Common name: A nomenclature system useful for naming simple organic molecules. It often fails for more complex molecules, in which case systematic or (better yet) IUPAC nomenclature is preferable.
The prefix “n-” (or normal) is used when all carbons form a continuous, unbranched (linear) chain. If a functional group (such as an alcohol) is present that functional group is on the end of the chain. Not to be confused with “nor”, which indicates a missing methyl group.
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|Common name: n-pentane IUPAC name: pentane||Common name: n-pentanol IUPAC name: 1-pentanol|
The prefix “iso” is used when all carbons except one form a continuous chain. This one carbon is part of an isopropyl group at the end of the chain.
|Common name: isopentane IUPAC name: 2-methylbutane||Common name: isopentyl alcohol IUPAC name: 3-methyl-1-butanol|
“Iso” can also indicate that the molecule is an constitutional isomer of another molecule with a common (or trivial) name.
|Common name: phthalic acid IUPAC name: benzene-1,2-dicarboxylic acid||Common name: isophthalic acid IUPAC name: benzene-1,3-dicarboxylic acid|
The prefix “neo” is used when all but two carbons form a continuous chain, and these two carbons are part of a terminal tert-butyl group.
|Common name: neopentane IUPAC name: 2,2-dimethylpropane||Common name: neopentyl alcohol IUPAC name: 2,2-dimethyl-1-propanol|
The prefix “sec” or “s” is used when the functional group is bonded to a secondary carbon. This prefix is only useful for a four-carbon chain. It is not applicable with a shorter chain, and it is often ambiguous when the chain has five or more carbons.