Potassium borohydride

Structural formula
General
Surname	Potassium borohydride
other names	Potassium boranate Potassium tetrahydroborate Potassium tetrahydridoborate
Molecular formula	KBH 4
Brief description	colorless solid
External identifiers / databases
CAS number 13762-51-1 EC number 237-360-5 ECHA InfoCard 100,033,949 PubChem 4192641 Wikidata Q15628404
properties
Molar mass	53.94 g mol −1
Physical state	firmly
density	1.17 g cm −3
Melting point	585 ° C (decomposition)
solubility	soluble in water (190 g / l) and methanol (39 g / l) practically insoluble in ethanol, ether and tetrahydrofuran
Refractive index	1.494 (20 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 261-301-311-331-314 EUH: 014 P: 280-305 + 351 + 338-309-310-370 + 378-402 + 404
Toxicological data	167 mg kg −1 ( LD 50 ,  rat ,  oral ) 230 mg kg −1 ( LD 50 ,  rabbit ,  transdermal )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Potassium borohydride is an inorganic chemical compound of borohydride .

Extraction and presentation

Potassium borohydride can be obtained by reacting sodium borohydride in methanol / water with aqueous potassium hydroxide solution .

${\displaystyle \mathrm {NaBH_{4}+KOH\longrightarrow KBH_{4}+NaOH} }$

It can also be made by reacting diborane with potassium tetramethoxyborohydride .

${\displaystyle \mathrm {3\ KB(OCH_{3})_{4}+2\ B_{2}H_{6}\longrightarrow 3\ KBH_{4}+4\ B(OCH_{3})_{3}} }$

properties

Potassium borohydride is a colorless solid that is soluble in water. It crystallizes in the sodium chloride lattice type with the space group Fm 3 m (space group no. 225) . At higher temperatures a conversion into a related tetragonal structure takes place. Even at high pressures, there is a transformation to a tetragonal (4 GPa) with the space group P 4 2 ₁ c (space group no.114) or orthorhombic form (7 GPa) with the space group Pnma (space group no.62 ) . There is also a change in the crystal structure at low temperatures. At 65–70 K the crystal structure changes to a tetragonal one with the space group P 4 ₂ / nmc (space group no. 137) .

use

Potassium borohydride is used as a specific reducing agent for carbonyl groups of aldehydes , ketones , acid chlorides and as a foaming agent for plastics. It can also be used as a starting material for the production of chloramphenicol , vitamin A , thiopenicol , atropine and scopolamine .

Individual evidence

1. ↑ ^{a b c d e f g h i j} Data sheet Potassium borohydride, 98% from AlfaAesar, accessed on September 2, 2017 ( PDF )(JavaScript required) .
2. ^ Egon Wiberg, Nils Wiberg: Inorganic Chemistry . Academic Press, 2001, ISBN 978-0-12-352651-9 , pp. 951 ( limited preview in Google Book Search).
3. ↑ ^{a b} Data sheet potassium borohydride (PDF) from Merck , accessed on September 2, 2017.
4. ↑ ^{a b} Michael Hirscher: Handbook of Hydrogen Storage New Materials for Future Energy Storage . John Wiley & Sons, 2010, ISBN 3-527-62981-5 , pp. 122 ( limited preview in Google Book search).
5. ↑ William A. Hart, OF Beumel, Thomas P. Whaley: The Chemistry of Lithium, Sodium, Potassium, Rubidium, Cesium and Francium Pergamon Texts in Inorganic Chemistry . Elsevier, 2013, ISBN 978-1-4831-8757-0 , pp. 399 ( limited preview in Google Book search).
6. ↑ Ravhi S. Kumar, Eunja Kim, Andrew L. Cornelius: Structural Phase Transitions in the Potential Hydrogen Storage Compound KBH ₄ under Compression. In: The Journal of Physical Chemistry C. 112, 2008, p. 8452, doi: 10.1021 / jp0765042 .
7. ↑ Yaroslav Filinchuk, Dmitry Chernyshov, Vladimir Dmitriev: Crystal chemistry of light metal borohydrides . In: Materials Science . 2010, arxiv : 1003.5378 .