Organic chemistry is the study of carbon compounds. Carbon can form many structures through single, double, and triple bonds and straight, branched, and ring arrangements. Crude oil is purified through fractional distillation to produce hydrocarbon fractions like methane, propane, and octane. Larger alkanes are cracked into smaller, more useful alkenes and alkanes. Alkanes undergo substitution reactions like combustion and halogenation. Alkenes contain carbon-carbon double bonds and react through addition reactions like halogenation and hydration to form alcohols.

1. INTRODUCTION TO ORGANIC CHEMISTRY
Ms. Seetahal

2. OBJECTIVES
• To explain the different types of structures that carbon can
form.
• To describe the process by which hydrocarbons are obtained.
• To describe the structure and reactions of alkanes.
• To describe the structure and reactions of alkenes.

3. CARBON COMPOUNDS
Types of carbon structures, functional groups and homologous series

4. CARBON COMPOUNDS
 Organic chemistry is the chemistry of carbon compounds
 Carbon forms a vast number of compounds because it can form strong
covalent bonds with itself
 This enables it to form long chains of carbon atoms, and hence an almost
infinite variety of carbon compounds are known
 Carbon always forms four covalent bonds which can be single, double or
triple bonds
 Carbon is able to form straight-chain, branched chain and ring structures.

5. FUNCTIONAL GROUP
• A functional group is a specific atom or group of atoms which
confer certain physical and chemical properties onto the
molecule
• Organic molecules are classified by the dominant functional
group on the molecule
• Organic compounds with the same functional group, but a
different number of carbon atoms, are said to belong to the
same homologous series.

6. HOMOLOGOUS SERIES
• each member has the same functional group
• each member has the same general formula
• each member has similar chemical properties
• each subsequent member differs by -CH2 –
• members have gradually changing physical properties, for example,
boiling point, melting point and density
• As a homologous series is ascended, the size of the molecule increases
• This has an effect on the physical properties, such as boiling point and
density which increases as the size of the molecule increases.

7. TYPES OF FORMULA
General, molecular and structural formula

8. TYPES OF FORMULA
• General Formulae
• This type of formula tells you the composition of any member
of a whole homologous series of organic compound
• For example, all of the alkanes have the general formula
CnH2n+2
• This tells you that however many carbon atoms there are in the
alkane, doubling this number and adding two will give you the
number of hydrogen atoms present in the alkane.

9. TYPES OF FORMULA
• Molecular Formulae
• This shows the actual number of each atom in a molecule, one
molecule at a time
• Structural Formulae
• This shows the spatial arrangement of all the atoms and bonds
in a molecule.

10. TYPES OF FORMULA

11. ORGANIC COMPOUNDS

12. HYDROCARBONS
Source of hydrocarbons, purification and its uses

13. HYDROCARBONS
• Crude oil is a finite resource which we find in the Earth’s crust
• It is also called petroleum and is a complex mixture of
hydrocarbons which also contains natural gas
• Hydrocarbons are compounds that are made of carbon and
hydrogen atoms only
• The hydrocarbon molecules in crude oil consist of a carbon
backbone which can be in a ring or chain, with hydrogen atoms
attached to the carbon atoms
• The mixture contains molecules with many different ring sizes and
chain lengths

14. CRUDE OIL
 Crude oil as a mixture is not a very useful substance but the different
hydrocarbons that make up the mixture, called fractions, are
enormously valuable, with each fraction having many different
applications
 Each fraction consists of groups of hydrocarbons of similar chain
lengths
 The fractions in petroleum are separated from each other in a process
called fractional distillation

16. CRUDE OIL
 Fractional distillation is carried out in a fractionating column which is
very hot at the bottom and cool at the top
 Crude oil enters the fractionating column and is heated so vapours rise
 Vapours of hydrocarbons with very high boiling points will
immediately condense into liquid at the higher temperatures lower
down and are tapped off at the bottom of the column
 Vapours of hydrocarbons with low boiling points will rise up the
column and condense at the top to be tapped off

17. CRUDE OIL
 The different fractions condense at different heights according to
their boiling points and are tapped off as liquids
 The fractions containing smaller hydrocarbons are collected at the top
of the fractionating column as gases
 The fractions containing bigger hydrocarbons are collected at the lower
sections of the fractionating column

19. CRACKING
 Long chain alkane molecules are further processed to produce other
products consisting of smaller chain molecules
 A process called cracking is used to convert them into short chain
molecules which are more useful
 Small alkenes and hydrogen are produced using this process
 Kerosene and diesel oil are often cracked to produce petrol, other
alkenes and hydrogen
 There are two methods used to crack alkanes: catalytic cracking
and steam cracking

21. ALKANES
Structure, reactions and physical properties

22. ALKANES
• Alkanes are a group of saturated hydrocarbons
• The term saturated means that they only have single carbon-carbon
bonds, there are no double bonds
• The general formula of the alkanes is CnH2n+2
• They are colourless compounds which have a gradual change in their
physical properties as the number of carbon atoms in the chain
increases
• Alkanes are generally unreactive compounds but they do undergo
combustion reactions, can be cracked into smaller molecules and can
react with halogens in the presence of light
• Methane is an alkane and is the major component of natural gas

24. NAMING OF ALKANES
• The names of all alkanes end in –ane.
• Alkanes can be either straight chain or branched compounds.
• The alkanes have many uses:
 methane – (natural gas) cooking, heating
 propane – used in gas cylinders for BBQ etc
 octane – used in petrol for cars

26. NAMING BRANCHED CHAIN
ALKANES
• There are some general rules which you should remember when naming
organic compounds:
• The longest unbranched chain containing the functional group is the
parent molecule, or simply the longest unbranched chain for alkanes.
Remember that the longest chain can go round a bend.
• Indicate the position of the functional group with a number, numbering
from the end nearest the functional group.
• Name the branches, and indicate the number of branches.

27. NAMING BRANCHED CHAIN
ALKANES
• Methyl indicates there is one carbon atom in the branch.
• Ethyl indicates there are two carbon atoms in the branch.
• The prefix 'di' indicates there are two branches.
• The prefix 'tri' indicates there are three branches.
• Indicate the position of the branches with a number, numbering from the end nearest
the functional group.
• For more than one branch, the branches are identified in alphabetical order, ignoring
any 'di', 'tri', etc, prefixes.
• Each branch needs to be numbered individually, even if they are attached to the same
carbon atom.

28. NAMING BRANCHED CHAIN
ALKANES

29. REACTIONS OF ALKANES
Alkanes undergo substitution reactions since they are saturated
compounds.
• Combustion
 Hydrocarbons undergo combustion in the presence of air
 Complete combustion occurs to form water and carbon dioxide gas
 For example, the simplest alkane, methane burns as follows:
• CH4 + 2O2 → CO2 + 2H2O

30. REACTIONS OF ALKANES
• Halogenation of alkanes: alkanes undergo halogenation with bromine
and chlorine. The halogen atom replaces the hydrogen on the alkane.
This reaction requires the presence of UV light.

31. TRENDS IN PHYSICAL PROPERTIES
• Some properties of hydrocarbons depend on the size of their molecules,
including boiling point, viscosity and flammability
• These properties influence how hydrocarbons are used as fuels

32. TRENDS IN PHYSICAL PROPERTIES
• Boiling Point
 The hydrocarbons are grouped together into homologous series according to their
functional group and common formula
 Gradation in the physical properties of a homologous series can be seen in the
trend in boiling points of the alkanes
 Each alkane has a boiling point that is higher than the one before it
 As the molecules get larger, the intermolecular forces of attraction between the
molecules becomes greater as there are more electrons in the molecules and
greater surface area contact between them
 This means that more heat is needed to separate the molecules, hence with
increasing molecular size there is an increase in boiling point

34. ALKENES
Structure and reactions

35. ALKENES
 Alkenes are a homologous series of hydrocarbon compounds with at least
one double bond between two of the carbon atoms on the chain
 The double bond can be written as carbon carbon double bond or as C=C
 The general formula for alkenes is:
• CnH2n
 Alkenes are generally more desirable than alkanes as they are more
reactive due to the presence of the carbon-carbon double bond, so they can
take part in reactions in which alkanes cannot, making them more useful
than alkanes
 They are used to make polymers and are the starting materials for the
production of many other chemicals

38. NAMING OF ALKENES
• The names of all alkenes end in-ene.
• Naming alkenes has the same rules as alkanes.
• However, the position of the carbon to carbon double bond must be identified. The
functional group is given the lowest possible number when numbering the carbon
atoms.
3-methylbut-1-ene

39. REACTIONS OF ALKENES
• Halogenation of Ethene
 Alkenes undergo addition reactions in which atoms of a
simple molecule add across the C=C double bond
 The reaction between bromine and ethene is an example of
an addition reaction
 The same process works for any halogen and any alkene in
which the halogen atoms always add to the carbon atoms
across the C=C double bond

41. REACTIONS OF ALKENES
• Bromine Water Test
 Alkanes and alkenes have different molecular structures
 All alkanes are saturated and alkenes are unsaturated
 The presence of the C=C double bond allows alkenes to react in ways
that alkanes cannot
 This allows us to tell alkenes apart from alkanes using a simple
chemical test called the bromine water test

43. REACTIONS OF ALKENES
• Combustion of Alkenes
 These compounds undergo complete and incomplete combustion but
because of the higher carbon to hydrogen ratio they tend to undergo
incomplete combustion, producing a smoky flame in air.
 Complete combustion occurs when there is excess oxygen so water and
carbon dioxide form e.g:
• C4H8 + 6O2 → 4CO2 + 4H2O
• butene + oxygen → carbon dioxide + water

44. REACTIONS OF ALKENES
• Incomplete combustion occurs when there is insufficient oxygen to burn
so a mixture of products can form, in addition to carbon monoxide,
carbon in the form of soot can be produced.
 This is more likely to occur in higher alkenes with larger number of
carbons
 This is seen as smoky yellow flames when the alkenes burn

45. REACTIONS OF ALKENES
• Hydrogenation
• Alkenes undergo addition reactions with hydrogen in which an alkane is
formed
• These are hydrogenation reactions and occur at 150ºC using a nickel
catalyst
• Hydrogenation reactions are used to manufacture margarine from
vegetable oils
• Vegetable oils are polyunsaturated molecules which are partially
hydrogenated to increase the Mr and turn the oils into solid fats

47. REACTIONS OF ALKENES
• Hydration
• Alkenes also undergo addition reactions with steam in which an alcohol is formed.
Since water is being added to the molecule it is also called a hydration reaction
• The reaction is very important industrially for the production of alcohols and it
occurs using the following conditions:
• Temperature of around 330ºC
• Pressure of 60 – 70 atm
• Concentrated phosphoric acid catalyst
 The ethanol and water are separated afterwards by fractional distillation

49. KEY POINTS
• Carbon can form many different types of organic structures due to its
ability to form different types of bonds(single, double or triple) as well
as different arrangements of structures(straight, branched and ring
structures).
• Crude oil contains hydrocarbons and can be purified by fractional
distillation. These produces important fractions that can be useful for
fuels and the petrochemical industry.
• Cracking involves breaking apart of hydrocarbons into smaller
molecules which are more useful.
• Alkanes and alkenes undergo substitution reactions.