Butanes, C4H10. Both n- and isobutene occur in natural gas and petroleum gas, and they may be separated by fractional distillation under pressure. The butanes are used as a liquid fuel and for the preparation of various compounds.

n-Butane, b.p., -0.5oC, may be prepared by the Wurtz reaction :

2CH3CH2I + 2Na  →  CH3CH2CH2CH3 +2NaI

Isobutane, b.p., -10.2oC, may be prepared by treating t-butyl iodide with a zinc-copper couple in ethanol :

(CH3)3CO   e; H+   (CH3)3CH + HI