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Formic acid (from Latin formica ‘ant), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure H−C(=O)−O−H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Esters, salts and the anion derived from formic acid are called formates. Industrially, formic acid is produced from methanol .
See also: Insect defenses
Formic acid is found naturally in insects, weeds, fruits and vegetables, and forest emissions. It appears in most ants and in stingless bees of the genus Oxytrigona . Wood ants from the genus Formica can spray formic acid on their prey or to defend the nest. The puss moth caterpillar (Cerura vinula) will spray it as well when threatened by predators. It is also found in the trichomes of 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).Formic acid is a naturally occurring component of the atmosphere primarily due to forest emissions.
As early as the 15th century, some alchemists and 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. 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, significant quantities became available as a byproduct of acetic acid production. It now finds increasing use as a preservative and antibacterial in livestock feed.
Cyclic dimer of formic acid; dashed green lines represent hydrogen bonds
Formic acid is a colorless liquid having a pungent, penetrating odor[12] at room temperature, comparable to the related acetic acid. Formic acid is about ten times stronger than acetic acid .
It is miscible with water and most polar organic solvents, and is somewhat soluble in hydrocarbons. In hydrocarbons and in the vapor phase, it consists of hydrogen-bonded dimers rather than individual molecules.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 supercool.
Formic acid readily decomposes by dehydration in the presence of concentrated sulfuric acid to form carbon monoxide and water:
HCO2H → H2O + CO
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.
HCO2H → H2 + CO2
Soluble ruthenium catalysts are also effective for producing carbon monoxide-free hydrogen
Formic acid shares most of the chemical properties of other carboxylic acids. 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. Formic acid shares some of the reducing properties of aldehydes, reducing solutions of metal oxides to their respective metal.
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 amines, and (in aqueous solution or in its azeotrope with triethylamine) for hydrogenation of ketones .
Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with alkenes. Formic acids and alkenes readily react to form formate esters. In the presence of certain acids, including sulfuric 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 .
In 2009, the worldwide capacity for producing formic acid was 720 thousand tonnes (1.6 billion pounds) per year, roughly equally divided between Europe (350 thousand tonnes or 770 million pounds, mainly in Germany) and Asia (370 thousand tonnes or 820 million pounds, mainly in China) while production was below 1 thousand tonnes or 2.2 million pounds per year in all other continents It is commercially available in solutions of various concentrations between 85 and 99 w/w % 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 thousand tonnes or 440 million pounds per year, BASF, Germany), Oulu (105 thousand tonnes or 230 million pounds, Eastman, Finland), Nakhon Pathom (n/a, LC Industrial), and Feicheng (100 thousand tonnes or 220 million pounds, Feicheng, China). 2010 prices ranged from around €650/tonne (equivalent to around $800/tonne) in Western Europe to $1250/tonne in the United States.
When methanol and carbon monoxide are combined in the presence of a strong base, the result is methyl formate, according to the chemical equation .
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 → HCOOH + CH3OH
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 → HCOOH + 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 .
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 has declined in importance so that the aforementioned dedicated routes to formic acid have become more important.
The catalytic hydrogenation of CO2 to formic acid has long been studied. This reaction can be conducted homogeneously.
Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the OxFA process . A 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.
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:
C2O4H2 → HCO2H + CO2
Another illustrative method involves the reaction between lead formate and hydrogen sulfide, driven by the formation of lead sulfide .
Pb(HCOO)2 + H2S → 2HCOOH + PbS
Formate is formed by the electrochemical reduction of CO2 (in the form of bicarbonate) at a lead cathode at pH 8.6:
HCO−
3 + H
2O + 2e− → HCO−
2 + 2OH−
or
CO
2 + H
2O + 2e− → HCO−
2 + OH−
If the feed is CO
2 and oxygen is evolved at the anode, the total reaction is:
CO2 + OH−
→ HCO−
2 + 1/2 O2
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.
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 .
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 has declined in importance so that the aforementioned dedicated routes to formic acid have become more important.
The catalytic hydrogenation of CO2 to formic acid has long been studied. This reaction can be conducted homogeneously.
Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the OxFA process . A 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.
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:
C2O4H2 → HCO2H + CO2
Another illustrative method involves the reaction between lead formate and hydrogen sulfide, driven by the formation of lead sulfide .
Pb(HCOO)2 + H2S → 2HCOOH + PbS
Formate is formed by the electrochemical reduction of CO2 (in the form of bicarbonate) at a lead cathode at pH 8.6:
HCO−
3 + H
2O + 2e− → HCO−
2 + 2OH−
or
CO
2 + H
2O + 2e− → HCO−
2 + OH−
If the feed is CO
2 and oxygen is evolved at the anode, the total reaction is:
CO2 + OH−
→ HCO−
2 + 1/2 O2
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.
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.
In 2009, the worldwide capacity for producing formic acid was 720 thousand tonnes (1.6 billion pounds) per year, roughly equally divided between Europe (350 thousand tonnes or 770 million pounds, mainly in Germany) and Asia (370 thousand tonnes or 820 million pounds, mainly in China) while production was below 1 thousand tonnes or 2.2 million pounds per year in all other continents.It is commercially available in solutions of various concentrations between 85 and 99 w/w %. 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 thousand tonnes or 440 million pounds per year, BASF, Germany), Oulu (105 thousand tonnes or 230 million pounds, Eastman, Finland), Nakhon Pathom (n/a, LC Industrial), and Feicheng (100 thousand tonnes or 220 million pounds, Feicheng, China). 2010 prices ranged from around €650/tonne (equivalent to around $800/tonne) in Western Europe to $1250/tonne in the United States.
When methanol and carbon monoxide are combined in the presence of a strong base, the result is methyl formate, according to the chemical equation .
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 → HCOOH + CH3OH
Hazard statements
H226 Flammable liquid and vapour.
H302 Harmful if swallowed.
H314 Causes severe skin burns and eye damage.
H331 Toxic if inhaled.
H370 Causes damage to organs.
– Precautionary statements
P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No
smoking.
P260 Do not breathe dust/fume/gas/mist/vapours/spray.
P280 Wear protective gloves/protective clothing/eye protection/face protection.
P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or
shower.
P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present
and easy to do. Continue rinsing.
P310 Immediately call a POISON CENTER/doctor.
P370+P378 In case of fire: Use sand, carbon dioxide or powder extinguisher to extinguish.
P403+P233 Store in a well-ventilated place. Keep container tightly closed.
P403+P235 Store in a well-ventilated place. Keep cool.
General notes
Do not leave affected person unattended. Remove victim out of the danger area. Keep affected person warm, still and
covered. Take off immediately all contaminated clothing. In all cases of doubt, or when symptoms persist, seek medic-
al advice. In case of unconsciousness place person in the recovery position. Never give anything by mouth.
Following inhalation
If breathing is irregular or stopped, immediately seek medical assistance and start first aid actions. In case of respirat-
ory tract irritation, consult a physician. Provide fresh air.
Following skin contact
Wash with plenty of soap and water.
Following eye contact
Remove contact lenses, if present and easy to do. Continue rinsing. Irrigate copiously with clean, fresh water for at
least 10 minutes, holding the eyelids apart.
Following ingestion
Rinse mouth with water (only if the person is conscious). Do NOT induce vomiting.
Special hazards arising from the substance or mixture
In case of insufficient ventilation and/or in use, may form flammable/explosive vapour-air mixture. Solvent vapours are
heavier than air and may spread along floors. Places which are not ventilated, e.g. unventilated below ground level
areas such as trenches, conduits and shafts, are particularly prone to the presence of flammable substances or mix-
tures.
Hazardous combustion products
Nitrogen oxides (NOx), Carbon monoxide (CO), Carbon dioxide (CO2).
Advice for firefighters
In case of fire and/or explosion do not breathe fumes. Co-ordinate firefighting measures to the fire surroundings. Do
not allow firefighting water to enter drains or water courses. Collect contaminated firefighting water separately. Fight
fire with normal precautions from a reasonable distance.
Getting an accurate diagnosis can be one of the most impactful experiences that you can have.
