Formamide: an Organic Reaction Solvent from which Product can be Easily Recovered

 Formamide is a clear, hygroscopic, oily liquid, miscible with water, methanol, acetone, acetic acid, dioxane, ethylene glycol, glycerol, and phenol. 

It is dried with solid sodium sulfate or calcium oxide.  Activated alumina is also reported to be suitable for drying formamide. High-purity formamide is vacuum distilled and packaged under dry nitrogen. 

Many compounds such as tannins, starch, lignin, polyvinyl alcohol, cellulose acetate, and nylon, dissolve in it. It also dissolves many ionic compounds that are insoluble in water, making it a great solvent for salty/sugary reactions.  Chlorides of copper, lead, zinc, tin, cobalt, iron, aluminum, nickel, and the acetates of the alkali metals as well as some inorganic sulfates and nitrates dissolve. Zinc chloride, stannous and stannic chlorides, ferric and ferrous chlorides, aluminum chloride, and copper chloride are all organic chemistry reagents that might consequently benefit if used in formamide.

The Leuckart reaction necessarily uses formamide since it is required also as a reactant. Formamide should be considered a replacement for reactions more commonly conducted in water. It is polar, protic, and both a hydrogen bond donor and acceptor. It has been used in microwave-assisted syntheses. It degrades in a microwave at 170 °C to CO & NH3 which may be done deliberately as a source of reactant CO or NH3.

Similar to water, at temperatures close to 200ºC hot formamide begins to dissolve a wide variety of commonly functionalized organic compounds and thus can be used as a solvent for organic reactions. At 200ºC these reactions run exceptionally fast. When cooled to room temperature, the organic products become practically insoluble and can be easily separated. Unlike many organic solvents, but similar to water, formamide does not deteriorate at high temperatures. As a result, the formamide filtrate could be repeatedly used as the solvent in the same reaction.  

Its high BP and decomposition to small amounts of HCN at reflux lead chemists to often prefer dimethylformamide (DMF). Neither formamide nor DMF is easily removed with a vacuum, but formamide has the lower solubility in benzene/toluene compared to DMF so it's possible to remove an organic reaction product from formamide by benzene extraction. Extraction with toluene or xylene would also be expected to be OK although it is not documented.

BP: 210°C

Density: 1.133 g/mL