Triethylamine

Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA is also a common abbreviation.[7][8] It is a colourless volatile liquid with a strong fishy odor reminiscent of ammonia. Like diisopropylethylamine (Hünig's base), triethylamine is commonly employed, usually as a base, in organic synthesis.

Triethylamine
Ball and stick model of triethylamine
Spacefill model of triethylamine
Names
Preferred IUPAC name
N,N-Diethylethanamine
Other names
(Triethyl)amine
Triethylamine (no longer IUPAC name[1])
Identifiers
3D model (JSmol)
Abbreviations TEA[2]
605283
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.064
EC Number
  • 204-469-4
KEGG
MeSH triethylamine
RTECS number
  • YE0175000
UNII
UN number 1296
Properties[3]
C6H15N
Molar mass 101.193 g·mol−1
Appearance Colourless liquid
Odor Fishy, ammoniacal
Density 0.7255 g mL−1
Melting point −114.70 °C; −174.46 °F; 158.45 K
Boiling point 88.6 to 89.8 °C; 191.4 to 193.5 °F; 361.7 to 362.9 K
log P 1.647
Vapor pressure 6.899–8.506 kPa
66 μmol Pa−1 kg−1
Acidity (pKa) 10.75 (for the conjugate acid) (H2O), 9.00 (DMSO)[4]
-81.4·10−6 cm3/mol
1.401
Thermochemistry
216.43 J K−1 mol−1
Std enthalpy of
formation (ΔfH⦵298)
 −169 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 −4.37763 to −4.37655 MJ mol−1
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H225, H302, H312, H314, H332
P210, P280, P305+351+338, P310
NFPA 704 (fire diamond)
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
3
0
Flash point −15 °C (5 °F; 258 K)
312 °C (594 °F; 585 K)
Explosive limits 1.2–8%
2 ppm (8 mg/m3) (TWA), 
4 ppm (17 mg/m3) (STEL)
Lethal dose or concentration (LD, LC):
  • 580 mg kg−1 (dermal, rabbit)
  • 730 mg kg−1 (oral, rat)
1425 ppm (mouse, 2 hr)[5]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 25 ppm (100 mg/m3)[6]
REL (Recommended)
 None established[6]
IDLH (Immediate danger)
 200 ppm[6]
Related compounds
Related amines
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis and properties

Triethylamine is prepared by the alkylation of ammonia with ethanol:[9]

NH3 + 3 C2H5OH → N(C2H5)3 + 3 H2O

The pKa of protonated triethylamine is 10.75,[4] and it can be used to prepare buffer solutions at that pH. The hydrochloride salt, triethylamine hydrochloride (triethylammonium chloride), is a colorless, odorless, and hygroscopic powder, which decomposes when heated to 261 °C.

Triethylamine is soluble in water to the extent of 112.4 g/L at 20 °C.[10] It is also miscible in common organic solvents, such as acetone, ethanol, and diethyl ether.

Laboratory samples of triethylamine can be purified by distilling from calcium hydride.[11]

In alkane solvents triethylamine is a Lewis base that forms adducts with a variety of Lewis acid such as I2, phenols and Cu(HFacac)2. However when latter Lewis acid forms an adduct with triethylamine, steric repulsion between the ethyl groups and the Cu complex results. Triethylamine is classified as a soft base and its acceptor properties are discussed in the ECW model.

Applications

Triethylamine is commonly employed in organic synthesis as a base. For example, it is commonly used as a base during the preparation of esters and amides from acyl chlorides.[12] Such reactions lead to the production of hydrogen chloride which combines with triethylamine to form the salt triethylamine hydrochloride, commonly called triethylammonium chloride. This reaction removes the hydrogen chloride from the reaction mixture, which can be required for these reactions to proceed to completion (R, R' = alkyl, aryl):

R2NH + R'C(O)Cl + Et3N → R'C(O)NR2 + Et3NH+Cl−

Like other tertiary amines, it catalyzes the formation of urethane foams and epoxy resins. It is also useful in dehydrohalogenation reactions and Swern oxidations.

Triethylamine is readily alkylated to give the corresponding quaternary ammonium salt:

RI + Et3N → Et3NR+I−

Triethylamine is mainly used in the production of quaternary ammonium compounds for textile auxiliaries and quaternary ammonium salts of dyes. It is also a catalyst and acid neutralizer for condensation reactions and is useful as an intermediate for manufacturing medicines, pesticides and other chemicals.

Triethylamine salts like any other tertiary ammonium salts are used as an ion-interaction reagent in ion interaction chromatography, due to their amphiphilic properties. Unlike quaternary ammonium salts, tertiary ammonium salts are much more volatile, therefore mass spectrometry can be used while performing analysis.

In alkane solvents triethylamine is a Lewis base that forms adducts with a variety of Lewis acid such as I2, phenols and Cu(HFacac)2. However when the latter Lewis acid forms an adduct with triethylamine, steric repulsion between the ethyl groups and the Cu complex results. Triethylamine is classified as a soft base and its donor properties are discussed in the ECW model.

Niche uses

Triethylamine is used to give salts of various carboxylic acid-containing pesticides, e.g. Triclopyr and 2,4-dichlorophenoxyacetic acid

Triethylamine is the active ingredient in FlyNap, a product for anesthetizing Drosophila melanogaster. Triethylamine is used in mosquito and vector control labs to anesthetize mosquitoes. This is done to preserve any viral material that might be present during species identification.

Also, the bicarbonate salt of triethylamine (often abbreviated TEAB, triethylammonium bicarbonate) is useful in reverse phase chromatography, often in a gradient to purify nucleotides and other biomolecules.

Triethylamine was found during the early 1940s to be hypergolic in combination with nitric acid, and was considered a possible propellant for early hypergolic rocket engines.[13]

Natural occurrence

Hawthorn flowers have a heavy, complicated scent, the distinctive part of which is triethylamine, which is also one of the first chemicals produced by a dead human body when it begins to decay. For this reason, it is considered as unlucky to bring Hawthorn (or May blossom) into the house. Gangrene is also said to possess a similar odour. On a brighter note, it is also described as 'the smell of sex', specifically of semen.[14]

References
  1. "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 671. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. X. Bories-Azeau, S. P. Armes, and H. J. W. van den Haak, Macromolecules 2004, 37, 2348 PDF
  3. The Merck Index (11th ed.). 9582.
  4. David Evans Research Group Archived 2012-01-21 at the Wayback Machine
  5. "Triethylamine". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  6. NIOSH Pocket Guide to Chemical Hazards. "#0633". National Institute for Occupational Safety and Health (NIOSH).
  7. "Ethanolamine Compounds (MEA, DEA, TEA And Others)". Safe Cosmetics. Retrieved 2020-06-17.
  8. "tetraethylammonium | Ligand page | IUPHAR/BPS Guide to PHARMACOLOGY". www.guidetopharmacology.org. Retrieved 2020-06-17.
  9. Eller, Karsten; Henkes, Erhard; Rossbacher, Roland; Höke, Hartmut (2000). "Amines, Aliphatic". doi:10.1002/14356007.a02_001. ISBN 3527306730. Cite journal requires |journal= (help)
  10. "MSDS - 471283". www.sigmaaldrich.com. Retrieved 2020-06-17.
  11. F., Armarego, W. L. (2012-10-17). Purification of Laboratory Chemicals. Chai, Christina Li Lin (Seventh ed.). Amsterdam. ISBN 9780123821621. OCLC 820853648.
  12. Sorgi, K. L. (2001). "Triethylamine". Encyclopedia of Reagents for Organic Synthesis. Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.rt217. ISBN 978-0471936237.
  13. Clark, John (1972). Ignition!: An Informal History of Liquid Rocket Propellants (PDF). Rutgers University, the State University of New Jersey. p. 13. ISBN 0-8135-0725-1.
  14. The book of general ignorance. John Lloyd & John Mitchinson. Faber & Faber 2006, The Hawthorn, BBC
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