A hydrocarbon is a compound that contains only the two elements carbon and hydrogen.
A hydrocarbon is a compound made up of only two elements: carbon and hydrogen. Malay: hidrokarbon · Chinese: 碳氢化合物.
Because carbon can bond to four other atoms and to itself in chains and rings, hydrocarbons range from the simplest gas, methane, to the long molecules in candle wax. The alkanes and the alkenes are the two hydrocarbon homologous series you meet in this chapter: alkanes are saturated, with single bonds only, while alkenes are unsaturated, carrying at least one carbon–carbon double bond. Most of our fuels, petrol, diesel, natural gas, are mixtures of hydrocarbons obtained from petroleum, and all of them burn in oxygen to release energy. Hydrocarbons are also the main source of the small molecules from which plastics are made, so the term reaches well beyond the laboratory bench.
Example. Ethane (C₂H₆) and ethene (C₂H₄) are both hydrocarbons because each contains carbon and hydrogen and nothing else. Ethane is a saturated alkane; ethene is an unsaturated alkene. Both burn in a plentiful supply of oxygen to give carbon dioxide and water, and both can be traced back to crude oil.
Confusion to avoid. Not every carbon compound is a hydrocarbon. As soon as a third element appears the compound stops being a hydrocarbon: ethanol (C₂H₅OH) contains oxygen, so it is a carbon compound but not a hydrocarbon, and the same is true of every alcohol, carboxylic acid and ester. Keep the definition strict, only carbon and hydrogen, nothing else.
Hydrocarbons are where the chapter begins, because the alkanes and alkenes set the pattern of naming, general formulae and reactions that the oxygen-containing families later build on, so a clear grasp of the term pays off across the whole of SPM Chemistry.
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