Nomenclature
For
nomenclature of alkenes in IUPAC system, the longest chain of carbon atoms
containing the double bond is selected. Numbering of the chain is done from the
end which is nearer to the double bond.
The
suffix ‘ene’ replaces ‘ane’
of alkanes. It may be remembered that first member of alkene series is: CH2
(replacing n by 1 in CnH2n) known as methene but has
a very short life. As already mentioned, first stable member of alkene series
is C2H4 known as ethylene (common) or ethene
(IUPAC).
For
example, a two-carbon alkene is called ethene and a three-carbon alkene is
called propene. Ethene
also is frequently called by its common name: ethylene.
IUPAC
names of a few members of alkenes are given below:
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