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Potassium hydride

Chemical compound From Wikipedia, the free encyclopedia

Potassium hydride

Potassium hydride, KH, is the inorganic compound of potassium and hydrogen. It is an alkali metal hydride. It is a white solid, although commercial samples appear gray. It is a powerful superbase that is useful in organic synthesis. It is sold commercially as a slurry (~35%) in mineral oil or sometimes paraffin wax to facilitate dispensing.[3]

Quick Facts Names, Identifiers ...
Potassium hydride
Thumb
  Potassium cation, K+
  Hydrogen anion, H−
Names
IUPAC name
Potassium hydride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.823
EC Number
  • 232-151-5
  • InChI=1S/K.H/q+1;-1 Y
    Key: OCFVSFVLVRNXFJ-UHFFFAOYSA-N Y
  • InChI=1S/K.H/q+1;-1
    Key: OCFVSFVLVRNXFJ-UHFFFAOYAO
  • Key: OCFVSFVLVRNXFJ-UHFFFAOYSA-N
  • [H-].[K+]
Properties
KH
Molar mass 40.1062 g/mol
Appearance white to gray crystalline powder
Density 1.43 g/cm3[1]
Melting point decomposes at ~400 °C[2]
reacts
Solubility insoluble in benzene, diethyl ether, carbon disulfide
Structure
cubic, cF8
Fm3m, No. 225
Thermochemistry
37.91 J/(mol⋅K)
−57.82 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 corrosive, pyrophoric, reacts violently with acids and water
NFPA 704 (fire diamond)
ThumbHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
3
3
2
W
Related compounds
Other cations
 Lithium hydride
Sodium hydride
Rubidium hydride
Caesium hydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation

Potassium hydride is produced by direct combination of the metal and hydrogen at temperatures between 200 and 350 °C:

2 K + H2 → 2 KH

This reaction was discovered by Humphry Davy soon after his 1807 discovery of potassium, when he noted that the metal would vaporize in a current of hydrogen when heated just below its boiling point.[4]: p.25 

Potassium hydride is soluble in fused hydroxides (such as molten sodium hydroxide) and salt mixtures, but not in organic solvents.[5]

Reactions

KH reacts with water according to the reaction:

KH + H2O → KOH + H2

As a superbase, potassium hydride is more basic than sodium hydride. It is used to deprotonate certain carbonyl compounds to give enolates. It also deprotonates amines to give the corresponding amides of the type KNHR and KNR2.[6]

Safety

KH can be pyrophoric in air, react violently with acids, and can ignite upon contact with oxidants. As a suspension in mineral oil, KH is less dangerous.

See also

References

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