Pentanoic acids

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The pentanoic acids (also valeric acids ) are a group of constitutionally isomeric saturated monocarboxylic acids with five carbon atoms. They have the general molecular formula C 5 H 10 O 2 and a molar mass of 102.13 g / mol. They can be thought of as being composed of a butyl and a carboxy group  (-COOH); this means that all four variants ( structural isomers ) are represented, some of which differ significantly in their properties. The 2-methyl butyric acid also comes in two enantiomeric forms - the ( R ) form and the ( S ) form - in which additionally differ from one another in their physiological properties. Thus there are a total of five isomeric pentanoic acids.

Pentanoic acids
Surname Valeric acid Isovaleric acid 2-methylbutyric acid Pivalic acid
other names n -pentanoic acid iso- pentanoic acid sec -pentanoic acid tert -pentanoic acid
Structural formula Valeric acid skeleton Isovaleric acid (R) - (-) - 2-methylbutyric acid
( R ) - (-) - 2-methylbutyric acid 		(S) - (+) - 2-methylbutyric acid
( S ) - (+) - 2-methylbutyric acid 		Pivalic Acid Structural Formulas V.1.svg
CAS number 109-52-4 503-74-2 32231-50-8 1730-91-2 75-98-9
PubChem 7991 10430 8314 ( racemate , CAS number: 116-53-0) 6417
Melting point -33.6 ° C to -34 ° C <−30 ° C <−80 ° C (racemate) 35-36 ° C
boiling point 184-187 ° C 175-177 ° C 177 ° C (racemate) 163-164 ° C
Water solubility 40 g l −1 at 20 ° C 25 g l −1 at 20 ° C 20 g l −1 at 20 ° C (racemate) 25 g l −1 at 20 ° C
odor unpleasant unpleasant pervasive cheesy, sweaty pleasantly sweet, fruity unpleasant

Occurrence and use

Cocoa beans contain ( R ) -2-methylbutyric acid.
Apples contain ( S ) -2-methylbutyric acid - the picture shows a James Grieve apple

Valeric acid occurs naturally in wood vinegar , isovaleric acid in essential oils , tea leaves and valerian roots , ( R ) -2-methylbutyric acid in cocoa beans, ( S ) -2-methylbutyric acid in many fruits such as apples and apricots. Pivalic acid is a synthetic substance. The natural pentanoic acids are used as esters for flavorings , isovaleric acid also for the production of sedatives and hypnotics . Due to the steric hindrance of the substance, pivalic acid is important in the medical field as a protected ester that is only slowly broken down and absorbed (e.g. as testosterone pivalate ).

nomenclature

According to the IUPAC - Nomenclature compounds having a are acyclic pentane -Struktureinheit as unbranched main chain in which the terminal methyl group by a carboxy group is replaced referred to as pentanoic acid. A permissible but not preferred alternative name is butanecarboxylic acid.

In addition to the parent compound valeric acid, there are therefore numerous other alkyl-substituted monocarboxylic acids without additional functional groups or unsaturated substituents, which are referred to as petanic acids but are not isomeric to valeric acid.

Examples:

Individual evidence

  1. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 96th edition. (Internet version :), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-438.
  2. ^ Jürgen Falbe, Manfred Regitz: RÖMPP Lexikon Chemie. Volume 6: T – Z , 10th edition, Thieme, 1999, ISBN 3-13-735110-3 .
  3. ↑ a b Entry on 3-methylbutyric acid in the GESTIS substance database of the IFA , accessed on February 22, 2017(JavaScript required) .
  4. ↑ a b David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-342. No. 7074.
  5. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 97th edition. (Internet version: 2016), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-220.
  6. ^ Jürgen Falbe, Manfred Regitz: RÖMPP Lexikon Chemie. Volume 2: Cm-G , 10th edition, Thieme, 1997, ISBN 3-13-734710-6 , p. 991.
  7. ↑ Entry on valeric acid in the GESTIS substance database of the IFA , accessed on February 22, 2017(JavaScript required) .
  8. ↑ a b Entry on 2,2-dimethylpropionic acid in the GESTIS substance database of the IFA , accessed on February 22, 2017(JavaScript required) .
  9. ↑ a b Entry on pentanoic acid. In: Römpp Online . Georg Thieme Verlag, accessed on July 6, 2013.
  10. ↑ a b Entry on 3-methylbutyric acid. In: Römpp Online . Georg Thieme Verlag, accessed on July 6, 2013.
  11. ↑ Entry on 2-methylbutyric acid in the GESTIS substance database of the IFA , accessed on February 22, 2017(JavaScript required) .
  12. ↑ Entry on Versatic acids. In: Römpp Online . Georg Thieme Verlag, accessed on July 6, 2013.
  13. ^ A b H. Günzler: Analytiker-Taschenbuch 21 . Springer DE, 2000, ISBN 3-540-66232-4 , pp. 39 ( limited preview in Google Book search).
  14. ↑ "How does apple juice get its aroma?"
  15. ^ Karl AD Swift: Current Topics in Flavors and Fragrances: Towards a New Millennium of Discovery . Springer, 1999, ISBN 0-7514-0490-X , p. 52 ( limited preview in Google Book search).
  16. ^ Carboxylic Acids and their Derivatives. Simple Carboxylic Acids Rule C-401. In: IUPAC Nomenclature of Organic Chemistry. Advanced Chemistry Development, Inc., Accessed August 13, 2020 .