Valeric acid or pentanoic acid is a straight-chain alkylcarboxylic acid with the chemical formulaCH3(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.
History
Valeric acid is a minor constituent of the perennial flowering plant valerian (Valeriana officinalis), from which it gets its name.[3] The dried root of this plant has been used medicinally since antiquity.[4] The related isovaleric acid shares its unpleasant odor and their chemical identity was investigated by oxidation of the components of fusel alcohol, which includes the five-carbon amyl alcohols.[5]
Valeric acid is one volatile component in swine manure. Other components include other carboxylic acids, skatole, trimethyl amine, and isovaleric acid.[6] It is also a flavor component in some foods.[7]
H2 + CO + CH3CH2CH=CH2 → CH3CH2CH2CH2CHO → valeric acid
It can also be produced from biomass-derived sugars via levulinic acid and this alternative has received considerable attention as a way to produce biofuels.[9][10]
Reactions
Valeric acid reacts as a typical carboxylic acid: it can form amide, ester, anhydride, and chloride derivatives.[11] The latter, valeryl chloride is commonly used as the intermediate to obtain the others.
Uses
Valeric acid occurs naturally in some foods but is also used as a food additive.[12] Its safety in this application was reviewed by an FAO and WHO panel, who concluded that there were no safety concerns at the likely levels of intake.[13] The compound is used for the preparation of derivatives, notably its volatile esters which, unlike the parent acid, have pleasant odors and fruity flavors and hence find applications in perfumes, cosmetics and foodstuffs.[8] Typical examples are the methyl valerates,[14]ethyl valerates,[15] and pentyl valerates.[16]
^Yan, Long; Yao, Qian; Fu, Yao (2017). "Conversion of levulinic acid and alkyl levulinates into biofuels and high-value chemicals". Green Chemistry. 19 (23): 5527–5547. doi:10.1039/C7GC02503C.
^Shahidi, Fereidoon; Rubin, Leon J.; d'Souza, Lorraine A.; Teranishi, Roy; Buttery, Ron G. (1986). "Meat flavor volatiles: A review of the composition, techniques of analysis, and sensory evaluation". CRC Critical Reviews in Food Science and Nutrition. 24 (2): 141–243. doi:10.1080/10408398609527435. PMID3527563.