Diethyl Ether
Properties
| State | Liquid (highly volatile) |
| Color | Colorless |
| Solubility | Slightly soluble in water (69 g/L at 20°C); miscible with most organic solvents |
| Melting Point | -116.3°C |
| Boiling Point | 34.6°C |
About Diethyl Ether
Diethyl ether is the solvent that built modern organometallic chemistry. The two ethyl groups flank an oxygen with two lone pairs, and those lone pairs are exactly the right Lewis basicity to coordinate to magnesium without quenching it. That is why a Grignard reagent forms in dry Et2O and not in toluene — the ether solvates the RMgX as a tetrahedral RMgX·(Et2O)2 complex, keeps it monomeric, and lets it react cleanly with a carbonyl. Take the ether away and the reaction stalls. Beyond Grignards, Et2O is a workhorse extraction solvent: low boiling point (34.6 °C), modest water solubility (about 7 wt%), good dissolving power for most neutral organics, and easy to strip. The drawbacks are notorious. The flash point is -45 °C and the autoignition temperature is only 160 °C, which means a hot plate or even a static spark will set vapor pools alight. Worse, on storage the alpha C-H bonds undergo radical autoxidation by molecular oxygen to form ethyl 1-hydroperoxy-ethyl ether — a peroxide that concentrates in the still-pot when you distill old ether. There are documented detonations of ether stills that had been operating routinely for years. Historically, William Morton's 1846 demonstration at Massachusetts General Hospital made it the first practical inhalation anesthetic and arguably the most important moment in surgical history, but it was replaced clinically decades ago because of the explosion risk in operating rooms.
Where you'll encounter it
If you have ever set up a Grignard prep in an undergrad lab — magnesium turnings under nitrogen, a jacketed addition funnel of bromobenzene, a slow-boil reflux that suddenly takes off — the solvent in that flask was almost certainly anhydrous diethyl ether. The same bottle gets used for liquid-liquid extractions when you want a faster strip than DCM allows. Old jars of ether on a shelf are a real lab-safety problem: any bottle more than a year old should be tested for peroxides with KI/starch paper before distillation, and bottles with crystals around the cap should be disposed of remotely without disturbing them.
Common Uses
- Solvent for Grignard reagent formation and lithium-halogen exchange in synthetic organic chemistry
- Liquid-liquid extraction solvent for neutral organics with low water solubility and easy rotovap removal
- Recrystallization antisolvent for crashing out polar compounds from THF, DCM, or alcohol solutions
- Starting fluid for cold-weather diesel and small gasoline engines via aerosol injection into intake manifolds
- Reaction solvent for organolithium chemistry below 0 °C where THF would coordinate too tightly
- Mobile phase in petroleum-ether/Et2O gradients for normal-phase TLC and column chromatography
- Extraction solvent for fats, oils, and waxes in food and feed analytical labs (Soxhlet method)
- Historical inhalation general anesthetic, first publicly demonstrated by William Morton in 1846
Safety Information
EXTREMELY FLAMMABLE — flash point -45 °C, autoignition temperature 160 °C, vapor density 2.6 (heavier than air, so vapors travel along benches and floors to ignition sources). OSHA PEL 400 ppm 8-hour TWA, ACGIH TLV 400 ppm with a 500 ppm STEL. Peroxide hazard is the more insidious problem: stored ether forms 1-ethoxyethyl hydroperoxide via radical autoxidation, and these peroxides concentrate when you distill. Test old bottles with KI/starch paper before any distillation. Do not distill to dryness. Add a peroxide scavenger like BHT or store over sodium wire / activated alumina. GHS: H224 (extremely flammable liquid and vapor), H302 (harmful if swallowed), H336 (drowsiness/dizziness), H400 with peroxide content. Use in a fume hood, ground all equipment to prevent static, no open flames anywhere on the bench.
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.