Chemistry-for-the-IB-MYP-4-5-pdf

ACTIVITY: Reflecting on the alkane series

ATL

• Communication skills: Organize and depict information logically; use a variety
of media to communicate with different audiences

1 Present models (e.g. with a molymod® kit) of three examples of alkanes from
Table 12.1. Describe the nature of the spatial arrangement of the hydrogen
atoms along the carbon chain.

2 Plot the relationship between the boiling points versus number of carbon atoms
(in one molecule) of the alkane, and predict the boiling point of octane C8H18.

3 Explain why the boiling point of the alkane increases with the length of the
carbon chain. (You may want to refer to Chapter 4.)

4 Deduce the formula of decane, an alkane containing ten carbon atoms, and
predict the physical state of a sample of decane at standard temperature and
pressure.

5 Suggest the source of the alkane composition of fossil fuels, based on the
information about alkanes found in modern living organisms.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

EXTENSION

Explore further: What is the occurrence of alkanes, such as methane and ethane,
in the solar system; planets, moons (satellites) and comets?

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ALKENES

The alkenes are another homologous series of hydrocarbons. Simple alkenes with
one carbon–carbon double bond have the general formula CnH2n, where n is the
number of carbon atoms in one molecule. Notice that all the names of alkenes end
with -ene. The alkenes in Table 12.2 are all gases at standard temperature and
pressure.

Reactions and uses of alkenes

In air, alkenes burn like alkanes. An example is the combustion of ethene:

However, alkenes are usually not burnt because they are more reactive than alkanes
and can be used to form a wide range of compounds for the chemical industry.

Addition reactions

An addition reaction is one in which a molecule combines with the alkene to form
one product. This is possible because of the reactive carbon–carbon double bond
in an alkene. Bromine reacts with ethene in an addition reaction. The bromine
molecule adds across the double bond of the ethene molecule:

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Many useful organic compounds are made from alkenes by addition reactions. For
example, the 1,2-dibromoethane (C2H4Br2) made from ethene was historically put
into leaded petrol as an anti-knocking agent, and to reduce the build-up of lead
residues by producing gaseous lead products.

Addition of hydrogen

Alkenes react with hydrogen gas to produce alkanes. This reaction is reduction and
also known as hydrogenation. A heated nickel catalyst must be used. An example is
the reaction of ethene with hydrogen to form ethane:

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EXTENSION

How is hydrogenation used in the production of margarine (Figure 12.7)?

ACTIVITY: Reflecting on the alkene series

ATL

• Critical-thinking skills: Practise observing carefully in order to recognize
problems; draw reasonable conclusions and generalizations; use models and
simulations to explore complex systems and issues

1 Present models (e.g. with a molymod® kit) of the three examples of alkenes in
Table 12.2.
a Describe the nature of the spatial arrangement of the hydrogen atoms located
near the double bond along the carbon chain.
b A structural isomer is a compound with the same atoms but in a different
spatial arrangement. Calculate how long a carbon chain needs to be before
structural isomers become possible.

2 Compare the trends in boiling points of the homologous series of alkanes with
the trends seen in the homologous series of alkenes.
a Identify the apparent effect of having a double bond within a molecule.
Suggest why this occurs.
b Predict the boiling point of pent-1-ene, C5H10 (or 1-pentene). The ‘1’
indicates the double bond is located between first and second carbon atoms
in the chain. If the double bond was found between the 2nd and 3rd carbons,
the molecule would be called pent-2-ene (or 2-pentene), and so on.
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3 Deduce the name, molecular formula, relative molecular mass and structural
formula of the next three members of the alkene homologous series.

4 Alkenes and organic compounds with carbon–carbon triple bonds, called
alkynes, are considered unsaturated.
a Suggest the meaning of ‘unsaturated’ in this context. Why is ‘unsaturated
margarine’ considered a healthy choice?
b Predict the names of the first six compounds in the alkyne homologous
series.
c Deduce the reactivity of alkynes compared with alkanes, given the following
information: alkynes are not necessarily more reactive than alkenes with the
same number of carbon atoms, but alkenes are more reactive than
unsaturated hydrocarbons (alkanes) with the same number of carbon atoms.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

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How do functional groups affect the
chemical properties of a molecule?

FUNCTIONAL GROUPS

Many organic compounds contain a group of atoms, or a single atom (which is not
hydrogen) known as a ‘functional group’, a chemical structure that is responsible
for many of its chemical and physical properties. Members of a homologous series
(containing the same functional group) have similar chemical properties.
With familiarity, you will begin to recognize how the reactivity of functional groups
can be used to create new organic molecules.

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ALCOHOLS

The hydroxyl functional group, –OH, results in a homologous series with the
general formula CnH2n+1OH. The first molecules in this series are methanol and
ethanol. Notice that the hydroxyl group attaches directly to a carbon atom in the
alkane chain (Table 12.3). Alkanes with a hydroxyl group attached have the ‘e’
ending of their name replaced with -ol.
The effect of the hydroxyl group is to give the end of the molecule polarity, which
allows the molecule to dissolve in water and react with sodium (in a reaction
similar to that of water).

Uses of alcohols

Alcohols are important solvents and chemicals in industry. They are used to make a
range of different organic compounds.

Making alcohols using an addition reaction of water to
an alkene

Alkenes can react by addition with water to produce alcohols. A molecule of water
is added across the carbon–carbon double bond of the alkene. This occurs when a
mixture of the alkene and steam is passed over a catalyst, hot concentrated
phosphoric(V) acid, (H3PO4):

ACTIVITY: Investigating the solubility of alcohols

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ATL

• Organization skills: Understand and use sensory learning preferences (learning
styles)

Alcohols are often diluted to fulfil different functions – for example, as alcoholic
drinks or in antifreeze in the cooling systems of engines. In this activity you will
investigate how the form of an alcohol molecule affects its solubility.

Safety: Wear eye protection and goggles. Methanol is toxic; avoid contact with
skin and inhaling fumes.

Materials and equipment

• gloves and safety glasses
• disposable pipettes
• 150 cm3 beakers
• a range of alcohols, for example: methanol, ethanol, propan-1-ol, butan-1-ol,

pentan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol.

Method

1 Design a table in which you list the alcohols you are testing, their formula,
relative molecular mass, and a column to record your observations.

2 Put on safety glasses and gloves.
3 Fill the small beakers with tap water.
4 Add a few drops of each alcohol to each beaker, to test for solubility.

Analysing results

1 Identify the alcohols that were miscible and immiscible in water.
2 Suggest how the length of the alkyl chain contributes to solubility.
3 Suggest a modification to the method that would help you detect droplets of

immiscible alcohols on the surface of the water.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion C:
Processing and evaluating.

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ACTIVITY: Reflecting on alcohols
ATL

• Transfer skills: Apply skills and knowledge in unfamiliar situations; inquire
into different contexts to gain a different perspective

1 Suggest why, when making ethanol using an addition reaction, a high
temperature (300 °C) and a high pressure (70 atmospheres) are used during
hydration (see Chapter 11).

2 Antifreeze, used in the radiators of cars in cold climates (Figure 12.8), contains
ethylene glycol (1,2-ethane-diol), a kind of alcohol. Suggest why this
compound is preferred to methanol (CH3OH).

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Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

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CARBOXYLIC ACIDS

The attachment of a carboxylic acid (carboxyl) functional group, –COOH, to an
alkane results in another homologous series. The carboxylic acid homologous
series has the general formula CnH2n+1COOH. A terminal (end) carbon is bonded
to both a hydroxyl group and an oxygen atom (Table 12.4). Alkanes with a carboxyl
group attached have the ‘e’ ending of their name changed to -oic acid.
The effect of the carboxyl group is to give the end of the molecule polarity, and
turns it into a typical weak acid (see Chapter 5) when dissolved in water.
However, alkanes are non-polar and this means carboxylic acids with more than
five carbon atoms (e.g. pentanoic acid) become increasingly immiscible in water as
the non-polar hydrocarbon chain increases in length.

The first carboxylic acid in the series is methanoic acid, HCOOH. Many ants
produce this compound (Figure 12.9), which explains why the common name for
methanoic acid is ‘formic acid’, from the Latin word formica, meaning ant. It is
also often used as a preservative and antibacterial agent on animal food, for tanning
leather and dyeing textiles, and in the making of rubber.

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You are likely to be familiar with the second carboxylic acid in the series, ethanoic
acid, CH3COOH. It is found in vinegar. Ethanoic acid is formed when ethanol is
oxidized, for example by acetic acid bacteria (Acetobacter). The equation for the
reaction is:

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ACTIVITY: Reflecting on carboxylic acids
ATL

• Critical-thinking skills: Interpret data; revise understanding of new information
and evidence; identify trends and forecast possibilities

1 List the first six compounds in the carboxylic acid homologous series.
2 Formulate equations to show the reactions between ethanoic acid (CH3COOH)

and magnesium, calcium oxide, sodium carbonate and sodium hydroxide.
3 During the 19th century, ‘vinegar plants’ were added to fermenting fruit in water

or fruit juice to produce vinegar in the home. These organisms needed to be
kept in the dark, and required oxygen. Identify the type of organism that a
‘vinegar plant’ actually was.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

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A NOMENCLATURE FOR THE
INCREDIBLE DIVERSITY OF ORGANIC
COMPOUNDS

Your introduction to organic compounds has only begun to touch on their incredible
variety. Each functional group can be represented by a general formula (Table
12.5). Each hydrogen atom along the parent chain can also be replaced with an
alkyl group, or an alkane missing a hydrogen in the molecule, forming a branched
chain, represented with an R symbol in the table. Common alkyl groups are the
methyl (–CH3), ethyl (–CH2CH3) and propyl (–CH2CH2CH3) groups. If an
organic compound has more than one alkyl group, these may be represented as R1,
R2 and so on.
For example, a haloalkane (or halogenoalkane) may be shown as RX where R is
the alkyl group and X represents the halogen, an atom in group 17 of the periodic
table such as bromine, chlorine or iodine.

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Links to: Language acquisition

The IUPAC system for naming organic compounds is another ‘language’: once
mastered, you have a tool for communicating with chemists everywhere.

Rules for naming functional groups

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Refer to Table 12.5.
1 A hydroxyl, –OH, group can replace any hydrogen on a parent alkane. Its

position can be indicated in the name by numbering the longest alkane chain and
counting from the end which gives the lowest position for the hydroxyl group.
For example, a propanol with a single hydroxyl group could be either propan-1-
ol or propan-2-ol, but not propan-3-ol.
2 Notice the prefix ‘di’ indicating that two halogens have been substituted. The
numbers indicate precisely the carbon atoms in the longest unbranched chain to
which the halogens have been attached. When more than one halogen is
involved, they need to be listed in alphabetical order.
3 The oxygen atom is attached to one of the carbon atoms, and therefore the total
number of atoms determining the length of the chain is (number of carbon atoms
in R1 + 1C + number of carbon atoms in R2). The functional group (>C=O) is
assigned the carbon with the lower number.
4 Name the alkyl group from the alcohol followed by the carboxylic acid group
(the group with the double bonded oxygen). The ‘ic’ of the acid is replaced by
the suffix ‘ate’.
5 Select the longer alkyl group (-ethyl), which provides the parent name, in this
case ethane. The shorter chain gets an -oxy suffix (not a prefix), in this case
methoxy.
6 Amines are complicated to name because each hydrogen atom can also be
substituted with an R group. Note that –NH2 is a functional group of amino
acids, used to synthesize proteins.

IUPAC rules for naming branched-chain alkanes

Use this example to understand the process of naming these structures.

1 Find the longest continuous chain (the parent structure). In this example, the
chain is eight carbons long, so it is an octane.

2 Number the carbons in sequence, starting at the end which will give the
substituent groups the smallest numbers. In the example, this required
numbering is from right to left, so the groups are attached to carbon atoms 3, 4
and 5 (total 12). In the alternative direction, these numbers would have been 4,

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5 and 6 (total 15).
3 Add the numbers to the names of the substituent groups. In this example: 3-

methyl, 4-methyl and 5-ethyl.
4 Use prefixes to indicate any groups that appear more than once, using commas

to separate the numbers. In this example, 3,4-dimethyl will be part of the name.
5 List the names of the alkyl groups in alphabetical order. Note that the prefixes

di, tri, penta and so on are ignored. Hyphens are used to separate numbers and
words. In this example, 5-ethyl-3,4-dimethyl will be part of the name.
6 Apply the correct punctuation. The name of the alkane is written as one word.
Therefore, the IUPAC name for this example is: 5-ethyl-3,4-dimethyloctane.

ACTIVITY: Applying IUPAC nomenclature to
organic compounds

ATL

• Critical-thinking skills: Practise observing carefully in order to recognize
problems; interpret data; test generalizations and conclusions

Work together or individually to respond to these questions.
1 State the name of a carboxylic acid that has an alkyl group, R, consisting of

five carbon atoms.
2 Present structural formulas of the following compounds:

a 3-ethyl-3-methylhexane
b 2,4-dimethylhexane
c 2,2,3,3-tetramethylpentane
d 2,6,10,14-tetramethylpentadecane (also known as ‘pristane’).
3 The IUPAC name for the compound in Figure 12.10 is 1,1, 1-trichloro-2,2-
bis(4-chlorophenyl)ethane.

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Suggest, from the IUPAC formula:
a the name of the ‘parent alkane’
b the carbon atom number to which the chlorine atoms are attached
c how the carbon atoms are counted in the ‘benzene’ structure.
4 Determine the IUPAC names of branched-chain structures with less than 10
carbon atoms in the parent alkane that have been suggested (sketched) by your
peers. Remember that you can count around corners; the chain does not have to
be straight!

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

ACTIVITY: Making esters

ATL

• Transfer skills: Apply skills and knowledge in unfamiliar situations; combine
knowledge, understanding and skills to create products of solutions

Esters are often used as food flavouring or perfumes. They are formed when
carboxylic acids react (reversibly) with alcohols, a reaction that also forms water.
For example, ethanoic acid reacts with ethanol in the presence of concentrated
sulfuric acid to form ethyl ethanoate and water. The sulfuric acid acts as a catalyst
and dehydrating agent.

The first part of the name comes from the alcohol (ROH), and the second part
(ending in -oate) is modified from the carboxylic acid (RCO2H).

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Safety: Wear eye protection and goggles. Methanol is toxic so avoid contact
with skin and inhaling fumes. Butanoic acid has a potent, disagreeable smell. It
should be used only in a fume cupboard.

Materials and equipment

• safety goggles and gloves
• a range of alcohols and organic acids, each with a dedicated pipette
• 2.0 M sulfuric acid
• 2 × 500 cm3 beaker
• 1.0 M sodium hydrogencarbonate solution
• test tubes
• kettle (if warm tap water is not available)

Method

Any combination of a carboxylic acid and an alcohol should result in the
formation of an ester with this method.
1 Put on safety goggles and gloves.
2 Fill the 500 cm3 beaker with the sodium hydrogencarbonate solution.
3 Fill the other beaker with warm water, to act as a water bath.
4 Add a few drops of a carboxylic acid to a clean, dry test tube.
5 Add a similar amount of alcohol.
6 Your teacher will add a drop or two of concentrated sulfuric acid.
7 Warm the mixture gently in the beaker of warm water for 5–10 minutes.
8 Pour the mixture in the test tube into a beaker with the sodium

hydrogencarbonate solution. The sodium hydrogencarbonate neutralizes the
acid catalyst and any unreacted carboxylic acid.
9 You should get some drops of ester left on the surface which can be carefully
smelled to appreciate the aroma of the ester.
10 Use different combinations of acids and alcohols to make five different esters.
You may wish to try some of the examples listed in Table 12.6, or make your
own combinations.

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Analysing results

1 Formulate IUPAC names for the esters and list them in the final column in
Table 12.6.

2 Formulate balanced equilibrium equations for the esters you synthesized.
3 Suggest why several of the esters you have made don’t usually smell exactly

the same as a delicious, ripe example of the fruit in which they may be found.
4 Explain why esters are immiscible in water, although alcohols and carboxylic

acids (with short length alkyl chains) tend to be water soluble.
5 Analyse the formula of an ester found in beeswax, to identify the formulas of

the carboxylic acid and the alcohol reactants used to form it:
CH3(CH2)14COO(CH2)29CH3.

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Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

EXTENSION

Go further: Discover common applications of ethanol (C2H5OH), propanone
(CH3COCH3) and ethyl ethanoate (CH3COOC2H5) used in the activity, above.

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THE SAME BUT NOT THE SAME:
ISOMERS

By physically modelling alkanes and alkenes you may have realized the same
carbon atoms could be bonded in very different ways. Compounds which have the
same molecular formula but different structural formulas are called isomers.
Isomerism is common in organic chemistry, because there are so many ways of
bonding carbon atoms to other atoms.

Structural isomers

The molecular formula of the two molecules in Figure 12.11 is C4H10, but their
structural formulas are different. These two molecules are examples of structural
isomers. They will tend to have similar chemical properties. The larger the
molecule, the more isomers are possible.

Equivalence: non-isomers

Single bonds may be able to rotate, but double and triple bonds cannot, resulting in
the formation of stereoisomers. As atoms rotate to different positions, the same
molecule may appear to be different. One way to recognize ‘chemical equivalence’
is to look for symmetry. If the two atoms you are comparing have symmetry
between themselves on the molecule, they are probably chemically equivalent.
Another way is to apply the IUPAC naming system.

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Geometric isomers

Double and triple bonds in unsaturated hydrocarbons cause rigidity, and this can
result in differences in spatial arrangements, called geometric isomerism. Trans
forms of a geometric isomers occur where chemical groups lie across the double
bond; cis forms where chemical groups lie on the same side of the double bond
(Figure 12.12).

Enantiomers

Enantiomers are non-superimposable mirror images (Figure 12.13). This also
applies to molecular structures where single bonds connect four different chemical
groups to a central, asymmetric carbon atom (Figure 12.14). These groups may be a
hydrogen atom, halogens or alkyl groups.

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Nearly all the chemical properties such as boiling point, density, refractive index
and viscosity of carbon enantiomers are identical, but they do differ in one
important way: they rotate plane polarized light in opposite directions. Polarized
light has been ‘filtered’ so that its electromagnetic vibrations are limited to a single
plane or direction. You may be familiar with this effect if you have ever reduced
the glare of bright sunlight by using polarizing sunglasses. The dextro, d or + form
of an enantiomer rotates polarized light clockwise, ‘to the right’ and the laevo, l or
– form rotates it anticlockwise, ‘to the left’. For this reason, enantiomers are also
referred to as optical isomers.

A deep time puzzle

Did the evolution of life involve ‘isomer competition’?
• Nearly all naturally occurring carbohydrates are of the d-form!
• All naturally occurring amino acids are of the l-form!
• The fatty acids found in the cell membranes of two major groups of microbes,

bacteria and Archaea, are optical isomers.
To date, no one really knows the reason for this observation! However, it is
speculated that at some early stage of chemical evolution, maybe even before
cellular life existed, molecular competition resulted in one type of stereoisomer
becoming prevalent.

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ACTIVITY: Reflecting on isomers
ATL

• Critical-thinking skills: Practise observing carefully in order to recognize
problems; interpret data; revise understanding based on new information and
evidence

1 Identify the number of different molecules shown below.

2 Present models (e.g. with a molymod® kit) of all the isomers (straight and
branched) for pentane, hexane and heptane.

3 Determine the mathematical relationship between the number of carbon atoms
and the number of isomers in these situations:
a single bonded structural isomers
b the effect of one double or triple bond in an unsaturated carbon chain 3, 5 or
7 carbons long.

4 Suggest how you could manufacture an ingredient to make sure that its
stereoisomer property is compatible with human consumption.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

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Links to: Mathematics

Mathematics provides a tool with which to abstract numerical information to
investigate patterns.

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Could other elements form the
building blocks of life?

ACTIVITY: Is life based on inorganic chemistry
possible?

ATL

• Creative-thinking skills: Consider multiple alternatives, including those which
may be unlikely or impossible; make unexpected or unusual connections
between objects and/or ideas; create original works and ideas; use existing
works and ideas in new ways; generate metaphors or analogies

All the elements in IUPAC group 14 share to some extent carbon’s chemical
bonding properties based on four valence electrons. Imagine a world not based on
carbon. This idea has often been used in science fiction. Could you match the
creativity of some of these efforts?
Your 700–1200 word story should include:
• a scientific explanation of the consequences of using a different element to form

a system of molecules (e.g. chains, branches, rings and functional groups)
• a moral, ethical, social, economic, political, cultural or environmental factor, as

found in all fine literature – including yours! For example, would recycling be
possible with your alternative group 14 element or would, as a result of their
chemistry, a logical response by your fictional characters provide moral or
social insight into our own world?
There are several possible presentations for this assignment, including as a
cartoon strip.
All sources should be fully documented. This could be presented separately.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion D:
Reflecting on the impacts of science.

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EXTENSION

Research non-carbon based life to find out about real life based on inorganic
molecules and speculation by a famous scientist about this.

Links to: Language and Literature

A role of fiction is to provide insight into other possible worlds, and to discuss
moral dilemmas objectively. Science fiction uses scientifically plausible contexts
to explore the consequences of innovations and futuristic technologies.

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To what extent can we live without
organic materials (apart from food)?

CRUDE OIL IS A FOSSIL FUEL

Crude oil or petroleum (from the Latin petra, meaning rock, and oleum, meaning
oil) is a dark, viscous (sticky) liquid found in the ground, especially under the sea,
consisting of many different hydrocarbons. Although less than 10 per cent of crude
oil is used in the chemical industry it is the most important raw material for the
organic chemical industry.
About half of the world’s crude oil is found in the Middle East. Crude oil and
natural gas (methane) are often found together, held in between layers of non-
porous rock in the ground. They are extracted by drilling a pipe through the rock
(Figure 12.15).

Separation and conversion of crude oil (petroleum)

Petroleum is a complex mixture of hydrocarbons, and every oil field has a different
composition. However, the main components of petroleums are alkanes, and after
the removal of impurities like sand and water, the refining process of any crude oil
involves the same stages: fractional distillation, cracking and reforming.

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Stage 1: Fractional distillation

Crude oil is heated and passed into a tall fractionating column (Figure 12.16)
where it undergoes fractional distillation (see Chapter 2). The hydrocarbon
molecules with the lowest boiling points pass to the top of the column, and those
with the highest boiling points remain at the bottom. Intermediate fractions of
increasing boiling points are also collected. The average relative molecular mass
of the fractions increases with boiling point.

This results in about six fractions (apart from natural gas) which are purified and
blended for use as petrol, diesel, kerosene (paraffin), solvents and oils (Table
12.7). The lighter fractions are used in the industrial production of organic
chemicals. When used in this way, they are called chemical feedstocks.

Laboratory distillation

Crude oil can be distilled using the apparatus shown in Figure 12.17. This process
must be demonstrated by your teacher, in a fume cupboard. Alternatively, you can
watch a brief video about the process and products here:
www.youtube.com/watch?v=26AN1LfbUPc.

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A more sophisticated arrangement for fractional distillation can be viewed here:
www.youtube.com/watch?v=0x2-
8dedmE4&list=PLXl9I2_9q0tbbEQrVx9wmj3pAgLnGW1xd&index=7.

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Stage 2: Cracking

There is less demand for the more viscous fractions, made up of molecules with
higher relative molecular masses and higher boiling points. The thicker liquids are
therefore often ‘cracked’ (Figure 12.18). This means that the larger molecules are
broken down (decomposed) into smaller ones suitable for making petrol, or for use
in the chemical industry. This can be done in two ways: using a high temperature, or
using a lower temperature and a solid catalyst.

Laboratory cracking

For safety reasons, the cracking of crude oil may be demonstrated by your teacher
in the laboratory using medicinal paraffin and the apparatus shown in Figure 12.19.
Alternatively, you can watch a brief video of the process here:
www.youtube.com/watch?v=AajLtkJxPk0.
A mixture of light hydrocarbon gases including ethene (C2H4) can be collected
over water. The gaseous mixture is flammable and decolorizes bromine and
potassium manganate(VII). A brief video of a test for the presence of an alkene can
be found here: www.youtube.com/watch?v=AajLtkJxPk0.

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ACTIVITY: Reflecting on impacts of shale oil
extraction or fracking

ATL

• Transfer skills: Apply skills and knowledge in unfamiliar situations; inquire in
different contexts to gain a new perspective

Oil shales are abundant and promise to replace petroleum as fossil fuel resources.
Mined rocks from surface deposits can be burnt directly, or may be processed
(‘retorted’) to make liquid fuels and lubricants. Oil and natural gas from deep
deposits can be released by using pressurized water, a process called ‘fracking’.
Watch the video to understand how it works: www.youtube.com/watch?
v=lB3FOJjpy7s
Use the Internet to investigate recent news stories about shale oil fracking or
mining.
• Reflect on how many of these stories are about economic, political,

environmental and social impacts.
• Evaluate the pros and cons of these new methods of oil extraction, and whether

we should exploit this resource.
• Present your findings as a written debate, leading to a conclusion based on the

aspects you consider more persuasive. Be sure to acknowledge your sources.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion D:
Reflecting on the impacts of science.

Stage 3: Reforming

Reforming is the third stage of the petroleum refining process. In the presence of
hydrogen and a heated catalyst, hydrocarbons with small chains of carbon atoms
are converted to more stable hydrocarbons with benzene rings (Figure 12.20).
Benzene is an aromatic compound. Like many aromatic compounds, it has a
characteristic smell. Although their smell may be sweet and even attractive, many
aromatics, including benzene, are very poisonous.

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The molecules of an aromatic compound contain one or more fused benzene rings.
For example, naphthalene, which is present in moth balls (Figure 12.21), is
composed of two benzene rings joined together.

Aromatic compounds contain a high proportion of carbon and for this reason they
often burn with luminous yellow flames producing black, sooty smoke. The benzene
ring is a stable structure and some medicinal drugs contain a benzene ring, for
example, aspirin and paracetamol (Figure 12.22).

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ORGANIC MATERIALS IN USE

Carbon compounds may occur naturally or are made by humans from fossil fuels. In
this section, you will consider the impact of some of these substances.

Soaps and detergents

Soap and soapless detergent molecules are examples of emulsifiers (see Chapter
2). Their molecules have ‘tadpole’ structures, with different chemical properties.
The long hydrocarbon chain ‘tail’ is hydrophobic (non-polar) and attracted to oils.
The carboxylic acid group in the ‘head’ is hydrophilic and attracted to water
(Figure 12.23).

As the hydrophobic ends of the soap or detergent molecules mix with particles of
grease, the hydrophilic heads remain in the water (Figure 12.24), which helps the
grease form a suspension that can be rinsed away.
Soapless detergents are made from concentrated sulfuric acid and hydrocarbons
obtained from petroleum refining. These synthetic detergents are more effective for
dissolving oils, because they are more soluble than soap. They also do not react
with the calcium ions found in ‘hard’ water, and therefore do not form a scum, bath
rings being an example.

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Soaps are made from renewable hydrocarbons, animal fats and vegetable oils
(Figure 12.25). The fats are reacted with concentrated sodium hydroxide and then
precipitated using a sodium chloride (NaCl) solution. The fats and oils contain
esters and the process of making soap is called saponification. For example,

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POLYMERS

Polymers are giant organic molecules made up of many smaller subunits called
monomers, which may be chemically identical or have identical functional groups.
‘Poly’ means ‘many’ and a single polymer may contain many tens of thousands of
monomers and consist of more than a hundred thousand atoms.
Naturally occurring polymers include nucleic acids, proteins, starch, cellulose,
latex and the silk of spider webs (Figure 12.26).

Synthetic polymers include a range of plastics, nylon and fibres. Most are products
of the oil or petrochemical industry.
Polymers form as a result of two types of reactions.

Condensation polymerization

During condensation polymerization, each time two monomers react, a small
molecule (usually water) is lost (eliminated). Nylon and Terylene are examples of
plastics formed by condensation polymerization. Figures 12.27 and 12.28 show the
reactions in a simplified form. In these schematic diagrams, the boxes represent
carbon chains (–CH2–CH2–CH2–CH2– units). The monomers used to make nylon
(Figure 12.27) form amide linkages. Nylon is therefore called a polyamide. The
monomers used to make Terylene (Figure 12.28) form ester linkages. Terylene is
therefore a polyester. In both reactions, each time two monomers bond, a molecule
of water is also formed.

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Watch the formation of nylon here: www.youtube.com/watch?v=y479OXBzCBQ.

Polymer Monomer
Protein Amino acid

Cellulose, starch Glucose

Nucleic acid (DNA, RNA) Nucleotide

Table 12.8 Natural condensation polymers, and their monomers

Condensation polymerization is also common in living tissues, where synthesis and
breakdown of polymers is catalysed by enzymes (Table 12.8).

In proteins, the monomers consist of 20 different types of amino acid and the amide
linkages are called peptide linkages. When a proteins is broken down into its
component amino acids (for example, during digestion), the process is known as
hydrolysis. Hydrolysis (Figure 12.29) is the reverse of condensation
polymerization. The amino acids can be separated and identified using paper
chromatography (see Chapter 2).

Addition polymerization

Alkenes can also ‘add on’ to one another, over and over again. This process, in
which many small unsaturated molecules add on to one another to form a large

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molecule, is known as addition polymerization.

For example, when an ethene molecule breaks a bond, it can be added to itself,
molecule by molecule, to form a poly(ethene) molecule or polythene. Each time the
bond of the ethene molecule breaks, a new carbon–carbon bond is formed between
the molecules. The arrows in the following equation show how (in a simplified
way) this happens.
The different properties of polymers or plastics can be created by using different
monomers. Any alkene or substituted hydrocarbon with a carbon–carbon double
bond is able to act as a monomer for addition polymerization. As a result, plastics
can be tailored for nearly every purpose. They are durable, lightweight and
relatively inexpensive to produce. Examples include packaging materials and
synthetic fibres (Figure 12.30).

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ACTIVITY: Reflecting on polymers
ATL

• Critical-thinking skills: Interpret data; draw reasonable conclusions and
generalizations

1 Identify the structural formula, name and unit formula of each of the polymers
in the table below.

2 Polytetrafluoroethene (PTFE or Teflon) is an addition polymer discovered in
1938 and prepared from tetrafluoroethene, C2F4. One of its first commercial
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uses was for storing uranium hexafluoride, UF6, used to make atomic bombs.
After the war it was used to make non-stick surfaces for frying pans.
a Present the structural formula and shape of tetrafluoroethene.
b Formulate a chemical equation to describe its polymerization.
c Calculate the percentage composition by mass of PTFE from its empirical

formula (repeating unit).
d State further contexts where Teflon could be useful

i as a storage container
ii to reduce friction.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowing and understanding.

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ACTIVITY: Does organic chemistry mean we should
synthesize any substance or molecules we want?
ATL

• Reflection skills: Demonstrate flexibility in the selection and use of learning
strategies; consider ethical, cultural and environmental implications

At the conclusion of this course, how can your chemical knowledge inform your
opinions? Your 700–1200 word assignment should:
• explain how a particular organic compound was created in order to address a

specific problem or issue
• discuss and evaluate how the use of the compound interacts with one of the

following factors: moral, ethical, social, economic, political, cultural or
environmental and then use your understanding to express and justify your own
opinion or verdict about its use.
There are several possible presentations for this final assignment.
All sources should be fully documented. This could be presented separately,
depending on your choice of communication format.

Assessment opportunities

• This activity can be assessed using Criterion D: Reflecting on the impacts of
science.

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A SEA OF PLASTIC

The first plastic was prepared in 1907. Today over a 100 million tonnes are used
every year, representing about 8 per cent of global fossil fuel use. For all their
convenience and versatility, synthetic polymers (plastics) pose a major problem:
they persist in the environment, filling landfill and drifting in the oceans. It is now
estimated that by 2050, all marine sea life will have ingested some plastic (Figure
12.31).

Every type of plastic can be recycled. However, the different types (Table 12.9) do
need to be sorted.

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Take action: Plastic – reduce and recycle

ATL

• Reflection skills: Consider ethical, cultural and environmental implications

• Your aim is to identify the plastic involved in 10 examples of locally collected
plastic waste.

Safety: Wear eye protection and gloves. Propanone is an irritant.

Materials and equipment

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• safety goggles and gloves
• propan-2-ol
• vegetable oil (e.g. peanut oil)
• propanone (acetone)
• small beakers
• scissors (to cut samples of each plastic)
• tweezers
• wooden peg
• copper wire
• Bunsen burner, lighter
• small beakers

Method

1 Put on safety goggles and gloves.
2 Cut a small sample of the plastic you intend to test.
3 Refer to the information in the dichotomous choice table overleaf. Each test

will divide the samples into two classes. Only continue testing a sample if you
have not yet been able to classify it.
4 Repeat for the remaining samples.
5 Dispose of your used plastic materials in the bin.

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Analysing results

1 State the type of plastic that was the most common.
2 Identify any plastics you were unable to classify.
3 Suggest why it was important to dislodge any adhering bubbles in the density

tests.
4 Estimate, based on your observations during this activity, the approximate

density of the propan-2-ol solution.
• Question 5 refers to the following information:

The effect that heat has on plastics is a crucial difference. Thermoplastics (or
thermosoftening plastics) change shape when they are heated and can be re-
melted and re-shaped. These polymers may be forced into moulds under pressure
(injection moulding) or can be forced through small holes (extrusion).
Thermosets cannot be re-melted and have to be moulded in manufacture.
5 Identify which type of plastic

a would be easier to recycle
b is likely to have more covalently bonded cross-links between the polymer

strands. These are stronger but generally have a similar effect to the borate
cross-links that stiffened slime (see Chapter 4).
• At least a third of plastics are used for packaging. What alternatives could be
used to reduce the volume of plastic to be recycled?

• Imagine you are a scientist commissioned by a local authority to review plastic
use and recycling in the locality. With reference to your scientific research in

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this activity, write a report for the local authority outlining how plastic waste
could be reduced, and how plastic recycling could be made more efficient.
• Summarize the societal, economic and environmental impact of your proposals.
• Make sure to document all your sources appropriately.

Assessment opportunities

• In this activity you have practised skills that are assessed using Criterion A:
Knowledge and understanding and Criterion D: Reflecting on the impacts of
science.

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