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Carbon Chemistry

Carbon can form four bonds. As a result, carbon forms a variety of structures and is therefore the
building block to life on this planet. Hydrocarbon means the compound contains hydrogen and
carbon. Carbon can form:
• straight chains

As a result carbon forms many three dimensional compounds.

Naming of the Alkalies, Alkenes, Alkynes and Alcohol Families
To name alkanes, alkene and alkynes we need to recognise that these carbon families form a
homologous series. Also the number of carbon atoms present is given a prefix specific to that number:

PrefixNumber of carbon atoms
Meth- 1
Eth-2
Prop-3
But-4
Pent-5
Hex-6
Hept-7
Oct-8
Non-9
Dec-10

Alkanes
The general formula for naming alkanes is:
CnH2n+2
where n represents the prefix number. For example, for the prefix prop, n=3:
C3  H(2×3) +2
= C3H8
To name this alkane add -ane to the prefix, i.e. propane.

Alkenes
The general formula for naming alkenes is:
CnH2n
where n represents the prefix number. For example, for the prefix but, n=4:

C4H2×4
= C4H8

To name this alkene add -ane to the prefix, i.e. butene.

Alkynes
The general formula for naming alkynes is:
CnH2n-2
where n represents the prefix number. For example, for the prefix pent, n=5:

C5H(2×5) – 2
C5H8

To name this alkene add -yne to the prefix, i.e. pentyne.

Alcohols
The naming of alcohols follow the same pattern as the other homologous series. It is important to note that the prefixes are different and the alcohols end in -ol.

Prefix Alkyl Group
Methyl-CH3
Ethyl-C2H5
Propyl-C3H7
Butyl-C4H9
Pentyl-C5H11
Hexyl-C6H13
Heptyl-C7H15
Octyl-C8H17
Nonyl-C9H19
Decyl-C10H21

To name an alcohol:

  1. Select the prefix.
  2. Add the -el, with alcohol. e.g. Methyl alcohol or Methanol
    Ethyl alcohol or Ethanol Chemical and Structural Formula of Alkanes, Alkenes, Alkynes and Alcohols

    Homologous Series Naming:
  3. These carbon compounds form with bonds between carbon and hydrogen

Alkanes:
These carbon compounds form with single bonds
between carbon and hydrogen.

Name FormulaNumber of
C atoms
Structure
MethaneCH41
Ethanec2H62
PropaneC3H83

Alkenes:
Like the alkanes these form with carbon and hydrogen but they contain double bonds.
Methene with 1 C atom does not exist as a stable molecule

Name FormulaNumber of
C atoms
Structure
EtheneC2H22
PropeneC3H83
ButeneC4H84

Aklynes:
This series forms a carbon to carbon triple bond. They also contain hydrogen.
Methyne with 1 C atom does not exist as a stable molecule

Alkanes:
These carbon compounds form with single bonds
between carbon and hydrogen.

Name FormulaNumber of
C atoms
Structure
Ethynec2H22
PropyneC3H43
ButyneC4H64

The alcohols are a carbon-hydrogen chain but also contain an -OH group.
This OH group is the alcohol group.

120
Name
FormulaNumber of C atomsStructure
MethanolCH3OH1
EthanolC2H5OH2
PropanolC3H7OH3
Alcohols:

Chemical and Physical Properties of Alkanes, Alkenes, Alkynes and Alcohols
The physical properties of alkanes, alkenes, alkynes and alcohols are summarised in the following table:

Homologous
Series
Properties
AlkanesInsoluble in water.
Less dense than water
AlkenesInsoluble in water.
Boiling and melting points increase with size of the molecule.
Smaller molecules are gases and the larger are solids.
AlkynesInsoluble in water.
Boiling and melting points increase with size of the molecule.
Smaller molecules are gases and the larger are solids.
AlcoholsAlcohols have a neutral pH.
Alcohols are soluble in water. Larger molecules are less soluble.

Alkanes generally burn very well in air and as a consequence are used as fuels. The burning of alkanes
can generate considerable heat.

Combustion Reactions:

Plentiful Supply of air:
Ethane + Oxygen Carbon dioxide Water
2C2H6 + 702 ---> 4C02 + H2O

Limited supply of air:
Ethane + Oxygen - - Carbon monoxide Water
2C2H6 + 502 ---> 4C02 + H2O
Very limited supply of air:
Ethane -I- Oxygen - Carbon monoxide Water
2C2H6 + 302 ---> 4C + 6H2O

NB: The carbon appears as black soot.

Aikenes
The burning of alkenes produces a sooty, more orangy-yellow flame than the alkanes. Alkenes can also
bum both incompletely and completely.
e.g. Complete combustion:

Ethene • Oxygen •-•+- Carbon dioxide ± Water
C2H4 +302 —–> 2CO2 + 2H2O

Triple Bond between the two C atoms.

The yellow-orange flame if apparent is due to the presence of carbon particles in the flame.

Alkynes
The most well known alkyne is acetylene (ethyne). This is used in oxy-acetylene welders to produce
intense heat. The energy from the heat is produced when the alkynes C-C triple bond breaks.
e.g.
Ethyne + Oxygen —> Carbon dioxide + Water
2C2H2 + 502 —> 4CO2 + 2H20 (and Intense Heat)

Alcohols
Alcohols are combustible. The most relevant example of the combustion of alcohols is ethanol.
Petrol can produce carbon monoxide and carbon, whereas ethanol is clean burning to carbon
dioxide and water.

Ethanol + Oxygen —-> Carbon dioxide + Water
C2H5OH + 302 —–> 2CO2 + 3H20

The reaction produces heat energy. This makes it suitable as a bio-fuel alternative to fossil fuels such as petrol.

Plastics from Alkenes

Plastics from Alkenes
Alkenes are the building blocks for plastics. Each individual alkene molecule’s double bond can break
and link to another molecule, This process is called polymerisation.

NB: then represents a repeating chain of n units.

One alkene molecule is called a monomer. The long chain of monomers is called a polymer, i.e. mono
means one, and poly means many.

The reaction with ethene is with n number of ethyne molecules:

When many chains are layered alongside each other a plastic sheet fors

Carbon chains form plastic layers

This type of reaction with different monomers as starting units forms the basis of all our plastics.