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.^[1]

Biochemistry

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

HCO₂⁻ → CO₂ + H⁺ + 2 e⁻

Formate esters

Formate esters have the formula ROC(O)H (alternative way of writing formula 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 in the presence of a strong base, such as sodium methoxide:^[1]

CH₃OH + CO → HCO₂CH₃

Hydrolysis of methyl formate gives formic acid and regenerates methanol:

HCO₂CH₃ → HCO₂H + CH₃OH

Formic acid is used for many applications in industry.

Formate esters often are fragrant or have distinctive odors. Compared to the more common ethyl esters, formate esters are less commonly used commercially because they are less stable.^[3] 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 to give finely powdered nickel metal:

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

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

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
• Phenyl formate HCOOC₆H₅
• Amyl Formate

References