Formate (IUPAC name: methanoate) is the conjugate base of formic acid. Formate is an anion () or its derivatives such as ester of formic acid. The salts and esters are generally colorless.
Fundamentals
When dissolved in water, formic acid converts to formate:
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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
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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.
These conversions are catalyzed by aromatase enzymes using O<sub>2</sub> as the oxidant. Specific conversions include testosterone to estradiol and androstenedione to estrone.
Formate is reversibly oxidized by the enzyme formate dehydrogenase from Desulfovibrio gigas:
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Formate esters
Formate esters have the formula HCOOR (alternative way of writing formula ROC(O)H or RO<sub>2</sub>CH). Many form spontaneously when alcohols dissolve in formic acid; contrariwise, they hydrolyze easily in base. Some formate esters arise by the addition of formic acid to alkenes.
An 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:
Reaction with phosphorus pentachloride does not chlorolyze the ester bond, instead forming an (unusual) dichloromethyl ether<!--dichloromethyl ether redirects (understandably) to bis(chloromethyl ether)-->. Ethyl formate is found in some confectionaries.