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Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid. It has the chemical formula HCOOH and structure . This acid is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. , salts, and the anion derived from formic acid are called . Industrially, formic acid is produced from methanol.
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.
It is Miscibility with water and most polar organic , and is somewhat soluble in . In hydrocarbons and in the vapor phase, it consists of Hydrogen bond dimers rather than individual molecules.
Treatment of formic acid with sulfuric acid is a convenient laboratory source of CO.
In the presence of platinum, it decomposes with a release of hydrogen and carbon dioxide.
Formic acid is a source for a formyl group for example in the formylation of N-Methylaniline to N-methylformanilide in toluene.
In synthetic organic chemistry, formic acid is often used as a source of hydride ion, as in the Eschweiler–Clarke reaction:
It is used as a source of hydrogen in transfer hydrogenation, as in the Leuckart reaction to make , and (in aqueous solution or in its azeotrope with triethylamine) for hydrogenation of .
Regenerating CO2 to make useful products, that displace incumbent fossil fuel based pathways is a more impactful process than CO2 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.
CO2 electrolysis is distinct from photosynthesis and offers a promising alternative to accelerate decarbonization. By converting CO2 into products using clean electricity, we reduce CO2 emissions in two ways: first and most simply by the amount of CO2 that is regenerated, but the second way is less obvious but even more consequential by avoiding the CO2 emissions otherwise generated by making these same products from fossil fuels. This is known as carbon displacement or abatement.
CO2 electrolysis holds promise for reducing atmospheric CO2 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.
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:
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:
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.
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. It is widely used to preserve winter feed for cattle, Organic Acids and Food Preservation, Maria M. Theron, J. F. Rykers Lues and is sometimes added to poultry feed to kill Escherichia coli bacteria. Use as a preservative for silage and other animal feed constituted 30% of the global consumption in 2009.
use formic acid as a miticide against the tracheal mite ( Acarapis woodi) and the Varroa destructor mite and Varroa jacobsoni.
Electrolytic conversion of electrical energy to chemical fuel has been proposed as a large-scale source of formate by various groups. The formate could be used as feed to modified Escherichia coli bacteria for producing biomass. Natural methylotroph microbes can feed on formic acid or formate.
Formic acid has been considered as a means of hydrogen storage. 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 °C, much higher than that of gasoline (−40 °C) or ethanol (13 °C).
It is possible to use formic acid as an intermediary to produce isobutanol from using microbes.
Formic acid is also used in place of mineral acids for various cleaning products, such as limescale remover and toilet bowl cleaner. Some formate esters are artificial flavorings and perfumes.
Formic acid application has been reported to be an effective treatment for .
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. Some chronic effects of formic acid exposure have been documented. Some experiments on bacterial species have demonstrated it to be a mutagen. Chronic exposure in humans may cause kidney damage. 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 Globally Harmonized System of Classification and Labelling of Chemicals for formic acid solutions:
Formic acid in 85% concentration is flammable, and diluted formic acid is on the U.S. Food and Drug Administration list of food additives., The principal danger from formic acid is from skin or eye contact with the concentrated liquid or vapors. The U.S. OSHA Permissible Exposure Level (PEL) of formic acid vapor in the work environment is 5 parts per million (ppm) of air.
(2025). 9783527306732 ISBN 9783527306732 Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the ideal gas law. Solid formic acid, which can exist in either of two polymorphs, consists of an effectively endless network of hydrogen-bonded formic acid molecules. Formic acid forms a high-boiling azeotrope with water (107.3 °C; 77.5% formic acid). Liquid formic acid tends to supercooling.
Chemical reactions
Decomposition
Formic acid readily decomposes by dehydration in the presence of concentrated sulfuric acid to form carbon monoxide and water:
Soluble ruthenium catalysts are also effective for producing carbon monoxide-free hydrogen.
Reactant
Formic acid shares most of the chemical properties of other . Because of its high acidity, solutions in alcohols form esters spontaneously; in Fischer esterifications of formic acid, it self-catalyzes the reaction and no additional acid catalyst is needed. (1989). 9780582462366, Longman Scientific & Technical. ISBN 9780582462366 Formic acid shares some of the redox properties of , reducing solutions of metal oxides to their respective metal. (2016). 9781509047697 ISBN 9781509047697
Addition to alkenes
Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with . Formic acids and alkenes readily react to form formate . In the presence of certain acids, including sulfuric acid and hydrofluoric acids, 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
An unstable formic anhydride, H(C=O)−O−(C=O)H, can be obtained by dehydration of formic acid with N, -dicyclohexylcarbodiimide in ether at low temperature.
Production
In 2009, the worldwide capacity for producing formic acid was per year, roughly equally divided between Europe (, mainly in Germany) and Asia (, mainly in China) while production was below per year in all other continents. It is commercially available in solutions of various concentrations between 85 and 99 w/w %. , the largest producers are BASF, Eastman Chemical Company, LC Industrial, and Feicheng Acid Chemicals, with the largest production facilities in Ludwigshafen ( per year, BASF, Germany), Oulu (, Eastman, Finland), Nakhon Pathom (n/a, LC Industrial), and Feicheng (, Feicheng, China). 2010 prices ranged from around €650/tonne (equivalent to around $800/tonne) in Western Europe to $1250/tonne in the United States.
From methyl formate and formamide
When methanol and carbon monoxide are combined in the presence of a strong base, the result is methyl formate, according to the chemical equation:
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 , by a process that cogenerates significant formic acid. This oxidative route to acetic acid has declined 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 to formic acid has long been studied. This reaction can be conducted homogeneously.
Oxidation of biomass
Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the OxFA process. A Keggin structure 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 followed by steam distillation. 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:
Another illustrative method involves the reaction between lead formate and hydrogen sulfide, driven by the formation of lead sulfide.
Electrochemical production
Formate is formed by the electrochemical reduction of CO2 (in the form of bicarbonate) at a lead cathode at pH 8.6:
or
If the feed is and oxygen is evolved at the anode, the total reaction is:
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. 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.
Uses
Agriculture
A major use of formic acid is as a preservative and bacteria agent in livestock feed. It arrests certain decay processes and causes the feed to retain its nutritive value longer,
Energy
Formic acid can be used directly in formic acid fuel cells or indirectly in hydrogen .
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 wettability.
Chromatography
Formic acid is used as a volatile pH modifier in HPLC and capillary electrophoresis. Formic acid is often used as a component of mobile phase in 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.
Other uses
Formic acid is also significantly used in the production of leather, including tanning (23% of the global consumption in 2009), and in dyeing and finishing textiles (9% of the global consumption in 2009) because of its acidic nature. Use as a coagulant in the production of rubber consumed 6% of the global production in 2009.
Safety
Formic acid has low toxicity (hence its use as a food additive), with an of 1.8g/kg (tested orally on mice). The concentrated acid is corrosive to the skin.
2–10% 10–90% >90%
See also
External links
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