Dimethylamine
Properties
| State | Gas at room temperature (bp 7°C); commonly sold as 40% aqueous solution |
| Color | Colorless |
| Solubility | Very soluble in water; soluble in ethanol and diethyl ether |
| Melting Point | -92°C |
| Boiling Point | 7°C |
About Dimethylamine
Dimethylamine is the small secondary amine that sits at the head of an enormous downstream chemical tree. It boils at 7 °C, so commercially it ships either as a liquefied gas under pressure or — much more commonly — as a 40% aqueous solution that handles like a strong base with a fishy ammonia smell. The pKaH of 10.73 makes it a stronger base than ammonia (9.25) and slightly stronger than methylamine, with the second methyl group adding inductive donation while the steric profile stays small enough that solvation does not penalize the protonated form heavily. Industrially, DMA is one of the highest-volume aliphatic amines in the world. Its biggest single sink is dimethylformamide synthesis: DMA plus carbon monoxide over a basic catalyst gives DMF, which then becomes the polar aprotic solvent of choice for fiber spinning (Spandex, acrylic), pharmaceutical synthesis, and PVC processing. DMA also feeds dimethylacetamide (DMAc) production, the dimethylamino-2-propanol intermediate for ion-exchange resins, and the N,N-dimethyl part of countless drug molecules — diphenhydramine (Benadryl), tramadol, venlafaxine, all carry N(CH3)2 groups that came from DMA. Agrochemically, the herbicide 2,4-D is most often sold as its dimethylammonium salt because the salt is water-soluble for spray formulation. The other side of DMA is environmental: DMA reacts with nitrous acid or nitrosating agents to produce N-nitrosodimethylamine (NDMA), an IARC Group 2A carcinogen. NDMA contamination has caused multiple drug recalls (ranitidine, valsartan, metformin), drinking-water disinfection-byproduct concerns, and rocket-propellant production sites are persistent NDMA contamination problems.
Where you'll encounter it
If you have ever caught a whiff of decomposing fish at low tide, that fishy note is partly trimethylamine and partly dimethylamine being released by bacterial reduction of trimethylamine N-oxide in marine flesh. In the lab, a 40% aqueous DMA solution is the routine starting material for installing N(CH3)2 groups in API synthesis — reaction with an acyl chloride gives a dimethylamide; reductive amination of a ketone with DMA·HCl/NaBH3CN installs the N(CH3)2 substituent that shows up in so many CNS drugs.
Common Uses
- Production of dimethylformamide via Reppe-type carbonylation of DMA with CO over methoxide catalyst
- Dimethylacetamide synthesis as a polymer-spinning and pharmaceutical reaction solvent precursor
- N,N-dimethylamino building block in the synthesis of antihistamines like diphenhydramine and chlorpheniramine
- Dimethylammonium salt formulations of phenoxy herbicides such as 2,4-D and dicamba for water-soluble sprays
- Reductive amination input for installing N(CH3)2 groups on ketones in CNS-drug synthesis (venlafaxine, tramadol)
- Rubber vulcanization accelerator precursor for the production of dithiocarbamates and thiurams
- Tanning agent and leather processing chemical for collagen crosslinking control
- Flotation reagent in mineral processing for selective collection of sulfide ores
Safety Information
Extremely flammable gas (anhydrous form) — flash point of the 40% aqueous solution is around 9 °C, autoignition 400 °C, flammability range 2.8-14.4 vol%. ACGIH TLV is 5 ppm 8-hour TWA with a 15 ppm STEL; OSHA PEL is 10 ppm 8-hour TWA. Corrosive — causes severe burns to skin, eyes, and respiratory tract. GHS: H220 (extremely flammable gas), H314 (severe skin burns and eye damage), H332+H335 (harmful if inhaled, respiratory irritation). The under-discussed hazard is N-nitrosation: DMA reacts cleanly with HNO2, organic nitrites, or any nitrosating environment to form NDMA, which is a potent hepatocarcinogen with a daily limit in pharmaceuticals of 96 ng/day. This is the chemistry behind the ranitidine and valsartan recalls. Keep DMA strictly separated from nitrites, nitrous acid, and any waste stream containing NOx species. Handle in a fume hood with full chemical-splash PPE.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.