Dimethylformamide

Dimethylformamide is the organic compound with the formula (CH₃)₂NC(O)H. Commonly abbreviated DMF, this colourless liquid is miscible with water and majority of organic liquids. DMF is a common solvent for chemical reactions. Pure dimethylformamide is odorless whereas technical grade or degraded dimethylformamide often has a fishy smell due to impurity of dimethylamine. Its name is derived from the fact that it is a derivative of formamide, the amide of formic acid.

Dimethylformamide is a polar (hydrophilic) aprotic solvent with a high boiling point. It facilitates reactions that follow polar mechanisms, such as S_N2 reactions. Dimethylformamide can be synthesized from formic acid and dimethylamine.^{[citation needed]} Dimethylformamide is not stable in the presence of strong bases like sodium hydroxide or strong acids such as hydrochloric acid or sulfuric acid and is hydrolyzed back into formic acid and dimethylamine, especially at elevated temperatures.

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Structure and properties

Due to the contribution of the two possible resonance structures of an amide, the bond order of the carbonyl C=O bond is reduced, while that of the carbon-nitrogen bond is increased. Thus the infrared spectrum of DMF shows a lower C=O stretching frequency at 1675 cm^-1[1] than an unsubstuted C=O bond. Also, because of the partial double bond character, the rotation about the C-N axis is slow, making the two methyl groups inequivalent on the NMR time scale, giving rise to two singlets of 3 protons each at δ 2.97 and 2.88,^[1] instead of one singlet of 6 protons in the proton NMR spectrum.

Applications

The primary use of dimethylformamide is as a solvent with low evaporation rate. Dimethylformamide is used in the production of acrylic fibers and plastics. It is also used as a solvent in peptide coupling for pharmaceuticals, in the development and production of pesticides, and in the manufacture of adhesives, synthetic leathers, fibers, films, and surface coatings.^[2]

It is used as a reagent in the Bouveault aldehyde synthesis and in the Vilsmeier-Haack reaction, another useful method of forming aldehydes.

DMF penetrates most plastics and makes them swell. It therefore frequently occurs as a component of paint strippers.

It is also used in the manufacturing of solvent dyes as an important raw material. It is consumed during reaction.

Production

Dimethyl formamide is produced with catalyzed reaction of dimethyl amine and carbon monoxide at low pressure and temperature. It may also be prepared on a laboratory scale by reacting dimethylamine with formic acid.

Precautions

Reaction with sodium hydride in DMF as a solvent are somewhat hazardous; exothermic decomposition has been reported at temperatures as low as 26 °C. On a laboratory scale any thermal runaway is (usually) quickly noticed and brought under control with an ice bath and this remains a popular combination of reagents. On a pilot plant scale, on the other hand, several accidents have been reported.

Toxicity

DMF has been linked to cancer in humans, and it is thought to cause birth defects. In some sectors of industry women are banned from working with DMF. For many reactions, it can be replaced with dimethyl sulfoxide. Most manufacturers of DMF list (Life) or (Chronic) as a health hazard in their MSDS since DMF is not readily disposed of by the body. According to IARC, DMF may be a possible carcinogen, although EPA does not consider it a cancer risk.

References

1. ^ ^{a b} Spectral Database for Organic Compounds, Dimethylformamide, accessed 27 Jan 2007.
2. ^ Redlich, C; Beckett, W. S.; Sparer, J.; Barwick, K. W.; Riely, C. A.; Miller, H.; Sigal, S. L.; Shalat, S. L.; and Cullen, M. R.; 1988. Liver disease associated with occupational exposure to the solvent dimethylformamide. Ann. Intern. Med. 108:680-686. PMID 3358569