A hydrocarbon is a compound containing only carbon and hydrogen atoms. As is the case in all organic compounds, carbon atoms make up the skeleton of hydrocarbons. Hydrocarbons can be broken down into 4 categories: alkanes, alkenes, alkynes and arenes.
Alkanes are compounds containing only carbon carbon single bonds. Alkanes can be straight chained, branched or cyclic. Straight chained and branched alkanes are said to be saturated because the maximum number of hydrogen atoms bonded to the carbons making up the skeleton whereas cyclic alkanes such as cyclohexanol are said to be unsaturated'. A non cyclic alkane has the formula CnH2n+2' where the n after C denotes the number of carbons in the alkane and the n after H the number of hydrogen atoms. A cyclic alkane on the other hand has the formula CnH2n.
Alkenes are hydrocarbons containing 1 or more carbon carbon double bonds. Alkenes are less stable and more reactive than alkanes. The simplest alkene is ethene, more commonly
known as ethylene. Ethylene has the formula C2H4.
Like cycloalkanes, alkenes have the formula CnH2n. The molecular geometry of the alkene is trigonal planar.