Triethylamine

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Triethylamine
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Abbreviations TEA[2]
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MeSH triethylamine
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UN number 1296
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Template:Longitem Template:Chembox Elements/molecular formula
Molar mass Template:Chem molar mass
Appearance Colourless liquid
Odor Fishy, ammoniacal
Density 0.7255 g mL−1
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Solubility miscible with organic solvents
log P 1.647
Vapor pressure 6.899–8.506 kPa
Template:Longitem 66 μmol Pa−1 kg−1
Acidity (pKa) 10.75 (for the conjugate acid) (H2O), 9.00 (DMSO)[4]
Template:Longitem −81.4·10−6 cm3/mol
Template:Longitem 1.401
Template:Longitem 216.43 J K−1 mol−1
Template:Longitem −169 kJ mol−1
Template:Longitem −4.37763 to −4.37655 MJ mol−1
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Explosive limits 1.2–8%
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Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. Like triethanolamine and the tetraethylammonium ion, it is often abbreviated TEA.[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 in organic synthesis, usually as a base.

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.[3] 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.[10]

In alkane solvents triethylamine is a Lewis base that forms adducts with a variety of Lewis acids, such as I2 and phenols. Owing to its steric bulk, it forms complexes with transition metals reluctantly.[11][12][13]

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.[14] Such reactions lead to the production of hydrogen chloride which combines with triethylamine to form the salt triethylamine hydrochloride, commonly called triethylammonium chloride. (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.

Niche uses

Triethylamine is commonly used in the production of anionic Polyurethane dispersions (resins dispersed in water rather than solvents) as a neutralizing agent.

Triethylamine is used to give salts of various carboxylic acid-containing pesticides, e.g. Triclopyr and 2,4-dichlorophenoxyacetic acid.Script error: No such module "Unsubst".

Triethylamine is the active ingredient in FlyNap, a product for anesthetizing fruit flies.Script error: No such module "Unsubst". It is also 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.Script error: No such module "Unsubst".

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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.Script error: No such module "Unsubst".

Triethylamine was discovered by the Germans during the early 1940s to be hypergolic in combination with nitric acid, and was used as a component in the German Wasserfall rocket.[15] The Soviet Scud missile used TG-02, a mixture of 50% xylidine and 50% triethylamine as a starting fluid to ignite its rocket engine.[16]Template:Better source needed

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. Due to the scent, it is considered unlucky in British culture to bring hawthorn into a house. Gangrene and semen are also said to possess a similar odour.[17]

References

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  1. ↑ Script error: No such module "citation/CS1".
  2. ↑ X. Bories-Azeau, S. P. Armes, and H. J. W. van den Haak, Macromolecules 2004, 37, 2348 PDF
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  4. ↑ a b David Evans Research Group Script error: No such module "webarchive".
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  16. ↑ Script error: No such module "citation/CS1".
  17. ↑ The book of general ignorance. John Lloyd & John Mitchinson. Faber & Faber 2006, The Hawthorn, BBC

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Further reading

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External links

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