Sodium tetraphenylborate

Structural formula
General
Surname	Sodium tetraphenylborate
other names	Calignost NaBPh4
Molecular formula	C 24 H 20 BNa
Brief description	colorless crystals
External identifiers / databases
CAS number 143-66-8 EC number 205-605-5 ECHA InfoCard 100.005.096 PubChem 2723787 ChemSpider 8591 Wikidata Q905430
properties
Molar mass	342.22 g · mol -1
Physical state	firmly
density	1.216 g cm −3
Melting point	> 300 ° C
solubility	soluble in water and ethanol
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 301 P: 301 + 310
Toxicological data	288 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Sodium tetraphenylborate (trade name: Kalignost ^® , short: NaPh ₄ B) is a chemical compound consisting of the elements boron , carbon , hydrogen and sodium . It has the constitutional formula Na [B (C ₆ H ₅ ) ₄ ].

history

Sodium tetraphenylborate was first synthesized by the German chemist and Nobel Prize winner Georg Wittig . His goal was to create five-string connections during this period. This "success" was denied to him. He could not observe any octet expansion for the elements boron to nitrogen . Failures were, for example, the reaction of triphenylboranes with phenyllithium (or of boron trihalides with Grignard compounds ), but he found sodium tetraphenylborate.

Extraction and presentation

Today NaPh ₄ B is produced through the reaction of phenyl Grignard reagents such as phenyl magnesium bromide with boron trifluoride . The tetraphenylboromagnesium bromide obtained from this reaction is dissolved in water, and sodium chloride solution is added.

properties

Chemical properties

The most important reaction of NaPh ₄ B is the precipitation of potassium ions in aqueous solution:

${\displaystyle \mathrm {K_{(aq)}^{+}+[B(C_{6}H_{5})_{4}]_{(aq)}^{-}\ \rightleftharpoons \ K[B(C_{6}H_{5})_{4}]_{(s)}\downarrow } }$

${\displaystyle \mathrm {K_{L}:\ 2{,}19\cdot 10^{-8}} }$

The solubility of potassium tetraphenylborate (KPh ₄ B) is accordingly 53.0 mg / l.

use

Sodium tetraphenylborate is most commonly used under the name Kalignost ^® in chemical analysis for the titrimetric and gravimetric determination of potassium. Ammonium , rubidium , cesium and thallium ions can also be determined. Also alkaloids can use NaPh ₄ B be quantified.

Sodium tetraphenylborate can be very useful in the inorganic separation process to differentiate ammonium and potassium ions. If Kalignost is carefully added to the solution, a white precipitate forms, which in one case collects in the upper part of the test tube and in the other case is distributed over the entire reaction volume.

safety instructions

Sodium tetraphenylborate is toxic if swallowed. General safety instructions when handling chemicals: Avoid skin and eye contact, do not inhale the substance, always consult a doctor in the event of an accident or if you feel unwell.

Individual evidence

1. ↑ ^{a b c d} Entry on sodium tetraphenylborate. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
2. ↑ Калугин О.Н., Панченко В.Г., Вьюнник И.Н. (Kalugin, Panchenko, V'yunnik): A Conductometric Study of Ionic Association and Interspecies Interactions in Solutions of 1-1 Electrolytes in ethyl acetate at 5-45 ° C . In: Журнал физической химии (Russian J. Phys. Chem.) . tape 79 , no. 4 , 2005, p. 734-739 (Russian, elibrary.ru - Original title: Кондуктометрическое исследование ионной ассоциации и межчастичных взаимодействий в растворах 1-1 электролитов в этилацетате при 5-45 .).
3. ↑ Sodium tetraphenylborate data sheet from AlfaAesar, accessed on March 14, 2010 ( PDF )(JavaScript required) .
4. ↑ ^{a b} Sodium tetraphenylborate data sheet from Sigma-Aldrich , accessed on May 14, 2017 ( PDF ).