Formula KH Boiling point 316 °C Appearance colourless crystals | Molar mass 40.1062 g/mol Density 1.47 g/cm³ | |
Potassium hydride, KH, is the inorganic compound of potassium and hydride, and is therefore classed as an alkali metal hydride. It is a white solid, although commercial samples appear gray. A powerful base that is useful in organic synthesis, it is also a dangerously reactive compound. For this reason it is sold commercially as a slurry (~35%) in mineral oil or sometimes paraffin wax to facilitate dispensing.
Contents
Preparation
Potassium hydride is produced by direct combination of the metal and hydrogen:
2 K + H2 → 2 KHThis 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.
Potassium hydride is soluble in fused hydroxides (such as molten sodium hydroxide) and salt mixtures, but not in organic solvents.
Reactions
KH reacts with water according to the reaction:
KH + H2O → KOH + H2Potassium hydride is a superbase that is stronger than sodium hydride. It is used to deprotonate certain carbonyl compounds to give enolates. It also deprotonated amines to give the corresponding amides of the type KNHR and KNR2.
Safety
KH is pyrophoric in air, reacts violently with acids and ignites upon contact with oxidants, including oxygen and other gases. This is why the commercial product is a suspension in mineral oil.