In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula -C4H9, derived from either of the two isomers of butane.

The isomer n-butane can connect either at one of the two terminal carbon atoms or at one of the two internal carbon atoms, giving rise to two "-butyl" groups:

  • Normal butyl or n-Butyl: CH3–CH2–CH2–CH2– (fully systematic name: butyl)
  • Secondary butyl or sec-Butyl: CH3–CH2–CH(CH3)– (fully systematic name: 1-methylpropyl)

The second, branched isomer of butane, isobutyl, can connect either at one of the three terminal carbons or at the central carbon, giving rise to another two groups:

  • Isobutyl: (CH3)2CH–CH2– (fully systematic name: 2-methylpropyl)
  • Tertiary butyl, tert-Butyl or t-butyl: (CH3)3C– (fully systematic name: 1,1-dimethylethyl)



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
Butyl-group-2D-skeletal.png n-butyl butyl butyl butan-1-yl
Isobutyl-group-2D-skeletal.png isobutyl isobutyl 2-methylpropyl 2-methylpropan-1-yl
Sec-butyl-group-2D-skeletal.png sec-butyl sec-butyl 1-methylpropyl butan-2-yl
Tert-butyl-group-2D-skeletal.png 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.

The butyl group's carbon that is connected to the rest (R) of the molecule is called the RI or R-prime carbon[citation needed]. The prefixes sec (from "secondary") and tert (from "tertiary") refer to the number of additional side chains connected to the first butyl carbon. The prefix "iso" (from "isomer") means "equal" while the prefix 'n-' stands for "normal".

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


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]

Tert-butyl effect

See also


  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 doi:10.1016/S0040-4039(00)87916-2

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Look at other dictionaries:

  • Butyl — Butyl; butyl; di·butyl; iso·butyl; tri·butyl; …   English syllables

  • butyl — [byo͞ot′ l] n. [< L butyrum, BUTTER + YL] 1. any of the four monovalent organic radicals (normal butyl, secondary butyl, tertiary butyl, isobutyl) having the same formula, C4H9, but differing in properties and structure ☆ 2. BUTYL RUBBER …   English World dictionary

  • Butyl... — Butyl...,   Bezeichnung der chemischen Nomenklatur für die vier von den Butanen abgeleiteten Gruppen mit der Summenformel C4H9; man unterscheidet n Butyl..., (CH2)3 CH3, sek. Butyl..., CH(CH3) C2H5, Isobutyl..., CH2 CH(CH3)2 und tert. Butyl...,… …   Universal-Lexikon

  • Butyl — Bu tyl, n. [L. butyrum butter + yl. See {Butter}.] (Chem.) A compound radical, regarded as butane, less one atom of hydrogen. [1913 Webster] …   The Collaborative International Dictionary of English

  • Butyl — (Valyl, Tetryl, Chem.), C8H9; das Radikal der B reihe, ist ein Kohlenwasserstoff, dem Äthyl analog, u. bildet sich bei der Zersetzung von valeriansaurem Kali durch den elektrischen Strom; es ist ein leichtes Öl von 0,69 spec. Gem., angenehm… …   Pierer's Universal-Lexikon

  • Butȳl — C4H9, einwertige Atomgruppe, die für die Butylverbindungen charakteristisch ist …   Meyers Großes Konversations-Lexikon

  • Butyl- — Bu|tyl [↑ But u. ↑ yl ] Symbol: Bu; systematisches Syn.: Butanyl : Präfixe für die Gruppen C4H9 , d. h. für H3C C2H4 CH2 (Butyl , früher: n Butyl ), H5C2 C̍H CH3 (sec Butyl ; Symbol: s Bu; systematisch: Butan 2 yl u. 1 Methylpropyl ) …   Universal-Lexikon

  • Butyl — Strukturformel Allgemeines Name Butan Andere Namen n Butan R 600 …   Deutsch Wikipedia

  • butyl — /byooh til, byooht l/, adj. Chem. containing a butyl group. [1865 70; BUT(YRIC) + YL] * * * …   Universalium

  • butyl — bu·tyl || bjuːtɪl adj. containing the butyl group (Chemistry) …   English contemporary dictionary