9701 · 29.1
Formulas, functional groups and the naming of organic compounds
Organic chemistry uses a universal language called IUPAC nomenclature to name the vast number of carbon-based compounds. This system relies on identifying the longest carbon chain, key functional groups, and their positions.
Need to know
What you need to know
- **Displayed Formula:** Shows every single atom and every single bond in the molecule. It is unambiguous but can be cumbersome for large molecules.
- **Structural Formula:** Shows the arrangement of atoms in a molecule in a condensed, unambiguous way, often on a single line (e.g., CH₃CH(OH)CH₂CH₃ for butan-2-ol).
- **Skeletal Formula:** A simplified representation where the carbon backbone is drawn as a series of lines. Carbon atoms are assumed to be at each junction and at the end of each line. Hydrogen atoms attached to carbons are not shown, as it's assumed each carbon has enough hydrogens to make a total of four bonds.
- **General Formula:** Represents a whole homologous series, like CₙH₂ₙ for alkenes.
Explanation
Decoding Organic Molecules
- Start with IUPAC basics: find the longest carbon chain, give the main functional group the lowest number, and add the correct suffix like -ol, -al, or -oic acid.
- Represent molecules in different ways: a displayed formula shows every atom and bond, a skeletal formula shows just the carbon backbone, and a general formula describes a whole family.
- Classify alcohols and amines as primary, secondary, or tertiary by counting how many carbon atoms are directly bonded to the carbon bearing the -OH or -NH₂ group.
- Learn to spot more complex functional groups which are derivatives of carboxylic acids: esters (–COOR), amides (–CONH₂), acyl chlorides (–COCl), and also nitriles (–C≡N).