Tetrahydroxyborate

Tetrahydroxyborate
Stereo, skeletal formula of tetrahydroxyborate with a dimension	Ball and stick model of tetrahydroxyborate
Names
	IUPAC name Tetrahydroxyborate
	Systematic IUPAC name Tetrahydroxyboranuide (substitutive); Tetrahydroxidoborate(1-) (additive)
Identifiers
CAS Number	15390-83-7 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:41132 ;
ChEMBL	ChEMBL1231419 ;
ChemSpider	154612 ;
Gmelin Reference	1966
PubChem CID	177595;
CompTox Dashboard (EPA)	DTXSID60934872 ;
	InChI InChI=1S/BH4O4/c2-1(3,4)5/h2-5H/q-1 Key: KCFLOKKYWBPKFN-UHFFFAOYSA-N ;
	SMILES O[B-](O)(O)O;
Properties
Chemical formula	H4BO4−
Molar mass	78.840 g mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Tetrahydroxyborate (systematically named tetrahydroxyboranuide and tetrahydroxidoborate(1−)) is an inorganic anion with the chemical formula [B(OH)
₄]⁻
(also written as B(OH)⁻
₄ or BH
₄O⁻
₄). It contributes no colour to tetrahydroxyborate salts. It is found in the mineral hexahydroborite, Ca(B(OH)₄)₂·2H₂O (originally formulated CaB₂O₄.6H₂O).^[2] It is classified as a weak base.

Chemical properties

Basicity

Tetrahydroxyborate can assimilate a proton into the anion by recombination:

B(OH)⁻
₄ + H⁺
→ B(OH)
₃ + H
₂O

Because of this capture of a proton (H⁺
), tetrahydroxyborate has Arrhenius-basic character. Its protonation product is boric acid. In aqueous solution, most tetrahydroxyborate ions are undissociated.^{[citation needed]}

B(OH)⁻
₄

{\ce {<<=>}}

B(OH)
₃ + OH⁻

Structure

It is a boron oxoanion with a tetrahedral geometry.^[3] It is isoelectronic with the hypothetical compound orthocarbonic acid.

Chemical reactions

Tetrahydroxyborate undergoes the typical chemical reactions of a hydroxyborate. Upon treatment with a standard acid, it converts to boric acid and a metal salt. Oxidation of tetrahydroxyborate gives perborate. When heated to a high temperature, tetrahydroxyborate salts decompose to produce metaborate salts and water, or to produce boric acid and a metal hydroxide:

n [B(OH)₄]⁻ → (BO⁻
₂)_n + 2n H₂O

[B(OH)₄]⁻ → B(OH)₃ + HO⁻

Production

Tetrahydroxyborate is produced by boric acid alkalinisation. In this process boric acid and hydroxide anions react to produce tetrahydroxyborate according to the following reaction:

B(OH)₃ + HO⁻ → [B(OH)₄]⁻

This process also involves aquatrihydroxyboron as an intermediate, and occurs in two steps. No catalyst is needed for alkalinisation (step 2).

B(OH)₃ + H₂O → [B(OH)₃H₂O]
[B(OH)₃H₂O] + HO⁻ → [B(OH)₄]⁻ + H₂O

Catalytic amounts of water are used for the process. By altering the process conditions, other borate anions may also be produced on the same production site.

Uses

Tetrahydroxyborate can be used as a cross-link in polymers.

Occurrence

The tetrahydroxyborate anion is found in Na[B(OH)₄],^[4] Na₂[B(OH)₄]Cl and Cu^II[B(OH)₄]Cl.


ball-and-stick model of the crystal structure of sodium tetrahydroxyborate	space-filling model of the crystal structure of sodium tetrahydroxyborate

References

^ ^a ^b "Tetrahydroxoborate(1-) (CHEBI:41132)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
^ Glossary of Geology,5th edition, 2005, ISBN 978-0922152766 ed. by Julia A. Jackson, James P. Mehl, Klaus K. E. Neuendorf, American Geological Institute
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 203–205. ISBN 978-0-08-037941-8.
^ L. J. Csetenyi; F. P. Glasser; R. A. Howie (June 1993). "Structure of sodium tetrahydroxyborate". Acta Crystallogr. C. 49 (6): 1039–1041. doi:10.1107/S0108270193000058.

[Tetrahydroxoborate(1-)_(CHEBI:41132)-1] "Tetrahydroxoborate(1-) (CHEBI:41132)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.

[2] Glossary of Geology,5th edition, 2005, ISBN 978-0922152766 ed. by Julia A. Jackson, James P. Mehl, Klaus K. E. Neuendorf, American Geological Institute

[G&E-3] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 203–205. ISBN 978-0-08-037941-8.

[4] L. J. Csetenyi; F. P. Glasser; R. A. Howie (June 1993). "Structure of sodium tetrahydroxyborate". Acta Crystallogr. C. 49 (6): 1039–1041. doi:10.1107/S0108270193000058.

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