Triethyl borate

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Triethyl borate
Triethyl borate.png
Triethyl borate molecule
IUPAC name
Triethyl borate
Other names
Boron triethoxide
Boric acid, triethyl ester
3D model (JSmol)
ECHA InfoCard 100.005.238
EC Number 205-760-9
Molar mass 145.99 g·mol−1
Appearance clear liquid
Density 0.858 g/cm3
Melting point −85 °C (−121 °F; 188 K)
Boiling point 118 °C (244 °F; 391 K)
Flash point 11 °C (52 °F; 284 K)
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

Triethyl borate, also called boron triethoxide or boric acid, triethyl ester, is a colorless, flammable liquid with the formula B(C2H5O)3. It is an ester of boric acid and ethanol.

It melts at −85 °C and boils at 118 °C. It is flammable, with flash point at 11 °C. It is a weak Lewis acid (AN = 17, Gutmann-Beckett method). [1]. It burns with a green flame and solutions of it in ethanol are therefore used in special effects and pyrotechnics.

It is formed by the reaction of boric acid and ethanol in the presence of acid catalyst, where it forms according to the equilibrium reaction:

B(OH)3 + 3 C2H5OH ⇌ (C2H5O)3B + 3 H2O

In order to increase the rate of forward reaction, the formed water must be removed from reaction media by either azeotropic distillation or adsorption. It is used as a solvent and/or catalyst in preparation of synthetic waxes, resins, paints, and varnishes. It is used as a component of some flame retardants in textile industry and of some welding fluxes.


  1. ^ M.A. Beckett, G.C. Strickland, J.R. Holland, and K.S. Varma, "A convenient NMR method for the measurement of Lewis acidity at boron centres: correlation of reaction rates of Lewis acid initiated epoxide polymerizations with Lewis acidity", Polymer, 1996, 37, 4629–4631. doi: 10.1016/0032-3861(96)00323-0

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