Organic compounds
What is organic chemistry
- Organic chemistry is the scientific study of the structure, properties, and reactions of organic compounds. Organic compounds are those which contain carbon
- For conventional reasons metal carbonates, carbon dioxide and carbon monoxide are not included in organic compounds
What is a hydrocarbon?
- A compound that contains only hydrogen and carbon atoms
Representing Organic Molecules
- Organic compounds can be represented in a number of ways:
- Empirical Formulae
- Molecular Formulae
- General Formulae
- Structural Formulae
- Condensed Structural Formulae
Empirical formulae
The empirical formula shows the simplest possible ratio of the atoms in a molecule
- For example: Hydrogen peroxide is H2O2 but the empirical formula is HO
Molecular formulae
- The molecular formula shows the actual number of atoms in a molecule
Molecular formula of butane
The molecular formula shows the actual number of atoms in a molecule
General formula
- The general formula shows a ratio of atoms in a family of compounds in terms of 'n' where n is a varying whole number
- For example, the general formula of a molecule that belong to the alkane family is CnH2n+2
Displayed formulae
- The displayed formulae shows the spatial arrangement of all the atoms and bonds in a molecule
- This is also known as the graphical formula
Displayed formula of 2-methylbutane
The displayed formula must show every bond in the molecule
Structural formulae
- In a structural formulae enough information is shown to make the structure clear, but most of the actual covalent bonds are omitted
- Only important bonds are always shown, such as double and triple bonds
- Identical groups can be bracketed together
- Side groups are also shown using brackets
Structural formula of pentane
The structural formula of pentane makes it clear that there are five carbon atoms in the chain and no other functional groups
Examiner Tip
For defining a hydrocarbon, you must specify that they are compounds which contain hydrogen and carbon atoms only, no other element is present.You may not be asked to name branched chain organic compounds but you will come across them. It is useful to know that the numbers in the names of these compounds refer to the position of the side chains with respect to the main chain.