N,N-Dimethylformamide: Properties, CAS 68-12-2 and Uses

N,N-Dimethylformamide, identified by CAS Registry Number 68-12-2, is a polar aprotic solvent with the molecular formula C3H7NO and a molar mass of 73.09 g/mol. The molecule contains a formyl group bonded to a dimethylamine residue. The amide carbonyl and the dimethylamino group participate in resonance, producing a high dipole moment and strong solvation of polar, ionic, and resinous species. DMF is miscible with water and most organic solvents but separate from low-molecular-weight aliphatic hydrocarbons.

What Is N,N-Dimethylformamide and Why Is CAS 68-12-2 Distinct Among Polar Aprotic Solvents?

The compound belongs to the dialkylformamide class and functions as a hydrogen-bond acceptor, not a hydrogen-bond donor. Its dielectric constant is 36.7 at 25 °C, and its dipole moment is approximately 3.86 D. These parameters place DMF between acetone and dimethyl sulfoxide in polarity, while its low protic activity prevents interference with nucleophiles and anionic intermediates. The solvent is hygroscopic, and absorbed water can hydrolyze DMF to formic acid and dimethylamine under acidic or basic conditions. This reactivity makes water specification, nitrogen blanketing, and closed-loop transfer standard controls in continuous process lines.

The measured physical-property data in Table 1 establish the design basis for distillation, drying, ventilation, and area classification.

Regulatory classification and exposure controls are consolidated in Table 2. The closed-cup flash point of 58 °C creates a flammable liquid hazard under GHS, while the autoignition temperature of 445 °C governs maximum surface temperatures for heated process equipment. The explosive range from 2.2 vol% to 15.2 vol% requires inert-gas blanketing on storage vessels and exhaust solvent concentration interlocks. Workplace air monitoring is performed by sorbent-tube sampling and gas chromatography according to NIOSH 2552.

Solvent Parameters for Polyacrylonitrile Spinning Dope Preparation

In dry-spun polyacrylonitrile precursor production, DMF is blended with PAN resin in continuous dissolvers, then degassed under vacuum and filtered through sintered-metal candle filters before spinneret extrusion. Dope viscosity is the primary control variable and is measured by rotational viscometer according to ISO 2555. Because PAN dope can gel upon moisture ingress, DMF water content is maintained below 0.1% w/w, and nitrogen blanketing is used on storage tanks and feed day tanks. Dope temperatures are commonly maintained below 80 °C to limit solvent decomposition and polymer discoloration; degassing is therefore performed at 50–70 °C under reduced pressure rather than at atmospheric reflux. Coagulation and solvent recovery operate as a closed loop. The extruded filaments pass through a water/DMF coagulation bath, residual solvent is removed by multi-stage washing and stretching, and recovered DMF is purified in distillation columns. Published data for specific manufacturing configurations is limited, but production lines using structured packing in solvent recovery typically report recovery efficiencies above 99% in environmental permit documentation. The key constraint is removal of residual solvent from the coagulated precursor to below 0.5% w/w before oxidative stabilization, because DMF evolution during carbonization can form carbon deposits in low-oxygen zones.

Active pharmaceutical ingredient manufacturing uses DMF as a reaction solvent in amide couplings, SNAr displacement, and peptide synthesis because it dissolves protected amino acids and coupling reagents while maintaining a high dielectric environment. Residual solvent control is governed by ICH Q3C: DMF is a Class 2 solvent with a permitted daily exposure of 8.8 mg/day. For a product administered at 10 g/day, the corresponding concentration limit is 880 ppm. Finished API and excipient batches are analyzed by headspace gas chromatography according to USP 467. The practical boundary is that vacuum distillation must be used to strip DMF from heat-sensitive APIs because DMF has a normal boiling point of 153 °C, but prolonged heating with acidic or basic impurities can hydrolyze the solvent to dimethylamine and formic acid, altering pH and forming salts.

When DMF Replaces NMP in Lithium-Ion Electrode Coating Formulations

Slot-die coating lines that substitute DMF for N-methyl-2-pyrrolidone in polyvinylidene fluoride binder solutions encounter a narrower solvent evaporation window. DMF has a lower viscosity of 0.92 mPa·s at 20 °C and a lower boiling point of 153 °C than NMP at 202 °C. Cathode slurries are measured on a cone-and-plate rheometer according to DIN EN ISO 3219 to set solids content and binder concentration. The lower viscosity can be exploited to raise solids at equivalent coatability, but the solvent also has a closed-cup flash point of 58 °C, requiring oven drying profiles with a first stage below the flash point and condensation or activated-carbon recovery sized for the higher vapor pressure. Drying tunnel length and line speed must be adjusted because DMF evaporates faster; published data for specific high-speed configurations is limited, but multi-zone ovens running NMP at 80–140 °C require DMF initial zones near 60–70 °C to avoid skinning and electrode cracking. Area classification follows ATEX Directive 2014/34/EU, and exhaust solvent concentration is held below 25% of the lower explosion limit. Fluoropolymer binder solutions are moisture-sensitive; DMF/water contamination can hydrolyze, so storage tanks require nitrogen blanketing. This substitution is not universal because the lower boiling point and capacity for thermal decomposition demand longer condensation residence times compared with NMP recovery.

When wet-process polyurethane coating is used for synthetic leather, a polyurethane resin is dissolved in DMF and applied to a fabric or release paper, then passed through a water/DMF coagulation bath. Water diffuses into the film and DMF diffuses out; the polymer precipitates as a microporous structure. The coagulation bath is maintained at 20–40 °C, and DMF concentration is controlled by continuous bleed to distillation. DMF is recovered from water by fractional distillation, which is energy-intensive because of the boiling-point difference and the miscibility of the binary mixture. Materials of construction for DMF service include 316L stainless steel and PTFE gaskets; PVC, polycarbonate, and EPDM are unsuitable due to swelling, plasticizer extraction, or stress cracking. Process drains and recovery sumps are sized for the full coagulation-bath volume to prevent aqueous DMF discharge during batch changeover.

Acetylene recovery units use DMF as a selective absorption solvent; acetylene is absorbed from cracked gas streams and released in a stripping step. DMF also serves as the reaction medium for Vilsmeier–Haack formylation, in which DMF and phosphorus oxychloride form the chloroiminium electrophile. Quench operations require controlled addition into water or aqueous base because the reaction mixture contains phosphorus oxychloride and generates heat. In laboratory peptide synthesis, DMF is used for Fmoc deprotection and resin swelling; the same residual-solvent restrictions govern scale-up. Stored DMF should be kept under nitrogen and away from strong oxidizers, acyl halides, and bromine; moisture ingress accelerates hydrolysis to formic acid and dimethylamine.