VCE Chemistry
Unit 3, Area of Study 2
2013
AREA OF STUDY 2
Organic chemical pathways
In this area of study students investigate systematic organic
chemistry including production of starting materials for particular
reaction pathways.
Students use molecular models and conduct simple laboratory
investigations to observe the properties and reactions of different
homologous series and functional groups.
Students investigate the use of biochemical fuels.
They design reaction pathways to prepare organic compounds from
given starting materials.
Students investigate how forensic analysis relies on the use of
organic chemicals (including DNA) and the role of organic chemicals
(including proteins) in the development of medicines.
Key knowledge:
This knowledge includes:
 Structure and systematic nomenclature of alkanes, alkenes,
amines, chloroalkanes, alkanols and carboxylic acids up to C10;
 Common reactions of organic compounds: addition reactions of
alkenes, substitution reactions of alkanes and primary
chloroalkanes, oxidation of primary alkanols, esterification;
 Principles of fractional distillation;
 Organic reaction pathways including the production of esters
from alkenes, condensation and polymerisation reactions that
produce large biomolecules;
 Primary, secondary and tertiary structure of proteins and the
function of protein catalysts (enzymes);
 Biochemical fuels including fermentation of sugars to produce
ethanol;
 The structure and
forensic analysis;
bonding
of
DNA
and
its
applications
in
 Use of proteins as markers for disease;
 Function of organic molecules in the design and synthesis of
medicines including the production of aspirin from salicylic
acid.
Assessment:
two separate SACs.
Assessment of this Area of Study includes
VCE Chemistry
Unit 3, Area of Study 2
2013
1. A written report of the practical activity: Synthesis of
Aspirin. The practical portion will be performed at La Trobe
University. This SAC will be held in week 5 of term 2.
2. An analysis of data relating to Biochemistry in the form of
structured questions. This SAC will be held in week 9 of term
2.
Chapter 9 Summary Notes
Compounds of Carbon
Key Knowledge addressed in this Chapter:
 structure and systematic nomenclature of alkanes,
alkenes, amines, chloroalkanes, alkanols and carboxylic
acids up to C10;
As so many compounds contain carbon, and their characteristics are so diverse, it is impossible to
study them all... they need to be classified. Chemists then look at various categories of carbon
compounds that have common characteristics.

Starting point = hydrocarbons, as these contain only two elements, hydrogen and carbon.

Hydrocarbons can be classified as alkanes, alkenes or alkynes.
The difference between these groups is their bonds between the carbon atoms:
alkanes have only single bonds
alkenes have at least one double bond
alkynes have at least on triple bond
Alkanes
Alkanes are the hydrocarbons with single bonds only. The simplest hydrocarbon is methane (CH4).
Methane is a colourless, odourless gas at room temperature -> you will all know it as natural gas, the
gas used in our ovens and stovetops, in heaters, the gas for Bunsen burners in our lab... what you
may not know is that the smell of gas is added, it’s not given off by methane as methane is
odourless.
Methane:
VCE Chemistry
Unit 3, Area of Study 2
2013
If we were to add another Carbon to methane, how many more hydrogen atoms would be added,
keeping in mind there are only single bonds?
Draw the Methane with the added carbon and hydrogen
= Ethane
A series of compounds can be formed by successively adding an extra carbon and two hydrogen
atoms,
Therefore our rule for the molecular formula of alkanes is:
CnH2n+2
The alkanes are an example of a
. This means it is a
group or family, where the compounds have similar structures and chemical properties and the
same general formula. Each member in the series differs by a -CH2- group from the previous member
Alkanes are also called saturated hydrocarbons =
Question: If a molecule has 30 carbon atoms, what is its molecular formula?
VCE Chemistry
Unit 3, Area of Study 2
2013
Nomenclature (the naming) of hydrocarbons
The naming of hydrocarbons is very systematic, the prefix (start of the word) and the suffix (end of
the word both provide information.
The prefix tells us how many carbon atoms are in the longest chain of the molecule. The suffix tells
us what type of bonding (single, double or triple) as it will be either ‘ane’, ‘ene’ or ‘yne’.
The prefixes include:
Prefix
Number of carbons
1
2
3
4
5
6
7
8
9
Properties and uses of alkanes
While the chemical properties of alkanes are similar, their physical properties vary systematically
with the length of the molecule. As the length increases, their melting and boiling points increase,
their viscosity increases, the volatility decreases and their solubility increases.
VCE Chemistry
Unit 3, Area of Study 2
2013
Explanation of physical properties:
Combustion reactions
The main reason for why alkanes are so highly consumed worldwide is they are abundant and they
are great fuels.
Alkanes are fuels because they react vigorously with oxygen from the air to release large quantities
of energy. These reactions are called combustion reactions. The main products of burning most
hydrocarbons are water and carbon dioxide.
When the Bunsen burner is going on the blue flame (i.e. when methane is burning) the following
reaction occurs:
The burning of petrol in a car engine involves the reaction:
2C8H18(l)
+ 25O2(g)
16CO2(g)
+ 18 H2O(g)
Cyclic molecules
A chain of carbon atoms can also be bent round to form a ring. The molecules formed this way are
called cyclic molecules.
Cyclopropane - C3H6
Cyclohexane - C6H12
VCE Chemistry
Unit 3, Area of Study 2
2013
Sometimes, as with _________________, three of the four outer-shell electrons from each carbon
atom form normal covalent bonds but the fourth electron is shared (delocalised) around the six
membered carbon ring. In all, there are six delocalised electrons in a benzene ring that are shared by
the six carbon atoms.
Benzene
Benzene and its delocalized electrons can be drawn in the following ways:
1. A shaded ring representing the delocalised electron
2. A shorthand representation, where the delocalised electrons are represented by a circle
inside the hexagon.
3. The delocalised electrons can also be represented by these structures
VCE Chemistry
Unit 3, Area of Study 2
2013
Alkenes:
Remember the naming tells us what types of bonds are between the carbon atoms:
Ane = all single bonds, ene= a double bond, yne = a triple bond
Alkene = hydrocarbons that contain a carbon-to-carbon double bond in their structure.
The general rule for the molecular formula of alkenes =
The simplest alkene is ethene (C2H4). Why is there no alkene equivalent of methane?
Are alkenes saturated?
Physical properties of alkenes:
Alkenes physical properties follow the same trends as the alkanes, as their length increases their
melting and boiling points increase, their viscosity increases, and their solubility decreases.
This is because as the size of the molecule increases, the strength of
also increases.
Uses of alkenes:
The most produced alkene is ethene. Ethene itself actually doesn’t have
many uses, but it is the building block of a vast array of Carbon chemicals.
Some examples include: Ethanol (a.k.a. alcohol), ethanoic acid (a.k.a.
vingegar), chloroethane, and many polymers (plastics).
VCE Chemistry
Unit 3, Area of Study 2
2013
Alkynes:
These are the hydrocarbons that contain a carbon-to-carbon triple bond.
The simplest example is ethyne.
The general rule for the molecular formula of alkynes =
Physical properties and uses:
Alkynes also follow the trends of alkanes and alkenes, in regards to dispersion forces, however due
to their triple bonds alkynes are much more reactive.
Because of this much higher reactivity, alkynes have very few practical uses.
The mostly used alkyne is ethyne, and its main use is in oxy-acetylene torches- where the energy
released by the combustion of ethyne with oxygen is used to cut steel and other metals.
Numbering Carbons
Naming compounds with multiple bonds is more complex than naming the alkanes as you need to
indicate where the multiple bond should go if there are two or more possible places for it to be.
Rule:
H3C
5
H
H
C
C
C
C
H
H
H
H
4
3
2
1
H
1-pentene
VCE Chemistry
Unit 3, Area of Study 2
2013
Drawing hydrocarbons
It is difficult to draw molecules to accurately represent their 3D structure. Using butane as an
example, each of its 4 carbons has 4 bonds. The expected tetrahedral arrangement exists around
each of these carbon atoms. As the complexity of the molecules increases, they are often drawn in
two dimensions for simplicity.
3D representation of butane
2D butane
Semi-structural diagrams
The molecular formula doesn’t tell us much about the structure of a molecule. This is why we draw
out the structural (valance) diagram of the molecule, but as the length and complexity of the
molecules increases it becomes too difficult to draw them. So a semi-structural diagram is used
instead.
Compound
Ethane
Butane
Nonane
Molecular
Formula
Semi-structural diagram
Structural Diagram
VCE Chemistry
Unit 3, Area of Study 2
2013
Structural isomers:
Butane has the molecular formula C4H10. There are two possible structures that can exist with this
molecular formula:
1.
2.
Molecules that have the same molecular formula but different structures are called structural
isomers. The names of structural isomers are different from one another. The first isomer is simply
called
but the second molecule actually goes by the name of
.
Naming side chains
Branched hydrocarbons are named by considering them as straight chains with side groups
attached. So in the case of the second butane molecule, it is seen as a propane molecule with a CH3
group attached to its second arm. The CH3 group is called a methyl group because its methane with
one less hydrogen (due to the join to the main chain).
As with our multiple bonds, if there is more than one position our side groups can be located along
the main chain; we need to number the carbons. Make sure to number starting from the end closest
to where the side groups come off.
Rules for naming
1.
2.
3.
4.
Identify the longest carbon chain
Number the carbons starting from the end closest to the branch
Name the side branches and main chain
Combine to write the full name
VCE Chemistry
Unit 3, Area of Study 2
2013
Can you name or draw the following molecules?
1. Name=
6. Name=
2. Draw: 2-methyl pentane
3. Name=
4. Name=
5. Name=
7. Draw: 3-ethyl2,2,dimethyloctane
8. Draw: 3-ethyloctane
VCE Chemistry
Unit 3, Area of Study 2
2013
Functional Groups
There are other atoms that bond to Carbon, which opens up a whole new range of carbon based
compounds.
DEFINITION: Functional Groups:
Many compounds can be produced by substituting a hydrogen atom in a hydrocarbon with different
functional groups.
Functional Groups are significant as they frequently dictate the chemical properties of molecules.
They can make the compounds more reactive and more polar than the standard hydrocarbons.
Common functional groups:
Name
Chloro
Hydroxyl (alcohol)
Carboxyl
Amino
Ester
Amide
Ether
Formula
VCE Chemistry
Unit 3, Area of Study 2
2013
The Chloroalkanes
It is possible to replace a hydrogen atom with a
chloroalkane.
The simplest chloroalkane is ______________________
Nomenclature:
atom in an alkane to form a
VCE Chemistry
Unit 3, Area of Study 2
2013
The alkanols (alcohols)
The simplest alkanol is
Is this molecule polar or non-polar?
Physical Properties of alkanols
The contrast between the properties of methane and methanol highlights how the functional group
dictates the properties of the molecule.
Property
State (at room temp.)
Solubility in H2O
Reactivity
Melting point
Boiling point
Methane
gas
insoluble
Less than methanol
Lower than methanol
-164.0°C
Methanol
liquid
soluble
More than methane
Higher than methane
65°C
Explanation: The difference in reactivity and solubility in water is due to the significant dipole in
methanol by the presence of the Oxygen. This dipole means that methanol is a
molecule. The state of methanol at room temp., and the higher melting and boiling points is due to
the Hydrogen which is bonded to the Oxygen, as it leads to
between molecules. These bonds are stronger than the dispersion forces between hydrocarbon
molecules.
Alkanols are a homologous series like the hydrocarbons, so they follow the trends of the boiling
point increasing with the size of the molecules increasing, due to strengthening dispersion forces,
but because of their functional group they also have hydrogen bonding between the molecules.
VCE Chemistry
Unit 3, Area of Study 2
2013
Uses


Methanol (CH3OH) is used as a solvent for many paints and varnishes. It is used for making
dyes, perfumes and many other chemicals.
Ethanol (CH3CH2OH) is the most commonly used alkanol in society; it is the basis for all
alcoholic beverages and is also a solvent for a wide range of inks and pharmaceuticals. The
use of ethanol blended with petrol (PLUS-Unleaded Petrol at United Petrol stations) is
becoming introduced into a lot of countries including Australia. Ethanol is used in
thermometers, spirit levels and it’s also a disinfectant. Methylated Spirits sold in
supermarkets and hardware stores as a cleaning product is mostly ethanol. Pure ethanol is
no longer used as there were issues with people drinking it. To deter would-be drinkers, a
small percentage of methanol is added as it has a foul taste and is toxic.
Nomenclature
Functional group
alkanol
Structure
-O-H
Suffix
-ol
Example
VCE Chemistry
Unit 3, Area of Study 2
2013
Carboxylic acids
The simplest carboxylic acid is
commonly named
.
Nomenclature:
Functional group
Structure
Carboxylic acid
O
Suffix
-oic acid
--C
O--H
Examples:
Ethanoic acid (acetic acid)
Palmitic acid
Physical properties of carboxylic acids
Although this group of carbon based molecules are acids, they are classified as
acids
as their reactions with metals and ionic compounds are usually less vigorous than reactions of acids
like hydrochloric acid (HCl).
Methanoic acid and ethanoic acid are soluble in water. The longer carboxylic molecules like palmitic
acid are waxy in appearance and relatively insoluble.
Uses



Methanoic acid (formic acid) is produced in the bodies of many ants. It’s what makes their
bites stingy and itchy!
Ethanoic acid (acetic acid) is more commonly known as vinegar.
Palmitic acid is manufactured in animals and is called a fatty acid. It can react with glycerol
to form a fat molecule or it can be reacted with sodium hydroxide to form soap.
VCE Chemistry
Unit 3, Area of Study 2
2013
Wine or vinegar???
When making wine it is essential that oxygen is kept from the fermenting fruit and this is because in
the presence of oxygen, bacteria and yeast create by fermentation ethanoic acid (vinegar) rather
than ethanol (alcohol).
A simplified version of the fermentation process is shown by these equations:
C6H12O6 (aq)
2C2H5OH (aq) + 2CO2 (g)
Glucose is fermented to ethanol and carbon dioxide.
In the presence of oxygen:
C6H12O6 (aq) + O2(g)
CH3COOH (aq) + H2O (l)
Glucose is fermented to ethanoic acid and water.
Amines