page_title: Alkane
section_title: Ecological relations
hierarchical_section_title: Alkane / Occurrence / Ecological relations
context_page_description: In organic chemistry, an alkane, or paraffin, is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carbon–carbon bonds are single. Alkanes have the general chemical formula CₙH₂ₙ₊₂. The alkanes range in complexity from the simplest case of methane, where n = 1, to arbitrarily large and complex molecules, like pentacontane or 6-ethyl-2-methyl-5- octane, an isomer of tetradecane.
  IUPAC defines alkanes as "acyclic branched or unbranched hydrocarbons having the general formula CₙH₂ₙ₊₂, and therefore consisting entirely of hydrogen atoms and saturated carbon atoms". However, some sources use the term to denote any saturated hydrocarbon, including those that are either monocyclic or polycyclic, despite their having a distinct general formula.
  In an alkane, each carbon atom is sp³-hybridized with 4 sigma bonds, and each hydrogen atom is joined to one of the carbon atoms. The longest series of linked carbon atoms in a molecule is known as its carbon skeleton or carbon backbone. The number of carbon atoms may be considered as the size of the alkane.
context_section_description: One example, in which both plant and animal alkanes play a role, is the ecological relationship between the sand bee (Andrena nigroaenea) and the early spider orchid (Ophrys sphegodes); the latter is dependent for pollination on the former. Sand bees use pheromones in order to identify a mate; in the case of A. nigroaenea, the females emit a mixture of tricosane (C₂₃H₄₈), pentacosane (C₂₅H₅₂) and heptacosane (C₂₇H₅₆) in the ratio 3:3:1, and males are attracted by specifically this odor. The orchid takes advantage of this mating arrangement to get the male bee to collect and disseminate its pollen; parts of its flower not only resemble the appearance of sand bees but also produce large quantities of the three alkanes in the same ratio as female sand bees. As a result, numerous males are lured to the blooms and attempt to copulate with their imaginary partner: although this endeavor is not crowned with success for the bee, it allows the orchid to transfer its pollen,
  which will be dispersed after the departure of the frustrated male to other blooms.
caption: Early spider orchid (Ophrys sphegodes)
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