Hydrocarbons

Definition:

Hydrocarbons are organic compounds composed exclusively of carbon (C) and hydrogen (H) atoms. They form the backbone of organic chemistry and are classified into families based on their structure and bonding. These includes Alkane & Alkene.

Functional Group & Homologous Series

A functional group is the atom (or group of atoms) that gives an organic compound its characteristic properties. For example, the –OH group is responsible for most of the reactions of alcohols, while the rest of the molecule remains relatively unreactive (due to stable carbon bonds).

Alkanes: Simple Hydrocarbons

Key Features:

• No functional groups: Alkanes contain only single covalent bonds (C–C and C–H).
• General formula: Cn ​ H2n+2 ​ (e.g., methane CH4 ​, ethane C2H6​).
• Physical properties:
  • Non-polar molecules → insoluble in water.
  • Boiling points increase with chain length (stronger van der Waals forces).

• Chemical properties:

• • Unreactive due to strong C–C and C–H bonds (undergo combustion and substitution reactions only).

Example:

Methane (CH4) burns completely to form CO2 ​ and H2​O:

CH4  ​+  2O2  ​→  CO2​  +  2H2​O