Trimethyl borate

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]

This chemical is quite flammable and burns with a green flame

Trimethyl borate

Names
IUPAC name Trimethyl borate
Other names Trimethoxyborane
Identifiers
CAS Number	121-43-7 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:38913 Y
ChemSpider	8157 Y
ECHA InfoCard	100.004.063
EC Number	204-468-9
PubChem CID	8470
UNII	82U64J6F5N Y
CompTox Dashboard (EPA)	DTXSID0037738
InChI InChI=1S/C3H9BO3/c1-5-4(6-2)7-3/h1-3H3 Y Key: WRECIMRULFAWHA-UHFFFAOYSA-N Y InChI=1/C3H9BO3/c1-5-4(6-2)7-3/h1-3H3 Key: WRECIMRULFAWHA-UHFFFAOYAY
SMILES O(B(OC)OC)C
Properties
Chemical formula	C3H9BO3
Molar mass	103.91 g·mol−1
Appearance	colourless liquid
Density	0.932 g/ml
Melting point	−34 °C (−29 °F; 239 K)
Boiling point	68 to 69 °C (154 to 156 °F; 341 to 342 K)
Solubility in water	decomposition
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	flammable
Related compounds
Other cations	Trimethyl phosphite Tetramethyl orthosilicate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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