2-Methylbutanoic acid

Last updated
2-Methylbutanoic acid
(R)-2-Methyl Butyric Acid-Structural Formula V.1.svg
(S)-2-Methyl Butyric Acid-Structural Formula V.1.svg
Names
Preferred IUPAC name
2-Methylbutanoic acid
Other names
2-Methylbutyric acid
Methylethylacetic acid
Identifiers
3D model (JSmol)
1098537
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.769 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • R/S:204-145-2
KEGG
PubChem CID
UNII
  • R/S:InChI=1S/C5H10O2/c1-3-4(2)5(6)7/h4H,3H2,1-2H3,(H,6,7)
    Key: WLAMNBDJUVNPJU-UHFFFAOYSA-N
  • R:Key: WLAMNBDJUVNPJU-SCSAIBSYSA-N
  • S:Key: WLAMNBDJUVNPJU-BYPYZUCNSA-N
  • R/S:CCC(C)C(=O)O
Properties [1]
C5H10O2
AppearanceClear colorless liquid
Density 0.94 g/cm3 (20 °C)
Melting point −90 °C (−130 °F; 183 K)
Boiling point 176 °C (349 °F; 449 K)
log P 1.18
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg
Danger
H302, H312, H314
P260, P264, P270, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P322, P330, P363, P405, P501
Flash point 83 °C (181 °F; 356 K) [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

2-Methylbutanoic acid, also known as 2-methylbutyric acid is a branched-chain alkyl carboxylic acid with the chemical formula CH3CH2CH(CH3)CO2H, classified as a short-chain fatty acid. It exists in two enantiomeric forms, (R)- and (S)-2-methylbutanoic acid. (R)-2-methylbutanoic acid occurs naturally in cocoa beans and (S)-2-methylbutanoic occurs in many fruits such as apples and apricots, [2] [3] as well as in the scent of the orchid Luisia curtisii . [4]

Contents

History

2-Methylbutanoic acid is a minor constituent of Angelica archangelica and the perennial flowering plant valerian ( Valeriana officinalis ), where it co-occurs with valeric acid and isovaleric acid. [5] The dried root of this plant has been used medicinally since antiquity. [6] The chemical identity of all three compounds was first investigated in the 19th century by oxidation of the components of fusel alcohol, which includes the five-carbon amyl alcohols. Among the products isolated was a compound which gave a (+) rotation in polarised light, indicating it to be the (2S) isomer. [7]

Preparation

Racemic 2-methylbutanoic acid can readily be prepared by a Grignard reaction using 2-chlorobutane and carbon dioxide. [8] It was the target of the first enantioselective synthesis in 1904 when the German chemist W. Marckwald heated ethyl(methyl)malonic acid with the chiral base brucine and obtained an optically active product mixture. [9] Either enantiomer of 2-methylbutanoic acid can now be obtained by asymmetric hydrogenation of tiglic acid using a ruthenium-BINAP catalyst. [10]

Reactions

The compound and its enantiomers react as typical carboxylic acids: they can form amide, ester, anhydride, and chloride derivatives. [11] The acid chloride is commonly used as the intermediate to obtain the others.

Uses

Racemic 2-methylbutanoic acid is a slightly volatile, colorless liquid with a pungent cheesy odor. [12] The smell differs significantly between the two enantiomeric forms. (S)-2-Methylbutyric acid has a pleasantly sweet, fruity odor [13] while (R)-2-methylbutanoic acid has a pervasive, cheesy, sweaty odor. [14] The main use of the materials, and their esters, is therefore as flavours and food additives. [2] [15] The compounds' safety in this application was reviewed by an FAO and WHO panel, who concluded that there were no concerns at the likely levels of intake. [16]

Biology

Since 2-methylbutanoic acid and its esters are natural components of many foods, they are present in mammals including humans. [17] [18]

See also

Related Research Articles

<span class="mw-page-title-main">Stereoisomerism</span> When molecules have the same atoms and bond structure but differ in 3D orientation

In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer.

In chemistry, a racemic mixture or racemate, is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates.

<span class="mw-page-title-main">Enantiomer</span> Stereoisomers which are non-superposable mirror images of each other

In chemistry, an enantiomer – also called optical isomer, antipode, or optical antipode – is one of two stereoisomers that are non-superposable onto their own mirror image. Enantiomers are much like one's right and left hands, when looking at the same face, they cannot be superposed onto each other. No amount of reorientation in three spatial dimensions will allow the four unique groups on the chiral carbon to line up exactly. The number of stereoisomers a molecule has can be determined by the number of chiral carbons it has. Stereoisomers include both enantiomers and diastereomers.

<span class="mw-page-title-main">Isobutyric acid</span> Carboxylic acid with chemical formula (CH3)2CHCO2H

Isobutyric acid, also known as 2-methylpropanoic acid or isobutanoic acid, is a carboxylic acid with structural formula (CH3)2CHCOOH. It is an isomer of n-butyric acid. It is classified as a short-chain fatty acid. Deprotonation or esterification gives derivatives called isobutyrates.

<span class="mw-page-title-main">Chirality (chemistry)</span> Geometric property of some molecules and ions

In chemistry, a molecule or ion is called chiral if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality. The terms are derived from Ancient Greek χείρ (cheir) 'hand'; which is the canonical example of an object with this property.

<span class="mw-page-title-main">Linalool</span> Chemical compound with a floral aroma

Linalool refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent. A colorless oil, linalool is classified as an acyclic monoterpenoid. In plants, it is a metabolite, a volatile oil component, an antimicrobial agent, and an aroma compound. Linalool has uses in manufacturing of soaps, fragrances, food additives as flavors, household products, and insecticides. Esters of linalool are referred to as linalyl, e.g. linalyl pyrophosphate, an isomer of geranyl pyrophosphate.

<span class="mw-page-title-main">Valeric acid</span> Carboxylic acid – CH3(CH2)3COOH

Valeric acid or pentanoic acid is a straight-chain alkyl carboxylic acid with the chemical formula CH3(CH2)3COOH. Like other low-molecular-weight carboxylic acids, it has an unpleasant odor. It is found in the perennial flowering plant Valeriana officinalis, from which it gets its name. Its primary use is in the synthesis of its esters. Salts and esters of valeric acid are known as valerates or pentanoates. Volatile esters of valeric acid tend to have pleasant odors and are used in perfumes and cosmetics. Several, including ethyl valerate and pentyl valerate are used as food additives because of their fruity flavors.

<span class="mw-page-title-main">Enantioselective synthesis</span> Chemical reaction(s) which favor one chiral isomer over another

Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric products in unequal amounts."

<span class="mw-page-title-main">Chiral auxiliary</span> Stereogenic group placed on a molecule to encourage stereoselectivity in reactions

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<span class="mw-page-title-main">3-Methylbutanoic acid</span> Carboxylic acid with chemical formula (CH3)2CHCH2CO2H CH3CH2

3-Methylbutanoic acid, also known as β-methylbutyric acid or more commonly isovaleric acid, is a branched-chain alkyl carboxylic acid with the chemical formula (CH3)2CHCH2CO2H. It is classified as a short-chain fatty acid. Like other low-molecular-weight carboxylic acids, it has an unpleasant odor. The compound occurs naturally and can be found in many foods, such as cheese, soy milk, and apple juice.

<span class="mw-page-title-main">2-Ethylhexanol</span> Chemical compound

2-Ethylhexanol (abbreviated 2-EH) is an organic compound with formula C8H18O. It is a branched, eight-carbon chiral alcohol. It is a colorless liquid that is poorly soluble in water but soluble in most organic solvents. It is produced on a large scale (>2,000,000,000 kg/y) for use in numerous applications such as solvents, flavors, and fragrances and especially as a precursor for production of other chemicals such as emollients and plasticizers. It is encountered in plants, fruits, and wines. The odor has been reported as "heavy, earthy, and slightly floral" for the R enantiomer and "a light, sweet floral fragrance" for the S enantiomer.

<span class="mw-page-title-main">Ethyl lactate</span> Chemical compound

Ethyl lactate, also known as lactic acid ethyl ester, is the organic compound with the formula CH3CH(OH)CO2CH2CH3. It is the ethyl ester of lactic acid. A colorless liquid, it is a chiral ester. Being naturally derived, it is readily available as a single enantiomer. It is commonly used as a solvent. This compound is considered biodegradable and can be used as a water-rinsible degreaser. Ethyl lactate is found naturally in small quantities in a wide variety of foods including wine, chicken, and various fruits. The odor of ethyl lactate when dilute is mild, buttery, creamy, with hints of fruit and coconut.

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Pivalic acid, also known as neovaleric acid, is a carboxylic acid with a molecular formula of (CH3)3CCO2H. This colourless, odiferous organic compound is solid at room temperature. A common abbreviation for the pivalyl or pivaloyl group (t-BuC(O)) is Piv and for pivalic acid (t-BuC(O)OH) is PivOH. It is an isomer of valeric acid, the other two isomers of it are 2-Methylbutanoic acid and 3-Methylbutanoic acid.

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Decenoic acid is any mono-carboxylic acid with an unbranched chain of ten carbons connected by eight single bonds and one double bond; that is, a chemical compound with formula HO(O=)C–(CH
2)
k–CH=CH–(CH
2)
7-k–H, where k is between 0 and 7 inclusive.

<span class="mw-page-title-main">4-Methylcyclohexanemethanol</span> Chemical compound

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References

  1. 1 2 Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  2. 1 2 Rettinger, Klaus; Burschka, Christian; Scheeben, Peter; Fuchs, Heike; Mosandl, Armin (1991). "Chiral 2-alkylbranched acids, esters and alcohols. Preparation and stereospecific flavour evaluation" (PDF). Tetrahedron: Asymmetry. 2 (10): 965–968. doi:10.1016/S0957-4166(00)86137-6.
  3. ↑ Karl A. D. Swift (1999). Current Topics in Flavours and Fragrances: Towards a New Millennium of Discovery. Springer. p. 52. ISBN   0-7514-0490-X.
  4. ↑ Genera Orchidacearum Vol 6, Ed. Alec M. Pridgeon et al., p. 207 (LUISIA).
  5. ↑ Chisholm, Hugh, ed. (1911). "Valeric Acid"  . Encyclopædia Britannica . Vol. 27 (11th ed.). Cambridge University Press. p. 859.
  6. ↑ Eadie, Mervyn J. (November 2004). "Could Valerian Have Been the First Anticonvulsant?". Epilepsia. 45 (11): 1338–1343. doi: 10.1111/j.0013-9580.2004.27904.x . PMID   15509234.
  7. ↑ Pedler, Alexander (1868). "On the isomeric forms of valeric acid". Journal of the Chemical Society. 21: 74–76. doi:10.1039/JS8682100074.
  8. ↑ "dl-Methylethylacetic acid". Organic Syntheses. 5: 75. 1925. doi: 10.15227/orgsyn.005.0075 .
  9. ↑ Marckwald, W (1904). "Ueber asymmetrische Synthese". Berichte der Deutschen Chemischen Gesellschaft. 37: 349–354. doi:10.1002/cber.19040370165.
  10. ↑ Matteoli, Ugo; Beghetto, Valentina; Scrivanti, Alberto (1999). "Asymmetric hydrogenation by an in situ prepared (S)-BINAP–Ru(II) catalytic system". Journal of Molecular Catalysis A: Chemical. 140 (2): 131–137. doi:10.1016/S1381-1169(98)00235-0.
  11. ↑ Jenkins, P. R. (1985). "Carboxylic acids and derivatives". General and Synthetic Methods. Vol. 7. pp. 96–160. doi:10.1039/9781847556196-00096. ISBN   978-0-85186-884-4.
  12. ↑ "2-Methylbutyric acid". The Good Scents Company. Retrieved 2020-09-30.
  13. ↑ "(S)-2-methylbutyric acid". The Good Scents Company. Retrieved 2020-09-30.
  14. ↑ "(R)-2-methylbutyric acid". The Good Scents Company. Retrieved 2020-09-30.
  15. ↑ Mariaca, Raul G.; Imhof, Miroslava I.; Bosset, J. O. (2001). "Occurrence of volatile chiral compounds in dairy products, especially cheese - A review". European Food Research and Technology. 212 (3): 253–261. doi:10.1007/s002170000250. S2CID   96864200.
  16. ↑ FAO/WHO Expert Committee on food additives (1998). "Safety evaluation of certain food additives and contaminants" . Retrieved 2020-09-30.
  17. ↑ "Metabocard for (S)-2-Methylbutanoic acid". Human Metabolome Database. 2019-07-23. Retrieved 2020-09-30.
  18. ↑ "Metabocard for Methyl (S)-2-Methylbutanoate". Human Metabolome Database. 2019-07-23. Retrieved 2020-09-30.

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