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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.
Each of the two isomers of butane give rise to two isomers of the butyl substituent. Thus, ''n''-butane can connect at either the terminal or an internal carbon atoms, giving rise to "''n''-butyl" and "''sec''-butyl" substituents.

★ '''n''-butyl' group; CH₃CH₂CH₂CH₂–, (fully systematic name "butyl")

★ '''sec''-butyl' group; CH₃CH₂(CH₃)CH–, (fully systematic name "1-methylpropyl")
The second, branched isomer of butane, isobutane can also connect either terminal methyl or internal carbon atoms, giving rise to "isobutyl" and "tertiary butyl" substituents, respectively.

★ 'isobutyl' group; (CH₃)₂CHCH₂–, (fully systematic name "2-methylpropyl")

★ '''tert''-butyl' group; (CH₃)₃C–, (fully systematic name "1,1-dimethylethyl")

Contents

Nomenclature

Some examples

Etymology

Tert-butyl effect

See also

References

Nomenclature

According to IUPAC nomenclature, "isobutyl", "''sec''-butyl", and "''tert''-butyl" are all retained trivial names.

skeletal formula	common name	IUPAC name	systematic name	alternate notation
	''n''-butyl	butyl	butyl	butan-1-yl
	isobutyl	isobutyl	2-methylpropyl	2-methylpropan-1-yl
	''sec''-butyl	''sec''-butyl	1-methylpropyl	butan-2-yl
	''tert''-butyl	''tert''-butyl	1,1-dimethylethyl	2-methylpropan-2-yl

Butyl is the largest substituent for which trivial names are commonly used for all isomers.

Some examples

The following are the four isomers of "butyl acetate":

butyl acetate	isobutyl acetate	sec-butyl acetate	tert-butyl acetate
''n''-butyl acetate	isobutyl acetate	''sec''-butyl acetate	''tert''-butyl acetate

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".

Tert-butyl effect

The tert-butyl substituent is very bulky and used in chemistry for kinetic stabilisation together with other bulky groups such as the related trimethylsilyl group. The effect that the t-butyl group exerts on the progress of a chemical reaction is called the 'tert-butyl effect'.
This effect is illustrated in the Diels-Alder reaction below where the tert-butyl substituent causes a reaction rate acceleration by a factor of 240 compared to hydrogen as the substituent.^[1]

See also

★ methyl

★ ethyl

★ propyl

★ pentyl / amyl

References

1. ''Factors affecting ease of ring formation. The effect of anchoring substitution on the rate of an intramolecular diels-alder reaction with furan-diene'' Serge Cauwberghs and Pierre J. De Clercq B. Tinant and J. P. Declercq Tetrahedron Letters Volume 29, Issue 20 , '1988', Pages 2493-2496