Formate

Structure of formate

Formate (IUPAC name: methanoate) is the anion derived from formic acid. Its formula is represented in various equivalent ways: CHOO⁻ or HCOO⁻ or HCO₂⁻. It is the product of deprotonation of formic acid. It is the simplest carboxylate anion. A formate (compound) is a salt or ester of formic acid.

Biochemistry

Formate is produced in large amounts in the hepatic (liver cells) mitochondria of embryonic cells and in cancer cells by the folate cycle.^[1]

Formate is reversibly oxidized by the enzyme formate dehydrogenase from Desulfovibrio gigas:^[2]

HCO₂⁻ → CO₂ + H⁺ + 2 e⁻

Formate esters and salts

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

Formate salts have the formula M(O₂CH). Such salts are prone to decarboxylation. For example, hydrated nickel formate, a salt, decarboxylates at about 200 °C to give finely powdered nickel metal:

Ni(O₂CH)₂(H₂O)_x → Ni + 2 CO₂ + x H₂O + H₂

Such fine powders are useful as hydrogenation catalyst.

Examples

• ethyl formate, CH₃CH₂(HCOO)
• sodium formate, Na(HCOO)
• caesium formate, Cs(HCOO); see Caesium: Petroleum exploration
• methyl formate, CH₃(HCOO)
• methyl chloroformate, CH₃OCOCl
• triethyl orthoformate
• trimethyl orthoformate, C₄H₁₀O₃

References

1. H Frederik Nijhout, et al, In silico experimentation with a model of hepatic mitochondrial folate metabolism, Theoretical Biology and Medical Modeling, 2006, 3:40, link http://www.tbiomed.com/content/3/1/40/abstract).
2. 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