Formate

Formate (IUPAC name: methanoate) is the conjugate base of formic acid. Formate is an anion (HCO−2) or its derivatives such as ester of formic acid. The salts and esters are generally colorless.[1]

Formate
Stereo skeletal formula of formate
Aromatic ball and stick model of formate
Aromatic ball and stick model of formate
Space-filling model of formate
Space-filling model of formate
Names
Preferred IUPAC name
Formate
Systematic IUPAC name
Methanoate
Other names
Formylate
Methylate
Isocarbonite
Carbonite(1-)
Hydrogencarboxylate
Metacarbonoate
Oxocarbinate
Oxomethyl oxide ion
Oxomethoxide
Identifiers
3D model (JSmol)
ChemSpider
MeSH Formates
UNII
  • O=C[O-]
Properties
HCOO−
 or HCO−
2
Molar mass 45.017 g mol−1
Conjugate acid Formic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Fundamentals

When dissolved in water, formic acid converts to formate:

HCO2H → HCO−2 + H+

Formate is a planar anion. The two oxygen atoms are equivalent and bear a partial negative charge. The remaining C-H bond is not acidic.

Biochemistry

Formate is a common C-1 source in living systems. It is formed from many precursors including choline, serine, and sarcosine. It provides a C-1 source in the biosynthesis of some nucleic acids. Formate (or formic acid) is invoked as a leaving group in the demethylation of some sterols.[2] These conversions are catalyzed by aromatase enzymes using O2 as the oxidant. Specific conversions include testosterone to estradiol and androstenedione to estrone.[3]

Formate is reversibly oxidized by the enzyme formate dehydrogenase from Desulfovibrio gigas:[4]

HCO−2 → CO2 + H+ + 2 e−

Formate esters

Formate esters have the formula HCOOR (alternative way of writing formula ROC(O)H or RO2CH). Many form spontaneously when alcohols dissolve in formic acid.

The most important formate ester is methyl formate, which is produced as an intermediate en route to formic acid. Methanol and carbon monoxide react in the presence of a strong base, such as sodium methoxide:[1]

CH3OH + CO → HCOOCH3

Hydrolysis of methyl formate gives formic acid and regenerates methanol:

HCOOCH3 → HCOOH + CH3OH

Formic acid is used for many applications in industry.

Formate esters often are fragrant or have distinctive odors. Compared to the more common acetate esters, formate esters are less commonly used commercially because they are less stable.[5] Ethyl formate is found in some confectionaries.[1]

Formate salts

Formate salts have the formula M(O2CH)(H2O)x. Such salts are prone to decarboxylation. For example, hydrated nickel formate decarboxylates at about 200 °C with reduction of the Ni2+ to finely powdered nickel metal:

Ni(HCO2)2(H2O)2 → Ni + 2 CO2 + 2 H2O + H2

Such fine powders are useful as hydrogenation catalysts.[1]

Examples
Copper(II) formate hydrate

References
  1. Werner Reutemann and Heinz Kieczka "Formic Acid" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a12_013
  2. Pietzke, Matthias; Meiser, Johannes; Vazquez, Alexei (2020). "Formate Metabolism in Health and Disease". Molecular Metabolism. 33: 23–37. doi:10.1016/j.molmet.2019.05.012. PMC 7056922. PMID 31402327.
  3. Lephart, E. D. (1996). "A Review of Brain Aromatase Cytochrome P450". Brain Res. Rev. 22 (1): 1–26. doi:10.1016/0165-0173(96)00002-1. PMID 8871783. S2CID 11987113.
  4. T. Reda, C. M. Plugge, N. J. Abram and J. Hirst, "Reversible interconversion of carbon dioxide and formate by an electroactive enzyme", PNAS 2008 105, 10654–10658. doi:10.1073/pnas.0801290105
  5. Johannes Panten and Horst Surburg "Flavors and Fragrances, 2. Aliphatic Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2015, Wiley-VCH, Weinheim.doi:10.1002/14356007.t11_t01
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