Consider the reactions represented in the flow diagram below.
Br
CH3
C
CH3
CH 3
reaction 2
reaction 1
AlcoholA
concentrated
H2SO4
CompoundB
(An alkene)
reaction 3
C4H8 Br2
:
Write down the:
2.1.
Type of reaction represented by reaction 1
Answer:
(1)
2.2.
NAME or FORMULA of the inorganic reactant needed for reaction 1
Answer:
(1)
2.3.
Type of alcohol (PRIMARY, SECONDARY or TERTIARY) of which alcohol
A is an example
Answer:
(1)
2.4.
Type of reaction represented by reaction 2
Answer:
(1)
2.5.
IUPAC name of compound B
Answer:
(2)
2.6.
Type of addition reaction represented by reaction 3
Answer:
(1)
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2.7.
Balanced equation for reaction 3 using structural formulae
Answer:
(4)
[9]
ACTIVITY 3
13 Marks; 13 Minutes
The flow diagram below shows how an alkene can be used to prepare other organic compounds.
The letters A to G represent different organic reactions
3.1.
Write down the type of reaction represented by:
3.1.1 A
Answer:
(1)
3.1.2 B
Answer:
(1)
3.1.3 E
Answer:
(1)
3.2.
Write down the IUPAC name of compound X.
Answer:
(2)
3.3.
For reaction D, write down:
3.3.1 The type of elimination reaction
Answer:
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(1)
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3.3.2 TWO reaction conditions
Answer:
3.4
(2)
Write down the:
3.4.1 FORMULA of an inorganic reactant needed for reaction F
Answer:
3.4.2 Balanced equation, using structural formulae, for reaction G
Answer:
(1)
(4)
[13]
8
Write down the IUPAC names of the compounds below:
B
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