General Definitions

  • Organic Chemistry is the study of compounds of Carbon.
  • Hydrocarbons are carbons consisting of carbon and hydrogen only, bonded together covalently. They are used as fuel and feedstock for the chemical industry. Main Sources: Coal, Methane, Crude Oil.
  • Structural isomers are compounds that have the same molecular formula but different structural formulas.

Homologous Series is defined as:

  1. A series of compounds of uniform chemical type.
  2. Showing gradations in physical properties.
  3. Having a general formula for its members.
  4. Each member having similar chemical properties & preparation.
  5. Each member differing from the previous by a CH2 unit.

Aliphatic Compounds

Definition: An aliphatic compound is a hydrocarbon that consists of straight and branched chains of carbon atom, or rings of carbon atoms that do not contain a benzene ring.


  • General Formula: CnH2n+2
  • All saturated compounds. i.e Single bonds only


  • General Formula: CnH2n
  • All unsaturated compounds. i.e Contains double bonds


  • General Formula: CnH2n-2
  • Contains a triple bond

Aromatic Compounds

Definition: Aromatic compounds are compounds that contain a benzene ring structure in their molecules.

Important aromatic compounds:

  • MethylBenzene: C7H8
  • EthylBenzene C8H10


  • Liquid at room temperature
  • Insoluble in water
  • Dissolves in cyclohexane


There are two main methods for manufacturing hydrogen.

  1. Steam reforming of Natural Gas. This involves reacting steam with methane in the presence of a suitable catalyst:
    CH4 + H2O –> 3H2 + CO
  2. Electrolysis of Water. This involves passing an electric current through water: H2O –> H2 + 1/2 O2