An organic compound with the general formula C_nH _{2n +2}. Alkanes are open-chain (aliphatic or noncyclic) hydrocarbons with no multiple bonds or functional groups. They consist of tetrahedral carbon atoms, up to 10⁵ carbons or more in length. The C-C σ bonds are formed from sp³ orbitals, and there is free rotation around the bond axis.