General Chemistry is a free introductory textbook on chemistry. See the editorial for more information....

Butane

Author: Hans Lohninger

Butane, C4H10, belongs to the group of alkanes. The term butane may refer to any of two structural isomers (n-butane and isobutane(1)), which differ considerably in their physical properties:

  n-butane isobutane
Chemical Structure
Density (g)
15 C, 1 atm
2.52 kg/m3 2.51 kg/m3
Density (l)
at boiling point, 1 atm
601.4 kg/m3 593.4 kg/m3
Melting point -138.4 C -159.6 C
Boiling point -0.5 C -11.7 C

Both isomers of butane are highly flammable, colorless, odorless,(2) easily liquefied gases. Butane gas is sold bottled as a fuel for cooking and camping, and as a fuel for cigarette lighters. Butane is also contained as a propellant in aerosol sprays. Isobutane is used as a refrigerant in household refrigerators and freezers and has largely replaced the ozone layer-depleting fluoro-chloro-hydrocarbons. Butane is extremely stable, has no corrosive action to metals, is slightly soluble in water (about 3.2 vol-% at 20C) and is readily soluble in ethanol, ethyl ether, or chloroform.

Isobutane (in mixture with argon) is used in Geiger counters, as a reagent gas in chemical ionization mass spectrometry, and as a quentching gas for the detector in X Ray Fluorescence (XRF).

Reactions

In oxygen-rich environments butane burns to form carbon dioxide and water vapor (with a flame temperature up to 1900 C):

2 C4H10 + 13 O2 8 CO2 + 10 H2O

n-Butane is the feedstock for the preparation of maleic anhydride:

2 CH3CH2CH2CH3 + 7 O2 2 C2H2(CO)2O + 8 H2O

n-Butane, like all hydrocarbons, undergoes free radical chlorination providing both 1-chloro- and 2-chlorobutanes. The chlorine radicals have to generated by UV radiation:

2 C4H10 + Cl2 2 C4H9Cl



(1) Please note that there are several chemical names for isobutane: trimethylmethane; 1,1-dimethylethane; 2-methylpropane; and i-butane.
(2) Small amounts of thiols are added to cooking and camping gas in order to be able to smell any gas leakage.



Last Update: 2011-02-20