Introduction to
organic chemistry
Learning Objectives
Candidates should be able:
to recall IGCSE work on crude oil and ‘cracking’.
 in a request for a structural formula, to give the minimal detail,
using conventional groups, for an unambiguous structure.
to draw and recognise displayed and skeletal formulae.
to recognise the shape of the benzene ring when it is present in
organic compounds.
to interpret and use some of the terminology associated with
organic chemistry.
Starter activity
Why carbon?
Carbon can form strong covalent bonds with itself to give chains and rings of
its atoms joined by C-C covalent bonds. This property is called catenation
and leads to the limitless variety of organic compounds possible.
Straight or branched?
Benzene – C6H6
Best representations – bonds
are
intermediate
between
single and double.
UK oil and gas
fields
Norway
Netherlands
Fractionating
columns
Fractional distillation
Uses of each fraction
Fuel gas
Petrol
/ gasoline
Naphtha
Paraffin /
Kerosine
Diesel fuel
Fuel and
lubricating
oil
Bitumen
Burned in the refinery to fuel the distillation
process, sold as LPG, purified and sold as
bottled camping gas
Fuel for cars and motorcycles, also used to make
chemicals.
Used to make chemicals.
Fuel for greenhouse heaters and jet engines,
manufacture of chemicals.
Fuel for lorries, trains.
Fuel for the heating systems of large buildings,
fuel for ships, lubricating oil.
Roofing, and road surfaces.

Alkanes

Cycloalkanes

Arenes (A2)
The names and molecular formulae
of the first 10 alkanes
methane
CH4
hexane
C6H14
ethane
C2H6
heptane
C7H16
propane
C3H8
octane
C8H18
butane
C4H10
nonane
C9H20
pentane
C5H12
decane
C10H22
Some more alkanes…….
11 Undecane
22 Docosane
33 Tritriacontane
12 Dodecane
23 Tricosane
40 Tetracontane
13 Tridecane
24 Tetracosane
50 Pentacontane
14 Tetradecane
25 Pentacosane
60 Hexacontane
15 Pentadecane
26 Hexacosane
70 Heptacontane
16 Hexadecane
27 Heptacosane
80 Octacontane
17 Heptadecane
28 Octacosane
90 Nonacontane
18 Octadecane
29 Nonacosane
100 Hectane
19 Nonadecane
30 Triacontane
132 Dotriacontahectane
20 Icosane
31 Hentriacontane
21 Henicosane
32 Dotriacontane



Homologous series: a series or family of organic
compounds with the same functional group, whose
members differ only in the addition of a CH2 group.
Functional group: the specific atom or group of
atoms that confers a particular chemical property on
a molecule, e.g. the –OH group in ethanol.
Saturated: the molecule contains the maximum
amount of hydrogen atoms possible, with no double or
triple bonds between atoms.
butane
methylpropane
Naming the alkanes
2-methylpentane
pent counts 5 carbons
an tells you there aren't any double bonds
2-methyl tells you to add a methyl group
on carbon 2
Finish by putting in the correct number of
hydrogen atoms
Naming the alkanes
2,2-dimethylbutane
2,3-dimethylbutane
3-ethyl-2-methylhexane
Structural formulae
Displayed formulae
3-dimensional structures
Skeletal formulae
Penguinone
Penguin
real name:
3,4,4,5-tetramethylcyclohexa-2,5-dienone
butane
cyclobutane
brokenwindowpane
mercedes benzene
Structural
isomerism
Learning Objectives
Candidates should be able:
describe structural isomerism
deduce the possible isomers for an organic molecule
of known molecular formula.
Chain isomerism
Structural Isomerism
What are isomers?
Isomers are molecules that have the same molecular
formula, but have a different arrangement of the atoms in
space.
(That excludes any different arrangements which are
simply due to the molecule rotating as a whole, or rotating
about particular bonds.)
TYPES OF ISOMERISM
CHAIN ISOMERISM
STRUCTURAL ISOMERISM
Same molecular formula but
different structural formulae
POSITION ISOMERISM
FUNCTIONAL GROUP
ISOMERISM
GEOMETRICAL ISOMERISM
STEREOISOMERISM
Same molecular
formula but atoms
occupy different
positions in space.
Occurs due to the restricted
rotation of C=C double bonds...
two forms… E and Z (CIS and
TRANS)
OPTICAL ISOMERISM
Occurs when molecules have a
chiral centre. Get two nonsuperimposable mirror images.
What are Structural Isomers
In structural isomerism, the atoms are arranged in a
completely different order.
STRUCTURAL ISOMERISM - INTRODUCTION
COMPOUNDS HAVE THE SAME MOLECULAR FORMULA
BUT DIFFERENT STRUCTURAL FORMULA
Chain
different arrangements of the carbon skeleton
similar chemical properties
slightly different physical properties
more branching = lower boiling point
STRUCTURAL ISOMERISM - INTRODUCTION
COMPOUNDS HAVE THE SAME MOLECULAR FORMULA
BUT DIFFERENT STRUCTURAL FORMULA
Chain
different arrangements of the carbon skeleton
similar chemical properties
slightly different physical properties
more branching = lower boiling point
Positional
same carbon skeleton
same functional group
functional group is in a different position
similar chemical properties - slightly different physical properties
STRUCTURAL ISOMERISM - INTRODUCTION
COMPOUNDS HAVE THE SAME MOLECULAR FORMULA
BUT DIFFERENT STRUCTURAL FORMULA
Chain
different arrangements of the carbon skeleton
similar chemical properties
slightly different physical properties
more branching = lower boiling point
Positional
same carbon skeleton
same functional group
functional group is in a different position
similar chemical properties - slightly different physical properties
Functional Group different functional group
different chemical properties
different physical properties
• Sometimes more than one type of isomerism occurs in the same molecule.
• The more carbon atoms there are, the greater the number of possible isomers
STRUCTURAL ISOMERISM - CHAIN
caused by different arrangements of the carbon skeleton
similar chemical properties
slightly different physical properties
more branching = lower boiling point
There are two structural isomers of C4H10. One is a straight chain molecule where all
the carbon atoms are in a single row. The other is a branched molecule where three
carbon atoms are in a row and one carbon atom sticks out of the main chain.
BUTANE
straight chain
2-METHYLPROPANE
branched
C4H10
STRUCTURAL ISOMERISM - CHAIN
DIFFERENCES BETWEEN CHAIN ISOMERS
Chemical
Isomers show similar chemical properties because
the same functional group is present.
Physical
Properties such as density and boiling point show trends according
to the of the degree of branching
Boiling Point
“straight” chain isomers have higher values than branched ones
the greater the degree of branching the lower the boiling point
branching decreases the effectiveness of intermolecular forces
less energy has to be put in to separate the molecules
- 0.5°C
straight chain
- 11.7°C
branched
greater branching
= lower boiling point
STRUCTURAL ISOMERISM - POSITIONAL
molecule has the same carbon skeleton
molecule has the same same functional group... BUT
the functional group is in a different position
have similar chemical properties / different physical properties
Example
POSITION
1 OF A DOUBLE BOND IN ALKENES
1
2
PENT-1-ENE
double bond between
carbons 1 and 2
2
3
PENT-2-ENE
double bond between
carbons 2 and 3
There are no other isomers with five C’s in the longest chain but there are three
other structural isomers with a chain of four carbons plus one in a branch.
Complete task 1 and task 2 in your hand out…..
Chain isomerism – isomers of pentane
STRUCTURAL ISOMERISM - POSITIONAL
molecule has the same carbon skeleton
molecule has the same same functional group... BUT
the functional group is in a different position
have similar chemical properties / different physical properties
Example
POSITION
2 OF A HALOGEN IN A HALOALKANE
1
1-CHLOROBUTANE
halogen on carbon 1
2
2-CHLOROBUTANE
halogen on carbon 2
BUT
2
is NOT
3-CHLOROBUTANE
Moving the chlorine along the chain makes new isomers; the position is measured from
the end nearest the functional group... the third example is 2- NOT 3-chlorobutane.
There are 2 more structural isomers of C4H9Cl but they have a longest chain of 3
STRUCTURAL ISOMERISM - POSITIONAL
molecule has the same carbon skeleton
molecule has the same same functional group... BUT
the functional group is in a different position
have similar chemical properties / different physical properties
RELATIVE POSITIONS ON A BENZENE RING
Example 3
1,2-DICHLOROBENZENE
ortho dichlorobenzene
1,3-DICHLOROBENZENE
meta dichlorobenzene
1,4-DICHLOROBENZENE
para dichlorobenzene
Complete task 3 ,4 and 5 in your hand out..
Chain and position isomers of
C4H9OH
butan-1-ol
butan-2-ol
2-methylpropan-1-ol
2-methylpropan-1-ol
Chain isomerism – isomers of hexane
Position isomerism
STRUCTURAL ISOMERISM – FUNCTIONAL GROUP
molecules have same molecular formula
molecules have different functional groups
molecules have different chemical properties
molecules have different physical properties
ALCOHOLS and ETHERS
ALDEHYDES and KETONES
ACIDS and ESTERS
MORE DETAILS FOLLOW
STRUCTURAL ISOMERISM – FUNCTIONAL GROUP
ALCOHOLS and ETHERS
Name
ETHANOL
METHOXYMETHANE
Classification
ALCOHOL
ETHER
Functional Group
R-OH
Physical properties
polar O-H bond gives rise
to hydrogen bonding.
get higher boiling point
and solubility in water
Chemical properties
Lewis base
Wide range of reactions
R-O-R
No hydrogen bonding
low boiling point
insoluble in water
Inert
STRUCTURAL ISOMERISM – FUNCTIONAL GROUP
ALDEHYDES and KETONES
Name
PROPANAL
PROPANONE
Classification
ALDEHYDE
KETONE
R-CHO
R-CO-R
Functional Group
Physical properties
polar C=O bond gives
dipole-dipole interaction
polar C=O bond gives
dipole-dipole interaction
Chemical properties
easily oxidised to acids of
same number of carbons
undergo oxidation under
extreme conditions only
reduced to 1° alcohols
reduced to 2° alcohols
STRUCTURAL ISOMERISM – FUNCTIONAL GROUP
CARBOXYLIC ACIDS and ESTERS
Name
PROPANOIC ACID
Classification
CARBOXYLIC ACID
Functional Group
R-COOH
METHYL ETHANOATE
ESTER
R-COOR
Physical properties
O-H bond gives rise
to hydrogen bonding.
get higher boiling point
and solubility in water
No hydrogen bonding
insoluble in water
Chemical properties
acidic
react with alcohols
fairly unreactive
hydrolysed to acids
What about benzene rings?
Functional group isomerism
A molecular formula C3H6O could be either
propanal (an aldehyde) or propanone (a ketone).
All three compounds are aromatic. Aspirin is also a carboxylic acid (
CO2H) and an ester ( CO2CH3). Tylenol is also an alcohol ( H) and
an amide ( CONH . Ibuprofen contains alkane substituents and a
carboxylic acid functional group
O
)
Combustion
Learning Objectives
Candidates should be able:
describe the combustion chemistry of alkanes and
how these reactions lead to their use as fuels in
industry, in the home and in transport
recognise the environmental consequences of:
•carbon monoxide, oxides of nitrogen and unburnt
hydrocarbons arising from the internal combustion
engine and of their catalytic removal
•gases that contribute to the enhanced greenhouse
effect
Starter activity
Combustion of alkanes
Alasken
Alkanes
vacation it
activation
plan on nor
non-polar
cheer mix it
exothermic
clues pinhole
nucleophiles
acne riot
reaction
police shelter
electrophiles
cubism onto
combustion
fans rap if
paraffins
bleats
stable
Combustion of hydrocarbons
C6H14
+ 9½O2

6CO2
+
7H2O
As chain length increases:
•More oxygen is needed for complete combustion
•The reactions become more exothermic
Incomplete combustion
Often the flame is yellow
and luminous
CH4
+
2O2

CO2
CH4
+
1½O2

CO
CH4
+
O2

C
+
+
+
2H2O
2H2O
2H2O
Bunsen Burner
Bunsen Burner
Carbon monoxide poisoning
Two children who died on Corfu were
killed by carbon monoxide poisoning,
Greek
officials
have
confirmed.
A
pathologist said very high levels of the gas
were found in the bodies of Christianne
Shepherd, seven and her brother Robert, six.
Carbon monoxide poisoning
Carbon monoxide, CO, poisons
the body by combining with
hemoglobin some 250 times
more tightly than O2, thus
hindering the transport of O2
to the body's tissues.
Air pollution
Can you complete the table?
Acid Rain
Emission
CO2
CO
CxHy
NO
NOx
SO2
Source
Complete
combustion
fuel
Complete
combustion
fuel
Chemical
equation
appropriate)
of CxHy +
(where Problems associated
with this emission
y
2
O2  xCO2 +
y
2
O2  xCO2 +
y
2
H2O
of
Unburnt
hydrocarbon fuel
N2 and O2 react
under high T
conditions of car
engine
2o
pollutant
formed
from
oxidation of NO
Combustion of S
impurities
in
fossil fuels
CxHy +
y 1
2
-
N2 + O2 
2NO
2NO + O2  2NO2
S + O2  SO2
H2O
Greenhouse
gas;
major contributor to
global warming.
Toxic gas; combines
with haemoglobin and
prevents
O2
transport. Leads to
photochemical smog.
Some
(especially
benzene) are toxic
and
carcinogenic.
Leads
to
photochemical smog.
Contributes
to
formation of acid
rain
and
photochemical smog.
Linked to respiratory
problems.
Choking gas; major
contributor
to
formation of acid
rain.
Catalytic converters
These help to promote the following reactions:
2CO + 2NO

N2
+
2CO2
CO and CxHx are also oxidised by the air:
CO + O2  CO2
e.g.
C7H16 + O2  7CO2 + 8H2O
Free-radical
substitution reactions
of alkanes
Learning Objectives
Candidates should be able:
describe the mechanism of free-radical substitution
at methyl groups with particular reference to the
initiation, propagation and termination reactions.
describe the substitution of alkanes by chlorine and
bromine.
Starter activity
chlorination of methane
i.e. homolytic breaking of covalent bonds
Overall reaction equation
CH4 + Cl2
CH3Cl + HCl
Conditions
ultra violet light
excess methane to reduce further substitution
ultra-violet
Cl2
Cl + Cl
initiation step
two
propagation
steps
CH4 + Cl
CH3 + HCl
CH3 + Cl2
CH3Cl + Cl
CH3 + Cl
CH3Cl
termination step
CH3 + CH3
CH3CH3
minor
termination step
Overall reaction equations
CH3Cl + Cl2
CH2Cl2 + HCl
CH2Cl2 + Cl2
CHCl3 + HCl
CHCl3 + Cl2
CCl4 + HCl
Conditions
ultra-violet light
excess chlorine
Cracking
Learning Objectives
Candidates should be able to suggest how ‘cracking’
can be used to obtain more useful alkanes and alkenes
of lower Mr from larger hydrocarbon molecules.
Starter activity
Why crack?
Fractionth
Gases
Petrol and naphtha
Kerosene
Gas oil
Residue
Approximate %
Crude oil
2
16
13
19
50
Demand
4
27
8
23
38
One example of a cracking reaction?
Thermal cracking
•Produces a high proportion of alkenes
•Temperatures range from 400-900oC
•Pressures up to 7000kPa
Catalytic cracking
•Produces a large proportion of branched alkanes,
cycloalkanes and aromatic hydrocarbons
•Uses zeolite (crystalline aluminosilicate) catalysts
•Temperature around 450oC
•Pressure just above atmospheric
Catalytic cracking
Zeolite catalyst
‘Cat’ cracker
Catalytic cracker