Chapter 8 – Compounds of
Carbon
Week 4, Lesson 1
Why is Carbon Important?
• Carbon compounds make up over 90% of all
chemical compounds.
• They also form the basis of living systems.
• The study of carbon compounds is now called
‘Organic Chemistry’.
• In its many millions of organic compounds,
carbon is associated with hydrogen and
commonly oxygen, sulfur, nitrogen and
chlorine.
Why is Carbon Important? Cont…
• If 200 atoms were selected from the human body you
would find that 126 atoms were hydrogen, 51 atoms
were oxygen, 19 atoms were carbon, 3 atoms were
nitrogen and 1 atom of all other elements.
• These proportions are the same when we are born and
are maintained throughout life.
• Food that we eat also contain these elements.
• Protein, CHO’s and fats all contain carbon, hydrogen and
oxygen.
• Proteins are also a source of nitrogen and sulfur and
some contain other elements.
• Vitamins and minerals are distributed across a number
of food and introduce traces of other elements that we
need in our diets.
How does Carbon form so many
Compounds?
• The electronic configuration of carbon is
1s22s22p2. It can form a variety of different
compounds because:
– Each carbon atom has four valence electrons, all
available for bonding with other atoms
– A carbon atom can form strong covalent bonds
with other carbon atoms
– Bonds between carbon atoms can be single or
multiple.
Natural Gas
• Is a widely used, clean-burning, efficient and
economical fuel. It is vital for out everyday
lives.
• Natural gas is used for cooking and heating in
homes.
• It is also used in the industry for gas-fired kilns
and gas-fired furnaces.
• Some vehicles are powered by compressed
natural gas.
Natural Gas cont…
• Natural gas is often found with deposits of petroleum.
• It is thought that natural gas and petroleum are formed by the
chemical degradation of organic matter from the remains of
land and aquatic plants lying in swampy water.
• With a lack of oxygen and, over time, with the build-up of
heat and pressure, this material is converted into many
different compounds of carbon and hydrogen.
• These compounds, which include molecules of different sizes,
are known as hydrocarbons.
• Natural gas is a mixture of many different compounds, mostly
small hydrocarbon molecules along with some other
chemicals.
Hydrocarbons
• Hydrocarbons can be classified into several
series or families.
• The simplest hydrocarbon, CH4, methane is
the first in the alkane series.
Alkanes
• Compounds which consist of carbon and
hydrogen only.
• They only contain single bonds.
• Each compound in the alkane series differs by
CH2.
• This series is known as a homologous series.
• Members of the same homologous series tend
to have very similar chemical properties.
• Alkanes have the molecular formula CnH2n+2.
Alkanes cont…
Representing Alkane Molecules
• In structural formulas, the focus is on the location of the
atoms relative to one another in the molecule as well as the
number and location of chemical bonds.
• Lone pairs are not included in a structural formula.
• In each of the alkanes;
– Each carbon atom forms a single bond to four other atoms.
– Each hydrogen atom forms a single bond to one carbon
atom
– The four atoms bonded to each carbon atom are arranged
in a tetrahedral manner, around the carbon.
Isomers
• When it comes to drawing the structural
formula for C4H10, there are two possible
arrangements that satisfy these requirements.
Isomers cont…
• You can see in the first structure the four carbon atoms are bonded in a
continuous chain. The overall molecule is linear and such are sometimes
called straight-chain molecules.
• The second structure has the four carbon atoms bonded in a branched
chain.
• These two molecules are known as isomers – as the have the same
molecular formula but a different arrangement of the atoms.
• Structural isomers have similar chemical properties but differ in some
physical properties such as melting and boiling temperature.
Hydrocarbons
• In the alkanes there are single covalent bonds
between the carbons.
• Because of these bonds, alkanes are said to be
saturated.
• Because there are only single bonded carbons,
each C atom is saturated by hydrogen atoms.
Alkenes
• Ethene is the molecular formula C2H4 and is
the first member of the alkenes.
• In alkenes there is one double bond between
two carbon atoms.
• Alkenes, like alkanes, differ by CH2, and as
such are also known as homologous series.
• They have the general formula of CnH2n.
Alkenes cont…
FORMULA
NAME
C2H4
Ethene
C3H6
Propene
C4H8
Butene
C5H10
Pentene
C6H12
Hexene
C7H14
Heptene
C8H16
Octene
C9H18
Nonene
C10H20
Decene
Representing Alkene Molecules
• Like the alkane, butene has more than one isomer.
• The four carbon atoms and eight hydrogen atoms can be
arranged in more than one way with each carbon atom
forming four bonds and each hydrogen atom forming one
• Two of the isomers are straight chained, with the only
difference being the position of the double bond.
• The third isomer has a branched chain.
• The alkenes are classified as unsaturated hydrocarbons.
• The double bond between two of the carbon atoms
mean that alkenes contain less hydrogen that the
maximum amount possible.
Butene
Semistructural Formulas
• When we want the structural formula to be
summarised without indicating the 3D
arrangement of the atoms we use the
semistructural formula.
• In a semistructural formula, the carbon atoms
and the attached hydrogen atoms, are listed in
the order in which they appear in the
structural formula.
• Single bonds are not indicated, but any double
or triple bonds are shown.
Semistructural Formulas
CH3CH2CH2CH3
CH2=CHCH3
Week 4, Lesson 2
Naming Carbon Compounds
• A naming system was developed in 1960’s to
make it easier to name and recognise carbon
compounds.
• This naming system was developed by the
International Union of Pure and Applied
Chemistry (IUPAC).
• This system provides a set of rules by which
chemists can derive the systematic name for a
given compound.
The Prefixes
The first part of the name refers to the number of carbons in one
molecule (in straight chain hydrocarbons).
Number of Carbon Atoms
1
2
3
4
5
6
7
8
9
10
Prefix
MethEthPropButPentHexHeptOctNonDec-
Straight Chain Hydrocarbons
• The end of the name is dependent on the type
of carbon bonds.
• The name of the the hydrocarbon ends in:
– ane: if all carbon-carbon bonds are single bonds
– ene: if one of the carbon-carbon bonds is a double
bond
– yne: if one of the carbon-carbon bonds is a triple
bond.
Unsaturated Compounds
• To name unsaturated straight chain
hydrocarbons:
1. Number the carbon atoms in the chain, starting at
the end that will give the first carbon involved in a
double bond, the smallest number possible.
2. Distinguish which prefix and ending should be used.
3. Name the hydrocarbon with the prefix, then the
number of the carbon that has the double bond,
then the ending.
Example…
• But-1-ene
• But-2-ene
Branched Hydrocarbons
• An alkyl group often forms a branch in a
branched-chain hydrocarbon.
• An alkyl group is an alkane molecule less one
hydrogen atom and is named based on the
alkane it is derived from. Eg –CH3 is a methyl
group.
Naming Branched Hydrocarbons
• Systematic naming requires us to:
– Identify the longest chain of carbon atoms in the
molecule.
– Identify the side group that forms the branch in
the chain
– Number the carbon atoms from one of the ends
of the longest chain so that the side group is
attached to the carbon with the smallest number
possible.