Introduction
| Site: | Prefrontal Learning Center |
| Course: | (a) interpret, and use the nomenclature, general formulae and displayed formulae of the following classes of compound: |
| Book: | Introduction |
| Printed by: | Guest user |
| Date: | Thursday, 5 December 2024, 3:47 AM |
1. Functional Group
An atom or group of atoms common to a series of organic compounds that effectively determines the principal chemical properties of the series.
| Alkane |  |
| Alkene |  |
| Alkyne |  |
| Benzene ring |  |
| Alkyl halide |     |
| Alcohol |  |
| Aldehyde |  |
| Ketone |  |
| Carboxylic acid |  |
| Nitrile |  |
| Ester |  |
| Acyl chloride |  |
| Amine |  |
| Amide |  |
2. Homologous Series
A series of compounds with the same functional
group and same general formula (where each member differs from the
next in molecular formula by a \(CH_2\) increment.
Characteristics of homologous series:
The members of the series have the following characteristics:
(a) Contain the same functional group
- each member has similar chemical properties (undergo the same type of reactions)
(b) contain the same general molecular formula
- each member have different physical properties
3. Formulae
3.1. Molecular Formula and Structural Formula
Molecular formula
o Shows the actual number of each type of atom in a compound
o Does not show the way the atoms are joined together
Structural formula
o Shows the arrangement of atoms within the molecule
o It shows the sequence in which the atoms are bonded to each other
 Butane |
 2-Methylpropane |
|
| Molecular formula | C4H10 | C4H10 |
| Structural formula | CH3CH2CH2CH3 | CH(CH3)3 |
 Ethanol |
|
| Molecular formula | C2H6O |
| Structural formula | CH3CH2OH not C2H5OH |
3.2. Displayed formula (Full structural formula)
o Shows all the bonds in the molecule as individual lines.
o Each line represents a pair of shared electrons
o Sometimes, the displayed formula can also show the spatial
arrangement (3-dimensional) of the atoms in a molecule.
3.3. Skeletal Formula
o All the hydrogen atoms are removed from carbon chains
o Leaving just a carbon skeleton with functional groups attached to it
(i.e. the H atoms of carbon chains are not explicitly shown)
o In a skeletal structure
(i) there is a carbon atom at each junction between bonds in a chain and
at the end of each bond (unless there is another functional group —
such as the -OH group in the butan-2-ol example);
(it) there are hydrogen atoms (which are not drawn) attached to each
carbon atom to make the total number of bonds on each carbon up
to 4.
4. Carbon Bonding and Molecular Structures
- Carbon forms covalent bonds with up to four other atoms.
- Carbon molecules can have different structures:
- Straight chain
- Branched chain
- Ring
5. Polymer and Monomer
5.1. Carbon-Based Molecules and Polymerization
- Many carbon-based molecules consist of numerous small subunits bonded together.
- Monomers are the individual subunits.
- Polymers are composed of many monomers.