Alkane molecules. Molecular models of three types of alkane (paraffin) molecule. They are, from left: butane (C4H10), isobutane (2-methylpropane, C4H10) and 2,2-dimethylpropane (C5H12). Carbon atoms are black and hydrogen atoms are white. Butane and isobutane both occur in natural gas and are produced during the cracking of petroleum. Both are used in refrigeration. Butane is also used for cooking and heating, for example in camping gas bottles. 2,2-dimethylpropane is a raw material in the production of isobutylene, which is used to make synthetic butyl rubber.