Trimethyl borate
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| Template:Longitem | Template:Chembox Elements/molecular formula |
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| Appearance | colourless liquid |
| Density | 0.932 g/ml |
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| Template:Longitem | Trimethyl phosphite Tetramethyl orthosilicate |
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Trimethyl borate is the organoboron compound with the formula B(OCH3)3. It is a colourless liquid that burns with a green flame.[1] It is an intermediate in the preparation of sodium borohydride and is a popular reagent in organic chemistry. It is a weak Lewis acid (AN = 23, Gutmann-Beckett method).[2]
Borate esters are prepared by heating boric acid or related boron oxides with alcohols under conditions where water is removed by azeotropic distillation. [1]
Applications
Trimethyl borate is the main precursor to sodium borohydride by its reaction with sodium hydride in the Brown-Schlesinger process:
- 4 NaH + B(OCH3)3 → NaBH4 + 3 NaOCH3
It is a gaseous anti-oxidant in brazing and solder flux. Otherwise, trimethyl borate has no announced commercial applications. It has been explored as a fire retardant, as well as being examined as an additive to some polymers.[1]
Organic synthesis
It is a useful reagent in organic synthesis, as a precursor to boronic acids, which are used in Suzuki couplings. These boronic acids are prepared via reaction of the trimethyl borate with Grignard reagents followed by hydrolysis:.[3][4]
- ArMgBr + B(OCH3)3 → MgBrOCH3 + ArB(OCH3)2
- ArB(OCH3)2 + 2 H2O → ArB(OH)2 + 2 HOCH3