IGCSE CHEMISTRY – TOPIC 4
ORGANIC CHEMISTRY
a) INTRODUCTION
• HYDROCARBON – compounds that contain ONLY hydrogen and
carbon atoms (e.g. methane, ethane, propane)
• EMPIRICAL FOMULA – simplest whole number ratio of atoms of each
element in the compound (e.g. for C2H6the empirical formula is CH3)
• MOLECULAR FORMULA – a chemical formula that shows the total
number and kinds of atoms in a molecule (e.g. for C2H6the molecular
formula is C2H6)
• GENERAL FORMULA – a formula that states the ratio of atoms of
each element in the formula of every compound in a particular
homologous series (e.g. for C2H6 the general formula is CnH2n+1)
• STRUCTURAL FORMULA – condensed representation that shows the
symbols for each atom in a compound, with
straight lines joining them to represent the
covalent bonds
• DISPLAYED FORMULA – the symbols for each
atom in a compound, with straight lines
joining them to show covalent bonds
• HOMOLOGOUS SERIES – a series of organic compounds that have
similar properties – same general formula, same functional group,
similar chemical reaction.
• FUNCTIONAL GROUP – a group of atoms bonded in a specific
arrangement that controls the property of the homologous series
• ISOMERISM – compounds that have the same molecular formula but
different structural formulae
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, NAMING COMPOUNDS, DISPLAYED AND STRUCTURAL FORMULAE:
• The first part of the name comes from the number of carbon atoms
in the hydrocarbon and the second part comes from the functional
group present:
FIRST PART OF THE NAME SEOND PART OF THE NAME
Name No. Carbon Atoms Name Family
Meth… 1 …ane Alkane
Eth…. 2 …ene Alkene
Prop… 3 …anol Alcohol
But… 4 …anoic Acid Carboxylic Acid
Pent… 5 …amine Anime
Hex… 6
• There are other rules, which include:
o When there is MORE THAN 1 CARBON, a functional group can
be located specially. Each carbon is numbered and these
numbers describe where the functional group is
o When 2 functional groups are present di- is used as a prefix to
the second part of the name
o Branching also needs to be considered, the carbon atoms with
the branches by their number
o When the location of functional groups and branches needs to
be described the functional group takes precedence so the
functional group has the lowest number
• When drawing structural and displayed formula, simple use straight
lines and write every single compound/element/atom
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ORGANIC CHEMISTRY
a) INTRODUCTION
• HYDROCARBON – compounds that contain ONLY hydrogen and
carbon atoms (e.g. methane, ethane, propane)
• EMPIRICAL FOMULA – simplest whole number ratio of atoms of each
element in the compound (e.g. for C2H6the empirical formula is CH3)
• MOLECULAR FORMULA – a chemical formula that shows the total
number and kinds of atoms in a molecule (e.g. for C2H6the molecular
formula is C2H6)
• GENERAL FORMULA – a formula that states the ratio of atoms of
each element in the formula of every compound in a particular
homologous series (e.g. for C2H6 the general formula is CnH2n+1)
• STRUCTURAL FORMULA – condensed representation that shows the
symbols for each atom in a compound, with
straight lines joining them to represent the
covalent bonds
• DISPLAYED FORMULA – the symbols for each
atom in a compound, with straight lines
joining them to show covalent bonds
• HOMOLOGOUS SERIES – a series of organic compounds that have
similar properties – same general formula, same functional group,
similar chemical reaction.
• FUNCTIONAL GROUP – a group of atoms bonded in a specific
arrangement that controls the property of the homologous series
• ISOMERISM – compounds that have the same molecular formula but
different structural formulae
63
, NAMING COMPOUNDS, DISPLAYED AND STRUCTURAL FORMULAE:
• The first part of the name comes from the number of carbon atoms
in the hydrocarbon and the second part comes from the functional
group present:
FIRST PART OF THE NAME SEOND PART OF THE NAME
Name No. Carbon Atoms Name Family
Meth… 1 …ane Alkane
Eth…. 2 …ene Alkene
Prop… 3 …anol Alcohol
But… 4 …anoic Acid Carboxylic Acid
Pent… 5 …amine Anime
Hex… 6
• There are other rules, which include:
o When there is MORE THAN 1 CARBON, a functional group can
be located specially. Each carbon is numbered and these
numbers describe where the functional group is
o When 2 functional groups are present di- is used as a prefix to
the second part of the name
o Branching also needs to be considered, the carbon atoms with
the branches by their number
o When the location of functional groups and branches needs to
be described the functional group takes precedence so the
functional group has the lowest number
• When drawing structural and displayed formula, simple use straight
lines and write every single compound/element/atom
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