View source for Formic acid

{{Redirects|Ant acid|substances that neutralize stomach acidity|antacid}}
{{short description|Simplest carboxylic acid (HCOOH)}}
{{Use dmy dates|date=January 2022}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 443825627
| Name = Formic acid
| ImageFile2 = formic acid 85 percent.jpg
| ImageSize2 = 120px
| ImageFileL1 = Formic_acid.svg
| ImageClassL1 = skin-invert-image
| ImageNameL1 = Skeletal structure of formic acid
| ImageFileR1 = Formic-acid-CRC-MW-3D-balls.png
| ImageClassR1 = bg-transparent
| 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 | isbn = 978-0-85404-182-4| last1 = Favre | first1 = Henri A. | last2 = Powell | first2 = Warren H. }}</ref>
| SystematicName = Methanoic acid<ref name=iupac2013 />
| OtherNames = {{Unbulleted list|Formylic acid|Methylic acid|Hydrogencarboxylic acid|Hydroxy(oxo)methane|Metacarbonoic acid|Oxocarbinic acid|Oxomethanol|Hydroxymethylene oxide}}
|Section1={{Chembox Identifiers
| CASNo = 64-18-6
| CASNo_Ref = {{cascite|correct|CAS}}
| Beilstein = 1209246
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 30751
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 116736
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 278
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB01942
| EINECS = 200-579-1
| Gmelin = 1008
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 0YIW783RG1
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = C00058
| PubChem = 284
| RTECS = LQ4900000
| SMILES = O=CO
| InChI = 1/HCOOH/c2-1-3/h1H,(H,2,3)
| InChIKey = BDAGIHXWWSANSR-UHFFFAOYAT
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/HCOOH/c2-1-3/h1H,(H,2,3)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = BDAGIHXWWSANSR-UHFFFAOYSA-N
 }}
|Section2={{Chembox Properties
| C=1 | H=2 | O=2
| Appearance = Colorless fuming liquid
| Odor = Pungent, penetrating, similar to [[vinegar]] ([[acetic acid]])
| Density = 1.220{{nbsp}}g/mL
| Solubility = Miscible
| SolubleOther = Miscible with [[diethyl ether|ether]], [[acetone]], [[ethyl acetate]], [[glycerol]], [[methanol]], [[ethanol]] <br /> Partially soluble in [[benzene]], [[toluene]], [[xylene]]s
| MeltingPtC = 8.4
| BoilingPtC = 100.8
| pKa = 3.745<ref name="Smith R">{{cite book |last1=Smith |first1=Robert M. |last2=Martell |first2=Arthur E. |title=Critical Stability Constants Volume 6: Second Supplement |date=1989 |publisher=Plenum Press |location=New York |isbn=0-306-43104-1 |page=299}}</ref>
| ConjugateBase = [[Formate]]
| Viscosity = 1.57{{nbsp}}c[[Poise (unit)|P]] at 268&nbsp;°C
| LogP = −0.54
| RefractIndex = 1.3714 (20&nbsp;°C)
| MagSus = {{val|-19.90|e=-6|u=cm3/mol}}
| VaporPressure = 35{{nbsp}}mmHg (20&nbsp;°C)<ref name=PGCH/>
 }}
|Section3={{Chembox Structure
| MolShape = [[wikt:planar|Planar]]
| Dipole = 1.41{{nbsp}}[[Debye|D]] (gas)}}
|Section5={{Chembox Thermochemistry
| DeltaHf = −425.0{{nbsp}}kJ/mol
| DeltaHc = −254.6{{nbsp}}kJ/mol
| Entropy = 131.8{{nbsp}}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 MSDS from JT Baker]
| MainHazards = Corrosive; irritant;<br />sensitizer
| NFPA-H = 3
| NFPA-F = 2
| NFPA-R = 0
| FlashPtC = 69
| AutoignitionPtC = 601
| ExploLimits = 14{{ndash}}34%{{citation needed|date=March 2015}}<br /> 18{{ndash}}57% (90% solution)<ref name=PGCH/>
| GHSPictograms = {{GHS02}} {{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314}}
| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}}
| LD50 = 700{{nbsp}}mg/kg (mouse, oral), 1100{{nbsp}}mg/kg (rat, oral), 4000{{nbsp}}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 |access-date = 26 March 2015}}</ref>
| PEL = TWA 5{{nbsp}}ppm (9{{nbsp}}mg/m<sup>3</sup>)<ref name=PGCH>{{PGCH|0296}}</ref>
| IDLH = 30{{nbsp}}ppm<ref name=PGCH/>
| REL = TWA 5{{nbsp}}ppm (9{{nbsp}}mg/m<sup>3</sup>)<ref name=PGCH/>
| LC50 = 7853{{nbsp}}ppm (rat, 15{{nbsp}}min)<br />3246{{nbsp}}ppm (mouse, 15{{nbsp}}min)<ref name=IDLH/>
 }}
|Section8={{Chembox Related
| OtherFunction_label = [[carboxylic acid]]s
| OtherFunction = [[Acetic acid]]<br />[[Propionic acid]]
| OtherCompounds = [[Formaldehyde]]<br />[[Methanol]]}}
}}

'''Formic acid''' ({{ety|la|formica|[[ant]]}}), [[Preferred IUPAC name|systematically named]] '''methanoic acid''', is the simplest [[carboxylic acid]]. It has the [[chemical formula]] HCOOH and structure {{chem2|H\sC(\dO)\sO\sH}}. This acid is an important intermediate in [[chemical synthesis]] and occurs naturally, most notably in some ants. [[Ester]]s, [[salt (chemistry)|salts]], and the [[anion]] derived from formic acid are called [[formate]]s. Industrially, formic acid is produced from [[methanol]].<ref>{{Cite web |title=Formic acid |url=https://www.acs.org/molecule-of-the-week/archive/f/formic-acid.html |access-date=2023-11-21 |website=American Chemical Society |language=en}}</ref>

==Natural occurrence==
{{See also|Insect defenses}}

Formic acid, which has a pungent, penetrating odor, is found naturally in insects, weeds, fruits and vegetables, and forest emissions.  It appears in most [[ants]] and in [[stingless bee]]s of the genus ''[[Oxytrigona]]''.<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 |s2cid=4999650 }}</ref><ref>{{cite journal| pmid=24302133 | doi=10.1007/BF01020539 | volume=13 | issue=5 | title=Formic acid in caustic cephalic secretions of stingless bee,Oxytrigona (Hymenoptera: Apidae) | year=1987 | journal=J Chem Ecol | pages=1079–86 | last1 = Roubik | first1 = DW | last2 = Smith | first2 = BH | last3 = Carlson | first3 = RG| bibcode=1987JCEco..13.1079R | s2cid=30511107 }}</ref> [[Formica rufa species group|Wood ants]] from the genus ''[[Formica]]'' can spray formic acid on their prey or to defend the nest. The [[Cerura vinula|puss moth caterpillar]] (''Cerura vinula'') will spray it as well when threatened by predators. It is also found in the [[trichome]]s of [[Urtica dioica|stinging nettle]] (''Urtica dioica''). Apart from that, this acid is incorporated in many fruits such as pineapple (0.21 mg per 100 g), apple (2 mg per 100 g) and kiwi (1 mg per 100 g), as well as in many vegetables, namely onion (45 mg per 100 g), eggplant (1.34 mg per 100 g) and, in extremely low concentrations, cucumber (0.11 mg per 100 g).<ref>{{cite journal| pmc=3349212 | pmid=22593694 | doi=10.1100/2012/564367 | volume=2012 | title=Phenolic compounds analysis of root, stalk, and leaves of nettle | year=2012 | journal=ScientificWorldJournal | article-number=564367 | last1 = Otles | first1 = S | last2 = Yalcin | first2 = B | doi-access=free }}</ref> Formic acid is a naturally occurring component of the [[Atmosphere of Earth|atmosphere]] primarily due 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>

==History==
As early as the 15th century, some [[alchemy|alchemists]] and [[natural history|naturalists]] were aware that ant hills give off an acidic vapor. 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=2063–2066 |year=1670 |last1=Wray |first1=J |bibcode=1670RSPT....5.2063W |doi-access=free }}</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 | last1 = 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.<ref name="Monarch">{{cite web|url=https://www.monarchchemicals.co.uk/Information/News-Events/962-/What-is-Formic-Acid|title=What is Formic Acid?|website=Monarch Chemicals|access-date=15 April 2025}}</ref>

Formic acid was long considered a [[chemical compound]] of only minor interest in the chemical industry. In the late 1960s, significant quantities became available as a byproduct of [[acetic acid]] production. It now finds increasing use as a preservative and antibacterial in [[livestock]] feed.<ref name="Monarch"/>

==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>{{cite web|url=https://www.osha.gov/chemicaldata/chemResult.html?recNo=468|title=OSHA Occupational Chemical Database – Occupational Safety and Health Administration|website=osha.gov|access-date=17 April 2015|archive-date=29 April 2021|archive-url=https://web.archive.org/web/20210429045534/https://www.osha.gov/chemicaldata/chemResult.html?recNo=468}}</ref> at room temperature, comparable to the related [[acetic acid]]. Formic acid is about ten times stronger of an acid than [[acetic acid]]; its (logarithmic) dissociation constant ([[Acid dissociation constant|pKa]]) is 3.745, compared to the pKa of 4.756 for acetic acid.<ref name="Smith R"/>

It is [[Miscibility|miscible]] with 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=978-3-527-30673-2 }}</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 |author= Roman M. Balabin |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, which can exist in either of two [[polymorphism (materials science)|polymorphs]], consists of an effectively endless network of hydrogen-bonded formic acid molecules. Formic acid forms a high-boiling [[azeotrope]] with water (107.3&nbsp;°C; 77.5% formic acid). Liquid formic acid tends to [[supercooling|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}}

==Chemical reactions==

===Decomposition===
Formic acid readily decomposes by dehydration in the presence of concentrated [[sulfuric acid]] to form [[carbon monoxide]] and water:
:HCO<sub>2</sub>H → H<sub>2</sub>O + CO

Treatment of formic acid with sulfuric acid is a convenient laboratory source of CO.<ref name="koch">{{cite journal |doi=10.15227/orgsyn.044.0001 |title=1-Adamantanecarboxylic Acid |journal=Organic Syntheses |date=1964 |volume=44 |page=1|first1=H.|last1=Koch|first2=W.|last2=Haaf }}</ref><ref name="coleman">{{OrgSynth|title=''p''-Tolualdehyde|author=Coleman, G. H.|author2=Craig, David|volume=12|pages=80|year=1932|doi=10.15227/orgsyn.012.0080}}</ref>

In the presence of [[platinum]], it decomposes with a release of [[hydrogen]] and [[carbon dioxide]].
:HCO<sub>2</sub>H → H<sub>2</sub> + CO<sub>2</sub>
Soluble [[ruthenium]] catalysts are also effective for producing carbon monoxide-free hydrogen.<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 |pages=3966–8}}</ref>

===Reactant===
Formic acid shares most of the chemical properties of other [[carboxylic acid]]s. Because of its high acidity, solutions in alcohols form esters spontaneously; in [[Fischer esterification]]s of formic acid, it self-catalyzes the reaction and no additional acid catalyst is needed.<ref>{{cite book |last1=Furniss |first1=Brian S. |last2=Hannaford |first2=Antony, J. |last3=Smith |first3=Peter W. G. |last4=Tatchell |first4=Austin S. |edition=5th |year=1989 |title=Vogel's Textbook of Practical Organic Chemistry |publisher=Longman Scientific & Technical |page=696, 701 |isbn=978-0-582-46236-6}}</ref> Formic acid shares some of the [[redox|reducing]] properties of [[aldehyde]]s, reducing solutions of metal oxides to their respective metal.<ref>{{Cite book|last1=Ozawa|first1=Naoto|last2=Okubo|first2=Tatsuo|last3=Matsuda|first3=Jun|last4=Sakai|first4=Tatsuo|title=2016 11th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT) |chapter=Observation and analysis of metal oxide reduction by formic acid for soldering |date=October 2016|pages=148–151|doi=10.1109/IMPACT.2016.7799990|isbn=978-1-5090-4769-7|s2cid=32545113}}</ref>

Formic acid is a source for a [[formyl]] group for example in the [[formylation]] of [[N-Methylaniline|''N''-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, as in the [[Eschweiler–Clarke reaction]]:
[[Image:Eschweiler-Clarke Reaction.svg|center|300px|The Eschweiler–Clark reaction]]

It is used as a source of hydrogen in [[transfer hydrogenation]], as in the [[Leuckart reaction]] to make [[amine]]s, and (in aqueous solution or in its [[azeotrope]] with [[triethylamine]]) for hydrogenation of [[ketone]]s.<ref name="Zhou2012">{{cite journal | last=Zhou | first=Xiaowei | display-authors=etal | title=Varying the ratio of formic acid to triethylamine impacts on asymmetric transfer hydrogenation of ketones | journal=Journal of Molecular Catalysis A: Chemical | volume=357 | year=2012 | issn=1381-1169 | doi=10.1016/j.molcata.2012.02.002 | pages=133–140}}</ref>

===Addition to alkenes===
Formic acid is unique among the alkenes 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|''N'',''{{prime|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>

==Production==
In 2009, the worldwide capacity for producing formic acid was {{convert|720|e3t|e9lb|abbr=off}} per year, roughly equally divided between Europe ({{convert|350|e3t|e6lb|abbr=off|disp=or}}, mainly in Germany) and Asia ({{convert|370|e3t|e6lb|abbr=off|disp=or}}, mainly in China) while production was below {{convert|1|e3t|e6lb|abbr=off|disp=or}} per year 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 |archive-url=https://web.archive.org/web/20110914202313/http://www.sriconsulting.com/CEH/Public/Reports/659.2000/ |archive-date=14 September 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]] ({{convert|200|e3t|e6lb|abbr=off|disp=or}} per year, BASF, Germany), [[Oulu]] ({{convert|105|e3t|e6lb|abbr=off|disp=or}}, Eastman, Finland), [[Nakhon Pathom]] (n/a, LC Industrial), and [[Feicheng]] ({{convert|100|e3t|e6lb|abbr=off|disp=or}}, 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/>

Regenerating CO<sub>2</sub> to make useful products, that displace incumbent fossil fuel based pathways is a more impactful process than CO<sub>2</sub> sequestration.

Both formic acid and CO (carbon monoxide) are C1 (one carbon molecules).  Formic is a hydrogen-rich liquid which can be transported and easily donates its hydrogen to enable a variety of condensation and esterification reactions to make a wide variety of derivative molecules.  CO, while more difficult to transport as a gas, is also one of the primary constituents of syngas useful in synthesizing a wide variety of molecules.

CO<sub>2</sub> electrolysis is distinct from photosynthesis and offers a promising alternative to accelerate decarbonization. By converting CO<sub>2</sub> into products using clean electricity, we reduce CO<sub>2</sub> emissions in two ways: first and most simply by the amount of CO<sub>2</sub> that is regenerated, but the second way is less obvious but even more consequential by avoiding the CO<sub>2</sub> emissions otherwise generated by making these same products from fossil fuels. This is known as carbon displacement or abatement.

CO<sub>2</sub> electrolysis holds promise for reducing atmospheric CO<sub>2</sub> levels and providing a sustainable method for producing chemicals, materials, and fuels. Its efficiency and scalability are active areas of research, but now also commercialization, aiming to make it a viable commercial technology for both carbon management and molecule production.<ref>{{Cite web |title=Rethinking CO2 in a Circular Economy {{!}} Carbon Capture Magazine |url=https://carboncapturemagazine.com/articles/rethinking-co2-in-a-circular-economy |access-date=2025-03-11 |website=carboncapturemagazine.com}}</ref>

===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/>
:CH<sub>3</sub>OH + CO → HCO<sub>2</sub>CH<sub>3</sub>

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:
:HCO<sub>2</sub>CH<sub>3</sub> + H<sub>2</sub>O → HCOOH + CH<sub>3</sub>OH

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]]:
:HCO<sub>2</sub>CH<sub>3</sub> + NH<sub>3</sub> → HC(O)NH<sub>2</sub> + CH<sub>3</sub>OH
:2 HC(O)NH<sub>2</sub> + 2H<sub>2</sub>O + H<sub>2</sub>SO<sub>4</sub> → 2HCO<sub>2</sub>H + (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>

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.{{citation needed|date=November 2017}}

===Niche and obsolete 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 [[alkane]]s, by a process that cogenerates significant formic acid.<ref name=Ullmann_2009/> This oxidative route to acetic acid has declined in importance so that the aforementioned dedicated routes to formic acid have become more important.{{cn|date=June 2024}}

====Hydrogenation of carbon dioxide====
The catalytic [[hydrogenation]] of [[Carbon dioxide|CO<sub>2</sub>]] to formic acid has long been studied. This reaction can be conducted homogeneously.<ref>{{Cite book | author = P. G. Jessop | title = Handbook of Homogeneous Hydrogenation | editor = J. G. de Vries, C. J. Elsevier | publisher = Wiley-VCH | location = Weinheim, Germany | date = 2007 | pages = 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 |page=2425 |year=2004 |last1=Jessop |first1=Philip G |last2=Joó |first2=Ferenc |last3=Tai |first3=Chih-Cheng }}</ref><ref>{{Cite web |last=Sampson |first=Joanna |date=2 August 2020 |title=Wireless device makes clean fuel from sunlight, CO2 and water |url=https://www.gasworld.com/wireless-device-makes-clean-fuel-from-sunlight-co2-and-water-/2019694.article |access-date=2020-08-26 |website=Gasworld |language=en}}</ref>

====Oxidation of biomass====
Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the [[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 |page=2759 |year=2011 |last1=Wölfel |first1=Rene |last2=Taccardi |first2=Nicola |last3=Bösmann |first3=Andreas |last4=Wasserscheid |first4=Peter |s2cid=97572039 }}</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 |page=7956 |year=2012 |last1=Albert |first1=Jakob |last2=Wölfel |first2=Rene |last3=Bösmann |first3=Andreas |last4=Wasserscheid |first4=Peter |bibcode=2012EnEnS...5.7956A |s2cid=93224286 }}</ref> A [[Keggin structure|Keggin-type]] polyoxometalate (H<sub>5</sub>PV<sub>2</sub>Mo<sub>10</sub>O<sub>40</sub>) is used as the homogeneous catalyst to convert sugars, wood, waste paper, or cyanobacteria to formic acid and CO<sub>2</sub> as the sole byproduct. Yields of up to 53% formic acid can be achieved.{{Citation needed|date=November 2018}}

====Laboratory methods====
In the laboratory, formic acid can be obtained by heating [[oxalic acid]] in [[glycerol]] followed by steam distillation.<ref name="chattaway">{{cite journal |doi=10.1039/CT9140500151 |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 |hdl=2027/mdp.39015067135775 |url=https://zenodo.org/record/2046509 }}</ref> Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediate. If the reaction mixture is heated to higher temperatures, [[allyl alcohol]] results. The net reaction is thus:
:C<sub>2</sub>O<sub>4</sub>H<sub>2</sub> → HCO<sub>2</sub>H + CO<sub>2</sub><!--esoteric and not useful to anyone: Another preparation is the acid [[hydrolysis]] of ethyl isonitrile (C<sub>2</sub>H<sub>5</sub>NC) using [[hydrochloric acid|HCl]] solution.<ref name="cohen">{{Cite book | author = Cohen, Julius B. | title = Practical Organic Chemistry | publisher = MacMillan | date = 1930}}</ref>
:C<sub>2</sub>H<sub>5</sub>NC + 2 H<sub>2</sub>O → C<sub>2</sub>H<sub>5</sub>NH<sub>2</sub> + HCO<sub>2</sub>H
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>{{Cite book | author = Arthur Sutcliffe | date = 1930 | title = Practical Chemistry for Advanced Students | edition = 1949 | publisher = John Murray | location = London}}</ref>
:Pb(HCOO)<sub>2</sub> + H<sub>2</sub>S → 2HCOOH + PbS

====Electrochemical production====
Formate is formed by the [[electrochemical reduction]] of CO<sub>2</sub> (in the form of [[bicarbonate]]) at a [[lead]] [[cathode]] at pH 8.6:<ref>{{cite journal |display-authors=etal|last1=B. Innocent |title=Electro-reduction of carbon dioxide to formate on lead electrode in aqueous medium |journal=Journal of Applied Electrochemistry |date=Feb 2009 |doi=10.1007/s10800-008-9658-4 |volume=39 |issue=2 |pages=227–232|s2cid=98437382 }}</ref>
:{{chem|HCO|3|-}} + {{chem|H|2|O}} + 2e<sup>−</sup> → {{chem|HCO|2|-}} + 2{{Chem|OH|-}}
or
:{{chem|CO|2}} + {{chem|H|2|O}} + 2e<sup>−</sup> → {{chem|HCO|2|-}} + {{Chem|OH|-}}
If the feed is {{chem|CO|2}} and oxygen is evolved at the anode, the total reaction is:
:{{CO2}} + {{chem|OH|-}} → {{chem|HCO|2|-}} + 1/2 {{O2}}

===Biosynthesis===
Formic acid is named after ants which have high concentrations of the compound in their venom, derived from [[serine]] through 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 November 1978|volume=543|issue=4|pages=484–496|doi=10.1016/0304-4165(78)90303-3|pmid=718985}}</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=117–26 |year=1975 |last1=Makar |first1=A.B |last2=McMartin |first2=K.E |last3=Palese |first3=M |last4=Tephly |first4=T.R }}</ref>

== Uses ==
===Agriculture===
A major use of formic acid is as a [[preservative]] and [[bacteria|antibacterial]] agent in livestock feed. It arrests certain decay processes and causes the feed to retain its [[Nutrition|nutritive]] value longer.

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/> It is widely used to preserve winter feed for [[cattle]],<ref>[https://books.google.com/books?id=7IrGwQTt1aMC&dq=formic+acid++winter+feed+for+cattle&pg=PA31 Organic Acids and Food Preservation], Maria M. Theron, J. F. Rykers Lues</ref> and is sometimes added to [[poultry]] 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 |page=750 |year=2005 |last1=Griggs |first1=J. P |last2=Jacob |first2=J. P |doi-access=free }}</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 |page=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 |doi-access=free }}</ref> Use as a preservative for silage and other animal feed constituted 30% of the global consumption in 2009.<ref name=CEH/>

[[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. |author2=Ritter, W. |author3=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>

===Energy===
Formic acid can be used directly in [[formic acid fuel cell]]s or indirectly in hydrogen [[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 |issue=1 |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=https://www.bbc.com/news/business-40403351 |publisher=[[BBC News]] |date=27 June 2017 |access-date=11 July 2017}}</ref>

Electrolytic conversion of electrical energy to chemical fuel has been proposed as a large-scale source of formate by various groups.<ref>{{Cite journal|last1=Yishai|first1=Oren|last2=Lindner|first2=Steffen N|last3=Gonzalez de la Cruz|first3=Jorge|last4=Tenenboim|first4=Hezi|last5=Bar-Even|first5=Arren|date=December 2016|title=The formate bio-economy|journal=Current Opinion in Chemical Biology|language=en|volume=35|pages=1–9|doi=10.1016/j.cbpa.2016.07.005|pmid=27459678}}</ref> The formate could be used as feed to modified ''[[Escherichia coli|E. coli]]'' bacteria for producing [[biomass]].<ref>{{cite journal |display-authors=etal|last1=Shmuel Gleizer |title=Conversion of ''Escherichia coli'' to Generate All Biomass Carbon from CO<sub>2</sub> |journal=Cell |date=Nov 2019 |doi=10.1016/j.cell.2019.11.009 |volume=179 |issue=6 |pages=1255–1263.e12|pmid=31778652 |doi-access=free |pmc=6904909 }}</ref><ref>{{Cite journal|last1=Kim|first1=Seohyoung|last2=Lindner|first2=Steffen N.|last3=Aslan|first3=Selçuk|last4=Yishai|first4=Oren|last5=Wenk|first5=Sebastian|last6=Schann|first6=Karin|last7=Bar-Even|first7=Arren|date=2020-02-10|title=Growth of E. coli on formate and methanol via the reductive glycine pathway|url=https://www.nature.com/articles/s41589-020-0473-5|journal=Nature Chemical Biology|language=en|pages=538–545|doi=10.1038/s41589-020-0473-5|issn=1552-4469|volume=16|issue=5|pmid=32042198|s2cid=211074951|url-access=subscription}}</ref> Natural [[methylotroph]] microbes can feed on formic acid or formate.

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=ChemSusChem |volume=1 |issue=10 |pages=805–8 |year=2008 |last1=Joó |first1=Ferenc |bibcode=2008ChSCh...1..805J }}</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 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). Pure formic acid is a liquid with a [[flash point]] of 69&nbsp;°C, much higher than that of gasoline (−40&nbsp;°C) or ethanol (13&nbsp;°C).{{citation needed|date=November 2017}}

It is possible to use formic acid as an intermediary to produce [[isobutanol]] from {{CO2}} using microbes.<ref>{{Cite web|url=https://newenergyandfuel.com/http://newenergyandfuel/com/2012/03/30/ucla-researchers-use-electricity-and-co2-to-make-butanol/|title=UCLA Researchers Use Electricity and CO2 to Make Butanol|date=30 March 2012 }}</ref><ref>{{Cite journal|title=Integrated Electromicrobial Conversion of CO2 to Higher Alcohols|first1=James C.|last1=Liao|first2=Kwang Myung|last2=Cho|first3=Yi-Xin|last3=Huo|first4=Peter|last4=Malati|first5=Wendy|last5=Higashide|first6=Tung-Yun|last6=Wu|first7=Steve|last7=Rogers|first8=David G.|last8=Wernick|first9=Paul H.|last9=Opgenorth|first10=Han|last10=Li|date=30 March 2012|journal=Science|volume=335|issue=6076|page=1596|doi=10.1126/science.1217643|pmid=22461604|bibcode=2012Sci...335.1596L|s2cid=24328552}}</ref>

===Soldering===
Formic acid has a potential application in [[soldering]]. Due to its capacity to reduce oxide layers, formic acid gas can be blasted at an oxide surface to increase solder [[Soldering#Flux|wettability]].{{cn|date=June 2024}}

===Chromatography===
Formic acid is used as a volatile pH modifier in [[High-performance liquid chromatography|HPLC]] and [[capillary electrophoresis]]. Formic acid is often used as a component of mobile phase in [[Reversed-phase chromatography|reversed-phase]] [[high-performance liquid chromatography]] (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>{{Cite web |url=https://www.novapublishers.com/catalog/product_info.php?products_id=48192 |title=Archived copy |access-date=7 November 2017 |archive-date=7 November 2017 |archive-url=https://web.archive.org/web/20171107112257/https://www.novapublishers.com/catalog/product_info.php?products_id=48192 }}{{full citation needed|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>

===Other uses===
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 and perfumes.

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 |s2cid=42351889 }}</ref>

==Safety==
Formic acid has low toxicity (hence its use as a food additive), with an {{LD50}} of 1.8{{nbsp}}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 |last1=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|access-date=28 May 2011|archive-date=20 September 2011|archive-url=https://web.archive.org/web/20110920200807/http://www.osha.gov/SLTC/healthguidelines/formicacid/recognition.html}}</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.{{cn|date=June 2024}}

The hazards of solutions of formic acid depend on the concentration. The following table lists the [[Globally Harmonized System of Classification and Labelling of Chemicals]] for formic acid solutions:{{citation needed|date=October 2021}}

{| class = "wikitable"
|-
! [[Concentration]] ([[weight percent]])
! Pictogram
! [[List of H-phrases|H-Phrases]]
|-
| 2–10%
| {{GHS07}}
| {{H-phrases|315}}
|-
| 10–90%
| {{GHS05}}
| {{H-phrases|313}}
|-
| >90%
| {{GHS05}}
| {{H-phrases|314}}
|}

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>{{CodeFedReg|21|186|1316}}, {{CodeFedReg|21|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]] (ppm) of air.<ref>{{Cite web |title=CDC - NIOSH Pocket Guide to Chemical Hazards - Formic acid |url=https://www.cdc.gov/niosh/npg/npgd0296.html |access-date=2024-11-01 |website=www.cdc.gov}}</ref>

==See also==
* [[Orthoformic acid]]
* [[Alternative fuel vehicle#Formic acid|Formic acid vehicle]]

==References==
{{Reflist}}

==External links==
{{Commons}}
{{EB1911 poster|Formic Acid}}
* [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)].

{{Molecules detected in outer space}}
{{Authority control}}

{{DEFAULTSORT:Formic Acid}}
[[Category:Formates| ]]
[[Category:Alkanoic acids]]
[[Category:Solvents]]
[[Category:Cleaning product components]]
[[Category:Organic compounds with 1 carbon atom]]