Nomenclature and General Principles: Classification of Hydrocarbons (For CBSE, ICSE, IAS, NET, NRA 2022)

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Classification of Hydrocarbons

Open-Chain or Aliphatic Compounds

  • This class includes all hydrocarbons (saturated and unsaturated) and their derivatives which have open-chain structures.
  • Saturated hydrocarbons are those which contain single bonds between all carbon atoms.



Unsaturated compounds contain a double or a triple bond between two carbon atoms.

For example,

Open Chain or Aliphatic Compounds

Closed-Chain or Cyclic Compounds

These compounds have at least one ring (cyclic) system.

These are divided into two sub-classes:

  • Homocyclic
  • Heterocyclic

Homocyclic or carbocyclic are those in which the ring is formed by carbon atoms only.

Homocyclic (carbocyclic) compounds can be divided into two groups:

Alicyclic Compound

This group includes saturated and unsaturated cyclic hydrocarbons which resembles with the aliphatic hydrocarbons in properties.

For example,

Alicyclic Compounds

Aromatic Compounds

  • The group of Homocyclic compounds having special set of properties are called aromatic compounds.
  • They have characteristic smell or aroma and called aromatic.
  • These include aromatic hydrocarbons and their derivatives. e. g.
Aromatic Compounds

Heterocyclic compounds contain one or more atom (usually , or atom) other than the carbon atoms. e. g.

Aromatic Compounds
Aromatic Compounds

Nomenclature of Organic Compounds

IUPAC (International Union of Pure and Applied Chemistry) defines naming the organic compounds throughout the world.

Homologous Series

  • A series of compounds in which the molecular formula of a compound differ from those of its neighbouring compounds by the group is known as Homologous Series.
  • For example, homologous series of open chain saturated hydrocarbons is known as alkanes.
  • Open chain unsaturated hydrocarbons form two series of compounds namely alkenes and alkynes, which contains carbon-carbon double bond and triple bond, respectively.

Homologous Series of Hydrocarbons

Homologous Series of Hydrocarbons

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