Alkanes

Alkanes are the simplest family of organic compounds. They contain only carbon and hydrogen atoms joined by single covalent bonds, making them saturated hydrocarbons. Despite their apparent simplicity, alkanes are enormously important — they are the primary components of crude oil and natural gas, and their combustion provides most of the world's energy.

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Structure and Bonding

Alkanes have the general formula CₙH₂ₙ₊₂. Each carbon atom forms four single (sigma, σ) bonds arranged in a tetrahedral geometry with bond angles of approximately 109.5°. The bonds are formed by the overlap of sp³ hybridised orbitals on carbon with either another sp³ orbital (C-C bond) or the 1s orbital of hydrogen (C-H bond).

Because all bonds are sigma bonds with free rotation, alkanes adopt a variety of conformations. The carbon backbone is often drawn as a zigzag to represent the tetrahedral angles.

Sigma Bonds

A sigma bond is formed by the head-on overlap of atomic orbitals along the bond axis. This creates a cylindrically symmetrical region of electron density between the two nuclei. The free rotation around sigma bonds is why alkanes are flexible molecules.

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Physical Properties

Boiling Points