Acyl group
In chemistry, an acyl group , acyl , acyl or alkanoyl is a functional group with the general structure R- (C = O) -, where R is an organyl radical ( alkyl , aryl or heteroaromatic group, etc.) or a Is hydrogen atom. The acyl group is formally derived from carboxylic acids , aldehydes or carboxylic acid chlorides in which an OH group , a hydrogen atom or a chloride has been substituted by a radical . The introduction of an acyl group into a molecule is called acylation . The functional group without reference to a radical R , i.e. - (C = O) -, is called the carbonyl group .
The acyl group with the undefined radical R is the generic term for the acetyl group ("Ac"), the formyl group , the benzoyl group and similar radicals. The acyl group should not match the acyloxy group - e.g. B. Acetyloxygruppe ("OAc") or Benzoyloxygruppe - be confused.
Acylium ion
An acylium ion is created when the unpaired electron is released, leaving a single positively charged cation (usually R – C + = O) behind. It is easily attackable by nucleophiles and therefore plays an important role as an intermediate in organic reactions , e.g. B. Friedel-Crafts acylation .
Among other things, it is also used for the esterification of organic acids substituted in the α-position in order to circumvent the steric hindrance .
It can be produced, for example, by dissolving carboxylic acids in concentrated sulfuric acid and then reacting this solution with alcohols .
Acyl radical
The general structural formula of the acyl radical, which only occurs as a (mostly) unstable intermediate state in a reaction mechanism, is given in the figure.
Examples
formal trunk connection | Remainder (R 1 ) | Remainder (R 2 ) | Acyl group |
Formic acid | -H | -OH | Formyl group |
acetic acid | -CH 3 | -OH | Acetyl group |
Propionic acid | -CH 2 CH 3 | -OH | Propionyl group |
Butyric acid | -CH 2 CH 2 CH 3 | -OH | Butyryl group |
Valeric acid | -CH 2 CH 2 CH 2 CH 3 | -OH | Valeryl group |
Benzoic acid | -C 6 H 5 | -OH | Benzoyl group |
amino acid | -OH | Acylamino group | |
Formyl chloride | -H | - Cl | Formyl group |
Acetyl chloride | -CH 3 | -Cl | Acetyl group |
Propionyl chloride | -CH 2 CH 3 | -Cl | Propionyl group |
Butyryl chloride | -CH 2 CH 2 CH 3 | -Cl | Butyryl group |
Valeryl chloride | -CH 2 CH 2 CH 2 CH 3 | -Cl | Valeryl group |
Benzoyl chloride | -C 6 H 5 | -Cl | Benzoyl group |
See also
Individual evidence
- ^ Brockhaus ABC chemistry. VEB FA Brockhaus Verlag, Leipzig 1965, p. 152.
- ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 1: A-Cl. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1979, ISBN 3-440-04511-0 , p. 61.
- ↑ Joachim Buddrus, Bernd Schmidt: Fundamentals of Organic Chemistry , 5th edition, de Gruyter Verlag, Berlin, 2015, p. 391, ISBN 978-3-11-030559-3 .