Which alkanes are used as fuels

Learning Objective describe the uses and sources of alkanes. Occurrence The most important sources for alkanes are oil and natural gas. Use of Alkanes Alkanes are important raw materials of the chemical industry and the principal constituent of gasoline and lubricating oils.

The following table provides a short survey of the different fractions of crude oil: C C 4 Propane and butane can be liquefied at fairly low pressures, and are used, for example, in the propane gas burner, or as propellants in aerosol sprays. Butane in used in cigarette lighters where the pressure at room temperature is about 2 bar. C 8 The alkanes from pentane to octane are highly volatile liquids and good solvents for nonpolar substances.

They are used as fuels in internal combustion engines. Since Alkanes are Saturated Hydrocarbons, they do not readily react. However, they can be made to react under certain conditions, so give useful products or energy output. Alkanes will react with Oxygen if they are given sufficient Activation Energy. This will result in a highly Exothermic reaction, producing Carbon Dioxide and Water , which makes Alkanes very useful as fuels. The reaction produces Branched Alkanes, and so is useful in improving Octane Number.

In general, for complete combustion:. Here are the equations for the complete combustion of propane, used in bottled gas:. Incomplete combustion occurs when the supply of air or oxygen is poor.

Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide. The names of all alkanes end with the suffix -ane e.

The chemical name of an alkane will include information about the number of carbons in the molecule such as in the example molecules above and their arrangement whether there are branches on the central carbon chain, for example. When two molecules have same molecular formula, but have the atoms arranged in a different way, they are called structural isomers. For example, both butane and 2-methylpropane shown below have the same molecular formula C 4 H 9 , but have the carbon atoms arranged differently.

Figure 4.