Formic anhydride, also called methanoic anhydride, is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

and a

structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are connected to one another. The chemical bonding within the molecule is al ...

of (H(C=O)−)₂O. It can be viewed as the

anhydride An acid anhydride is a type of chemical compound derived by the removal of water molecules from an acid (chemistry), acid. In organic chemistry, organic acid anhydrides contain the functional group . Organic acid anhydrides often form when one ...

formic acid Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid. It has the chemical formula HCOOH and structure . This acid is an important intermediate in chemical synthesis and occurs naturally, most notably in some an ...

(HCOOH).

Preparation

Formic anhydride can be obtained by reaction of formyl fluoride with excess

sodium formate Sodium formate, HCOONa, is the sodium salt of formic acid, HCOOH. It usually appears as a white deliquescent powder. Preparation For commercial use, sodium formate is produced by absorbing carbon monoxide under pressure in solid sodium hydroxide ...

and a catalytic amount of formic acid in ether at −78 °C.George A. Olah, Yashwant D. Vankar; Massoud Arvanaghi; Jean Sommer (1979), ''Formic Anhydride''. Angewandte Chemie International Edition Engl., volume 18, issue = 8, page = 614. . It can also be produced by reacting formic acid with ''N'','-dicyclohexylcarbodiimide ((−N=)₂C) in ether at −10 °C.G. Wu, S. Shlykov, F. S. Van Alseny, H. J. Geise, E. Sluyts, B. J. Van der Veken (1995), ''Formic Anhydride in the Gas Phase, Studied by Electron Diffraction and Microwave and Infrared Spectroscopy, Supplemented with Ab-Initio Calculations of Geometries and Force Fields''. J. Phys. Chem., volume 99, issue 21, pages 8589–8598 It can also be obtained by

disproportionation In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation state. The reverse of disproportionatio ...

of acetic formic anhydride.R. Schijf, J. W. Scheeren, A. van Es, W. Stevens (1965) ''Mixed carboxylic acid anhydrides: IV. formic anhydride''. Recueil des Travaux Chimiques des Pays-Bas, volume 84, issue 5, pages 594–596.

Properties

Formic anhydride is a liquid with boiling point 24 °C at 20

mmHg A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high. Currently, it is defined as exactly , or approximately 1 torr = atmosphere = &nb ...

. It is stable in

diethyl ether Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...

solution. It can be isolated by low-temperature, low-pressure distillation, but decomposes on heating above room temperature. At room temperature and higher, it decomposes through a decarbonylation reaction into formic acid and

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

. Due to its instability, formic anhydride is not commercially available and must be prepared fresh and used promptly. The decomposition of formic anhydride may be catalyzed by formic acid. Formic anhydride can be detected in the gas-phase reaction of

ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...

with

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

.A. Vaccani, A. Bauder and Hs. H. Günthar (1975), ''The Microwave Spectrum of Formic Anhydride''. Abstracts of OSU International Symposium on Molecular Spectroscopy 1970-1979 The molecule is planar in the gas phase.

References

{{reflist Carboxylic anhydrides

Preparation

Properties

See also

References