AlkanesHydrocarbons which contain only single bonds are called alkanes. They are called saturated hydrocarbons because there is a hydrogen in every possible location. This gives them a general formula CnH2n+2. The first four alkanes are methane, ethane, propane, and butane with the Lewis symbols shown below. Past this number of carbons, the -ane suffix is retained and the number prefixes penta-, hexa-, hept-, oct-, non-, dec-, etc are used. Alkyl groups are used as substituents, and alkane derivatives have many applications. The alkanes are highly combustible and are valuable as clean fuels, burning to form water and carbon dioxide. Methane, ethane, propane and butane are gases and used directly as fuels. Alkanes from pentane up to around C17H36 are liquids. Gasoline is a mixture of alkanes from pentane up to about decane. Kerosene contains alkanes from about n=10 to n=16. Above n=17 they are solids at room temperature. Alkanes with higher values of n are found in diesel fuel, fuel oil, petroleum jelly, paraffin wax, motor oils, and for the highest values of n, asphalt. Alkane derivatives are used in hundreds of products such as plastics, paints, drugs, cosmetics, detergents, insedticides, etc., so the fossil fuel resource from which we obtain the alkanes is much too valuable to burn it all as a motor fuel.
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Index Carbon compounds Chemistry concepts Reference Shipman, Wilson, Todd Sec 15.2 | ||
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Alkyl GroupsIf a hydrogen is removed from an alkane, it can be used as a substituent functional group called an alkyl group. Alkyl groups are named by dropping the -ane suffix of the alkanes and adding the suffix -yl. Methane becomes a methyl group, ethane an ethyl group, etc.
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Index Carbon compounds Chemistry concepts Reference Shipman, Wilson, Todd Sec 15.2 | |||
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Alkane DerivativesAlmost an unlimited number of derivatives can be made from the alkanes since any hydrogen can be substituted by an alkyl group, a halide, etc. If the substituent is an alkyl group, then the derivative will have the same empirical formula as a larger alkane, so the empirical formula for an organic compound is insufficient to identify it. For example, if a methyl group is substituted for for one the hydrogens on the center carbon of a propane molecule, the result is called methylpropane. It has the same molecular formula as butane. These two molecules are said to be structural isomers.
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Index Carbon compounds Chemistry concepts Reference Shipman, Wilson, Todd Sec 15.2 | |||
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Hydrocarbon Naming ConventionBecause of the multitude of ways organic molecules may be formed, a set of rules for naming alkane derivatives is a part of the IUPAC system for organic compounds.
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Index Carbon compounds Chemistry concepts Reference Shipman, Wilson, Todd Sec 15.2 | ||
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