butyric acid butyric acid butyric acid skeletal structure of butyric acid flat structure of butyric acid names preferred iupac name butanoic acid other names ethylacetic acid1-propanecarboxylic acidpropylformic acidc4:0 (lipid numbers) identifiers cas number butyric acid: 107-92-6 ybutyrate: 461-55-2 y 3d model (jsmol) butyric acid: interactive image chebi butyric acid: chebi:30772 y chembl butyric acid: chembl14227 y chemspider butyric acid: 259 ybutyrate: 94582 y drugbank butyric acid: db03568 y echa infocard 100.003.212 ec number butyric acid: 203-532-3 iuphar/bps butyric acid: 1059 kegg butyric acid: c00246 y mesh butyric+acid pubchem cid butyric acid: 264butyrate: 104775 rtecs number butyric acid: es5425000 unii butyric acid: 40uir9q29h y un number 2820 comptox dashboard (epa) butyric acid: dtxsid8021515 inchi inchi=1s/c4h8o2/c1-2-3-4(5)6/h2-3h2,1h3,(h,5,6) ykey: feriucnnqqjtoy-uhfffaoysa-n ybutyric acid: inchi=1/c4h8o2/c1-2-3-4(5)6/h2-3h2,1h3,(h,5,6)key: feriucnnqqjtoy-uhfffaoyap smiles butyric acid: o=c(o)ccc properties chemical formula c3h7cooh molar mass 88.106 g·mol−1 appearance colorless liquid odor unpleasant, similar to vomit or body odor density 1.135 g/cm3 (−43 °c) 0.9528 g/cm3 (25 °c) melting point −5.1 °c (22.8 °f; 268.0 k) boiling point 163.75 °c (326.75 °f; 436.90 k) sublimationconditions sublimes at −35 °c δsublho = 76 kj/mol solubility in water miscible solubility miscible with ethanol, ether. slightly soluble in ccl4 log p 0.79 vapor pressure 0.112 kpa (20 °c) 0.74 kpa (50 °c) 9.62 kpa (100 °c) henry's lawconstant (kh) 5.35·10−4 l·atm/mol acidity (pka) 4.82 magnetic susceptibility (χ) −55.10·10−6 cm3/mol thermal conductivity 1.46·105 w/m·k refractive index (nd) 1.398 (20 °c) viscosity 1.814 cp (15 °c) 1.426 cp (25 °c) structure crystal structure monoclinic (−43 °c) space group c2/m lattice constant a = 8.01 å, b = 6.82 å, c = 10.14 åα = 90°, β = 111.45°, γ = 90° dipole moment 0.93 d (20 °c) thermochemistry heat capacity (c) 178.6 j/mol·k std molarentropy (s⦵298) 222.2 j/mol·k std enthalpy offormation (δfh⦵298) −533.9 kj/mol std enthalpy ofcombustion (δch⦵298) 2183.5 kj/mol hazards ghs labelling: pictograms signal word danger hazard statements h314 precautionary statements p280, p305+p351+p338, p310 nfpa 704 (fire diamond) 3 2 0 flash point 71 to 72 °c (160 to 162 °f; 344 to 345 k) autoignitiontemperature 440 °c (824 °f; 713 k) explosive limits 2.2–13.4% lethal dose or concentration (ld, lc): ld50 (median dose) 2000 mg/kg (oral, rat) safety data sheet (sds) external msds related compounds related carboxylic acids propionic acid, pentanoic acid related compounds 1-butanol butyraldehyde methyl butyrate except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). infobox references butyric acid (/ˈbjuːtɪrɪk/; from ancient greek: βούτῡρον, meaning "butter"), also known under the systematic name butanoic acid, is a straight-chain alkyl carboxylic acid with the chemical formula ch3ch2ch2co2h. it is an oily, colorless liquid with an unpleasant odor. isobutyric acid (2-methylpropanoic acid) is an isomer. salts and esters of butyric acid are known as butyrates or butanoates. the acid does not occur widely in nature, but its esters are widespread. it is a common industrial chemical and an important component in the mammalian gut. history butyric acid was first observed in impure form in 1814 by the french chemist michel eugène chevreul. by 1818, he had purified it sufficiently to characterize it. however, chevreul did not publish his early research on butyric acid; instead, he deposited his findings in manuscript form with the secretary of the academy of sciences in paris, france. henri braconnot, a french chemist, was also researching the composition of butter and was publishing his findings, and this led to disputes about priority. as early as 1815, chevreul claimed that he had found the substance responsible for the smell of butter. by 1817, he published some of his findings regarding the properties of butyric acid and named it. however, it was not until 1823 that he presented the properties of butyric acid in detail. the name butyric acid comes from ancient greek: βούτῡρον, meaning "butter", the substance in which it was first found. the latin name butyrum (or buturum) is similar. occurrence triglycerides of butyric acid compose 3–4% of butter. when butter goes rancid, butyric acid is liberated from the glyceride by hydrolysis. it is one of the fatty acid subgroup called short-chain fatty acids. butyric acid is a typical carboxylic acid that reacts with bases and affects many metals. it is found in animal fat and plant oils, bovine milk, breast milk, butter, parmesan cheese, body odor, vomit, and as a product of anaerobic fermentation (including in the colon). it has a taste somewhat like butter and an unpleasant odor. mammals with good scent detection abilities, such as dogs, can detect it at 10 parts per billion, whereas humans can detect it only in concentrations above 10 parts per million. in food manufacturing, it is used as a flavoring agent. in humans, butyric acid is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (hca2), a gi/o-coupled g protein-coupled receptor. butyric acid is present as its octyl ester in parsnip (pastinaca sativa) and in the seed of the ginkgo tree. production industrial in industry, butyric acid is produced by hydroformylation from propene and syngas, forming butyraldehyde, which is oxidised to the final product. h2 + co + ch3ch=ch2 → ch3ch2ch2chooxidation→butyric acid it can be separated from aqueous solutions by saturation with salts such as calcium chloride. the calcium salt, ca(c4h7o2)2 · h2o, is less soluble in hot water than in cold. microbial biosynthesis one pathway for butyrate biosynthesis. relevant enzymes: acetoacetyl-coa thiolase, nad- and nadp-dependent 3-hydroxybutyryl-coa dehydrogenase, 3-hydroxybutyryl-coa dehydratase, and nad-dependent butyryl-coa dehydrogenase. butyrate is produced by several fermentation processes performed by obligate anaerobic bacteria. this fermentation pathway was discovered by louis pasteur in 1861. examples of butyrate-producing species of bacteria: clostridium butyricum clostridium kluyveri clostridium pasteurianum faecalibacterium prausnitzii fusobacterium nucleatum butyrivibrio fibrisolvens eubacterium limosum the pathway starts with the glycolytic cleavage of glucose to two molecules of pyruvate, as happens in most organisms. pyruvate is oxidized into acetyl coenzyme a catalyzed by pyruvate:ferredoxin oxidoreductase. two molecules of carbon dioxide (co2) and two molecules of hydrogen (h2) are formed as waste products. subsequently, atp is produced in the last step of the fermentation. three molecules of atp are produced for each glucose molecule, a relatively high yield. the balanced equation for this fermentation is c6h12o6 → c4h8o2 + 2co2 + 2h2 other pathways to butyrate include succinate reduction and crotonate disproportionation. actionresponsible enzyme acetyl coenzyme a converts into acetoacetyl coenzyme aacetyl-coa-acetyl transferase acetoacetyl coenzyme a converts into β-hydroxybutyryl coaβ-hydroxybutyryl-coa dehydrogenase β-hydroxybutyryl coa converts into crotonyl coacrotonase crotonyl coa converts into butyryl coa (ch3ch2ch2c=o−coa)butyryl coa dehydrogenase a phosphate group replaces coa to form butyryl phosphatephosphobutyrylase the phosphate group joins adp to form atp and butyratebutyrate kinase several species form acetone and n-butanol in an alternative pathway, which starts as butyrate fermentation. some of these species are: clostridium acetobutylicum, the most prominent acetone and butanol producer, used also in industry clostridium beijerinckii clostridium tetanomorphum clostridium aurantibutyricum these bacteria begin with butyrate fermentation, as described above, but, when the ph drops below 5, they switch into butanol and acetone production to prevent further lowering of the ph. two molecules of butanol are formed for each molecule of acetone. the change in the pathway occurs after acetoacetyl coa formation. this intermediate then takes two possible pathways: acetoacetyl coa → acetoacetate → acetone acetoacetyl coa → butyryl coa → butyraldehyde → butanol fermentable fiber sources highly-fermentable fiber residues, such as those from resistant starch, oat bran, pectin, and guar are transformed by colonic bacteria into short-chain fatty acids (scfa) including butyrate, producing more scfa than less fermentable fibers such as celluloses. one study found that resistant starch consistently produces more butyrate than other types of dietary fiber. the production of scfa from fibers in ruminant animals such as cattle is responsible for the butyrate content of milk and butter. fructans are another source of prebiotic soluble dietary fibers which can be digested to produce butyrate. they are often found in the soluble fibers of foods which are high in sulfur, such as the allium and cruciferous vegetables. sources of fructans include wheat (although some wheat strains such as spelt contain lower amounts), rye, barley, onion, garlic, jerusalem and globe artichoke, asparagus, beetroot, chicory, dandelion leaves, leek, radicchio, the white part of spring onion, broccoli, brussels sprouts, cabbage, fennel and prebiotics, such as fructooligosaccharides (fos), oligofructose, and inulin. reactions butyric acid reacts as a typical carboxylic acid: it can form amide, ester, anhydride, and chloride derivatives. the latter, butyryl chloride, is commonly used as the intermediate to obtain the others. uses butyric acid is used in the preparation of various butyrate esters. it is used to produce cellulose acetate butyrate (cab), which is used in a wide variety of tools, paints, and coatings, and is more resistant to degradation than cellulose acetate. cab can degrade with exposure to heat and moisture, releasing butyric acid. low-molecular-weight esters of butyric acid, such as methyl butyrate, have mostly pleasant aromas or tastes. as a consequence, they are used as food and perfume additives. it is an approved food flavoring in the eu flavis database (number 08.005). due to its powerful odor, it has also been used as a fishing bait additive. many of the commercially available flavors used in carp (cyprinus carpio) baits use butyric acid as their ester base. it is not clear whether fish are attracted by the butyric acid itself or the substances added to it. butyric acid was one of the few organic acids shown to be palatable for both tench and bitterling. the substance has been used as a stink bomb by the sea shepherd conservation society to disrupt japanese whaling crews. pharmacology human enzyme and gpcr binding inhibited enzymeic50 (nm)entry note hdac116,000 hdac212,000 hdac39,000 hdac42,000,000lower bound hdac52,000,000lower bound hdac62,000,000lower bound hdac72,000,000lower bound hdac815,000 hdac92,000,000lower bound ca1511,000 ca21,032,000 gpcr targetpec50entry note ffar22.9–4.6full agonist ffar33.8–4.9full agonist hca22.8agonist pharmacodynamics butyric acid (pka 4.82) is fully ionized at physiological ph, so its anion is the material that is mainly relevant in biological systems. it is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (hca2, also known as gpr109a), a gi/o-coupled g protein-coupled receptor (gpcr), like other short-chain fatty acids (scfas), butyrate is an agonist at the free fatty acid receptors ffar2 and ffar3, which function as nutrient sensors that facilitate the homeostatic control of energy balance; however, among the group of scfas, only butyrate is an agonist of hca2. it is also an hdac inhibitor (specifically, hdac1, hdac2, hdac3, and hdac8), a drug that inhibits the function of histone deacetylase enzymes, thereby favoring an acetylated state of histones in cells. histone acetylation loosens the structure of chromatin by reducing the electrostatic attraction between histones and dna. in general, it is thought that transcription factors will be unable to access regions where histones are tightly associated with dna (i.e., non-acetylated, e.g., heterochromatin). therefore, butyric acid is thought to enhance the transcriptional activity at promoters, which are typically silenced or downregulated due to histone deacetylase activity. pharmacokinetics butyrate that is produced in the colon through microbial fermentation of dietary fiber is primarily absorbed and metabolized by colonocytes and the liver for the generation of atp during energy metabolism; however, some butyrate is absorbed in the distal colon, which is not connected to the portal vein, thereby allowing for the systemic distribution of butyrate to multiple organ systems through the circulatory system. butyrate that has reached systemic circulation can readily cross the blood–brain barrier via monocarboxylate transporters (i.e., certain members of the slc16a group of transporters). other transporters that mediate the passage of butyrate across lipid membranes include slc5a8 (smct1), slc27a1 (fatp1), and slc27a4 (fatp4). metabolism butyric acid is metabolized by various human xm-ligases (acsm1, acsm2b, ascm3, acsm4, acsm5, and acsm6), also known as butyrate–coa ligase. the metabolite produced by this reaction is butyryl–coa, and is produced as follows: adenosine triphosphate + butyric acid + coenzyme a → adenosine monophosphate + pyrophosphate + butyryl-coa as a short-chain fatty acid, butyrate is metabolized by mitochondria as an energy (i.e., adenosine triphosphate or atp) source through fatty acid metabolism. in particular, it is an important energy source for cells lining the mammalian colon (colonocytes). without butyrates, colon cells undergo autophagy (i.e., self-digestion) and die. in humans, the butyrate precursor tributyrin, which is naturally present in butter, is metabolized by triacylglycerol lipase into dibutyrin and butyrate through the reaction: tributyrin + h2o → dibutyrin + butyric acid biochemistry butyrate has