Potassium carbide

Structural formula
General
Surname	Potassium carbide
other names	Dipotassium acetylide
Molecular formula	K 2 C 2
Brief description	yellow solid
External identifiers / databases
CAS number 22754-96-7 PubChem 102011382 Wikidata Q15714553
properties
Molar mass	102.22 g mol −1
Physical state	firmly
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium carbide (dipotassium dicarbide) is a chemical compound from the group of carbides . In addition to this compound, KC ₈ , KC ₁₆ and other potassium carbides are known.

Extraction and presentation

Potassium carbide can be produced in a single phase by reacting potassium dissolved in liquid ammonia with acetylene and then heating the hydrogen acetylide obtained in a high vacuum. The first synthesis of sodium carbide and potassium carbide was carried out by Moissan in the late 19th century. Depending on the temperature, KHC ₂ can also arise.

The connection cannot be established by the reaction of potassium with carbon .

Potassium carbide can also be obtained by decomposing potassium methoxide at 300 ° C or by reacting potassium cyanide with magnesium .

${\displaystyle \mathrm {6\ KOCH_{3}\longrightarrow K_{2}C_{2}+2\ K_{2}CO_{3}+2\ C+9\ H_{2}} }$

${\displaystyle \mathrm {2\ KCN+3\ Mg\longrightarrow K_{2}C_{2}+Mg_{3}N_{2}} }$

properties

Crystal structure of potassium carbide

Potassium carbide is a yellow solid that ignites on contact with water. The compound crystallizes tetragonally in the space group I 4 ₁ / acd (space group no. 142) and can be interpreted as a distorted variant of the antifluorite structure. At temperatures above room temperature (420 K), in analogy to the alkaline earth metal acetylides, a reversible phase transformation (1st order) into a cubic high-temperature modification with the space group Fm 3 m (space group no. 225) occurs, which has an undistorted antifluorite structure corresponds to disordered C ₂ ^2– dumbbells.

use

Potassium carbide can be used to make ethynyl steroids and 1,4-dicarbonyl compounds.

Individual evidence

1. ^ ^{A b c d e} T. Y. Kosolapova: Carbides Properties, Production, and Applications . Springer Science & Business Media, 2012, ISBN 978-1-4684-8006-1 , p. 64 ( limited preview in Google Book search).
2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
3. ↑ ^{a b} S. Hemmersbach, B. Zibrowius, U. Ruschewitz: Na ₂ C ₂ and K ₂ C ₂ : synthesis, crystal structure and spectroscopic properties. In: Journal of Inorganic and General Chemistry. 625, 1999, p. 1440, doi : 10.1002 / (SICI) 1521-3749 (199909) 625: 9 <1440 :: AID-ZAAC1440> 3.0.CO; 2-R .
4. ↑ Chris Woodford: Potassium . Marshall Cavendish, 2003, ISBN 978-0-7614-1463-6 , pp. 11 ( limited preview in Google Book search).
5. ↑ L. Bretherick: Bretherick's Handbook of Reactive Chemical Hazards . Elsevier, 2016, ISBN 978-1-4831-6250-8 , pp. 1996 ( limited preview in Google Book Search).
6. ^ Encyclopedia of Reagents for Organic Synthesis . John Wiley & Sons, Ltd, 2001, ISBN 978-0-470-84289-8 , Dipotassium Acetylide, doi : 10.1002 / 047084289x.rd450 / abstract .