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'{{Use dmy dates|date=July 2013}} {{Chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 443825627 | Name = Formic acid | ImageFile2 = formic acid 85 percent.jpg | ImageSize2 = 120px | ImageFileL1 = Formic_acid.svg | ImageNameL1 = Skeletal structure of formic acid | ImageFileR1 = Formic-acid-CRC-MW-3D-balls.png | ImageNameR1 = 3D model of formic acid | PIN = Formic acid<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 745 | doi = 10.1039/9781849733069-FP001 | isbn = 978-0-85404-182-4}}</ref> | SystematicName = Methanoic acid<ref name=iupac2013 /> | OtherNames = Carbonous acid; Formylic acid; Hydrogen carboxylic acid; Hydroxy(oxo)methane; Metacarbonoic acid; Oxocarbinic acid; Oxomethanol |Section1={{Chembox Identifiers | DrugBank_Ref = {{drugbankcite|correct|drugbank}} | DrugBank = DB01942 | SMILES = O=CO | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 0YIW783RG1 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = C00058 | InChI = 1/HCOOH/c2-1-3/h1H,(H,2,3) | InChIKey = BDAGIHXWWSANSR-UHFFFAOYAT | ChEMBL_Ref = {{ebicite|correct|EBI}} | ChEMBL = 116736 | StdInChI_Ref = {{stdinchicite|changed|chemspider}} | StdInChI = 1S/HCOOH/c2-1-3/h1H,(H,2,3) | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = BDAGIHXWWSANSR-UHFFFAOYSA-N | CASNo = 64-18-6 | CASNo_Ref = {{cascite|correct|CAS}} | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 30751 | PubChem = 284 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 278 | RTECS = LQ4900000 | EINECS = 200-579-1 }} |Section2={{Chembox Properties | C=1 | H=2 | O=2 | Appearance = Colorless fuming liquid | Odor = Pungent, penetrating | Density = 1.220 g/mL | Solubility = Miscible | SolubleOther = Miscible with [[ether]], [[acetone]], [[ethyl acetate]], [[glycerol]], [[methanol]], [[ethanol]] <br/> Partially soluble in [[benzene]], [[toluene]], [[xylene]]s | MeltingPtC = 8.4 | BoilingPtC = 100.8 | pKa = 3.77<ref>Brown, H. C. et al., in Braude, E. A. and Nachod, F. C., ''Determination of Organic Structures by Physical Methods'', Academic Press, New York, 1955.</ref> | Viscosity = 1.57 c[[Poise|P]] at 268&nbsp;°C | LogP = −0.54 | RefractIndex = 1.3714 (20&nbsp;°C) | MagSus = -19.90·10⁻⁶ cm³/mol | VaporPressure = 35 mmHg (20&nbsp;°C)<ref name=PGCH/> }} |Section3={{Chembox Structure | MolShape = [[Wiktionary:planar|Planar]] | Dipole = 1.41 [[Debye|D]] (gas)}} |Section5={{Chembox Thermochemistry | DeltaHf = &minus;425.0 kJ/mol | DeltaHc = &minus;254.6 kJ/mol | Entropy = 131.8 J/mol&nbsp;K }} |Section6={{Chembox Pharmacology | ATCvet = yes | ATCCode_prefix = P53 | ATCCode_suffix = AG01 }} |Section7={{Chembox Hazards | ExternalSDS = [http://www.jtbaker.com/msds/englishhtml/f5956.htm JT Baker] | MainHazards = Corrosive; irritant;<br />sensitizer | NFPA-H = 3 | NFPA-F = 2 | NFPA-R = 1 | FlashPtC = 69 | AutoignitionPtC = 601 | ExploLimits = 14{{ndash}}34%{{citation needed|date=March 2015}}<br/> 18%{{ndash}}57% (90% solution)<ref name=PGCH/> | RPhrases = {{R10}} {{R35}} | SPhrases = {{S1/2}} {{S23}} {{S26}} {{S45}} | LD50 = 700 mg/kg (mouse, oral), 1100 mg/kg (rat, oral), 4000 mg/kg (dog, oral)<ref name=IDLH>{{cite web |url = https://www.cdc.gov/niosh/idlh/64186.html |title = Formic acid |work = Immediately Dangerous to Life or Health Concentrations (IDLH) |publisher = National Institute for Occupational Safety and Health |date = 4 December 2014 |accessdate = 26 March 2015}}</ref> | PEL = TWA 5 ppm (9 mg/m³)<ref name=PGCH>{{PGCH|0296}}</ref> | IDLH = 30 ppm<ref name=PGCH/> | REL = TWA 5 ppm (9 mg/m³)<ref name=PGCH/> | LC50 = 7853 ppm (rat, 15 min)<br/>3246 ppm (mouse, 15 min)<ref name=IDLH/> }} |Section8={{Chembox Related | OtherFunction_label = [[carboxylic acid]]s | OtherFunction = [[Acetic acid]]<br/>[[Propionic acid]] | OtherCompounds = [[Formaldehyde]]<br/>[[Methanol]]}} }} '''Formic acid''', systemically named methanoic acid, is the simplest [[carboxylic acid]]. The [[chemical formula]] is [[hydrogen|H]][[carbon|C]][[oxygen|O]][[hydroxide|OH]] or HCO₂H. It is an important intermediate in [[chemical synthesis]] and occurs naturally, most notably in some ants. The word "formic" comes from the [[Latin]] word for ant, ''[[formica]]'', referring to its early isolation by the [[distillation]] of ant bodies, and the trivial name in some languages means "ant-acid", such as Dutch ''[[wikt:mierenzuur|mierenzuur]]'', Danish ''[[wikt:myresyre|myresyre]]'', Faroese ''[[wikt:meyrusýra|meyrusýra]]'', Français ''[[wikt:fr:acide formique|acide formique]]'' and German ''[[wikt:Ameisensäure|Ameisensäure]]''. [[Ester]]s, salts, and the anions derived from formic acid are called [[formate]]s. ==Properties== [[File:Formic Acid Hydrogenbridge V.1.svg|thumb|left|Cyclic dimer of formic acid; dashed <span style="color:green;">'''green'''</span> lines represent hydrogen bonds]] Formic acid is a colorless liquid having a pungent, penetrating odor<ref>[https://www.osha.gov/chemicaldata/chemResult.html?recNo=468].</ref> at room temperature. It is [[Miscibility|miscible]] with [[water (molecule)|water]] and most polar [[organic chemistry|organic]] [[solvent]]s, and is somewhat soluble in [[hydrocarbon]]s. In hydrocarbons and in the vapor phase, it consists of [[Hydrogen bond|hydrogen-bond]]ed [[dimer (chemistry)|dimers]] rather than individual molecules.<ref name=Ullmann_2009>{{cite book |doi=10.1002/14356007.a12_013 |chapter=Formic Acid |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Reutemann |first1=Werner |last2=Kieczka |first2=Heinz |isbn=3-527-30673-0 }}</ref><ref name=Balabin_2009>{{cite journal |doi=10.1021/jp9002643 |pmid=19344174 |title=Polar (Acyclic) Isomer of Formic Acid Dimer: Gas-Phase Raman Spectroscopy Study and Thermodynamic Parameters |journal=The Journal of Physical Chemistry A |volume=113 |issue=17 |pages=4910–8 |year=2009 |last1=Balabin |first1=Roman M |bibcode=2009JPCA..113.4910B }}</ref> Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the [[ideal gas law]].<ref name=Balabin_2009/> Solid formic acid (two [[polymorphism (materials science)|polymorphs]]) 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. <!--Please leave the clear left template in, as the image file for this section forces the next section's title to improperly format-->{{clear|left}} ==Natural occurrence== {{See also|Insect defenses}} In nature, it is found in most ants.<ref>{{cite journal |doi=10.1097/ACI.0b013e328339f325 |pmid=20445444 |title=Ant venoms |journal=Current Opinion in Allergy and Clinical Immunology |volume=10 |issue=4 |pages=342–6 |year=2010 |last1=Hoffman |first1=Donald R }}</ref> The wood ants from the genus [[Formica]] can spray formic acid on their prey or to defend the nest. It is also known from the trichomes of [[stinging nettle]] (''Urtica dioica''). Formic acid is a naturally occurring component of the atmosphere due primarily to forest emissions.<ref>{{cite journal |doi=10.1029/91GL01565 |title=Emission of formic and acetic acids from tropical Savanna soils |journal=Geophysical Research Letters |volume=18 |issue=9 |pages=1707–10 |year=1991 |last1=Sanhueza |first1=Eugenio |last2=Andreae |first2=Meinrat O |bibcode=1991GeoRL..18.1707S }}</ref> ==Production== In 2009, the worldwide capacity for producing formic acid was 720,000 tonnes/annum, roughly equally divided between Europe (350,000, mainly in Germany) and Asia (370,000, mainly in China) while production was below 1000 tonnes/annum in all other continents.<ref name=CEH>{{cite web|url=http://www.sriconsulting.com/CEH/Public/Reports/659.2000/|title=CEH Marketing Research Report: FORMIC ACID|author1=S. N. Bizzari |author2=M. Blagoev |date=June 2010|work=Chemical Economics Handbook|publisher=SRI consulting|accessdate=July 2011}}</ref> It is commercially available in solutions of various concentrations between 85 and 99 w/w %.<ref name = Ullmann_2009/> {{As of|2009}}, the largest producers are [[BASF]], [[Eastman Chemical Company]], [[LC Industrial]], and [[Feicheng Acid Chemicals]], with the largest production facilities in [[Ludwigshafen]] (200,000 tonnes/annum, BASF, Germany), [[Oulu]] (105,000, Eastman, Finland), [[Nakhon Pathom]] (n/a, [[LC Industrial]]) and [[Feicheng]] (100,000, Feicheng, China). 2010 prices ranged from around €650/tonne (equivalent to around $800/tonne) in Western Europe to $1250/tonne in the United States.<ref name=CEH/> ===From methyl formate and formamide=== When [[methanol]] and [[carbon monoxide]] are combined in the presence of a strong [[Base (chemistry)|base]], the result is [[methyl formate]], 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&nbsp;°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 + 2H₂O + H₂SO₄ → 2HCO₂H + (NH₄)₂SO₄ A disadvantage of this approach is the need to dispose of the [[ammonium sulfate]] byproduct. This problem has led some manufacturers to develop energy-efficient methods of separating formic acid from the excess water used in direct hydrolysis. In one of these processes (used by [[BASF]]) the formic acid is removed from the water by [[liquid-liquid extraction]] with an organic base.{{fact|date=November 2017}} ===Niche chemical routes=== ====By-product of acetic acid production==== A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals. At one time, [[acetic acid]] was produced on a large scale by oxidation of alkanes, by 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 [[Carbon dioxide|CO₂]] to formic acid 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>{{cite journal |doi=10.1016/j.ccr.2004.05.019 |title=Recent advances in the homogeneous hydrogenation of carbon dioxide |journal=Coordination Chemistry Reviews |volume=248 |issue=21–24 |pages=2425 |year=2004 |last1=Jessop |first1=Philip G |last2=Joó |first2=Ferenc |last3=Tai |first3=Chih-Cheng }}</ref> ====Oxidation of biomass==== Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass ([[OxFA process]]).<ref>{{cite journal |doi=10.1039/C1GC15434F |title=Selective catalytic conversion of biobased carbohydrates to formic acid using molecular oxygen |journal=Green Chemistry |volume=13 |issue=10 |pages=2759 |year=2011 |last1=Wölfel |first1=Rene |last2=Taccardi |first2=Nicola |last3=Bösmann |first3=Andreas |last4=Wasserscheid |first4=Peter }}</ref><ref>{{cite journal |doi=10.1039/C2EE21428H |title=Selective oxidation of complex, water-insoluble biomass to formic acid using additives as reaction accelerators |journal=Energy & Environmental Science |volume=5 |issue=7 |pages=7956 |year=2012 |last1=Albert |first1=Jakob |last2=Wölfel |first2=Rene |last3=Bösmann |first3=Andreas |last4=Wasserscheid |first4=Peter }}</ref> A [[Keggin structure|Keggin-type]] polyoxometalate (H₅PV₂Mo₁₀O₄₀) is used as the homogeneous catalyst to convert sugars, wood, waste paper or cyanobacteria to formic acid and CO₂ as the sole byproduct. Yields of up to 53% formic acid can be achieved. ====Laboratory methods==== In the laboratory, formic acid can be obtained by heating [[oxalic acid]] in [[glycerol]] and extraction by steam distillation.<ref name="chattaway">{{cite journal |doi=10.1039/CT9140500151 |url=http://hdl.handle.net/2027/mdp.39015067135775?urlappend=%3Bseq=177 |title=XX.—Interaction of glycerol and oxalic acid |journal=[[Journal of the Chemical Society, Transactions]] |volume=105 |pages=151–6 |year=1914 |last1=Chattaway |first1=Frederick Daniel }}</ref> Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediary. If the reaction mixture is heated to higher temperatures, [[allyl alcohol]] results. The net reaction is thus: :C₂O₄H₂ → CO₂H₂ + CO₂<!--esoteric and not useful to anyone: Another preparation 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 + 2H₂O → 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]]).--> Another illustrative method involves the reaction between [[lead formate]] and [[hydrogen sulfide]], driven by the formation of [[lead sulfide]].<ref>Arthur Sutcliffe (1930) Practical Chemistry for Advanced Students (1949 Ed.), John Murray, London.</ref> :Pb(HCOO)₂ + H₂S → 2HCOOH + PbS ===Biosynthesis=== Formic acid is named after ants which have high concentrations of the compound in their venom. In ants formic acid is derived from [[serine]] thought a [[5,10-Methenyltetrahydrofolate]] intermediate<ref>{{cite journal|last1=Hefetz|first1=Abraham|last2=Blum|first2=Murray|title=Biosynthesis of formic acid by the poison glands of formicine ants|journal=Biochimica et Biophysica Acta (BBA) - General Subjects|date=1 Nov 1978|volume=543|issue=4|pages=484-496|doi=10.1016/0304-4165(78)90303-3|pmid=718985|url=https://www.sciencedirect.com/science/article/pii/0304416578903033?via%3Dihub}}</ref>. The conjugate base of formic acid, formate, also occurs widely in nature. 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 |doi=10.1016/0006-2944(75)90147-7 |pmid=1 |title=Formate assay in body fluids: Application in methanol poisoning |journal=Biochemical Medicine |volume=13 |issue=2 |pages=117 |year=1975 |last1=Makar |first1=A.B |last2=McMartin |first2=K.E |last3=Palese |first3=M |last4=Tephly |first4=T.R }}</ref> == Uses == A major use of formic acid is as a [[preservative]] and [[bacteria|antibacterial]] agent in livestock feed. In Europe, it is applied on [[silage]] (including fresh hay) to promote the fermentation of [[lactic acid]] and to suppress the formation of [[butyric acid]]; it also allows fermentation to occur quickly, and at a lower temperature, reducing the loss of nutritional value.<ref name = Ullmann_2009/> Formic acid 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]].<ref>[https://books.google.com/books?id=7IrGwQTt1aMC&pg=PA31&dq=formic+acid++winter+feed+for+cattle&hl=en&sa=X&ei=iXYdVfr_AYOGyQTpsYHwCQ&ved=0CC8Q6AEwAA#v=onepage&q=formic%20acid%20%20winter%20feed%20for%20cattle&f=false Organic Acids and Food Preservation], Maria M. Theron, J. F. Rykers Lues</ref> In the [[poultry]] industry, it is sometimes added to feed to kill ''[[Escherichia coli|E. coli]]'' bacteria.<ref>{{cite journal |doi=10.1093/japr/14.4.750 |title=Alternatives to Antibiotics for Organic Poultry Production |journal=The Journal of Applied Poultry Research |volume=14 |issue=4 |pages=750 |year=2005 |last1=Griggs |first1=J. P |last2=Jacob |first2=J. P }}</ref><ref>{{cite journal |doi=10.3382/japr.2006-00116 |title=Effect of Formic Acid and Plant Extracts on Growth, Nutrient Digestibility, Intestine Mucosa Morphology, and Meat Yield of Broilers |journal=The Journal of Applied Poultry Research |volume=16 |issue=4 |pages=555 |year=2007 |last1=Garcia |first1=V |last2=Catala-Gregori |first2=P |last3=Hernandez |first3=F |last4=Megias |first4=M. D |last5=Madrid |first5=J }}</ref> Use as preservative for silage and (other) animal feed constituted 30% of the global consumption in 2009.<ref name=CEH/> Formic acid is also significantly used in the production of leather, including [[Tanning (leather)|tanning]] (23% of the global consumption in 2009<ref name=CEH/>), and in dyeing and finishing textiles (9% of the global consumption in 2009<ref name=CEH/>) because of its acidic nature. Use as a coagulant in the [[production of rubber]]<ref name = Ullmann_2009/> consumed 6% of the global production in 2009.<ref name=CEH/> Formic acid is also used in place of mineral acids for various cleaning products,<ref name =Ullmann_2009/> such as [[limescale]] remover and [[household cleaner|toilet bowl cleaner]]. Some formate [[esters]] are artificial flavorings or perfumes. [[Beekeeper]]s use formic acid as a [[miticide]] against the tracheal mite (''[[Acarapis woodi]]'') and the [[Varroa destructor|''Varroa destructor'' mite]] and [[Varroa jacobsoni|''Varroa jacobsoni'' mite]].<ref>{{cite journal |author= Hoppe, H., Ritter, W., & Stephen, E. W. C.|year= 1989 |title= The control of parasitic bee mites: Varroa jacobsoni, Acarapis woodi and Tropilaelaps clareae with formic acid.|journal= American bee journal}}</ref> Formic acid application has been reported to be an effective treatment for [[wart]]s.<ref name="pmid11589750">{{cite journal |doi=10.1046/j.1365-4362.2001.01242.x |pmid=11589750 |title=Topical formic acid puncture technique for the treatment of common warts |journal=International Journal of Dermatology |volume=40 |issue=6 |pages=415–9 |year=2001 |last1=Bhat |first1=Ramesh M |last2=Vidya |first2=Krishna |last3=Kamath |first3=Ganesh }}</ref> Formic acid is being investigated for use in [[fuel cell]]s.<ref>{{cite journal |doi=10.1016/j.jpowsour.2004.12.031 |title=Performance characterization of Pd/C nanocatalyst for direct formic acid fuel cells |journal=Journal of Power Sources |volume=144 |pages=28–34 |year=2005 |last1=Ha |first1=S |last2=Larsen |first2=R |last3=Masel |first3=R.I |bibcode=2005JPS...144...28H }}</ref><ref>{{cite news |title=Ant power: Take a ride on a bus that runs on formic acid |author=Jorn Madslien |url=http://www.bbc.com/news/business-40403351 |publisher=[[BBC News]] |date=27 June 2017 |accessdate=11 July 2017}}</ref> Formic acid is often used as a component of mobile phase in reversed-phase high-performance liquid chromotagraphy (RP-HPLC) analysis and separation techniques for the separation of hydrophobic macromolecules, such as peptides, proteins and more complex structures including intact viruses. Especially when paired with mass spectrometry detection, formic acid offers several advantages over the more traditionally used phosphoric acid.<ref>https://www.novapublishers.com/catalog/product_info.php?products_id=48192{{full|date=November 2017}}</ref><ref>{{cite journal |doi=10.1016/S0021-9673(01)88415-6 |pmid=6304128 |title=Reversed-phase high-performance liquid chromatography of virus proteins and other large hydrophobic proteins in formic acid containing solvents |journal=Journal of Chromatography A |volume=252 |pages=241–54 |year=1982 |last1=Heukeshoven |first1=Jochen |last2=Dernick |first2=Rudolf }}</ref> ==Chemical reactions== Formic acid is about 10x stronger than [[acetic acid]]. It is used as a volatile pH modifier in [[High-performance liquid chromatography|HPLC]] and [[capillary electrophoresis]]. Formic acid is a source for a [[formyl]] group for example in the [[formylation]] of methylaniline to N-methylformanilide in [[toluene]].<ref>{{OrgSynth | title = ''N''-Methylformanilide | collvol = 3 | collvolpages = 590 | year = 1955 | prep = cv3p0590 | authorlink=Louis Fieser |author=L. F. Fieser |author2=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]]. [[Image:Eschweiler-Clark Reaction Scheme.png|center|300px|The Eschweiler–Clark reaction]] As mentioned [[#Decomposition|below]], formic acid readily decomposes with concentrated [[sulfuric acid]] to form [[carbon monoxide]]. :CH₂O_2(L) + H₂SO₄_(L) → H₂SO₄_(L) + H₂O_(L) + CO_(G) ==Reactions== Formic acid shares most of the chemical properties of other [[carboxylic acid]]s. Because of its high acidity, 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.{{Citation needed|date=March 2016}} ===Decomposition=== Heat and especially acids cause formic acid to decompose to [[carbon monoxide]] (CO) and water (dehydration). Treatment of formic acid with [[sulfuric acid]] is a convenient laboratory source of CO.<ref>{{OrgSynth|author=Koch, H.; Haaf, W.|title=1-Adamantanecarboxylic Acid|year=1973|collvol=5|collvolpages=20|prep=cv5p0020}}</ref><ref>{{OrgSynth|title=''p''-Tolualdehyde|author=G. H. Coleman, David Craig|collvol=2|collvolpages=583|year=1943|prep=cv2p0583}}</ref> In the presence of platinum, it decomposes with a release of [[hydrogen]] and [[carbon dioxide]]. :CH₂O₂ → H₂ + CO₂ Soluble ruthenium catalysts are also effective.<ref name="Fellay2008">{{cite journal |doi=10.1002/anie.200800320 |pmid=18393267 |title=A Viable Hydrogen-Storage System Based on Selective Formic Acid Decomposition with a Ruthenium Catalyst |journal=Angewandte Chemie International Edition |volume=47 |issue=21 |year=2008 |last1=Fellay |first1=Céline |last2=Dyson |first2=Paul J. |last3=Laurenczy |first3=Gábor }}</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).<ref name="Fellay2008" /> Formic acid has been considered as a means of [[hydrogen storage]].<ref>{{cite journal |doi=10.1002/cssc.200800133 |pmid=18781551 |title=Breakthroughs in Hydrogen Storage-Formic Acid as a Sustainable Storage Material for Hydrogen |journal=Chem ''Sus'' ''Chem'' |volume=1 |issue=10 |pages=805–8 |year=2008 |last1=Joó |first1=Ferenc }}</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 three and a half times as much as compressed hydrogen gas can attain at 350 bar pressure (14.7 g L⁻¹). Pure formic acid is a liquid with a flash point of +69&nbsp;°C, much higher than that of gasoline (&minus;40&nbsp;°C) or ethanol (+13&nbsp;°C).{{fact|date=November 2017}} ===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.<ref>{{cite journal |doi=10.1002/cber.19660990410 |title=Die Synthese sekundärer Carbonsäuren nach der Ameisensäure-Methode |journal=Chemische Berichte |volume=99 |issue=4 |pages=1149–52 |year=1966 |last1=Haaf |first1=Wolfgang }}</ref> ===Formic acid anhydride=== An unstable [[formic anhydride]], H(C=O)−O−(C=O)H, can be obtained by dehydration of formic acid with [[N,N'-dicyclohexylcarbodiimide]] in ether at low temperature.<ref name=gwu>{{cite journal |doi=10.1021/j100021a022 |title=Formic Anhydride in the Gas Phase, Studied by Electron Diffraction and Microwave and Infrared Spectroscopy, Supplemented with Ab-Initio Calculations of Geometries and Force Fields |journal=The Journal of Physical Chemistry |volume=99 |issue=21 |pages=8589–98 |year=1995 |last1=Wu |first1=G |last2=Shlykov |first2=S |last3=Van Alseny |first3=F. S |last4=Geise |first4=H. J |last5=Sluyts |first5=E |last6=Van Der Veken |first6=B. J }}</ref> ==History== Some [[alchemy|alchemists]] and [[natural history|naturalists]] were aware that ant hills give 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 English naturalist [[John Ray]], in 1671.<ref>{{cite journal |doi=10.1098/rstl.1670.0052 |title=Extract of a Letter, Written by Mr. John Wray to the Publisher January 13. 1670. Concerning Some Un-Common Observations and Experiments Made with an Acid Juyce to be Found in Ants |journal=Philosophical Transactions of the Royal Society of London |volume=5 |issue=57–68 |pages=2063 |year=1670 |last1=Wray |first1=J }}</ref><ref>{{cite book | url = https://books.google.com/books?id=i1eS9LAe3PsC&pg=PA51 | title = History of the process and present state of animal chemistry | author1 = Johnson | first1 = W. B. | year = 1803}}</ref> Ants secrete the formic acid for attack and defense purposes. Formic acid was first synthesized from [[hydrocyanic acid]] by the French chemist [[Joseph Gay-Lussac]]. In 1855, another French chemist, [[Marcellin Berthelot]], developed a synthesis from [[carbon monoxide]] similar to the process used today. Formic acid was long considered a [[chemical compound]] of only minor interest in the chemical industry. In the late 1960s, however, significant quantities became available as a byproduct of [[acetic acid]] production. It now finds increasing use as a preservative and antibacterial in [[livestock]] feed. ==Safety== Formic acid has low toxicity (hence its use as a food additive), with an [[LD50]] of 1.8 g/kg (tested orally on mice). The concentrated acid is corrosive to the skin.<ref name=Ullmann_2009/> 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 journal |doi=10.1136/jnnp.72.4.423 |pmid=11909893 |pmc=1737836 |year=2002 |author1=Sadun |first1=A. A |title=Mitochondrial optic neuropathies |journal=Journal of Neurology, Neurosurgery, and Psychiatry |volume=72 |issue=4 |pages=423–5 }}</ref> Some chronic effects of formic acid exposure have been documented. Some experiments on bacterial species have demonstrated it to be a [[mutagen]].<ref name="osha.gov">{{cite web|url=http://www.osha.gov/SLTC/healthguidelines/formicacid/recognition.html|title=Occupational Safety and Health Guideline for Formic Acid|publisher=OSHA|accessdate=28 May 2011}}</ref> Chronic exposure in humans may cause kidney damage.<ref name="osha.gov"/> Another possible effect 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 containing vessel. 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%–10% | Irritant ('''Xi''') | {{R36/38}} |- | 10%–90% | Corrosive ('''C''') | {{R34}} |- | >90% | Corrosive ('''C''') | {{R35}} |} Formic acid in 85% concentration is flammable, and diluted formic acid is on the U.S. Food and Drug Administration list of food additives.<ref>U.S. 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 U.S. [[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]]). ==See also== * [[Orthoformic acid]] ==References== {{Reflist|30em}} ==External links== {{Commons}} {{EB1911 poster|Formic Acid}} * [http://etd.rau.ac.za/theses/available/etd-09082004-124908/ Carbon monoxide as reagent in the formylation of aromatic compounds]. * [http://www.inchem.org/documents/icsc/icsc/eics0485.htm International Chemical Safety Card 0485]. * [https://www.cdc.gov/niosh/npg/npgd0296.html NIOSH Pocket Guide to Chemical Hazards]. * [http://chemsub.online.fr/name/Formic_acid.html ChemSub Online (Formic acid)]. * [http://www.mitegone.com/media.asp#combhandbook Formic Acid Use in Beekeeping: Handbook and Manual of Treatments]. * [https://www.youtube.com/watch?v=bsIKVbA0JRs Formic Acid Use by ants: topical application on the cuticle]. {{Molecules detected in outer space}} {{Authority control}} {{DEFAULTSORT:Formic Acid}} [[Category:Formates]] [[Category:Alkanoic acids]] [[Category:Solvents]] [[Category:Cleaning product components]]'