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'{{chembox | Watchedfields = changed | verifiedrevid = 265697768 | Name = Formic acid | ImageFileL1 = Ameisensäure Keilstrich.svg | ImageSizeL1 = 120px | ImageNameL1 = Skeletal structure of formic acid | ImageFileR1 = Formic-acid-CRC-MW-3D-balls.png | ImageSizeR1 = 120px | ImageNameR1 = 3D model of formic acid | IUPACName = Formic acid<br/>Methanoic acid | OtherNames = Hydrogen carboxylic acid<br/>Formylic acid<br/>Aminic acid | Section1 = {{Chembox Identifiers | SMILES = O=CO | CASNo = 64-18-6 | CASNo_Ref = {{cascite}} | ChEBI = 30751 | ChemSpiderID = 278 | RTECS = LQ4900000 | ATCvet = yes | ATCCode_prefix = P53 | ATCCode_suffix = AG01 }} | Section2 = {{Chembox Properties | C = 1 | H = 2 | O =2 | Appearance = Colorless, fuming liquid | Density = 1.22 g/mL, liquid | Solubility = Miscible | MeltingPtC = 8.4 | BoilingPtC = 101 | pKa = 3.744 | Viscosity = 1.57 c[[Poise|P]] at 26 °C }} | Section3 = {{Chembox Structure | MolShape = [[Planar]] | Dipole = 1.41 [[Debye|D]](gas) }} | Section7 = {{Chembox Hazards | ExternalMSDS = [http://sciencelab.com/msds.php?msdsId=9924098 ScienceLab.com] | MainHazards = Corrosive; irritant;<br />sensitizer. | NFPA-H = 3 | NFPA-F = 2 | NFPA-R = 1 | FlashPt = 69 °C (156 °F) | RPhrases = {{R10}} {{R35}} | SPhrases = {{S1/2}} {{S23}} {{S26}} {{S45}} }} | Section8 = {{Chembox Related | Function = [[carboxylic acid]]s | OtherFunctn = [[Acetic acid]]<br/>[[Propionic acid]] | OtherCpds = [[Formaldehyde]]<br/>[[Methanol]]}} }} '''Formic acid''' (systematically called '''methanoic acid''') is the simplest [[carboxylic acid]], but can also be viewed as an [[aldehyde]]. Its [[Chemical formula|formula]] is [[hydrogen|H]][[carbon|C]][[oxygen|O]]OH or HCO₂H. It is an important intermediate in [[chemical synthesis]] and occurs [[naturally]], most notably in the [[venom]] of [[bee]] and [[ant]] [[stinger|sting]]s. In fact, its name comes from the [[Latin]] word for ant, ''[[formica]]'', referring to its early isolation by the [[distillation]] of ant bodies. An [[ester]] or salt derived from formic acid is referred to as formate. ==Properties== Formic acid is [[Miscibility|miscible]] with [[water (molecule)|water]] and most polar [[organic chemistry|organic]] [[solvent]]s, and somewhat soluble in [[hydrocarbon]]s. In hydrocarbons and in the vapor phase it consists of [[Hydrogen bond|hydrogen-bond]]ed dimers rather than individual molecules.<ref name=Ullmann_2009>Werner Reutemann and Heinz Kieczka “Formic Acid” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a12_013}}</ref> Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the [[ideal gas law]]. Solid formic acid (two [[polymorph]]s) consists of an effectively endless network of hydrogen-bonded formic acid molecules. This relatively complicated compound also forms a low-boiling azeotrope with water (22.4%) and liquid formic acid also tends to supercool. ==Reactions== Formic acid shares most of the chemical properties of other [[carboxylic acid]]s. Reflecting its high acidity, its solutions in alcohols form esters spontaneously. Formic acid shares some of the [[redox|reducing]] properties of [[aldehyde]]s, reducing solutions of gold, silver, and platinum to the metals. ===Decomposition=== Heat and especially acids cause formic acid to decompose to carbon monoxide and water. Treatment of formic acid with [[sulfuric acid]] is a convenient laboratory source of CO. In the presence of platinum, it decomposes with release of [[hydrogen]] and [[carbon monoxide]]. Soluble ruthenium catalysts are also effective.<ref>C. Fellay, P. J. Dyson, G. Laurenczy, A Viable Hydrogen-Storage System Based On Selective Formic Acid Decomposition with a Ruthenium Catalyst, ''Angew. Chem. Int. Ed.'', '''2008''', ''47'', 3966–3970.</ref>.<ref>G. Laurenczy, C. Fellay, P. J. Dyson, Hydrogen production from formic acid. ''PCT Int. Appl.'' (2008), 36pp. CODEN: PIXXD2 WO 2008047312 A1 20080424 AN 2008:502691</ref>. Carbon monoxide free hydrogen has been generated in a very wide pressure range (1-600 bar). Formic acid has even been considered as a material for hydrogen storage.<ref>F. Joó, Breakthroughs in Hydrogen Storage – Formic Acid as a Sustainable Storage Material for Hydrogen, ''ChemSusChem'' '''2008''', ''1'', 805–808.</ref> The co-product of this decomposition, carbon dioxide, can be rehydrogenated back to formic acid in a second step. Formic acid contains 53 g L^-1 hydrogen at room temperature and atmospheric pressure, which is twice as much as compressed hydrogen gas can attain at 350 bar pressure. Pure formic acid is a liquid with a flash point - ignition temperature of + 69 °C, much higher than that of gasoline (– 40 °C) or ethanol (+ 13 °C). ===Addition to alkenes=== Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with [[alkene]]s. Formic acids and alkenes readily react to form formate [[ester]]s. In the presence of certain acids, including [[sulfuric acid|sulfuric]] and [[hydrofluoric acid]]s, however, a variant of the [[Koch reaction]] occurs instead, and formic acid adds to the alkene to produce a larger carboxylic acid. ===Formic acid anhydride=== The reaction of [[formyl fluoride]] with [[sodium formate]] affords formic anhydride. The other three methods involved the use of [[dehydrating agent]]s. The formic anhydride, however, is only stable in ethereal solution and decomposes upon attempted distillation.<ref>{{cite journal | journal = [[Angew. Chem. Int. Ed. Engl.]] | doi = 10.1002/anie.197906141 | author = [[George A. Olah]]; Yashwant D. Vankar; Massoud Arvanaghi; Jean Sommer | volume = 18 | issue = 8 | pages = 614 | title = Formic Anhydride | year = 1979}}</ref> ==Production== ===From methyl formate and formamide=== When [[methanol]] and [[carbon monoxide]] are combined in the presence of a strong [[Base (chemistry)|base]], the formic acid derivative [[methyl formate]] results, according to the [[chemical equation]]:<ref name=Ullmann_2009/> :CH₃OH + CO → HCO₂CH₃ In industry, this reaction is performed in the liquid phase at elevated pressure. Typical reaction conditions are 80 °C and 40 atm. The most widely-used base is [[sodium methoxide]]. [[Hydrolysis]] of the methyl formate produces formic acid: :HCO₂CH₃ + H₂O → HCO₂H + CH₃OH Efficient hydrolysis of methyl formate requires a large excess of [[water]]. Some routes proceed indirectly by first treating the methyl formate with [[ammonia]] to give [[formamide]], which is then hydrolyzed with [[sulfuric acid]]: :HCO₂CH₃ + NH₃ → HC(O)NH₂ + CH₃OH :2 HC(O)NH₂ + 2 H₂O + H₂SO₄ → 2HCO₂H + (NH₄)₂SO₄ This approach suffers from the need to dispose of the [[ammonium sulfate]] byproduct. This problem has led some manufacturers to develop energy efficient means for separating formic acid from the large excess amount of water used in direct hydrolysis. In one of these processes (used by [[BASF]]) the formic acid is removed from the water via [[liquid-liquid extraction]] with an organic base. ===By-product of acetic acid production=== A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals. [[Acetic acid]] once was produced on a large scale by oxidation of alkanes, via a process that cogenerates significant formic acid. This oxidative route to acetic acid is declining in importance, so that the aforementioned dedicated routes to formic acid have become more important. ===Hydrogenation of carbon dioxide=== The catalytic hydrogenation of CO₂ has long been studied. This reaction can be conducted homogeneously.<ref>P. G. Jessop, in ''Handbook of Homogeneous Hydrogenation'' (Eds.: J. G. de Vries, C. J. Elsevier), Wiley-VCH, Weinheim, Germany, '''2007''', pp. 489–511.</ref><ref>P. G. Jessop, F. Joó, C.-C. Tai, Recent advances in the homogeneous hydrogenation of carbon dioxide, ''Coord. Chem. Rev.'', '''2004''', ''248'', 2425–2442.{{doi|10.1016/j.ccr.2004.05.019}}</ref> ===Laboratory methods=== In the laboratory, formic acid can be obtained by heating [[oxalic acid]] in anhydrous [[glycerol]] and extraction by steam distillation. Another preparation (which must be performed under a fume hood) is the acid [[hydrolysis]] of ethyl isonitrile (C₂H₅NC) using [[hydrochloric acid|HCl]] solution.<ref name="cohen">Cohen, Julius B.: ''Practical Organic Chemistry'' MacMillan 1930</ref> :C₂H₅NC + 2 H₂O → C₂H₅NH₂ + HCO₂H The isonitrile can be obtained by reacting [[ethyl amine]] with [[chloroform]] (note that the fume hood is required because of the overpoweringly objectionable odor of the [[isonitrile]]). ==Uses== The principal use of formic acid is as a [[preservative]] and [[bacterium|antibacterial]] agent in livestock feed. When sprayed on fresh [[hay]] or other [[silage]], it arrests certain decay processes and causes the feed to retain its nutritive value longer, and so it is widely used to preserve winter feed for [[cattle]]. In the [[poultry]] industry, it is sometimes added to feed to kill [[salmonella]] bacteria. ===Reagent in organic chemistry=== Formic acid is a source for a [[formyl]] group for example in the [[formylation]] of methylaniline to N-methylformanilide in [[toluene]].<ref>{{OrgSynth | ''N''-Methylformanilide | collvol = 3 | collvolpages = 590 | year = 1955 | prep = cv3p0590 | author = [[Louis Fieser|L. F. Fieser]] and J. E. Jones }}</ref> In [[organic synthesis|synthetic organic chemistry]], formic acid is often used as a source of [[hydride]] ion. The [[Eschweiler-Clarke reaction]] and the [[Leuckart-Wallach reaction]] are examples of this application. It or more commonly its azeotrope with triethylamine, is also used as a source of hydrogen in [[transfer hydrogenation]]. ===Other uses=== *It is used to process organic latex (sap) into raw [[rubber]]. *[[Beekeeper]]s use formic acid as a [[miticide]] against the Tracheal ([[Acarapis woodi]]) mite and the [[Varroa destructor|Varroa mite]]. *It is of minor importance in the [[textile]] industry and for the [[tanning]] of [[leather]]. *Some formate [[esters]] are artificial flavorings or perfumes. *It is the active ingredient in some brands of household [[limescale]] remover. *It is used in laboratories as a solvent modifier for [[HPLC]] and [[Capillary electrophoresis|CE]] separations of proteins and peptides, especially when the sample is being prepared for [[mass spectrometry]] analysis. *[[Formic acid fuel cell|Fuel cells that use modified formic acid]] have been reported. ==History== Some [[alchemy|alchemists]] and [[natural history|naturalists]] were aware that ant hills gave off an acidic vapor as early as the 15th century. The first person to describe the isolation of this substance (by the distillation of large numbers of ants) was the [[England|English]] naturalist [[John Ray]], in 1671. Ants secrete the formic acid for attack and defense purposes. Formic acid was first synthesized from [[hydrocyanic acid]] by the [[France|French]] chemist [[Joseph Gay-Lussac]]. In 1855 another French chemist, [[Marcellin Berthelot]], developed a synthesis from [[carbon monoxide]] that is similar to that used today. Formic acid was long considered a [[chemical compound]] of only minor industrial interest in the chemical industry. In the late 1960s, however, significant quantities of it became available as a byproduct of [[acetic acid]] production. It now finds increasing use as a preservative and antibacterial in [[livestock]] feed. ==In nature== In [[nature]], it is found in the [[sting (pain)|stings]] and [[bites]] of many [[insects]] of the order [[Hymenoptera]], mainly [[ant]]s and is also present in [[stinging nettle]]s{{Fact|date=July 2009}}. It is also a significant [[combustion]] product resulting from alternative fueled [[vehicles]] burning [[methanol]] (and [[ethanol]], if contaminated with [[water]]) when mixed with [[gasoline]].{{Fact|date=November 2008}} ==Safety== 85 % formic acid is flammable and diluted formic acid is on the US Food and Drug Administration list of food additives<ref>US Code of Federal Regulations: 21 CFR 186.1316, 21 CFR 172.515</ref>. The principal danger from formic acid is from skin or eye contact with the concentrated liquid or vapors. The US [[Occupational Safety and Health Administration|OSHA]] Permissible Exposure Level ([[Permissible exposure limit|PEL]]) of formic acid vapor in the work environment is 5 parts per million parts of air ([[Parts per million|ppm]]). Formic acid is readily metabolized and eliminated by the body. Nonetheless, it has specific [[toxic]] effects; the formic acid and [[formaldehyde]] produced as metabolites of [[methanol]] are responsible for the [[optic nerve]] damage causing blindness seen in methanol poisoning.<ref>{{cite web|url=http://www.newton.dep.anl.gov/askasci/chem03/chem03561.htm|title=Methanol and Blindness|publisher=Ask A Scientist, Chemistry Archive|dateformat=dmy|accessdate=22 May 2007}}</ref> Some chronic effects of formic acid exposure have been documented. Some animal experiments have demonstrated it to be a [[mutagen]], and chronic exposure may cause liver or kidney damage. Another affect of chronic exposure is development of a skin [[allergy]] that manifests upon re-exposure to the chemical. Concentrated formic acid slowly decomposes to carbon monoxide and water, leading to pressure buildup in the container it is kept in. For this reason 98 % formic acid is shipped in plastic bottles with self-venting caps. The hazards of solutions of formic acid depend on the concentration. The following table lists the [[Directive 67/548/EEC|EU classification]] of formic acid solutions: {| class = "wikitable" ! [[Concentration]] ([[weight percent]]) ! Classification ! [[List of R-phrases|R-Phrases]] |- | 2%&ndash;10% | Irritant ('''Xi''') | {{R36/38}} |- | 10%&ndash;90% | Corrosive ('''C''') | {{R34}} |- | >90% | Corrosive ('''C''') | {{R35}} |- |} An [[assay]] for formic acid in body fluids, designed for determination of formate after methanol poisoning, is based on the reaction of formate with bacterial formate dehydrogenase.<ref>{{cite journal |journal= Biochem Med |date=1975 |volume=13 |issue=2 |pages=117–26 |title= Formate assay in body fluids: application in methanol poisoning |author= Makar AB, McMartin KE, Palese M, Tephly TR |doi=10.1016/0006-2944(75)90147-7 |pmid=1}}</ref> ==References== {{reflist|2}} ==External links== {{commons|Formic acid|Formic acid}} * [http://etd.rau.ac.za/theses/available/etd-09082004-124908/ Carbon monoxide as reagent in the formylation of aromatic compounds]. * [http://ecb.jrc.it/ European Chemicals Bureau]. * [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc04/icsc0485.htm International Chemical Safety Card 0485]. * [http://www.cdc.gov/niosh/npg/npgd0296.html NIOSH Pocket Guide to Chemical Hazards]. * [http://chemsub.online.fr/chemsearch/cas_number_64-18-6.html ChemSub Online (Formic acid)]. [[Category:Formates]] [[Category:Carboxylic acids]] [[Category:Organic acids]] [[Category:Solvents]] [[ar:حمض الفورميك]] [[bs:Metanska kiselina]] [[bg:Мравчена киселина]] [[ca:Àcid fòrmic]] [[cs:Kyselina mravenčí]] [[cy:Asid fformig]] [[da:Myresyre]] [[de:Ameisensäure]] [[et:Metaanhape]] [[el:Μεθανικό οξύ]] [[es:Ácido fórmico]] [[eo:Formika acido]] [[eu:Azido formiko]] [[fa:اسید فرمیک]] [[fr:Acide méthanoïque]] [[ga:Aigéad formach]] [[ko:폼산]] [[hr:Mravlja kiselina]] [[id:Asam format]] [[is:Maurasýra]] [[it:Acido formico]] [[he:חומצה פורמית]] [[la:Acidum formicum]] [[lv:Skudrskābe]] [[hu:Hangyasav]] [[mk:Мравја киселина]] [[nl:Mierenzuur]] [[ja:ギ酸]] [[no:Maursyre]] [[nn:Maursyre]] [[pl:Kwas mrówkowy]] [[pt:Ácido metanoico]] [[ro:Acid formic]] [[qu:Sisi p'uchqu]] [[ru:Муравьиная кислота]] [[sk:Kyselina mravčia]] [[sl:Mravljinčna kislina]] [[sr:Мравља киселина]] [[sh:Mravlja kiselina]] [[su:Asam format]] [[fi:Muurahaishappo]] [[sv:Myrsyra]] [[th:กรดฟอร์มิก]] [[tr:Formik asit]] [[uk:Мурашина кислота]] [[vi:Axít formic]] [[zh:甲酸]]'