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In organic chemistry, butyl is a four-carbon alkyl substituent with chemical formula -C4H9 . It is derived from either of the two isomers of the alkane called butane.
Nomenclature and examples
Each of the two isomers isomers of butane give rise to two isomers of monosubstituted butanes. Thus,n-butane can be substituted at either the terminal or an internal carbon atoms, giving rise to IUPAC name butyl derivatives.
- Examples
- n-butanol, also known as 1-butyl alcohol or 2-hydroxybutane: CH3CH2CH2CH2OH
- sec-butyl bromide, also known as 2-butyl bromide and 2-bromobutane: CH3CHBrCH2CH3
The second, branched isomer of butane, isobutane can also be substituted at either terminal methyl or internal carbon atoms, giving rise to "isobutyl" and "tertiary butyl" derivatives, respectively.
- Examples
- iso-butyl bromide, also known as 1-bromo-2-methylpropane: (CH3)2CHCH2Br
- tert-butyl bromide, , also known as 2-bromo-2-methylpropane: (CH3)3CBr
Butyl is the largest substituent for which trivial names are commonly used for all isomers.
Other examples
This is methyl tertiary butyl ether (an ether). The butyl group (which is tert-butyl, see below) is to the left of the oxygen atom; the rest of the molecule can be thought of as a methoxy group.
Etymology
As the number of carbons in an alkyl chain increases, butyl is the last to be named historically instead of through Greek numbers. The name is derived from butyric acid, a four carbon carboxylic acid found in rancid butter. The name of butyric acid, in turn, comes from Latin butyrum, "butter".
See also
"Butyl"