Butane is the general name for two related alkane hydrocarbon with the molecular formula C4H10: n-butane (1-butane) and iso-butane (i-butane, isobutane, 2-methylpropane). Butanes are highly flammable, colorless, easily liquefied gases that are used as fuel for cigarette lighters and portable stoves and as propellants in aerosol sprays.
n-Butane has the following chemical structure:
H H H H
| | | |
H - C - C - C - C - H
| | | |
H H H H
Butane exists as two isomers:
n-butane is a fully hydrogenated linear chain of four carbon atoms: CH3CH2CH2CH3. Its boiling point is −0.6 °C and its melting point is −138.3 °C.
iso-butane, or isobutane, has the formula CH3CH(CH3)2, and the systematic name 2-methylpropane. Its boiling point is −11.7 °C and its melting point is −159.6 °C.
Recent concerns with depletion of the ozone layer by freon gases have led to increased use of isobutane as a gas for refrigeration systems, especially in domestic refrigerators and freezers. When used as a refrigerant, isobutane is also known as R600a .
Alkanes are unreactive, as their C-C and C-H bonds are very strong. They do not react with acids, alkalis, metals, or oxidising agents. It may seem surprising, but petrol (octane) has no reaction with concentrated sulphuric acid, sodium metal or potassium manganate.
It burns to form carbon dioxide and steam:
butane + oxygen -> carbon dioxide + steam
Burning camping gas forms carbon dioxide and steam (plentiful supply of air) and also carbon (soot) and carbon monoxide (in a limited supply of air).
Common uses for Butane gas are as a bottled supply for cooking and camping, when referred to as calor gas. It is also widely used as a petrol component and a feedstock for the production of base petrochemicals in steam cracking.
Last updated: 07-30-2005 18:16:33