Hydrocarbons

A hydrocarbon is a chemical compound consisting entirely of hydrogen and carbon covalently bonded with each other.   These compounds are "pure" hydrocarbons in contrast to hydrocarbons with bonded compounds or impurities of sulphur or nitrogen, which are "impure" hydrocarbons, such as petroleum and coal, which are imprecisely called hydrocarbons.   The majority of (impure) hydrocarbons found naturally occur in petroleum, natural gas, and coal formed by decomposed organic matter provides an abundance of carbon and hydrogen to form limitless chains of both atoms. ^{Wiki n.p.}

Hydrocarbons are grouped by the following types: ^{Wiki n.p.}

• Saturated hydrocarbons (alkanes) have single bonds of carbon and hydrogen.   Petroleum fuels and are either found as linear or branched forms of alkanes (paraffins).   The general formula for saturated hydrocarbons is C_nH_2n+2.   Examples are methane, CH₄ (marsh gas), ethane, C₂H₆, and propane, C₃H₈.
  
  
• Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms.   Those with one double bond are called alkenes with the formula C_nH_2n.   Examples are ethene, C₂H₄ (ethylene) and propene, C₃H₆ (propylene).  Those containing triple bonds are called alkynes with the formula C_nH_2n-2.   Examples are ethyne, C₂H₂ (acetylene) and propyne, C₃H₄ (methylacetylene).
  
  
• Cycloalkanes (naphthenes) are saturated hydrocarbons containing one or more carbon rings to which hydrogen atoms are attached.   The general formula for a saturated hydrocarbon containing one ring is C_nH_2n.   An example is cyclopropane, C₃H₆.
  
  
• Aromatic hydrocarbons (arenes), have one or more rings of 6 carbon atoms connected to each other by alternating single and double covalent bonds.   The simplest of these is benzene, C₆H₆.

Hydrocarbons can be gases (e.g. methane and propane), liquids (e.g. benzene), solids (e.g. paraffin wax and naphthalene) or polymers (e.g. polyethylene, polypropylene and polystyrene).   They occur in different isomers   For example, straight-chain alkanes are sometimes indicated by the prefix n- (for normal) where a non-linear isomer exists.   Simple branched alkanes often have a common name using a prefix like iso- and neo- to distinguish them from linear alkanes, for example n-pentane, isopentane, and neopentane. ^{Wiki n.p.}