Download Hydrocarbons and Fuels - Deans Community High School

Unit 2 Nature’s Chemistry
Organic Chemistry
In this unit traditional organic chemistry is
studied in the context of a wide range of
everyday consumer goods.
The chemistry of the important functional
groups within these substances is emphasised,
as are the characteristic chemical reactions.
Unit 2 Nature’s Chemistry
Organic Chemistry
Prior Knowledge
From previous work you should know and understand the following:
1.
2.
3.
4.
5.
That molecular structure and physical properties of
hydrocarbons are related.
The names, molecular and structural formula of alkanes (C1-C8),
alkenes (C2-C8) and cycloalkanes (C3-C8) straight and
branched.
How to identify isomers and draw their structural formulae.
What is meant by saturated and unsaturated carbon compounds
and how they can be distinguished.
Addition reactions involving unsaturated hydrocarbons
Unit 2 Nature’s Chemistry
Organic Chemistry
Prior Knowledge
From previous work you should know and understand the following:
6. Alcohols functional group –OH and properties of alcohols
7. The names, molecular and structural formula of alcohols (C1C8), straight and branched.
8. Carboxylic acids functional group COOH and properties of
carboxylic acids
9. The names, molecular and structural formula of carboxylic acids
(C1-C8), straight and branched.
Organic Chemistry
Originally, chemical compounds were divided into 2 classes:
Inorganic or Organic
Organic compounds were derived from living things. It
was believed that they contained a ‘vital force’ and could
not be made from inorganic compounds (non-living sources).
Organic chemistry is the study of carbon compounds
Organic Chemistry
Organic chemistry is basically the study of compounds
containing carbon (with the exclusion of oxides and
carbonates).
There are so many compounds containing carbon that a
whole branch of chemistry is devoted to their study.
Organic molecules may be
as simple as methane, CH4
or as complicated as
cholesterol
HO
Revision from National 5
•
•
•
•
•
Alkanes
Alkenes
Alcohols
Carboxylic Acids
Esters
Homologous series
A homologous series are a family of organic compounds with
the same general formula. They have a common
functional group.
Examples of homologous groups include:
Homologous
series
General formula Functional
group
Alkanes
CnH2n + 2
Alkenes
CnH2n
C=C
Alkynes
CnH2n - 2
C=C
Alkanols
CnH2n + 1 OH
R – OH
Alkanoic acids
CnH2n + 1 COOH
R – COOH
Alkanals
CnH2n + 1 CHO
R – CHO
Alkanes and Alkenes
Alkane general formula
C n H 2n+2
Alkene general formula
C n H 2n
Structural formula
H H H
H
C
C
C
H
H H H
Straight Chain
Name
H
H C H
H
H
H C C C
H
H
Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
No C’s
1
2
3
4
5
6
7
8
Branched chains and
unsaturated C=C bond
CH3CH2CH3
CH3 (CH2)2CH3
CH3CH2CH2CH3
Condensed formula
Molecular formula C4H9
Naming Compounds of Carbon
Alkanes
1.
2.
3.
4.
5.
Identify the longest chain
Identify the ‘branches’ and name them.
Number the carbon atoms on the longest chain, at the end giving
the lowest numbers for the branches.
Write the branches in alphabetical order.
If there are more branches with the same name use di, tri etc
Alkenes
1.
2.
3.
4.
5.
Identify the longest chain, that contains a double bond.
Identify the ‘branches’ and name them.
Number the carbon atoms on the longest chain, starting from
the end nearest the double bond. Pick the lowest number to
describe the position of the double bond.
Write the branches in alphabetical order.
If there are more branches with the same name use di, tri etc
Naming Organic Compounds, Alkanes
H
H
H
H
H
H
H
CH3
C
C
C
C
C
C
C
H
CH2
H
H
H
CH2
H
1 CH3
H
CH2
10 CH3
1. Decide on the type of compound
(ie. consider functional group)
2. Select the longest chain.
3. Name the compound
with the branched chains
in alphabetical order.
alkane
10 C’s  decane
7-ethyl-3-methyldecane
H
H
C2H5 H
C
C
C
2
3
C = C
H
CH3
H
H
1. Decide on the type of compound
(ie. consider functional group)
1
CH3
H
alkene
2. Select the longest chain
7 C’s  heptene
3. Number the C atoms so that
the functional group has the
lowest number
hept-2-ene
4. Name the compound
with the branched chains
in ascending order.
5,5-dimethylhept-2-ene
H
H
CH3
H
H
H
C
C
C
C
C
H
CH3
Cl
H
H
1. Decide on the type of compound
(ie. consider functional group)
2. Select the longest chain
H
halogen (chloroalkane)
5 C’s  pentane
3. Name the compound
3-chloro-2,2-dimethylpentane
with the branched chains
and halogen in alphabetical order.
Structural Isomers
There are two types
1. Chain isomerism.
Here the isomers have different arrangements of carbon
atoms or different chains. For example there are two
compounds with the molecular formula C4H10
H
H
H
H
H
C
C
C
C
H
H
H
H
butane
H
H
H
H
H
C
C
C
H
CH3 H
H
2-methylpropane
Here, you can see that 2-methylpropane has a side chain.
2. Position Isomerism. E.g Alkene isomers
Here the isomers have the same carbon skeleton and
functional group but the position of the functional group
is different.
H H
H
H H H
H
C
C
C
H
H
Cl
H
1-chloropropane
H
H
H
H
C
C
C
H
H
OH
propan-1-ol
H
H
C
C
C
H
Cl
H
H
2-chloropropane
H
H
H
H
C
C
C
H
OH
H
propan-2-ol
H
CH3 CH
CH2
CH3
propene
CH3 CH
CH3
CH
CH3
CH
C
CH3
CH CH3
2,4-dimethy pent-2-ene
But-2-ene
CH3
CH2 CH
C
CH3
CH2 CH3
a) 3,3-dimethyl-1-pentene
Naming Alkanols & Isomers
• Just like the alkenes, the alkanols have isomers that are
dependent on the position of the functional group, in this case
the hydroxyl group (-OH).
Example;
and
Draw and name the structure below!
Now complete exercise 2.3
Move onto textbook – list some uses of alkanols.
Uses of Alcohols
• Drinks – the alcohol in beers and spirits is
ethanol.
• As a fuel – ethanol can be mixed with petrol
(Gasohol)
• Methylated spirits – industrial alcohol
• As a solvent – in perfumes and cosmetics
Carboxylic (Alkanoic) Acids
Carboxylic acids, sometimes known as
alkanoic acids, are a homologous group of
organic acids which contain the carboxyl
functional group:
• The third member is;
propanoic acid
• What do you think the name of the first and second
members are?
Uses of Carboxylic Acids
• Vinegar is a solution of ethanoic acid.
• Ethanoic acid can also be used as a preservative in the food
industry.
• Carboxylic acids are used in household cleaning products
including soap
• In manufacture of important organic compounds), acetic
anhydride (used in aspirins), cellulose acetate (used in
synthetic fibres), various dyes, perfumes & medicines.
• As a solvent it dissolves phosphorus, sulphur & iodine.
• Carboxylic acids can be used to make chemicals called
esters.
Making an Ester
Esters are made by reacting a carboxylic acid with an
alcohol. This is known as esterification and is a
CONDENSATION
reaction.
The name of the ester
comes from the alcohol and
carboxylic acid!
Ethanoic Acid + Ethanol
H
O
H H
H-C - C
HO-C-C-H
OH
H H
H
Ethyl ethanoate
CH3COOC2H5
+
Water
H2O
Key area:
Esters, Fats and Oils
Esters
Overview
In this section, learn about the
characteristic chemistry and
uses of esters, and find out how
they are made by condensation
reactions and broken down by
hydrolysis.
a) Esters
Learning intention
Learn how esters are named and
identified and how to draw the
structural formula of an ester.
Esters
Esterification, Alkanoic acids reacting with Alkanols.
Alcohol + Carboxylic Acid  Ester + Water
H+
Esters have sweet smells and are more volatile than
carboxylic acids.
They are responsible for sweet fruit smells.
280 aromas make up a strawberry smell!!
•3-methylbutyl ethanoate in bananas.
•2-aminobenzoate is found in grapes.
Uses of Esters
• We imitate these smells by
manufacturing flavourings.
• Esters are also used in perfumes.
• Esters can also be used as solvents in
glues.
• Polyesters are used to make
plasticisers.
• Methyl ester is a biodiesel.
b) Making and naming
Esters
Learning intention
Learn about how esters are
formed
by
condensation
reactions of carboxylic acids
and alcohols.
Making Esters
One way of preparing esters is to condense an alcohol
with a carboxylic acid:
O
O
C
R
O
alcohol
H +
H
R'
O
carboxylic acid
C
R
O
R' + H2 O
ester
The reaction is slow at room temperature and the yield of
ester is low. The rate can be increased by heating the
reaction mixture and by using concentrated sulphuric acid
as a catalyst. The presence of the concentrated sulphuric
acid also increases the yield of ester.
Making an Ester
Esters are made by reacting a carboxylic acid with an alcohol.
This is known as esterification and is a CONDENSATION
reaction.
The name of the ester comes from the alcohol and
carboxylic acid!
Ethanoic Acid + Ethanol
H
O
H H
H-C - C
HO-C-C-H
H
H H
Ethyl ethanoate
CH3COOC2H5
+
Water
H2O
Naming Esters
R-yl
R-OH + R’-COOH  R’-COOR + Water
First, the 1st word comes from
the alcohol. The name ends in –yl.
Second
First
O
C2H5
C
O C2H5
CH3 CH2 COO CH2 CH3
ethyl propanoate
R’-oate
Second, find the C=O in the
carboxylate group, this gives the
2nd word with the ending –oate.
This comes from the acid.
Activity 1.1 Making Ester
Experiment
• The aim of this experiment is to
prepare an ester and to identify some
of the characteristic properties of
esters.
• Look at the next two slides
Ester formation
Condensation Reaction
O
R C
O
+
O
R
H
O
R
O
C
+
R
O
H
H
Ester link
H
O
R
R
C
O
CH3COOH + CH3OH
ethanoic acid
methanol
CH3COOCH3 + H20
methyl ethanoate
The reaction is brought about by heating a mixture of a carboxylic acid
and an alcohol with a little concentrated sulphuric acid. (which acts as a
catalyst and absorbs the water produced).
Animation esterification
Making esters
Collect a
workcard
Procedure
Decide which alcohol and carboxylic acid you need to make each
ester in the table.
1. Before collecting the alcohol and carboxylic acid set up a water
bath using the larger beaker and heat the water until it boils. Turn
off the Bunsen.
2. Add the alcohol to a test tube to a depth of about 1 cm. To this
add about the same volume of carboxylic acid. If the acid is a solid
then use a spatulaful.
3.In the interests of safety your teacher/lecturer may carry out
the next step.
Add about 5 drops of concentrated sulphuric acid to the reaction
mixture.
Making esters
4. Soak the paper towel in cold water, fold it up and wrap it round the
neck of the test tube. Secure it with a rubber band. This
arrangement acts as a condenser when the reaction mixture is being
heated.
5. Place a loose plug of cotton wool in the mouth of the test tube.
This will contain any chemicals which may spurt out of the reaction
mixture when it is heated.
6.Place the test tube in the hot water bath
Making esters
7. While the reaction mixture is being heated add about 20 cm3
of sodium hydrogencarbonate solution to the small beaker.
8. After about 10 minutes, take the test tube from the water
bath and remove the plug of cotton wool. Slowly pour the
reaction mixture into the sodium hydrogencarbonate solution.
This neutralises the sulphuric acid and any remaining
carboxylic acid and so removes the smell of the carboxylic
acid.
9. Gently swirl the contents of the beaker and look to see if
there is any sign of the ester separating from the aqueous
mixture.
10. To smell the ester with your nose at least 30 cm from the
mouth of the beaker gently waft the vapour towards your nose
and take just a sniff.
1.3 Uses of Esters
Learning intention
Learn about the many everyday
uses of esters.
Uses of esters
Esters are oily liquids with generally very pleasant fruity smells and
have a range of uses.
Many esters are used as flavourings and in perfumes.
Natural fruit flavours contain subtle blends of some of the esters in
the table below:
Esters are also used as non-polar industrial solvents.
Name
3-methylbut-1-yl ethanoate
Methyl Butanoate
3-Methylbutyl Butanoate
Ethyl heptanoate
2-Methylpropyl methanoate
Benzyl ethanoate
Ethyl methanoate
Methyl 2-aminobenzoate
Benzyl butanoate
Shortened Structural Formula Odour/Flavour
CH3COOCH2CH2CH(CH3)CH3 Banana
C2H5COOC4H9
Pear drops
Pineapple
C3H7COOCH2CH(CH3)C2H5
Apple
CH3COOC3H7
Pear
Grape, cherry
Raspberry
C3H7COOC5H11
Apricot, Strawberry
CH3COOCH2C6H5
Peach, flowers
C6H4(NH2)COOCH3
C3H7COOCH2C6H5
Grapes
Cherry
Uses of esters
Factors affecting perfume design e.g. using esters:
Designing a perfume - several issues to address by way
of design factors.
The perfume needs to be a mixture of compounds to
give a prolonged perfumery effect.
The perfumer chemist has to design the mixture to give
a particular fragrance which includes ...
the top note - the first fragrant molecule to be
released,
and the low note, the last molecule to be vapourised.
Uses of esters
Esters are also used as non-polar industrial solvents.
Some of the smaller esters are quite volatile and
are used as solvents in adhesives, inks and paints –
pentyl ethanoate is used in nail varnish for example.
Uses of esters
Ethyl ethanoate is one of a number of solvents used
to extract caffeine from coffee and tea.
De-caffeinated products produced with ethyl
ethanoate are often described on the packaging as
"naturally decaffeinated" because ethyl ethanoate
is a chemical found naturally in many fruits.
Uses of esters
Caffeine (C8H10N4O2) is an example of a class of compounds
called alkaloids which are produced by plants.
The name alkaloid means “alkali-like”, where alkali is a base
and hence refers to these basic properties.
Carryout the experiment to extract caffeine from tea.
Uses of esters
Caffeine is more soluble in the
organic solvent ethyl ethanoate
than in water, so we will
extract caffeine into the
organic solvent to separate it
from glucose, tannins, and
other water soluble compounds
using a separating funnel.
.
The ethyl ethanoate portions
can be combined and the ethyl
ethanoate
removed
by
evaporation to leave the
caffeine
http://www.periodicvideos.com/videos/mv_caffeine.htm
1.4 VOCs
http://greencleaning.about.com/od/GreenCleaningResources
/g/Volatile-Organic-Compounds-Vocs-What-They-Re-AllAbout.htm
1.5 Hydrolysis of Esters
Learning intention
Learn how esters can be broken
down by hydrolysis into the
parent carboxylic acid and
alcohol. The process is the
reverse of condensation –
making esters. Process is called
HYDROLYSIS
Hydrolysing Esters
Condensation
Alcohol + Carboxylic Acid  Ester + Water
Hydrolysis
Alcohol + Carboxylic Acid  Ester + Water
The ester is split up by the chemical action of water, hydrolysis.
The hydrolysis and formation of an ester is a reversible reaction.
O
R C
O
R
+
H
Bonds broken
Ester + Water
+
O
O
H
R C
O
O
R
H
H
Bonds formed
Carboxylic Acid + Alcohol
http://www.ltscotland.org.uk/highersciences/chemistr
y/consumerchemistry/fruitflavours/makingesters.asp
Examine some old perfume bottles
What do you notice?
Use all your senses
Percentage Yield
• You could be asked to calculate the mass produced if an
experiment is working at x% efficiency or calculate the
percentage yield.
• Always follow the basic principles for all calculations
• Start with a balanced chemical equation
• Write down what you are told in the question
• and what you are trying to work out.
For percentage yield you need to know 2 things
The actual yield in the experiment and the
theoretical yield (from mole calculation).
percentage yield = actual yield x 100
theoretical yield
actual yield - usually given in question
theoretical yield - Can be calculated from the
equation
Percentage yields
CH3COOH + CH3CH2CH2OH <=> CH3COOCH2CH2CH3 + H2O
4.3 g of propyl ethanoate was produced when 6 g
of ethanoic acid was reacted with propan-1-ol.
What is the percentage yield of the ester?
Percentage yield = actual yield/theoretical yield x 100%
• Example
• C6H6 + HNO3 -> C6H5NO2 + H2O
• 18.72g of benzene, C6H6, enters a
reaction chamber with excess nitric
acid. After a time, 22.14g of
nitrobenzene C6H5NO2 is obtained.
• Calculate the percentage yield.
18.72g
78g
Worked Answer
xg
123g
theoretical X g = 18.72 x 123
78
= 29.52g
% yield = actual x 100 = 22.14
theoretical
29.52
= 75%
• 2009
• 8. Ammonia is produced in industry by the
Haber Process.
• N2(g) + 3H2(g)
-->
2NH3(g)
• (c) Under certain conditions, 500 kg of
nitrogen reacts with excess hydrogen to
produce 405 kg of ammonia.
• Calculate the percentage yield of ammonia
under these conditions.
• Show your working clearly.
Worked Answer
Fats and oils
Overview
In this section, study the
chemistry and structure of
edible fats and oils, and learn
how the difference in melting
points of fats and oils can be
explained in terms of structural
differences.
1.7 Edible fats and oils
Learning intention
Learn about the characteristic
properties of fats and oils and
study how they are formed by a
condensation
reaction
of
glycerol with fatty acids.
Fats in our Diet
We eat fats to provide us with energy.
Fats provide more energy per gram than carbohydrates.
Fat molecules are insoluble in water, and tend to group together and form
a large droplet. This is how fat is stored in the adipose tissue.
We store our extra energy as fat.
Questions ;
Are Fats/Oils polar or non-polar?
What van der waal forces exist between fat molecules?
The type of fat or oils we eat is important. Animal fats contain important fat
soluble vitamins. Oils, are thought to be healthier than solid fats, as
they are less likely to be deposited inside our arteries.
However, there is an ongoing debate about which fats are better for us.
Polyunsaturated fats are considered to be less potentially harmful to the
heart.
Origins of Fats and oils
Naturally occuring
Animal fat
Vegetable oil
Marine oil
lard
suet
sunflower oil
coconut oil
cod liver oil
whale oil
Fats and Oils
50% of your
brain is fat.
Fats and oils are a range of substances all based on glycerol,
propane-1,2,3-triol.
Glycerol reacts with fatty acids to form a fat or oil molececule with
___ ester groups
Natural fats and oils are a mixture of triglyceride compounds.
H
H
C
O
H
H
C
O
H
H
C
O
H
H
Glycerol
propane-1,2,3-triol
An alcohol with three –OH groups
Glycerol + 3 fatty acids = Fat/oil
Each OH group in the glycerol can combine chemically with one carboxylic fatty acid
molecule. The resulting molecules are fats and oils.
Question: What is the name of this reaction?
They are described as triglycerides. (tri esters)
The hydrocarbon chain in each can be from 4 to 24 C’s long.
The C’s can be single bonded (saturated) or double bonded
(unsaturated).
Fats and oils
Fats and oils are ESTERS of glycerol and
long chain carboxylic acids
Fats and oils
Fats and oils are built from an alcohol with three -O-H groups.
glycerol
Systematic name is propane-1,2,3-triol
Fatty Acids – Saturated and
Unsaturated
C17H35COOH
H3C
CH2
CH2
C17H33COOH
H3C
CH2
CH2
CH2
Stearic Acid (suet, animal fat) Saturated
CH3(CH2)16COOH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3(CH2)7CH=CH(CH2)7COOH
CH2
CH2
CH2
CH2
CH
Humans fatty acids
Oleic acid
47%
Palmitic acid
24%
Linoleic acid
10%
Stearic acid
8%
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
O
C
OH
Oleic Acid (olive oil) Unsaturated
CH2
CH2
O
C
OH
Octadec-9-enoic acid
Fats and oils
The other components of fat molecules are carboxylic acids
such as
Stearic acid
Systematic name is octadecanoic acid
In fats – the acid always has an even number of carbon atoms.
Fats and oils
Removal of water in the condensation reaction gives -
The molecular formula shown above suggests that the fat
molecule is shaped like an E, but the molecule is actually
shaped more like this:
b) The melting point of
fats and oils
Learning intention
Learn
how
differences
in
structure of fats and oils lead
to differences in strength of
intermolecular
forces,
and
therefore to differences in
melting points.
.
Fats and oils
Fats are mainly built from carboxylic fatty acids with
C-C single bonds. They are said to be saturated
and are linear (straight) in shape.
Stearic acid in beef fat
Oils have some C=C bonds in the carboxylic fatty acids
from which they are made. They are said to be more
Unsaturated and are not linear (straight in shape)
Oleic acid in olive oil
Fats and oils
Oil
Double bonds in oil make the molecule, slightly bent,
not linear, so they are less compact.
This means they are Less tightly packed molecules
And their LDF are weaker, making oils liquid.
Fat
Fat molecules pack together more tightly due to their
linear shape. So LDP forces are stronger,
This makes fats solid at room temperature.
Fat
Oil
Fat molecules pack together
tightly, so stronger LDF,
making fats solid at room
temperature.
Double bonds in oil make
the molecule less compact.
Less tightly packed molecules make
oils liquid because the London Forces
between molecules are weaker.
Unsaturation in fats and oils
1. Using a plastic pipette, add five drops of olive oil to 5 cm3 of
hexane in a conical flask.
2. Use a burette filled with a dilute solution of bromine water
(0.02 moll–1) (Harmful and irritant). Read the burette.
Scholar
animation
available
Unsaturation in fats and oils
3. Run the bromine water slowly into the oil solution.
Shake vigorously after each addition. The yellow
colour of bromine disappears as bromine reacts with
the oil. Continue adding bromine water to produce a
permanent yellow colour.
4. Read the burette. Subtract to find the volume of
bromine water needed in the titration.
5. Repeat the experiment with: five drops of
cooking oil (vegetable) and five drops of cooking oil
(animal).
Fats and Oils
The degree of saturation in a fat or oil can be determined by the
Iodine Number. (bromine can also be used).
The iodine reacts with the C=C bonds, so the greater the iodine
number, the greater the number of double bonds.
Fat
Av Iodine
No
Butter
40
Beef Fat
45
Lard
50
Olive Oil
80
Peanut Oil
100
Soya Bean
Oil
180
Solid fats – butter, beef fat & lard have low
iodine numbers because they are more
saturated than the unsaturated oils.
Margarine is made from vegetable oils, butter
from animal fats. One reason why margarine
spreads better!
Omega 3 fatty acids make up a large % of
your brain’s fat.
In practice both fats and oils are mixtures of esters
containing both saturated and unsaturated compounds.
Beef Fat
Olive oil
In general oils have a higher proportion of unsaturated
molecules.
Catalytic Hydrogenation of Oils
(Hardening)
The addition of hydrogen, using a nickel catalyst to
an unsaturated oil will ‘harden’ the oil.
The hydrogen is added across the double bond.
It makes it more linear so will increase it’s m.p. So
the oil becomes a solid!
Question: Give another name for this porcess?
This process is used to make margarine, otherwise
margarine would be a liquid when taken out of the
fridge.
Yellow margarine song
http://www.youtube.com/watch?v=7rzJNy_WZG4
Summary of the Chemistry of Fats and Oils
http://www.educationscotland.gov.uk/highersci
ences/chemistry/animations/oilsfats.asp
Structures of Fats and Oils
Hydrolysis of a fat or oil produces a molecule of glycerol (alcohol) for
every 3 carboxylic acid molecules. The carboxylic acids are usually called
long chain fatty acids. Most fats and oils are, in fact, esters of
propane-1,2,3-triol, sometimes called, triesters.
H
O
H
C
O
C
O
R1
H
C
O
C
O
R2
C
R
H
C
O
3
H
Glycerol
part
Fatty acid part
Triesters.
R 1,R 2,R 3 are long carbon chains,
which can be the same or different
Hydrolysis
Glycerol + Fatty Acids
Key area: Proteins
Overview
In this section, study the
structure and function of
proteins. Learn about how they
are formed from amino acids in
condensation reactions, and how
they are broken down by
hydrolysis.
a) Function of proteins
Learning intention
Learn about the function of
proteins in living things.
Proteins
b) Making Protiens Amino Acids
Learning intention
Learn about the characteristic
chemistry of amino acids, the
building blocks of proteins.
• Introduction to proteins
An animation of three proteins which demonstrate
common structural elements despite their very
different functions.
Amino acids
All proteins contain the elements C,O,H, N. They are condensation polymers,
made by amino acids linking together.
Amino acids contain an Amine group -NH2 and an acid group -COOH
Amino Acids
H R
O
H N C
C
R
O H
NH2CHCOOH
Most proteins contain
20+ different amino
acids
H
When R is Hydrogen, the amino acid is glycine (Gly) (aminoethanoic acid)
When R is CH3, the amino acid is alanine (Ala) (2-aminopropanoic acid)
Amino acids
c) Amide links
Learning intention
Learn how proteins are formed
by condensation reactions of
amino acids to produce amide
(peptide) links.
Protein Polymers and
Essential Amino Acids
Proteins are condensation polymers, made by amino acids
linking together. An amine group of one molecule links to
the carboxyl group of another molecule to form an amide
link or peptide bond.
Our body makes proteins by joining together amino acids
in the right order to make the correct proteins.
However, The body cannot make every type of amino acids that it needs.
So our diet must contain essential amino acids. (about 10 of them).
We synthesise the others.
Protein Polymers
CH3
H
H
O
N–C-C
OH
H
H
+
CH3
H
O
N–C-C
OH
H
H
+
glycine
alanine
H
N–C-C
H
O
OH
H
alanine
Tripeptide, ala-gly-ala
CH3 O
H H O
H CH3
H
O
N–C– C - N–C–C- N–C-C
OH
H
H
H
H
Polypeptide chain can have
10000
amino acids
amide (peptide) link
+ 2H2O
Protein Structures
Some proteins are composed of a single polypeptide chain, but many consist
of two or more polypeptide chains.
Proteins are classified according to their shape into fibrous and globular
proteins.
Fibrous proteins
These have their polypeptide chains interwoven. The polypeptide chains are
held together by hydrogen bonding, between the N-H and the C=O groups.
This gives these proteins their properties of toughness, insolubility, and
resistance to change in pH and temperature. So they are found in skin,tissue,
(collagens), hair, nails (keratins).
Globular proteins
Proteins which operate within cells need to be soluble. The polypeptide chains
are coiled together in spherical shapes. E.g. Haemoglobin and many hormones.
e.g. Insulin, was the first protein structure to be worked out.
Enzymes are globular proteins.
Protein Structures
Silk is a typical example of a fibrous protein.
Silk
This view shows the
protein chains contain 2
different amino acids.
This view shows
the individual
atoms in the
protein chains.
Protein Structures
Albumin, in egg white, is a globular protein..
Albumin
backbone view
atom view
Protein Structures
Enzymes are globular proteins. The structure of amylase is
shown below.
Starch molecule in the enzyme’s active site.
Enzyme Activity
Enzymes catalyse chemical reactions in the body. Each
enzyme has a unique shape held together by many weak
bonds. Changes to pH and temperature can denature the
enzyme. This changes the enzyme’s shape and stops it
working properly.
Narrow optimum range
Enzyme
activity
Temp or pH
The bonds that hold most biological enzymes
are broken around 60oC.
Enzyme Activity, Lock and Key
The critical part of an enzyme molecule is called its active
site.
This is where binding of the substrate to enzyme occurs and
where catalysis takes place.
Most enzymes have one active site per molecule.
Substrate
Enzyme
Scholar
animation
available
Enzyme Activity, Lock and Key
Substrate
Enzyme
Active site
Enzyme Activity, Lock and Key
The substrate becomes activated
Enzyme
Enzyme Activity, Lock and Key
The substrate becomes activated
Enzyme
Enzyme Activity, Lock and Key
The complex molecule splits
Enzyme
Enzyme Activity, Lock and Key
The complex molecule splits
Enzyme
Practical Task
• Factors Affecting Enzyme Activity
• Collect a work card
• Does temperature and pH effect
enzymes?
d) Hydrolysis of protein
Learning intention
Learn how proteins are broken
down to amino acids by the
process of hydrolysis.
http://www.educationscotland.gov.uk/higherscience
s/chemistry/animations/chemicalequations.asp
This animation illustrates the process of protein
formation by the condensation of the carboxylic acid
and amine groups of amino acids. It also looks at the
reverse process of protein hydrolysis
Protein hydrolysis
Proteins are broken down during digestion.
Digestion involves the hydrolysis of proteins to form amino acids
Protein
+ 2H2O
Amino
acids
Chromatography
Chromatography can be used to separate a mixture of
different inks. Some example questions…
R
G
B
X
1) Ink X contains two
different colours. What
are they?
1
2
3
2) Which ink is ink Z
made out of?
Z
Identifying amino acids by
chromatography
In the lab a protein can be
hydrolysed
back
to
its
constituent
amino
acids
by
refluxing
with
concentrated
hydrochloric acid for several
hours.
Amino acids can be identified by
the use of paper (or thin layer)
chromatography.
A piece of chromatography paper
is spotted with some amino acids
suspected as being present and
also with the hydrolysed protein.
Identifying amino acids by chromatography
By comparing the position of
the spots of the known
amino acids with that of the
hydrolysed
protein,
the
amino acids in the protein
can be identified.
•Add your results to the
diagram
•The hydrolysed fruit juice
contained?
Scholar
animation
available
Key area:
Chemistry of cooking
Overview
In this section, learn how
functional groups in volatile
molecules
influence
food
flavour, and find out how
cooking affects the structure
of protein in food.
a) Flavour in food
Learning intention
Learn how the chemistry of
certain functional groups in
volatile molecules in foods
influence flavour.
The chemistry of flavour
The chemistry of flavour
Molecules responsible for flavour in vegetables are normally trapped
inside the cell walls. During cooking the cell walls are damaged for two
reasons:
• Chemical damage occurs as the cell walls, which are made of
cellulose, break down.
• Physical damage occurs as water inside the cells boils forming steam
and the cell walls break open.
The chemistry of flavour
A major issue in cooking is to retain molecules responsible
for flavour in the food – overcooking can result in loss of
these molecules. One destination for lost flavour
molecules is in the cooking water. This will occur if the
flavour molecules are water-soluble. If this is the case,
many of the flavour molecules will be lost down the drain
when the cooking water is poured away.
The chemistry of flavour
• What is flavour? Illustrates the idea that flavour
is taste plus aroma, and shows tasting experiments
in which a blindfolded taster holds his nose and
becomes unable to identify flavour.
• Chocolat coulant Heston Blumenthal describes how
to make a pudding containing chocolate and cheese
and explains why this unlikely-sounding
combination tastes good.
• Fire and spice: the molecular basis for flavour
Explains the stereochemical theory of odour which
suggests that a molecule that fits into an
olfactory receptor can fire nerve cells, ultimately
producing a particular odour perception
b) Flavour in foodChanges upon heating
Learning intention
Learn how heating proteincontaining foodstuffs leads to a
change in food texture as
intermolecular
forces
are
broken.
Changes in protein structure
on heating
• Within proteins, the long chain molecules may be
twisted to form spirals, folded into sheets, or
wound around to form other complex shapes. The
chains are held in these forms by intermolecular
bonding between the side chains of the
constituent amino acids. When proteins are
heated, during cooking, these intermolecular bonds
are broken allowing the proteins to change shape
(denature).These changes alter the texture of
foods.
• Cooking meat Experiments in which different cuts
of meat are cooked under different conditions to
determine the optimum cooking temperature.
Key area:
Oxidation of foods
Overview
In this section, learn how
oxidation reactions in foods
convert alcohols to aldehydes
and ketones, and study the role
of
antioxidants
in
the
preservation of foods.
.
a) Oxidation of alcohols
Learning intention
In this section, learn about the
products
of
oxidation
of
primary, secondary and tertiary
alcohols.
Find
out
about
important mild oxidising agents
and learn how to spot an
oxidation reaction in a carbon
compound.
Classification of alcohols
H
H
H
C
C
H
OH
CH3
H
H
C
CH3
H
O
H3C C
CH3
H
H
H
H
C
C
C
H
OH
H
propan-2-ol
H
CH3
Secondary alcohol,
One Hydrogen joined
to the C bonded to
the OH group
Primary alcohol,
Two Hydrogens joined
to the C bonded to
the OH group
O
Tertiary alcohol,
No Hydrogens joined
to the C bonded to
the OH group
CH3
H
H3C
C
CH3
OH
2-methylpropan-2-ol
Oxidation of Alcohols
Primary alcohols can be oxidised by a number of oxidising agents, in two
stages, 1st Stage - Hydrogen is lost; 2nd Stage - oxygen is gained.
When applied to carbon compounds, oxidation results in an increase in
the oxygen to hydrogen ratio.
1st
H
R
C
O
oxidation
H
+
O
R
O
R
C
H
+
H2O
aldehyde
O H
2nd
C
H
aldehyde
+
O
oxidation
O
R
C
O
H
Carboxylic acid
Secondary alcohols can be oxidised to form ketones,
Tertiary alcohols do not undergo oxidation.
O
R
C
ketone
R1
b) Aldehydes and
Ketones
Learning intention
Learn about the characteristic
functional groups and chemical
reactions of aldehydes and
ketones. Study how aldehydes
and ketones are named and
drawn.
Aldehydes and Ketones Uses
H
+ C=O
Methanal, a 40% solution in water is formalin,
and is used to make polymers (including Kevlar)
C=O
Ethanal, Its trimer (CH3CHO)3 is used as a
sleep inducing drug. It also causes a hangover
C=O
Butanone, is a solvent used to make VHS tapes.
H
CH3
H
CH3CH2
CH3
CH3
CH3
Butan-2-one
C=O
C4H8O
Propanone, nail varnish remover and
is used in the making of perspex
Aldehydes and Ketones
Distinguishing tests
(Using mild oxidising agents.)
Aldehydes are oxidised to carboxylic acids
Ketones do not react with mild oxidising agents
1. Fehlings solution contains Cu2+ ions (blue) which form Cu+ ions
(orange-red) in the presence of aldehydes.
2. Tollens’ reagent contains Ag+ ions, which form Ag in the presence
of aldehydes (silver mirror test)
3. Acidified Potassium dichromate orange Cr2O72-(aq) to green Cr3(aq)
Oxidation
Collect a
workcard
Procedure
1. Before collecting the carbonyl compounds X and Y set up a water bath and heat
the water until it boils. Turn off the Bunsen.
2. Add sulphuric acid to each of two test tubes to a depth of about 2 cm. Then add
potassium dichromate solution to both to give a total depth of about 3 cm in each.
3. To one of these test tubes add about 5 drops of compound X and to the other
add about 5 drops of compound Y.
4.Place both test tubes in the water bath and observe and record any changes.
5.Add Benedict's solution to each of two test tubes to a depth of about 3 cm.
6. Repeat steps 3 and 4.
7. Add Tollens' reagent to each of two very clean test tubes to a depth of about 3
cm.
8. Repeat steps 3 and 4 and immediately after, wash the contents of the test
tubes down the drain with large amounts of water.
Oxidation of Aldehydes and Ketones –
What’s Happening?
INTRODUCTION
Both aldehydes and ketones contain the carbonyl group.
C
O
In aldehydes a hydrogen atom is bonded to the carbonyl group but in
ketones the carbonyl group is always flanked by carbon atoms:
O
C H
aldehyde
O
C
C C
ketone
This structural difference accounts for the fact that aldehydes can
undergo mild oxidation to form carboxylic acids but ketones resist
oxidation. Oxidising agents can therefore be used to distinguish between
aldehydes and ketones.
The aim of this experiment is to use the mild oxidising agents, acidified
potassium dichromate solution, Benedict's solution and Tollens' reagent, to
distinguish between two given carbonyl compounds one of which is an
aldehyde and the other a ketone.
Oxygen to Hydrogen Ratio
• These are different definitions from those met
previously and only apply in carbon chemistry.
• oxidation
•
eg C2H5OH → CH3CHO
•
O:H
1:6
1:4
•
• Oxidation of ethanol to ethanal has increased the
O:H ratio. Ethanal can also be reduced back to
ethanol and this would be a decrease of the ratio.
• Try examples in your notes
Oxidation of food
• Oxidation reactions can occur when food is
exposed to oxygen in the air.
• Foods containing fats or oils are at the greatest
risk of oxidation.
• Antioxidants can help prevent oxidation
Foods rich in fats and oils
Oxidation of Fats
Fats and oils, or foods containing them, are the most likely to have
problems with oxidation.
The oxidation of unsaturated oils and fats primarily takes place via a
free-radical process where the C=C bond is attached by the free
radical
Fats react with oxygen and even if a food has a very low fat content
it may still need the addition of an antioxidant to stop the free
radical process.
Fat
Fat
Oxygen
http://www.understandingfoodadditives.org
Effects of oxidation on food
When fats react with oxygen they are broken
down, causing:
–
deterioration of flavour (rancidity) due to
production of aldehydes, ketones and
carboxylic acids
– loss of colour
– loss of nutritional value
– a health risk from toxic oxidation products.
Antioxidants Added to Food
Antioxidants are commonly used in:
•vegetable oil
•snacks (extruded)
•animal fat
•meat, fish, poultry
•margarine
•dairy products
•mayonnaise / salad dressing
•baked products
•potato products (instant mashed potato)
As the fat decomposes and reacts with oxygen, chemicals
called peroxides are produced. These change into the
substances characteristic of the smell and soapy flavour of a
rancid fat.
Antioxidants prevent the formation of peroxides and so slow
the process of the food 'going off'. Some antioxidants react
with oxygen itself and so prevent the formation of peroxides.
Air-tight packaging, using inert gases like nitrogen, vacuum
packing and refrigeration can all be used to delay the oxidation
process. However, these can still be inefficient and adding
antioxidants can be an effective way of extending the shelf
life of a product.
http://www.understandingfoodadditives.org
Fat breaking down
Fat
Oxygen
Fat molecules
CH3
CH2
CH2
CH2
CH2
CH2
CH2
C
O
O
H
Fat
O
C
H
O
C
H
C
H
H
C
CH2
CH2
CH2
O
O
CH2
C
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH
CH
CH3
R
CH2CH2CH2CH CH CH3
Radicals attack near the double bond
(NB ‘R’ represents the remainder of
the fat molecule)
c) Antioxidants
Learning intention
Learn about the chemistry of
the antioxidant molecules which
prevent oxidation reactions in
foods from taking place.
Lesson Starter
1. There are many flavour and aroma compounds found
in chocolate. Two examples are shown below.
a. Which family of organic molecules does 1,3diphenylpropan-2-one belong to?
b. Describe a test that could be used to distinguish
between these two compounds.
c. Draw the product made when phenylethanal
undergoes oxidation.
d. What is meant by oxidation?
Antioxidants
• Antioxidants are chemicals that are added to
food to prevent the food from ‘going off’.
• An antioxidant is a substance that slows down or
prevents the oxidation of another chemical.
• Anti oxidants can provide electrons to stop the
loss of electrons (oxidation) from continuing!
They are free radical scavengers (and reducing
agents)
Antioxidants
Learning Intentions
 State what is
meant by an
antioxidant.
 Describe how
antioxidants work.
 Give examples of
common
antioxidants.
Antioxidants
Antioxidants are molecules which
prevent oxidation. This is important in
the preservation of food as it spoils
when it is oxidised.
Vitamin C
• Vitamin C is a powerful antioxidant. It
is present in many fruits and
vegetables.
• Vitamin C is also known as ascorbic
acid.
Vitamin E
• Vitamin E is a powerful antioxidant.
• There are many sources of vitamin E...
How do antioxidants work?
• Antioxidants are compounds which will
easily oxidise – they lose electrons. This
means they oxidise in the place of the
substance you are trying to protect (in this
case the food). They give electrons to Free
Radicals
Vitamin C
Oxidised
Other uses for antioxidants
• As well as their properties to prevent food
spoilage antioxidants are believed to be
beneficial to our health, in particular
preventing ageing and a diet rich in
antioxidants is thought to prevent forms
of cancer.
Antioxidants in action
Oxidation
occurs when
the apple is
left exposed
to air
The apple is
protected
when dipped in
orange juice
containing the
antioxidant
vitamin C
Antioxidants
Oxidation reactions happen when chemicals in
the food are exposed to oxygen in the air.
In natural conditions, animal and plant tissues
contain their own antioxidants but in foods,
these natural systems break down and
oxidation is bound to follow.
Oxidation of food is a destructive process,
causing loss of nutritional value and changes in
chemical composition.
Oxidation of fats and oils leads to rancidity
and, in fruits such as apples, it
can result in the formation of compounds
which discolour the fruit.
Antioxidants are added to food to slow the
rate of oxidation and, if used properly, they
can extend the shelf life of the food in which
they have been used.
http://www.understandingfoodadditives.org
Antioxidants and health
benefits
There may be health benefits from the use of
antioxidants. Oxidation reactions in the body could be
linked to the build-up of fatty deposits that cause
blockages in arteries that can cause heart attacks.
Antioxidants may be important in preventing this and
there could also be a link with the prevention of
certain cancers, arthritis and other conditions –
antioxidant stop damage to our cells. The picture is not
yet clear and a great deal of research needs to be
undertaken.
http://www.understandingfoodadditives.org
Do antioxidants help us live
longer?
Studies involving 230,000 men and women across
the UK have shown that there is no convincing
proof that antioxidants have any effect on how
long people can live. However 40% of women and
30% of men are reportedly taking these
supplements and spending over £333 million on
them per year.
Impact of antioxidants on
health
Free radicals in living cells
Free radicals are present in all living cell and are a part of the cell
processes. However excessive free radicals in our cells can attack
the cell membranes (the outer coat of the cell). This attack causes
cell and tissue damage.
Radicals can also break strands of DNA (the genetic material in the
cell). Some of the chemicals known to cause cancer, do so by forming
free radicals.
The imbalance between free radicals and antioxidants can lead to
disease and ill health. The 4 main non-enzymatic antioxidants
metalonin, α-tocopherol (Vitamin E), ascorbic acid (Vitamin C) and βcarotene (precursor for Vitamin A) can be found in a range of foods
in our diet. However medical opinions are divided as regards the
impact these antioxidants have our on general health.
Free Radicals and Oxidative
damage – food (and skin)
• Oxidation reactions can produce free radicals.
• A free radical is a highly reactive species
containing an unpaired electron.
• Free radicals can damage food by removal of an
electron.
• Antioxidant molecules ‘mop up’ free radicals to
protect the foodstuff. They are Free radical
Scavengers
Free Radicals and Antioxidants
•
•
Free radicals are atoms or groups of atoms with an odd (unpaired) number of
electrons and can be formed when oxygen interacts with certain molecules.
Once formed these highly reactive radicals can start a chain reaction, like
dominoes. Their chief danger comes from the damage they can do when they
react with important cellular components such as DNA, or the cell membrane.
Cells may function poorly or die if this occurs. To prevent free radical damage
the body has a defense system of antioxidants.
Antioxidants are molecules which can safely interact with free radicals and
terminate the chain reaction before vital molecules are damaged. Although
there are several enzyme systems within the body that scavenge free radicals,
the principle micronutrient (vitamin) antioxidants are vitamin E, beta-carotene,
and vitamin C. The body cannot manufacture these micronutrients so they
must be supplied in the diet – i.e. fruits and veg as well as other foods.
Radical now in a stable pair
Damaging free radical
Neutralised free
radical
Electron
transferred
Antioxidant
Antioxidant
converted to a
stable free radical
How does an antioxidant cancel
out a free radical?



The antioxidant molecule donates an electron to
the potentially damaging free radical.
A stable electron pair is formed, stabilising the
free radical.
The antioxidant itself becomes oxidised (loses an
electron).
Antioxidants are also Reducing
Agents
In a redox reaction, one reactant is
oxidised (_________electrons) and the other is reduced
(_________ electrons).
E.g.
Note: The electron donor is the _________ agent and the
electron acceptor is the _________ agent.
Antioxidants are _________ agents. They stop oxidation
of food etc by __________ electrons to molecules.
The table shows some typical antioxidants:
http://www.understandingfoodadditives.org
Antioxidant
E-number
Typical foods
Ascorbic acid (vitamin C)
E300
Beers, cut fruits, jams, dried potato. Helps to prevent cut and pulped foods from going brown by
preventing oxidation reactions that cause the discolouration. Can be added to foods, such as potato, to
replace vitamin C lost in processing.
Tocopherols
E306
Oils, meat pies. Obtained from soya beans and maize. Reduces oxidation of fatty acids and some
vitamins.
Butylated hydroxyanisole
(BHA)
E320
Oils, margarine, cheese, crisps. Helps to prevent the reactions that break down fats and cause the food to
go rancid .
Citric acid
E330
Jam, tinned fruit, biscuits, alcoholic drinks, cheese, dried soup. Naturally-occuring in citrus fruits like
lemons. Helps to increase the anti-oxidant effects of other substances. Helps to reduce the reactions that
can discolour fruits. May also be used to regulate pH in jams and jellies.
Vitamin C (ascorbic acid)
• The antioxidant vitamin C can act as a reducing
agent (electron donor), preventing oxidation
(electron loss) from the foodstuff.
C6H8O6
Ascorbic
acid
C6H6O6 + 2H+ + 2eDehydroascorbic acid
Examples of
Antioxidants
Vitamin C - Ascorbic Acid
Ascorbic acid is also known as Vitamin C and is commonly found in fruits
and vegetables. It is one of the essential vitamins and the human body is
unable to synthesize it. It can be easily oxidised and acts as a hydroxyl
or superoxide anion radical scavenger.
This is Vitamin C
HO
H
HO
HO
O
O
OH
This is Vitamin C acting as a Free radical Scavenger. R● is a free radical.
The Vitamin C is oxidised and give a hydrogen to bond with the R●. It is now
not a free radical.
β-carotene
This is a precursor to vitamin A. It is a highly red-orange pigment found in
plants and fruits. In particular it gives carrots their orange colour. It
helps human cells to absorb vitamin A.
H3C
H3C
CH3
CH3
CH3
CH3
CH3
CH3
H3C
CH3
Melatonin
This is a hormone which helps to regulate sleep in our bodies.
This compound can be termed as a terminal or suicidal
antioxidant as once it has removed the free radicals it has to
be replaced.
H3C
O
HN
HN
CH3
O
α-tocopherol
This is a form of vitamin E and can be found in vegetable oil,
nuts and seeds. It has been suggested that it is good for the
skin.
CH3
HO
H
H3C
H
CH3
CH3
CH3
O
CH3
CH3
CH3
Practical Task
The Assignment
Investigating the levels of Antioxidants
in different fruits and vegetables.
Key Area:
Soaps, Detergents and
Emulsions
Soaps,Detergents and
Emulsions
Overview
In this section, learn about the
chemistry of soap-making, find
about how soaps and detergents
clean, and study the chemistry
of emulsions and emulsifiers.
a) Making soap
Learning intention
Find out how soaps are formed
by alkaline hydrolysis of fats
and oils.
Soaps
Soaps are salts of fatty acids.
Alkaline hydrolysis is used to make sodium salts of fatty acids Soaps
are formed by the alkaline hydrolysis of fats and oils by sodium or
potassium hydroxide by boiling under reflux conditions:
.
H
H
H
H
C
C
C
O
O
O
O
C
O
H
C H
17 35
C
O
C H
C
C H
17 35
17 35
H
Glyceryl tristearate
+ 3NaOH
H
C
O
H
H
C
O
H
H
C
O
H
H
Glycerol
+ 3 C17H35COO -- Na +
Sodium stearate
(soap)
http://www.educationscotland.gov.uk/hi
ghersciences/chemistry/animations/s
oapformation.asp
This animation describes the formation
of soap by the alkaline hydrolysis of
fats / oils followed by neutralisation
to form sodium salts of fatty acids.
The structure
of soap
Hydrophobic
tail
COO- Na
+
Hydrophilic
head
The long covalent hydrocarbon chain gives rise to the hydrophobic (water hating)
and oil-soluble (non-polar) properties of the soap molecule (represented in yellow).
The charged carboxylate group (represented in blue) is attracted to water
molecules (hydrophilic). In this way, soaps are composed of a hydrophilic head and a
hydrophobic tail:
Detergents
Example of Detergent
Structure
Making Soap Practical
b) Cleansing action of
soap and detergents
Learning intention
Learn how the characteristic
structure of soap and detergent
molecules
allows
effective
cleaning of oily stains to take
place.
Cleansing action of soaps
The following ball (blue for hydrophilic head group) and stick (yellow
for hydrophobic tail group) diagram represents the initial interaction
of soap on addition to water and material with a grease stain:
When the solution containing soap and water is agitated (stirred
vigorously) the interactions of hydrophobicity and hydrophilicity
become apparent. The hydrophobic, non-polar, tails burrow into the
greasy, non-polar molecule – like attracting like. In the same way
the polar hydrophilic head groups are attracted to polar water
molecules. The head groups all point up into the water at the top of
the grease stain.
The attraction of the head group to the surrounding water,
via polar-to-polar interactions, is so strong that it causes
mechanical lift of the grease molecule away from the material
on which it was deposited. The hydrophobic tails are anchored
into the grease due to non-polar to non-polar attraction. In
combination, these effects allow for the removal of the
grease stain.
http://www.educationscotland.
gov.uk/highersciences/chemis
try/animations/cleansingsoap.a
sp
Experiment
•
•
•
•
•
Collect 3 measuring cylinders
Measure 50cm3 of distilled water
50 cm3 of soap solution
Make up a 50% soap solution
Add a spatula of MnO2 to each
• Record observations
• Explain the chemistry of what you see
c) Emulsions in food
Learning intention
Learn about the characteristics
of an emulsion, and study the
chemistry of typical emulsifier
molecules.
Emulsifier molecules
An emulsion contains small droplets of one liquid dispersed in an another
liquid.
Emulsions in food are mixtures of oil and water.
To prevent oil and water components separating into layers, a soap-like
molecule known as an emulsifier is added.
Emulsifiers for use in food are commonly made by reacting edible oils with
glycerol to form molecules in which either one or two fatty acid groups are
linked to a glycerol backbone rather than the three normally found in edible
oils. The one or two hydroxyl groups present in these molecules are
hydrophilic whilst the fatty acid chains are hydrophobic.
The presence of this emulsifier is shown on packaging by E-numbers, E471 and is
one of the most common on food packaging.
Emulsifiers
Mayonnaise contains oil and water. The emulsifier
keeps these mixed and without it the oil and
water separate.
Emulsifiers in food
Emulsifiers in food
Emulsifiers are among the most frequently used
types of food additives. They are used for many
reasons.
Emulsifiers can help to make a food appealing. They
are used to aid in the processing of foods and also
to help maintain quality and freshness.
In low fat spreads, emulsifiers can help to prevent
the growth of moulds which would happen if the oil
and fat separated.
Emulsifiers in food
Foods that Commonly Contain Emulsifiers
Biscuits
Toffees
Bread
Extruded snacks
Chewing gum
Margarine / low fat
spreads
Breakfast cereals
Frozen desserts
Coffee whiteners
Cakes
Ice-cream
Topping powders
Desserts / mousses
Dried potato
Peanut butter
Soft drinks
Chocolate coatings
Caramels
http://www.ltscotland.org.uk/higherscience
s/chemistry/animations/emulsions.asp
This animation explains the difference
between a stable and an unstable emulsion,
and goes on to show how addition of an
emulsifier can stabilise an emulsion which is
otherwise unstable.
The chemical structure of a typical
emulsifier is described and this is used to
explain the favourable properties of
emulsifiers
Emulsifiers Practical
Key area: Fragrances
Overview
In this section, learn about the
chemistry of terpenes and
essential oils, key components of
fragrances.
a) Essential oils
Learning intention
Learn about the constitution,
properties and uses of essential
oils.
Essential oils
• Essential oils are the concentrated extracts
of volatile, non-water-soluble aroma
compounds from plants.
• Essential oils are widely used in perfumes,
cosmetic products, cleaning products and as
flavourings in foods.
Essential oils
• Essential oils are mixtures of organic
compounds.
• Terpenes are the key components in most
essential oils.
The history of essential oils
• The benefits of essential oils have been
recognised for thousands of years.
• Their use is described in the New Testament of
the Bible.
• They were used in anointing rituals and in healing
the sick.
The history of essential oils


The ancient Egyptians used essential oils for
embalming, religious rites and medicinal
purposes.
King Tut’s tomb was found to contain 50 jars
of essential oil when it was opened in 1922.
Modern uses
Cosmetics
Dentistry
Perfumes
Cleaning
Flavours
Essential oils
Adhesives
Insect
repellents
Medical
What are essential oils?
• ‘Essential’ refers to the fact that the oil carries
the distinctive essence (scent) of the plant.
• Concentrated, volatile, non-water soluble aroma
compounds extracted from plants.
• Contain no artificial substances, unlike perfumes
and fragrance oils.
Essential oils – composition
• Essential oils are mixtures of organic compounds.
• Terpenes are the key components of all essential
oils.
Essential oils – chemistry
• The distinctive character of an essential oil
can be attributed to the functional group
present in its key molecule.
• Esters, aldehydes, ketones and alcohols are
all found in essential oils.
Essential oils – perfume
• The ester linalyl acetate is found in the
essential oil lavender.
• This ester is often added to perfumes.
H3C
C
CH3
O
C
H3C
CH2
CH
O
CH3
C
CH2
Linalyl acetate
CH2
CH
Essential oils – cleaning
• The essential oil known as lemon oil contains the
terpene d-limonene.
• It is known for its ability to act as a natural
solvent
andCHa cleanser.
H C
3
2
C
CH
H2C
CH2
H2C
CH
C
CH3
Limonene
(skin of citrus fruits)
Hospital Cleaners
• Certain essential oils kill bacteria and fungi
(including MRSA and E. coli) within 2 minutes of
contact.
• Essential oils are blended into soaps and shampoos
used in hospitals to eradicate deadly ‘super bugs’.
Essential oils – cosmetics
• The essential oil geraniol is added to some
cosmetics to balance and revitalise the skin.
CH3
CH3
C
H3C
C
CH2
CH
CH2
Geraniol
CH2
CH
OH
Essential oil – cold sores
• Melissa oil contains the terpene
citral, which is used to combat cold
sores.
CH3
C
H3C
CH
CH2
CH2
Citral
CH3
H
C
C
CH
O
Essential oils – toothpaste
• The essential oil thymol has antiseptic
properties.
CH3
C
HC
CH
C
CH
HO
C
CH
H3C
Thymol
CH3
Steam distillation
• Steam distillation is one of the methods used
to extract essential oils from plants.
• Steam passes over the plant and extracts
the essential oil.
• The mixture evaporates and passes into the
condenser.
• The essential oil vapour is chilled and
collected.
Steam distillation
Essential oils – summary
• Concentrated extracts of volatile, non-watersoluble aroma compounds from plants.
• Widely used in perfumes, cosmetics, cleaning
products and flavourings.
• Mixtures of organic compounds.
• Terpenes are the key components of most
essential oils.
b) Terpenes
Learning intention
Learn about the chemistry and
uses of terpenes, a key group of
unsaturated molecules based
upon isoprene.
Terpenes
• The name ‘terpene’ is derived
from the Greek word ‘terebinth’.
• Terebinth is a type of pine tree
from which terpene-containing
resins are obtained.
What are terpenes?
• Natural organic compounds.
• Components of a variety of fruit and
floral flavours and aromas.
• Used in perfumes, essential oils and
medicines.
Essential oils contain terpenes
• Lavender – used to relieve tension.
• Ylang-ylang – used to treat anxiety.
• Lemon oil – aids good circulation.
• Essential oils often contain a mixture
of terpenes.
Spices contain terpenes
• Terpenes in plants can be oxidised to
produce the compounds responsible for
the distinctive aroma of spices.
• Terpenes containing oxygen or other
functional groups are known as
‘terpenoids’.
• Common spices containing terpenes
include cloves, cinnamon and ginger.
Terpenes are unsaturated
• Terpenes are unsaturated compounds.
• All terpenes are built up from units of
isoprene.
Isoprene
• Isoprene is the common name for
2-methylbuta-1,3-diene
CH3
H2C
C
H3C
CH
CH2
C
CH2
H2C
CH
Isoprene
Head
Tail
CH3
C
CH2
CH
=
CH2
Isoprene
(2-methylbuta-1,3-diene)
One isoprene unit contains five carbon
atoms
Building terpenes from isoprene
Isoprene units can be linked:
• head to tail to form linear terpenes
• in rings to form cyclic terpenes.
Myrcene – a linear terpene
Head
CH2 H3C
CH2
CHH23C
H3C
C
H2C
Head
Tail
C
CH
H3C
C
C
CH
Tail
CH2
CH
CH
HH22CC
• Myrcene is a component of plants, including
bay, ylang-ylang and thyme.
Limonene – a cyclic terpene
CH2
H3C
C
CH
H2C
CH2
H2C
CH
C
CH3
Limonene
(skin of citrus fruits)
Menthol – a cyclic terpenoid
CH3
H3C
CH
CH
OH
H2C
CH
H2C
CH2
CH
CH3
Menthol
(peppermint)
This terpene has been
oxidised to a terpenoid
Absinthe – a cyclic terpenoid
CH3
H3C
This terpene has been
oxidised to a terpenoid
CH
C
H2C
CH2
HC
C
CH
CH3
Thujone
(Absinthe)
O
Camphor – a cyclic terpenoid
CH3
H3C
C
CH
CH2
CH2
C
H2C
H3C
C
O
Camphor
(Camphor tree)
a-Selinene – a cyclic terpene
CH2
H2C
H2C
CH
C
3 isoprene units
CH3
CH2
C
CH2
C
CH2
CH2
C
H
CH3
-Selinene
CH2
15 carbon atoms
β-carotene – a linear terpene
H3C
H3C
C
C
H2C
C
CH2
CH
C
CH
H2C
CH
C
CH2
C
CH2
CH3
CH3
CH3
CH2
CH
CH
CH3
8 isoprene units
40 carbon atoms
CH
CH
-carotene
C
CH3
CH
CH
CH
CH
CH
C
CH
C
CH3
C
CH
H3C
CH3
Questions
• Which unit makes up every terpene?
• How many carbons are there in an
isoprene unit?
• What is the systematic name for
isoprene?
• What is an oxidised terpene known as?
Answers
• Which unit makes up every terpene?
Isoprene unit
• How many carbons there are in an isoprene
unit?
Five
• What is the systematic name for isoprene?
2-methylbuta-1,3-diene
• What is an oxidised terpene known as?
Terpenoid
Summary
• Terpenes are unsaturated compounds formed
by joining together isoprene units.
• Terpenes are components in a wide variety of
fruit and floral flavours and aromas.
• Terpenes can be oxidised within plants to
produce the compounds responsible for the
distinctive aroma of spices.
Key area:
Skin care products
Overview
In this section, learn about the
effect of UV-light on the skin,
including the chemistry of freeradical reactions and the role of
UV-scavengers
in
skin-care
products.
a) Effect of ultra-violet
light
Learning intention
Learn how high energy UV-light
causes damage to skin by
breaking bonds in molecules.
Sun, sea, sand and ….
Ultraviolet radiation (UV)
Image of the sun taken with
ultraviolet imaging telescope
• Ultraviolet radiation is broken into three types of
wavelengths:
• UV-A: This is the longest wavelength and is not
absorbed by the ozone. It penetrates the skin deeper
than UV-B.
• UV-B: Responsible for sunburns. It is partially blocked
by the ozone layer.
• UV-C: This is totally absorbed by the earth's
atmosphere; we encounter it only from artificial
radiation sources.
Ultraviolet radiation (UV)
Ultraviolet radiation (UV) is a highenergy form of light, present in
sunlight. Exposure to UV light can
result in molecules gaining sufficient
energy for bonds to be broken.
UV damage to DNA
Damage to DNA causes mutations which stop the DNA
functioning properly
The radiation excites DNA molecules in skin cells, causing
new covalent bonds to form between adjacent cytosine
bases, producing a bulge. This mutation can result in
cancerous growths, and is known as is commonly seen in
skin cancers.
Skin cancer – malignant
melanoma
In the UK, 2,000 people a year die from malignant
melanoma, and the number is increasing.
Natural defence - Melanin
Melanin is a pigment that is produced when your
skin is exposed to sunlight. It absorbs the UV
radiation found in sunlight to help protect your
skin. This results in your skin becoming darker, a
tan which is a sign that it has been damaged by UV
rays.
Melanin stops you burning so easily but it does not
prevent the other harmful effects of UV
radiation, such as cancer and premature ageing.
Photo ageing
• In the skin, UV radiation
causes collagen to break
down.
• The body tries to rebuild
the collegen, disorganized
collagen fibers known as
solar scars can form.
• When the skin repeats this
imperfect rebuilding process
over and over wrinkles
develop.
There’s no such thing as a healthy
tan
Photoageing caused by UVA
Exposed to sun
(through car window)
TAXI Driver
Not exposed to sun
The effects of UV - ageing of skin
How to protect yourselfSunscreen
• Sunscreen works by combining organic
and inorganic active ingredients.
• Inorganic ingredients like zinc oxide
or titanium oxide reflect or scatter
ultraviolet (UV) radiation.
• Organic ingredients absorb UV
radiation, dissipating it as heat.
UV photography reveals sun damage
This article illustrates how dermatologists use ultraviolet
(UV) photography to show their patients how the sun has
damaged the skin.
Your health, your choices: Sunburn
NHS information on sunburn, including symptoms,
causes, treatment and prevention.
Sunblock
Guidance from the School of Medicine at the University of
California, San Francisco, on the use of sunblock to
prevent skin cancer. Lists common active ingredients of
sunblock.
UV Radiation and Children: A study of sunglass use
to prevent ocular damage from sun exposure
M. Bauer, W. Catanio, W. Fahrman, B. Godard, R. Irwin, A. Opyd
New England College of Optometry, Boston, MA
Purpose
To determine if children are wearing sunglasses regularly.
Results cont’d
Conclusions cont’d
Figure 2. The comparison of children and adult sunglass wear.
Despite the public consciousness of UV damage there has been little
public education involved in the prevention of cataracts, pterygia, or
photokerititis. The most obvious and cost effective form of
prevention is the use of sunglasses.4 Sunglasses are available in
various styles and sizes, with 100% UV protection, at low cost.
Comparative amount of sunglass use in children and
parents
Number of responses
To investigate whether or not parents are aware of the harmful
effects of UV radiation on young children's eyes.
160
140
120
100
80
60
parents
children
40
20
0
Introduction
Never
Sometimes
Always
Amount
Figure 3. Percent of children that wear sunglass in relation to
parental use.
Up to 80% of a lifetime sun exposure is obtained before the age
18. Children require special protection as they are at the highest
risk for developing ocular damage or diseases caused by
overexposure to Ultraviolet radiation from sunlight.
It is important that parents teach their children how to enjoy fun in
the sun safely. With the right precautions, the chance of developing
ocular damage can be greatly reduced. It has been proven that
simple measures, such as the use of brimmed hats and sunglasses, as
personal protection measures can effectuate up to an 18-fold
difference in ocular UV exposure.2
a. UV damage to
cornea5
b. Pterygium5
d. Skin cancer6
c. Cataract5
Figure 1. Ocular disease manifestations.
Methods
A six-item survey was composed to access parental knowledge and
awareness of the adverse effects of sunlight on the eyes. The
surveys were handed out, with permission, at an elementary school
and a pediatrician’s office in New Jersey and Rhode Island.
Different states were surveyed in order to make the results
generalizable throughout the United States. Results of the survey
were analyzed in order to determine if public education would be
beneficial to this issue. An educational pamphlet was made in order
to inform the public on the negative effects of sunlight on the eyes.
% of children that wear sunglasses
Frequency of sunglass wear in children
Acute eye damage can occur from single outings on bright days.
Photokeratitis, (solar corneal damage) is a temporary but painful
burn on the surface of the eye (cornea). This self-healing injury
typically resolves in 24 hours with no permanent damage.1
Chronic UV exposure contributes to the development of many eye
disorders: Pterygium is an abnormal growth of fibro-vascular tissue
from the corner of the eye. If severe, a pterygium can grow over
the cornea, threatening vision loss and requires surgery to be
removed; Cataract is a clouding of the normally clear, natural lens
inside the eye. The clouded lens prevents light from reaching the
retina therefore reducing vision; Skin Cancer can develop on the
eyelids and surrounding skin. Basal cell carcinomas, squamous cell
carcinomas, and malignant melanomas can all occur from chronic UV
exposure2,3 (Figure 1).
The segment of the population at greatest risk to accrue damage
from ultraviolet radiation is children from the ages of birth to
adolescence. UV absorption by the natural lens of the eye varies
throughout life. Immediately after birth, nearly all of the UV light
is transmitted by the lens. During childhood, lens transmittance
decreases, and by the age of 25, the lens absorbs UV light almost
completely.2 Regardless of the fact that an overwhelming number of
parents thought that childhood was the ideal age to start wearing
sunglasses, only 11% answered that their children always wore
sunglasses. Children’s lack of wearing sunglasses could be due to the
fact that manufactures and advertisement companies are not using
this age group as a demographic
120.0
5.8
100.0
5.6
18.8
80.0
60.0
38.9
65.3
Child Always
Child Sometimes
56.3
Child Never
40.0
55.6
20.0
28.9
25.0
0.0
Parent Always
Parent
Sometimes
Parent
Never
Parental sunglass use
Figure 4. Parental awareness of ultraviolet radiation damage to the
eye.
UV damage awareness
No
22%
Yes realistic
28%
Results
Of the 800 surveys distributed, 235 were returned and analyzed.
Parental educational background of those surveyed included college
57%, high school/GED 21%, graduate/masters 18%, and some high
school 4%. When asked if they always, sometimes, or never wore
sunglasses it was found that the majority of parents sometimes wore
sunglasses. It was also found that the majority of their children
sometimes wore sunglasses (Figure 2,3).When asked if their child
would wear sunglasses if given a pair, 76% said yes. The majority of
parents felt that childhood was the ideal age to start wearing
sunglasses, with 75% of the responses. It was found that the
majority of the people surveyed knew that UV radiation was
damaging to the eyes (figure 4). Of these parents 50% were unable
to provide a correct possible outcome. The top three incorrect
answers
were
blindness,
glaucoma,
and
sensitivity/squinting/soreness. The top three obtained correct
answers were cataract, damage to retina, and damage to cornea.
Yes false
50%
Conclusions
According to the results found in the previous section, 78% of adults
surveyed were aware that ultraviolet radiation is damaging. However,
half of them where unaware of the actual pathologies involved. The
severity of sun exposure was also greatly underestimated. Common
incorrect answers were blindness, glaucoma, watery eyes, and
wrinkles. These general trends lead to several possible conclusions.
One being that further education is a possible solution to the lack of
adequate sunglass use.
target. The most common answer
of why children would not wear sunglasses was that they found them
uncomfortable.
More research on the design of children’s
sunglasses could be beneficial to this issue.
In conclusion, there is a serious lack of education on the damaging
ocular effects of sun exposure. Moreover, there is little
preventative behavior in preventing these potentially serious
diseases. Because it is known that sunglass protection is most vital in
childhood, it is alarming to see that a majority of youth are not
protecting their eyes.
This preliminary survey showed that there is a potential need for
public health education on the adverse effect of UV radiation on the
eye and the protection methods that could possible prevent these
effects. A larger scale survey would be beneficial to determine
nation wide parental knowledge on this subject. Future research
would determine the most effective educational program. In order
to aid the education process an ocular sun safety flyer will be
distributed to optometric offices across the state of
Massachusetts.
References
1. Cronly-Dillon, J, Rosen, E. S., & Marshall, J. Hazards of light : myths & realities :
eye and skin : proceedings of the First International Symposium of the Northern
Eye Institute. University of Manchester, July 1985.
2. Friedlaender, Mitchell. Ultraviolet Radiation and the Eye. International
Ophthalmology Clinics. 2005;45:49-52
3. Parisi, Alfio V., Green, A., & Kimlin, M. G. Diffuse Solar UV Radiation and
Implications for Preventing Human Eye Damage. Photochemistry and
Photobiology. 2000;73:135-139.
4. Van Kuijk J.G.M, Frederik. Effects of Ultraviolet Light on the Eye: Role of
Protective Glasses. Environmental Health Perspectives. 1991;96:177-184
5. Ocular Image Database, New England College of Optometry Library [Internet].
[Cited 2006 Apr 26]. http://ncoimagesdb.ne-optometry.edu/ocular.asp.
6. Basal Cell Carcinoma (BCC), University of Utah John A. Moran Eye center
[Internet]. [Cited 2006 Apr 26].
http://www.insight.med.utah.edu/opatharch/lid/basal_cell_carcinoma_bcc.htm.
Acknowledgements
A special thank you to Dr. Clifford Scott and Dr. Li Deng for their
help with this public health project.
b) Free radical reactions
Learning intention
Study the chemistry of free
radical chain reactions.
Hydrogen and chlorine
When UV light breaks bonds free radicals are
formed.
Free radicals have unpaired electrons and, as
a result, are highly reactive.
Free radical chain reactions include the
following steps: initiation, propagation and
termination.
Hydrogen and chlorine
1) Initiation
U.V. light provides the energy for the homolytic
fission of halogen into reactive halogen atoms or
free radicals (atoms with an unpaired electron).
Cl2(g) → Cl.(g) + .Cl(g)
Hydrogen and chlorine
2) Propagation
In this stage, free radicals collide with other
species but the number of free radicals is
maintained (hence the term propagation).
H2(g) + .Cl → H.(g) + HCl(g)
H.(g) + Cl2(g) → HCl(g) + Cl. (g)
These reactions continue until reactants are used
up, or until free radicals are used up by collision
with each other.
Hydrogen and chlorine
3) Termination
In this stage, free radicals are used up by collision
with each other.
H.(g) + .Cl(g) → HCl(g)
H.(g) + .H(g) → H2(g)
Cl.(g) + .Cl(g) → Cl2(g)
Free radical Substitution Methane
Another free radical reaction takes place when halogen is substituted into an
alkane in the presence of UV light. This reaction is not explosive and results in
the decolourisation of bromine.
Alkanes react with bromine in the presence of U.V. light, though the reaction
with bromine is slow. The reaction can be shown as follows:
CH4(g) + Br2(g) → CH3Br(g) + HBr(g)
The presence of acid HBr in the product can be shown with moist pH paper.
However, the reaction does not end here and further substitution can occur
with hydrogen atoms progressively replaced by halogen atoms.
The slow substitution reaction follows a free radical chain reaction, initiated
by U.V. light (hν). For convenience, the reaction can be split into three stages.
Free radical Substitution Methane
1) Initiation
U.V. light provides the energy for the homolytic fission of halogen into
reactive halogen atoms or free radicals (atoms or molecular fragments
with an unpaired electron).
Br2(g) → Br.(g) + .Br(g)
Free radical Substitution Methane
2) Propagation
In this stage, free radicals collide with other species but the number
of free radicals is maintained (hence the term propagation).
CH3-H(g) + .Br → CH3.(g) + HBr(g)
CH3.(g) + Br2(g) → CH3 - Br(g) + Br. (g)
These reactions continue until reactants are used up, or until free
radicals are used up by collision with each other.
Free radical Substitution Methane
3) Termination
In this stage, free radicals are used up by collision with each other.
Br.(g) + .Br(g) → Br2(g)
CH3.(g) + .Br(g) → CH3 - Br(g)
CH3.(g) + .CH3(g) → CH3 - CH3(g)
The product of the last equation is ethane. However, to minimise the
range of possible products, an excess of the original alkane is used and
the products separated from the excess alkane by distillation.
Free radical Substitution Methane
Evidence to support this mechanism
The reaction is initiated by U.V. light and, once started,
can continue in the dark.
Other substitution products are made such as CH2Br2,
CHBr3, CBr4 together with longer alkanes (and smaller
amounts of substitution products of these alkanes.
However, these other substitution products can be
minimised by using an excess of the original alkane to try
to ensure collision of the relatively small number of free
radicals produced by sunlight quickly uses up the bromine.
c) Free-radical
scavengers
Learning intention
Learn about the chemistry of
the
free-radical
‘scavenger’
molecules which are included in
many skin-care products.
Free Radical Scavengers
Many cosmetic products contain free radical scavengers.
These are molecules which can react with free radicals to form stable
molecules and prevent chain reactions.
Melatonin and Vitamin E are examples of natural free radical scavengers.
Melatonin
Free radical scavengers are also added to food products and to plastics.
As UV light can cause wrinkling of skin, some skin-care products claim to
contain chemicals which prevent wrinkling. These are claimed to be anti-aging
creams.
Free radicals remove electrons from skin cells and damage them and wrinkles
start to develop.
• Here is a banned advert. This time Nivea Visage is suggesting that the cream
could deliver permanent benefits
Do they work?
• There is a range of antioxidants used in anti-wrinkle creams, and
some are better at penetrating the skin than others.
• The antioxidants used in skin care are derived from Vitamins A, E
and C
• The derivatives of Vitamins A (retinol) and E combat free
radicals. Vitamin C is used in the construction of collagen.
• Other antioxidants work by exfoliating the dead skin on the
surface to reveal newer, younger-looking skin underneath.
• Still others create a barrier to prevent moisture loss from the
skin.
• Claims for retinol derivatives say it can reduce the
appearance of lines and reduce skin roughness, and
blotchiness. There is some research that says
retinol can increase the thickness of the
epidermis. But as the molecules are large, they
can't fit though the skin unless combined with
substances that make the holes in the lipid matrix
bigger.
• Vitamin E is the most widely used ingredient in
skin care products, used for its moisturising and
antioxidant properties.
Predicting Physical
Properties of Molecules
from Functional Groups
Learning intentions
To become familiar with identifying key
functional groups within molecules.
To be able to explain the influence of
functional groups on intermolecular forces.
To be able to predict the physical
properties of molecules from functional
groups present.
Butanoic acid has a powerful, unpleasant odour. It is
found in rancid butter, Parmesan cheese and vomit.
Carboxyl group
Can you identify and name the functional group
present in butanoic acid?
Aqueous solutions of methanal are commonly used in
embalming to preserve human or animal remains.
Carbonyl group
Can you identify and name the functional group present
in methanal?
Is methanal an aldehyde or a ketone?
Aldehyde
The molecule below is found in the disinfectant Dettol,
which we instantly recognise by its distinctive smell.
Dettol (chloroxylenol) helps us fight unwanted
bacteria.
Hydroxyl
group
Can you identify and name the functional group
present in Dettol?
4-formamidobenzoic acid is used in pharmaceutical
compositions.
Carboxyl
group
Amide group
Can you identify and name two functional groups
present on the 4-formamidobenzoic acid molecule?
Cinnamon is a tasty spice used to flavour biscuits,
cakes and pies. Cinnamon also has medicinal
properties.
Carbonyl
group
Carbon-tocarbon double
bond
Can you identify and name two functional groups in
cinnamon?
Is cinnamon an aldehyde or a ketone? Aldehyde
What is the strongest type of intermolecular force of
attraction between cinnamon molecules?
(Hint: Think about the bond polarity of the functional
groups present!)
Methyl anthranilate occurs naturally in grapes and
is used as grape flavouring in drinks and chewing
gum.
Ester link
Amino group
Can you identify and name the two functional
groups present in methyl anthranilate?
Vitamin C is needed in your diet for the growth and
repair of tissues in all parts of your body.
Ester link
Carbon-tocarbon double
bond
Hydroxyl
group
Can you identify and name three different types of
functional group on the structure of vitamin C?
Which is the strongest type of intermolecular force
of attraction between molecules of vitamin C?
Is vitamin C a polar or a non-polar molecule?
Is vitamin C soluble in water or in hexane?
(Hint: Think about which functional groups are present!)
Glucose is a simple sugar that is used as an energy
source by many living organisms.
Is glucose soluble in water or in hexane? Justify your
answer with reference to the functional groups present.
2-methylpropane is a branched hydrocarbon that is
used as a refrigerant.
Is 2-methylpropane soluble in water or in hexane?
Justify your answer with reference to the structure.