1
INTRODUCTION TO ORGANIC CHEMISTRY
Different ways of showing the SAME molecule
1. MOLECULAR formula: the formula that shows the ACTUAL number of
atoms of each element in the molecule.
E.g. C3H8
2. DISPLAYED formula: this formula shows every atom and every bond in
the molecule.
一 is a single bond
＝is a double bond
☰ is a triple bond
E.g. the displayed formula of propane is..
3. STRUCTURAL formula: this formula shows the unique arrangement of
atoms in a molecule in a simplified form, without showing all the bonds.
Each carbon atom is written separately, with the atoms or groups that
are attached to it.
E.g. structural formula of propane: CH3CH2CH2CH3
4. SKELETAL formula: in skeletal notation, the carbon atoms are not drawn
at all! Instead, straight lines represent single carbon bonds and carbon
atoms are assumed to be the points where the bonds meet. Neither
hydrogen atoms nor C-H bonds are
drawn.
E.g. skeletal formula for propane is..
, 2
The skeletal formula for propENE is…
The double line represents the double
carbon bond!
5. EMPIRICAL formula: a formula that shows the simplest whole number
ratio of the atoms of each element present in a compound.
E.g.
Drawing more difficult formula
Examples:
1. Draw the displayed formula of this compound when given its structural
formula.
CH3CH(CH3)CH2CH3
★ The brackets in the structural formula mean that it's coming off
the MAIN chain.
The displayed formula for this compound would be:
2.
, 3
3.
Draw the skeletal formula of this compound^:
This shows that there are 4 carbon atoms in the compound, and that the
5th carbon atom is branching off from the SECOND carbon atom in a
methyl group (CH3).
Organic nomenclature
Organic nomenclature is a set of rules devised to create systematic names for
organic compounds.
RULES OF ORGANIC NOMENCLATURE (IUPAC):
1. Find the LONGEST carbon chain in the compound.
2. Identify if there are any side chains present e.g. a methyl group (CH3)
3. Count the POSITION of the carbon atom from which the sidechain is
bonded to (must be the LOWEST number!)
4. The substituents (sidechains) are written in alphabetical order, followed
by the base chain.
5. A comma goes between two numbers, and hyphens go between a letter
and a number.
INTRODUCTION TO ORGANIC CHEMISTRY
Different ways of showing the SAME molecule
1. MOLECULAR formula: the formula that shows the ACTUAL number of
atoms of each element in the molecule.
E.g. C3H8
2. DISPLAYED formula: this formula shows every atom and every bond in
the molecule.
一 is a single bond
＝is a double bond
☰ is a triple bond
E.g. the displayed formula of propane is..
3. STRUCTURAL formula: this formula shows the unique arrangement of
atoms in a molecule in a simplified form, without showing all the bonds.
Each carbon atom is written separately, with the atoms or groups that
are attached to it.
E.g. structural formula of propane: CH3CH2CH2CH3
4. SKELETAL formula: in skeletal notation, the carbon atoms are not drawn
at all! Instead, straight lines represent single carbon bonds and carbon
atoms are assumed to be the points where the bonds meet. Neither
hydrogen atoms nor C-H bonds are
drawn.
E.g. skeletal formula for propane is..
, 2
The skeletal formula for propENE is…
The double line represents the double
carbon bond!
5. EMPIRICAL formula: a formula that shows the simplest whole number
ratio of the atoms of each element present in a compound.
E.g.
Drawing more difficult formula
Examples:
1. Draw the displayed formula of this compound when given its structural
formula.
CH3CH(CH3)CH2CH3
★ The brackets in the structural formula mean that it's coming off
the MAIN chain.
The displayed formula for this compound would be:
2.
, 3
3.
Draw the skeletal formula of this compound^:
This shows that there are 4 carbon atoms in the compound, and that the
5th carbon atom is branching off from the SECOND carbon atom in a
methyl group (CH3).
Organic nomenclature
Organic nomenclature is a set of rules devised to create systematic names for
organic compounds.
RULES OF ORGANIC NOMENCLATURE (IUPAC):
1. Find the LONGEST carbon chain in the compound.
2. Identify if there are any side chains present e.g. a methyl group (CH3)
3. Count the POSITION of the carbon atom from which the sidechain is
bonded to (must be the LOWEST number!)
4. The substituents (sidechains) are written in alphabetical order, followed
by the base chain.
5. A comma goes between two numbers, and hyphens go between a letter
and a number.
