Dichloromethane
Properties
| State | Liquid (volatile) |
| Color | Colorless |
| Solubility | Slightly soluble in water (20 g/L at 20°C); miscible with most organic solvents |
| Melting Point | -96.7°C |
| Boiling Point | 39.6°C |
About Dichloromethane
Dichloromethane is the workhorse extraction solvent of organic chemistry, and almost every property that makes it useful traces back to a small, polar, fully halogenated structure. Density 1.33 g/cm³ — heavier than water, so the organic layer settles to the bottom of a separatory funnel and you can drain it cleanly. Boiling point 39.6 °C — low enough to strip on a rotovap at 30 °C bath temperature without cooking your product. Dipole moment 1.6 D and miscibility with most aprotic organics — dissolves a remarkable spread of compounds from nonpolar hydrocarbons up through polar carbonyls. And it does not burn under ordinary lab conditions, which makes it a relatively forgiving choice next to ethers and ketones. In synthesis, DCM is the default for Swern oxidations (with DMSO/oxalyl chloride at -78 °C), Friedel-Crafts acylations, peptide-coupling reactions with EDC/HOBt, and anything involving acid chlorides where you cannot afford a nucleophilic solvent. In chromatography, DCM/MeOH gradients are the standard polar workup for normal-phase silica. Industrially, it strips paint, decaffeinates coffee (the European-style process), extracts hops, and serves as a process solvent in polycarbonate production. The dark side: DCM is a 2A IARC carcinogen, it crosses the alveolar membrane efficiently, and CYP2E1 metabolizes it to carbon monoxide. People have died of carbon monoxide poisoning while stripping bathtubs in unventilated bathrooms.
Where you'll encounter it
If you have run a single aqueous workup in a teaching lab or a process group, you have pulled the bottom layer off a DCM/water sep funnel. In a typical workflow you quench a reaction, dilute with water, extract three times with DCM, combine organics, dry over MgSO4 or Na2SO4, filter, and rotovap. The whole sequence takes ten minutes and works for the vast majority of small-molecule syntheses. DCM also shows up as the mobile phase modifier in normal-phase flash columns — a 95:5 DCM/MeOH gradient is the textbook system for moderately polar amines and amides.
Common Uses
- Default extraction solvent for aqueous workups in small-molecule organic synthesis labs worldwide
- Mobile phase for normal-phase silica chromatography, typically with a methanol gradient
- Reaction solvent for Swern oxidation, Friedel-Crafts acylation, and EDC/HOBt peptide couplings
- Industrial paint stripper for furniture refinishing, aircraft, and architectural coatings
- Process solvent in pharmaceutical manufacturing for crystallization and recrystallization steps
- Decaffeination solvent for coffee beans in the European direct-contact process
- Hop oil extraction in brewing and supercritical-fluid co-solvent applications
- Reaction medium for polycarbonate production via interfacial polymerization with bisphenol A and phosgene
Safety Information
IARC Group 2A (probably carcinogenic to humans). OSHA PEL is 25 ppm 8-hour TWA with a 125 ppm STEL — significantly tighter than the older 500 ppm limit. ACGIH TLV is 50 ppm. The acute hazard people underestimate is carboxyhemoglobinemia: CYP2E1 metabolizes DCM to CO, so working with bulk DCM in a poorly ventilated space can give you blood COHb levels comparable to a heavy smoker. GHS: H302 (harmful if swallowed), H315 (skin irritation), H319 (eye irritation), H335 (respiratory irritation), H336 (drowsiness), H351 (suspected carcinogen), H373 (target organ toxicity, repeated exposure — liver). Use in a fume hood, wear nitrile gloves (DCM permeates standard nitrile in 5-10 minutes — change gloves quickly after a spill), and never use it in a confined space without active ventilation. The EPA banned consumer paint-stripping use in 2019 after a string of deaths.
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.