Borinic acid

Borinic acid
Names
IUPAC name
Borinic acid
Systematic IUPAC name
Boranol
Other names
Boranol, Hydroxyborane, Dihydridohydroxidoboron
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
141192
  • InChI=1S/BH3O/c1-2/h2H,1H2
    Key: UYANAUSDHIFLFQ-UHFFFAOYSA-N
  • BO
Properties
BH3O
Molar mass 29.83 g·mol−1
reaction in water
Structure
distorted trigonal bipyramid
Related compounds
Related compounds
 Boronic acid
Boric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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General chemical structure of borinic acids (organoborinic acids)
General chemical structure of borinate esters

Borinic acid, also known as boronous acid, is an oxyacid of boron with formula H
2BOH. Borinate is the associated anion of borinic acid with formula H
2BO−
; however, being a Lewis acid, the form in basic solution is H
2B(OH)−
2.

Borinic acid can be formed as the first step in the hydrolysis of diborane:[1]

BH3 + H2O → H2BOH + H2

Borinic acid itself is unstable and only lasts for a few seconds during the hydrolysis reaction. However, by using microwave spectroscopy various properties can be determined. The B-O distance is 1.352 Å, O-H distance 0.96 Å, B-H length is probably 1.2 Å. The angle between bonds at the oxygen atom BOH = 112° and the angles at boron are cis-HBO 121°, and trans-HBO = 117°. The dipole moment is 1.506 Debye.[2]

Borinic acid can form esters such as methoxyborane. This too is unstable only lasting about ten seconds. It can be formed by heating diborane and methanol gas together.[3]

By substituting organic components instead of hydrogen, more generic borinic acids (containing RR'BOH) or borinic esters (RR'BOR") can be formed. Esters will tend to be stable in acidic conditions, but in alkaline conditions the boron atom can gain a negative charge and attach two hydroxyl groups, or two ester bonds. RR'B−(OH)2 or RR'B−(OR")2. The anionic borinate ion can very easily form esters with diols such as ethylene glycol or sugars.[citation needed]

  1. ^ Weiss, H. G.; Shapiro, I. (5 March 1953). "Mechanism of the Hydrolysis of Diborane in the Vapor Phase1". Journal of the American Chemical Society. 75 (5): 1221–1224. doi:10.1021/ja01101a061.
  2. ^ Kawashima, Yoshiyuki; Takeo, Harutoshi; Matsumura, Chi (1 January 1981). "Microwave spectrum of borinic acid BH2OH". The Journal of Chemical Physics. 74 (10): 5430. Bibcode:1981JChPh..74.5430K. doi:10.1063/1.440947.
  3. ^ Kawashima, Y.; Takeo, H.; Matsumura, C. (1984). "Microwave Spectrum of Methoxyborane, CH3OBH2". Ohio State University. hdl:1811/16666.