# Valeric acid

**Valeric acid**, systematically named **pentanoic acid**, is a straight-chain saturated fatty acid with five carbon atoms and the formula CH₃(CH₂)₃COOH (C₅H₁₀O₂). It is a colorless liquid with a penetrating, unpleasant rancid odor, and it occurs naturally in plants and fruits, serves as a flavoring and fragrance ingredient, and is produced industrially as a chemical intermediate.<sup>[1](https://webbook.nist.gov/cgi/cbook.cgi?ID=C109524&Mask=181)</sup><sup> • </sup><sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup>

| Key fact | Detail |
|---|---|
| Identity | Pentanoic acid; CAS 109-52-4; formula C₅H₁₀O₂; molecular weight 102.13 g/mol<sup>[1](https://webbook.nist.gov/cgi/cbook.cgi?ID=C109524&Mask=181)</sup> |
| Physical form | Colorless liquid; boiling point 186–187 °C; melting point −34.5 °C; relative density 0.94<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup> |
| Acidity | pKa 4.84 at 25 °C in water, typical of short-chain carboxylic acids<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> |
| Solubility | 2.4 g per 100 mL in water; miscible with alcohol and ether<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup><sup> • </sup><sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> |
| Flavoring status | FEMA number 3101, JECFA flavor number 90; JECFA (1997) found no safety concern at current levels of intake as a flavoring agent<sup>[4](https://www.fao.org/food/food-safety-quality/scientific-advice/jecfa/jecfa-flav/details/en/c/278/)</sup> |
| Pesticide use | Stenching agent or odorant at not more than 2% in pesticide formulations<sup>[5](https://www.epa.gov/ingredients-used-pesticide-products/inert-reassessment-document-valeric-acid-normal-cas-no-109-52-4)</sup> |
| Hazard | Corrosive to eyes, skin, and respiratory tract; combustible, with explosive limits of 1.6–7.6 vol% in air<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup> |

## Names and structure

The compound is a straight, saturated-chain alkyl carboxylic acid: a five-carbon chain terminating in a carboxyl group, written CH₃(CH₂)₃COOH.<sup>[6](https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/valeric-acid)</sup> The systematic IUPAC name is pentanoic acid, and the retained common name valeric acid appears alongside older synonyms including valerianic acid, propylacetic acid, and 1-butanecarboxylic acid.<sup>[1](https://webbook.nist.gov/cgi/cbook.cgi?ID=C109524&Mask=181)</sup> In the older trivial nomenclature for fatty acids, the acid group C₅ is called valeric and its acyl group valeryl.<sup>[7](https://www.acdlabs.com/iupac/nomenclature/79/r79_328.htm)</sup>

Its structural isomer isovaleric acid (3-methylbutanoic acid) shares the formula C₅H₁₀O₂ but has a branched chain; the two differ measurably in physical properties, with isovaleric acid boiling lower (176.5 °C versus 186.1 °C) and dissolving more readily in water.<sup>[8](https://one.oecd.org/document/ENV/JM/MONO%282018%2929/en/pdf)</sup>

## Physical and chemical properties

Valeric acid is a weak acid that dissociates in water with pKa 4.84 at 25 °C, so at neutral pH it exists largely as the valerate anion.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> It is a mobile liquid with a relative density of 0.94 (less dense than water), a vapor pressure of 0.02 kPa at 20 °C, and a relative vapor density of 3.52, meaning its vapor is heavier than air.<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup> Its octanol/water partition coefficient, log Pow 1.39, indicates moderate hydrophobicity, and an estimated bioconcentration factor of 7 suggests low potential to accumulate in aquatic organisms.<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup><sup> • </sup><sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> The estimated soil adsorption coefficient (Koc 140) places it in the high-mobility class in soil.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup>

The odor is distinctive and powerful: described as unpleasant and similar to butyric acid, with an odor threshold reported between 0.00062 and 0.0008 ppm.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> This potency underlies its use as an odorant.<sup>[5](https://www.epa.gov/ingredients-used-pesticide-products/inert-reassessment-document-valeric-acid-normal-cas-no-109-52-4)</sup>

## Natural occurrence and metabolism

Valeric acid has a role as a plant metabolite and has been reported in organisms including hops (*Humulus lupulus*) and the fungus *Penicillium herquei*; it is found in the essential oil of *Boronia anemonifolia*, in pineapple fruits, and in dalieb fruit pulp.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> It is also present in dairy and meat products.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup>

As a five-carbon member of the short-chain fatty acids (SCFAs), alongside acetate, propionate, butyrate, and hexanoate, valerate is one of the least studied SCFAs of the human gut metabolome.<sup>[9](https://pubmed.ncbi.nlm.nih.gov/38375842/)</sup><sup> • </sup><sup>[10](https://backend.orbit.dtu.dk/ws/files/360806053/Phd_Thesis_Chrysoula_Dimopoulou_Nov23.pdf)</sup> Bacterial valerate production occurs during anaerobic fermentation of sugars through a reverse beta-oxidation step, essentially a two-carbon chain elongation of propionate.<sup>[10](https://backend.orbit.dtu.dk/ws/files/360806053/Phd_Thesis_Chrysoula_Dimopoulou_Nov23.pdf)</sup><sup> • </sup><sup>[17](https://www.nature.com/articles/s41396-021-00893-2)</sup> In the mammalian body, ingested valeric acid is described as metabolized by splitting into acetic acid and pyruvic acid.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup>

## Uses

**Flavor and fragrance.** Valeric acid is a registered flavoring agent or adjuvant in US food regulation (21 CFR 172.515 and 173.315) and a listed fragrance ingredient on the IFRA transparency list.<sup>[11](https://hfpappexternal.fda.gov/scripts/fdcc/index.cfm?id=VALERICACID&set=FoodSubstances)</sup><sup> • </sup><sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> The Joint FAO/WHO Expert Committee on Food Additives evaluated it in 1997 and concluded there was no safety concern at current levels of intake when used as a flavoring agent.<sup>[4](https://www.fao.org/food/food-safety-quality/scientific-advice/jecfa/jecfa-flav/details/en/c/278/)</sup>

**Industrial intermediate.** The US EPA's inert reassessment document records its use as a stenching agent or odorant, limited to not more than 2% in pesticide formulations, and as an intermediate in the manufacture of flavors and perfumes, ester-type lubricants, plasticizers, and vinyl stabilizers.<sup>[5](https://www.epa.gov/ingredients-used-pesticide-products/inert-reassessment-document-valeric-acid-normal-cas-no-109-52-4)</sup> Other recorded uses include the manufacture of solvents, rodenticides, and fungicides, and application as a sugarcane ripening agent, the subject of a 1975 US patent.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup> Industrial synthesis is by oxidation of amyl alcohol or by fermentation processes.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup>

## Microbial production

Because odd-chain carboxylic acids are harder to obtain from conventional feedstocks than even-chain ones, several bioprocesses target valerate specifically. [Anaerobic fermentation](https://www.edgepedia.org/anaerobic-fermentation) of crude glycerol from biodiesel production in a 13.1-L [anaerobic filter](https://www.edgepedia.org/anaerobic-filter) produced valerate at 0.86–1.81 g COD L⁻¹ day⁻¹ as one of the two main carboxylates over a 114-day run.<sup>[12](https://agris.fao.org/search/en/providers/122535/records/65de2d544c5aef494fdaa10c)</sup> A process using *Megasphaera hexanoica* for carbon elongation achieved the highest reported production and productivity of valeric acid by anaerobic fermentation at the time, with extractive fed-batch culture roughly doubling productivity over previous results.<sup>[13](https://pmc.ncbi.nlm.nih.gov/articles/PMC6700076/)</sup> A synthetic co-culture of *Anaerotignum neopropionicum* and *Clostridium kluyveri* upgraded dilute ethanol streams to valerate and heptanoate, converting 96.6% of ethanol and producing valerate at 5.7 mmol L⁻¹ d⁻¹ in continuous operation.<sup>[14](https://pmc.ncbi.nlm.nih.gov/articles/PMC10189929/)</sup> Valeric acid from such streams can be upgraded to esters: a combined fermentation, electrochemistry, and catalysis route converted crude glycerol to valeric acid (5.3 ± 0.69 g/L as the dominant chain-elongation product) and then to ethyl valerate, a fruity flavor compound.<sup>[15](https://www.sciencedirect.com/science/article/abs/pii/S0960852419308041)</sup> Valeric acid also serves as a direct precursor to 3-hydroxyvalerate, a monomer of the bioplastic copolymer PHBV.<sup>[16](https://pmc.ncbi.nlm.nih.gov/articles/PMC12455835/)</sup>

## Investigated bioactivity

A narrative review of preclinical work identifies valeric acid as one of the potent histone deacetylase (HDAC) inhibitors among the SCFAs, a mechanism it shares with butyrate. In in-vitro and in-vivo studies it has shown anti-cancer, anti-diabetic, antihypertensive, anti-inflammatory, and immunomodulatory activity, and it affects molecular pathways relevant to Alzheimer's disease, [Parkinson's disease](https://www.edgepedia.org/parkinsons-disease), and epilepsy. The review's authors note that these findings must be tested under clinical conditions before any therapeutic use.<sup>[9](https://pubmed.ncbi.nlm.nih.gov/38375842/)</sup>

## Safety

Valeric acid is corrosive to the eyes, skin, and respiratory tract and corrosive on ingestion; inhalation causes burning sensation, cough, and sore throat, and eye contact can cause severe burns.<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup> It is combustible, with explosive vapor/air mixtures possible above 86 °C, a flash point of 86 °C (closed cup), an auto-ignition temperature of 400 °C, and explosive limits of 1.6–7.6 vol% in air.<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup> It is classified for transport as UN 3265, hazard class 8 (corrosive), and is harmful to aquatic organisms.<sup>[3](https://inchem.org/documents/icsc/icsc/eics0346.htm)</sup> Its low volatility from water ([Henry's law](https://www.edgepedia.org/henrys-law) constant 4.72 × 10⁻⁷ atm·m³/mole) means evaporation is not an important environmental fate process.<sup>[2](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)</sup>

## References

1. [Pentanoic acid, NIST Chemistry WebBook, SRD 69](https://webbook.nist.gov/cgi/cbook.cgi?ID=C109524&Mask=181)
2. [Pentanoic Acid, CID 7991, PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/Pentanoic-Acid)
3. [ICSC 0346: Valeric Acid, International Chemical Safety Cards (ILO/WHO/EC)](https://inchem.org/documents/icsc/icsc/eics0346.htm)
4. [JECFA flavouring evaluation: Valeric acid, FAO](https://www.fao.org/food/food-safety-quality/scientific-advice/jecfa/jecfa-flav/details/en/c/278/)
5. [Inert Reassessment Document for Valeric Acid, normal, CAS No. 109-52-4, US EPA](https://www.epa.gov/ingredients-used-pesticide-products/inert-reassessment-document-valeric-acid-normal-cas-no-109-52-4)
6. [Valeric Acid, ScienceDirect Topics overview](https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/valeric-acid)
7. [Table VI, IUPAC nomenclature of organic chemistry (1979), ACD/Labs](https://www.acdlabs.com/iupac/nomenclature/79/r79_328.htm)
8. [OECD, SIDS Initial Testing Proposal data table for short-chain fatty acids](https://one.oecd.org/document/ENV/JM/MONO%282018%2929/en/pdf)
9. [Molecular Targets of Valeric Acid: A Bioactive Natural Product for Endocrine, Metabolic, and Immunological Disorders, PubMed](https://pubmed.ncbi.nlm.nih.gov/38375842/)
10. [Dimopoulou, C. (2023). PhD thesis, Technical University of Denmark, section 1.4.2 Valeric acid](https://backend.orbit.dtu.dk/ws/files/360806053/Phd_Thesis_Chrysoula_Dimopoulou_Nov23.pdf)
11. [Substances Added to Food (formerly EAFUS): Valeric Acid, US FDA](https://hfpappexternal.fda.gov/scripts/fdcc/index.cfm?id=VALERICACID&set=FoodSubstances)
12. [Anaerobic production of valeric acid from crude glycerol via chain elongation, AGRIS](https://agris.fao.org/search/en/providers/122535/records/65de2d544c5aef494fdaa10c)
13. [An Efficient New Process for the Selective Production of Odd-Chain Carboxylic Acids Using Megasphaera hexanoica, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC6700076/)
14. [Upgrading dilute ethanol to odd-chain carboxylic acids by a synthetic co-culture of Anaerotignum neopropionicum and Clostridium kluyveri, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10189929/)
15. [Fruity flavors from waste: A novel process to upgrade crude glycerol to ethyl valerate, ScienceDirect](https://www.sciencedirect.com/science/article/abs/pii/S0960852419308041)
16. [Characterizing the growth of PHA-producing microorganisms on short-chain carboxylic acids, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC12455835/)
17. [The occurrence and ecology of microbial chain elongation of carboxylates in soils, The ISME Journal](https://www.nature.com/articles/s41396-021-00893-2)

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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Carbonyl and carboxyl chemistry › Carboxylic acids › Aliphatic monocarboxylic acids › Medium-chain saturated acids (C5–C11)*

*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*

*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*

License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license