Isobutane, also known as i-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. An isomer of butane, it is a colorless, odorless gas. Isobutane is the simplest alkane with a tertiary carbon atom, and is used as a precursor molecule in the petrochemical industry, such as in the synthesis of isooctane.