This document provides an overview of organic chemistry concepts. It defines organic compounds as hydrocarbons and related compounds containing carbon. Carbon atoms can bond together in chains, allowing for a large number of organic compounds. Saturated compounds have single carbon bonds while unsaturated have double or triple bonds. Common hydrocarbons include alkanes (single bonds), alkenes (double bonds), and alkynes (triple bonds). The document also discusses the structure and reactions of important organic compound classes like alkenes, alcohols, acids, and polymers.

1. Organic chemistry
IGCSE Chemistry 0620

2. What are organic
compounds?
 Organic compounds are hydrocarbons and
related compounds
 Hydrocarbons are compounds made up of
carbon and hydrogen only.
 Carbon atoms can join one to another to form
carbon chain with different number of carbon
atoms. Because of this there are huge
number of organic compounds.
 This property of carbon is called ‘catenation’.

3. Saturated and unsaturated
compounds
 If all bonds between carbon atoms are
single, the compounds are saturated
compounds.
 If a double or a triple bond is present
between carbon atoms, the compounds
are called unsaturated.
 In saturated compounds, all valencies of
carbon atoms are fully used up. So
saturated compounds are not reactive.

4.  Single bond hydrocarbons are called
ALKANES
 Double bond hydrocarbons are called
ALKENES
 Triple bond hydrocarbons are called
ALKYNES
(You need to know only about alkanes and
alkenes)

5. Saturated Hydrocarbons

6.  Unsaturated compounds have one or more
valencies in carbon atoms are free.
 Second and third bonds are temporary. So
if other atoms available, unsaturated
compounds are very reactive.

7. Alkenes

8. Naming hydrocarbons
 Each organic compound has two parts in their
names:
 Prefix depends on how many carbon atoms
present.
 1 carbon compound Meth-
 2 carbon compound Eth-
 3 carbon compound Prop-
 4 carbon compound But-
 5 carbon compound pent-
 6 carbon compound hex-

9. Naming hydrocarbons
 Suffix (second part) depends on the
bond between carbon atoms.
 Single bond –ane
 Double bond –ene
 Triple bond –yne

10. Alkanes

12. Crude oil
 Crude oil is a source of many
hydrocarbons
 Crude oil is formed from the dead bodies
of animals (mainly aquatic) which were
living millions of years ago.
 These bodies are covered with sand and
mud.
 Due to changes in temperature and
pressure, the animal bodies are changed
in to a dark viscous liquid called crude
oil(petroleum).

13. Crude oil
 Crude oil is pumped out from the oil wells.
 Important substances from crude oil are
separated in an oil refinery.

14. Fractional distillation of crude
oil
 Various useful substances are separated
from crude oil by fractional distillation.
Fractions with low boiling points with low
density are collected at the top.
 Following increase when coming down in the
fractionating column:
 Density
 Molecular mass (No of C atoms)
 Viscosity
 Colour darker
 Boiling point

16. Fuels
 Fuels give out energy.
 Coal, natural gas, petrol etc are fuels
 Natural gas is mainly methane.
 Hydrocarbons burn in air to produce
carbon dioxide and water together with
energy(heat)
 Methane + oxygen  Carbon dioxide +
water
CH4 + 2O2  CO2 + 2H2O
 Ethane + oxygen  carbon dioxide +
water

17. Functional group
 Double bond =
 Alcohol -OH
 Carboxylic acid –COOH
 Halide -Cl -Br -I
 Group of compounds with similar
properties is called HOMOLOGOUS
SERIES
 Examples: Alkanes, Alkenes, Alcohols,
Carboxylic acids etc

18. Alcohols
 Methanol (1Carbon alcohol)
 CH3OH
 Ethanol (2 Carbon alcohol)
 C2H5OH or CH3-CH2-OH
 Propanol (3 Carbon alcohol)
 C3H7OH or CH3-CH2-CH2-OH

19. Carboxylic acids
 Methanoic acid (1Carbon acid)
 HCOOH
 Ethanoic acid (2 Carbon acid)
 CH3COOH
 Propanoic acid (3 Carbon acid)
 CH3CH2COOH

20. Alkanes
 Alkanes are saturated hydrocarbons.
So they are not reactive.
 Alkanes burn in oxygen to form carbon
dioxide and water.
 CH4 + 2O2  CO2 + 2H2O
 Energy is given out when alkanes
burn. So alkanes are present in fuels.
 Petrol and diesel are mixtures of
alkanes.

21. Substitution reaction
 If atoms are replaced by other atoms,
the reaction is called substitution
reactions.
 Alkanes show substitution reaction.
Hydrogen atoms are replaced by more
reactive halogen atoms in presence of
light.
 Here light works as a catalyst.

23. Alkenes
 Alkenes are unsaturated compounds
having a double bond between carbon
atoms.
 Alkenes are highly reactive.
 They also burn in oxygen to produce
carbon dioxide gas and water.
 Ethene + Oxygen  Carbon dioxide +
Water
 C2H4 + 3O2  2CO2 + 2H2O

24. Addition reaction
 Unsaturated compounds undergo
addition reaction.
 Atoms are added to the double bond
to form a single product (No
replacement). This kind of reaction is
called addition reaction.
 During addition reaction, double bond
compounds(less stable) change into
single bond compounds (stable)
 Alkenes Alkanes

25.  Addition of halogen (bromine)
 Ethene + Bromine  dibromo ethane
 CH2=CH2 + Br2 CH2Br-CH2Br
 Addition of hydrogen
 Heat and a catalyst (Nickel) are needed for
the addition of hydrogen to alkene.
 Ethene + Hydrogen  Ethane (Heat & Ni
needed)
 CH2=CH2 + H2  CH3-CH3
 Addition of water
 Heat and high pressure are needed for this.
 Ethene + steam  Ethanol
 CH2=CH2 + H2O  CH3-CH2-OH

26. Polymerisation
 Small molecules(monomers) join one
another to form a large molecule
(polymer).
 This kind of reaction is called
polymerisation.
 At high temperature and pressure,
alkenes undergo polymerisation to
form different polymers (Plastics)
 During polymerisation, double bond
becomes single.

27.  Ethene  Poly ethene (Polythene)
 …CH2=CH2 + CH2=CH2 + CH2=CH2 + CH2=CH2….
 -CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2
 The above reaction can be summarised as
 nCH2=CH2  -(CH2-CH2)-n
 Another example is chloroethene when
polymerised, we get polychloroethene (PVC)
 nCH2=CHCl  -(CH2-CHCl)-n
 Propene when polymerised we get
polypropene (another plastic)

28. Test for unsaturated compounds
 Saturated compounds have single bonds
between carbon atoms
 Unsaturated compounds have a
double/triple bond between carbon atoms.
 When an unsaturated compound is
passed through bromine water, the colour
will change from orange brown to
colourless.
 This is because of the addition reaction
with unsaturated compound and bromine.
 CH2=CH2 + Br2  CH2Br-CH2Br
(orange brown) (colourless)

29. Alcohols
 Common alcohols are methanol, ethanol and
propanol
 CH3OH, C2H5OH, C3H7OH
 Ethanol is present in alcoholic drinks. Also
used in hospitals, industries (as a solvent)
and different types of medicines. Widely used
as fuel for car engines.
 Methanol is poisonous
 Propanol is a good solvent used to clean
audio and video heads.

30. Ethanol
 Two methods of making ethanol are:
 Batch process
 In this method glucose is fermented using
yeast. Enzymes in yeast change glucose
into ethanol and carbon dioxide (anaerobic
respiration by yeast)
 Glucose  ethanol + carbon dioxide
 C6H12O6  2C2H5OH + 2CO2
 Ethanol formed is separated by distillation

31.  Continuous process
 In this process, ethene is treated with
super heated steam at high temperature
and pressure in presence of concentrated
acid as a catlyst (addition)
 CH2=CH2 + H-OH  CH3-CH2OH
 Ethene is a by-product during the
petroleum industry.
 The production of ethanol takes place
continuously.

32. Advantages and
disadvantages
 Batch process
 Advantage: environmental friendly
 Disadvantage: Takes long period of
time for yeast to ferment
 Continuous process
 Advantage: quick and continuous
production
 Disadvantage: can cause pollution
and expensive (need of fuel)

33. Cracking
 It is opposite of polymerisation
 Large molecules are broken down into
small molecules using catalyst or heat.
 Most petroleum products are large
hydrocarbon molecules.
 These large molecules are cracked into
small molecules which are present in
petrol (5-10 carbon atoms).
 Alkenes will be formed when alkanes are
cracked

34.  Fermentation: Yeast changes glucose into
alcohol and carbon dioxide gas is called
fermentation. Fermentation is anaerobic
respiration.
 Ethene formed as by-product during
cracking is useful in the manufacture of
ethanol.
 C12H26  C8H18 + 2C2H4
(large alkane) (useful alkane) Ethene
 Ethanol when burns in oxygen (air), it
gives out carbon dioxide, water and
energy.
 Ethanol + Oxygen  Carbon dioxide +
water

35. Acids
 Important carboxylic acids are:
 Methanoic acid, Ethanoic acid and Propanoic
acid
H-COOH CH3-COOH C2H5-COOH
Ethanoic acid is prepared by the oxidation of
ethanol using potassium manganate(VII).
 C2H5OH + 2(O)  CH3COOH + H2O
 Acid present in vinegar is Ethanoic acid.
 Alcohol (wine) turns sour if left open in air (acid
formation)
 Ethanoic acid is a weak acid(Hydrogen ions are

36. Esterification
 When an organic acid reacts with an alcohol,
ester and water are formed. This is done in
presence of conc sulphuric acid.(dehydrating
agent)
 Example: Ethanol reacts with ethanoic acid
will produce ethyl ethanoate ester and water.
 C2H5OH + CH3COOHC2H5OOCCH3 + H2O
Ethanol Ethanoic acid Ethyl ethanoate
water
 Propanol + Ethonoic acid  Propyl ethanoate +
water
 C3H7OH + CH3COOH C3H7OOCCH3 +
H2O

37.  Methyl propanoate is formed from which
alcohol and acid?
 Methanol and Propanoic acid
 Write formula of Methanol, Propanoic acid
and methyl propanoate
 CH3OH, C2H5COOH, CH3OOCC2H5
 Write names of any two esters, alcohol
and acid from which they are formed and
write their formulas.
 Esters are sweet smelling substances
(found in fruits). So they are used to make
perfumes.

38. Macromolecules
 Macromolecules are large molecules
(polymers) formed from small molecules
(monomers).
 Macromolecules are synthetic(man made) or
natural.
 Synthetic polymers.
 Poly ethene, poly propene and chloro ethene
are polymers formed by the addition
polymerisation (of double bond monomers).
 Non biodegradable plastics stay in soil and
cause soil pollution. Bio-degradable plastics
can be removed by micro organisms.

39. Condensation polymers
 Some polymers are made from non-double
bond compounds.
 Example: Nylon is a polymer from an amine
and acid. Water molecules removed.
OR

40.  Another example is Terylene
 Water molecules removed

41. Natural polymers
 Mainly carbohydrates, proteins and fats
 These are food constituents
 Carbohydrates macromolecules such as
starch is made up of simple sugars like
glucose or fructose. -OH + HO- groups
joined here.
 Water molecules removed.

42.  Complex carbohydrates when
hydrolyse turn into simple sugars back
 Starch + water glucose
 Hydrolysis is breaking large molecules
into smaller ones by adding water. In
our body, digestive enzymes help in
hydrolysis.

43. Proteins and fats
 Proteins are made up of amino acids.
 Many amino acid molecules join to form
proteins.
 Amino group (-NH2) is basic and acid
group (-COOH) is acidic.
 So amino group and acid group react to
form amide link (peptide bond). Water is
removed during the process.

44. • Proteins on hydrolysis give the amino acids.
• Fats and oils(lipids) are macromolecules of fatty acids
and glycerol.
• Glycerol and fatty acids are joined like that in terylene
• Fats on digestion (hydrolysis) gives fatty acids and
glycerol.
• Fats when hydrolyse with alkali we get soaps.
• Amino acids from protein molecules are separated and
identified by chromatography.

45. THE END