Triethylamine
Properties
| State | Liquid (colorless with strong fishy/ammoniacal odor) |
| Color | Colorless |
| Solubility | Miscible with water below 19°C; partially miscible above 19°C (LCST behavior); miscible with most organic solvents |
| Melting Point | -115°C |
| Boiling Point | 89°C |
About Triethylamine
Triethylamine is the lab-default non-nucleophilic base — the bottle every synthetic organic chemist keeps within arm's reach of the fume hood for soaking up HCl whenever an acyl chloride, sulfonyl chloride, or chlorosilane reagent goes into a flask. As a tertiary amine with no N-H bond, TEA can deprotonate or capture protons (conjugate acid pKa around 10.75) but its three ethyl groups create enough steric hindrance around the nitrogen lone pair that nucleophilic attack on a carbon electrophile is dramatically slowed — fast for protons, slow for carbons. That kinetic split is what makes TEA the textbook auxiliary base in acylations (acid chloride + alcohol + Et3N → ester + Et3N·HCl), silyl protections (TBS-Cl or TMS-Cl + alcohol + Et3N), Schotten-Baumann amide formations, Sonogashira and other Pd cross-couplings where it doubles as base and amine ligand, and the workup for any reaction that generates HCl. The Et3N·HCl byproduct precipitates from most non-polar organic solvents (it's only sparingly soluble in DCM, ether, hexanes), making post-reaction filtration trivial. Beyond synthesis, TEA is used as a mobile phase modifier in reverse-phase HPLC of basic analytes (caps free silanols and sharpens peaks of amines), as the nitrogen-source comonomer for ion-exchange resin synthesis (route to quaternary ammonium strong-base resins), and as a curing accelerator in epoxy formulations. The compound has unusual aqueous behavior: it shows lower critical solution temperature (LCST) phase separation around 19 °C, miscible with water below that point and forming two layers above.
Where you'll encounter it
If you've ever walked past an organic chemistry lab and caught the unmistakable fishy ammonia smell of a Schotten-Baumann reaction in progress, you've smelled triethylamine doing the work of acid scavenging. The detection threshold sits around 0.5 ppb — so low that a spilled drop in a hood will perfume the entire wing of a building within minutes. In a peptide chemistry lab, TEA or its bulkier cousin diisopropylethylamine (DIPEA, Hünig's base) is what you add to every coupling reaction to neutralize the HCl coming off HBTU or HATU activation. In a process chemistry pilot plant, TEA is dosed continuously into a Sonogashira reactor by metering pump because it both scavenges HCl and ligates the Pd catalyst. The lower critical solution temperature behavior shows up in undergraduate physical chemistry labs as a demonstration: warm a 50:50 TEA-water mixture from 15 to 25 °C in a graduated cylinder and watch the single phase break into two layers right around 19 °C.
Common Uses
- Standard non-nucleophilic base for acid scavenging in acylations, silylations, and Schotten-Baumann reactions
- HPLC mobile phase modifier (0.1-0.5%) for sharper peaks of basic amine analytes on silica columns
- Catalyst and base in Pd-catalyzed Sonogashira, Heck, and Buchwald-Hartwig cross-coupling reactions
- Comonomer for quaternary ammonium strong-base ion-exchange resin synthesis
- Curing accelerator and tertiary-amine catalyst in epoxy and polyurethane formulations
Safety Information
GHS: H225 (highly flammable liquid, flash point -15 °C), H302 (harmful if swallowed), H311 (toxic in contact with skin), H314 (causes severe skin burns and eye damage), H332 (harmful if inhaled), H335 (respiratory irritation). The advisory exposure limit sits far below the older enforceable one because the odor threshold (~0.5 ppb) is below the irritant threshold and operators stop noticing the smell long before they stop being exposed. Vapors form explosive mixtures with air from -15 °C upward; ignition sources must be excluded near open containers. Use only in a working fume hood; even brief skin contact with the neat liquid causes painful chemical burns within seconds. Store in flame-rated cabinet away from acids and oxidizers.
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. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.