Potassium hydride

Last updated
Potassium hydride
IUPAC name
Potassium hydride
3D model (JSmol)
ECHA InfoCard 100.028.823 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 232-151-5
PubChem CID
  • InChI=1S/K.H/q+1;-1 Yes check.svgY
  • InChI=1S/K.H/q+1;-1
  • [H-].[K+]
Molar mass 40.1062 g/mol
Appearancewhite to gray crystalline powder
Density 1.43 g/cm3 [1]
Melting point decomposes at ~400 °C [2]
Solubility insoluble in benzene, diethyl ether, carbon disulfide
cubic, cF8
Fm3m, No. 225
37.91 J/(mol⋅K)
-57.82 kJ/mol
Occupational safety and health (OHS/OSH):
Main hazards
corrosive, pyrophoric, reacts violently with acids and water
NFPA 704 (fire diamond)
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).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

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]



Potassium hydride is produced by direct combination of the metal and hydrogen:

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]


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]


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

Related Research Articles

<span class="mw-page-title-main">Alkali metal</span> Group of highly reactive chemical elements

The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitute group 1, which lies in the s-block of the periodic table. All alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour. This family of elements is also known as the lithium family after its leading element.

<span class="mw-page-title-main">Hydroxide</span> Chemical compound

Hydroxide is a diatomic anion with chemical formula OH. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. The corresponding electrically neutral compound HO is the hydroxyl radical. The corresponding covalently bound group –OH of atoms is the hydroxy group. Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry.

<span class="mw-page-title-main">Potassium</span> Chemical element, symbol K and atomic number 19

Potassium is the chemical element with the symbol K and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge. In nature, potassium occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame. It is found dissolved in seawater, and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

<span class="mw-page-title-main">Sodium</span> Chemical element, symbol Na and atomic number 11

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope is 23Na. The free metal does not occur in nature, and must be prepared from compounds. Sodium is the sixth most abundant element in the Earth's crust and exists in numerous minerals such as feldspars, sodalite, and halite (NaCl). Many salts of sodium are highly water-soluble: sodium ions have been leached by the action of water from the Earth's minerals over eons, and thus sodium and chlorine are the most common dissolved elements by weight in the oceans.

<span class="mw-page-title-main">Base (chemistry)</span> Type of chemical substance

In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century.

In chemistry, a hydride is formally the anion of hydrogen (H). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.

<span class="mw-page-title-main">Potassium hydroxide</span> Inorganic compound (KOH)

Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.

<span class="mw-page-title-main">Iodoform</span> Chemical compound

Iodoform (also known as triiodomethane and, inaccurately, as carbon triiodide) is the organoiodine compound with the chemical formula CHI3. A pale yellow, crystalline, volatile substance, it has a penetrating and distinctive odor (in older chemistry texts, the smell is sometimes referred to as that of hospitals, where the compound is still commonly used) and, analogous to chloroform, sweetish taste. It is occasionally used as a disinfectant.

<span class="mw-page-title-main">Aldol condensation</span> Type of chemical reaction

An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties react to form a β-hydroxyaldehyde or β-hydroxyketone, and this is then followed by dehydration to give a conjugated enone.

<span class="mw-page-title-main">Lithium aluminium hydride</span> Chemical compound

Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li[AlH4] or LiAlH4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthesis, especially for the reduction of esters, carboxylic acids, and amides. The solid is dangerously reactive toward water, releasing gaseous hydrogen (H2). Some related derivatives have been discussed for hydrogen storage.

<span class="mw-page-title-main">Sodium hydride</span> Chemical compound

Sodium hydride is the chemical compound with the empirical formula NaH. This alkali metal hydride is primarily used as a strong yet combustible base in organic synthesis. NaH is a saline (salt-like) hydride, composed of Na+ and H ions, in contrast to molecular hydrides such as borane, methane, ammonia, and water. It is an ionic material that is insoluble in all solvents (other than molten Na), consistent with the fact that H ions do not exist in solution. Because of the insolubility of NaH, all reactions involving NaH occur at the surface of the solid.

The Cannizzaro reaction, named after its discoverer Stanislao Cannizzaro, is a chemical reaction which involves the base-induced disproportionation of two molecules of a non-enolizable aldehyde to give a primary alcohol and a carboxylic acid.

<i>n</i>-Butyllithium Chemical compound

n-Butyllithium C4H9Li (abbreviated n-BuLi) is an organolithium reagent. It is widely used as a polymerization initiator in the production of elastomers such as polybutadiene or styrene-butadiene-styrene (SBS). Also, it is broadly employed as a strong base (superbase) in the synthesis of organic compounds as in the pharmaceutical industry.

A superbase is a compound that has a particularly high affinity for protons. Superbases are of theoretical interest and potentially valuable in organic synthesis. Superbases have been described and used since the 1850s.

<span class="mw-page-title-main">Germane</span> Chemical compound

Germane is the chemical compound with the formula GeH4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is tetrahedral. It burns in air to produce GeO2 and water. Germane is a group 14 hydride.

Potassium <i>tert</i>-butoxide Chemical compound

Potassium tert-butoxide (or potassium t-butoxide) is a chemical compound with the formula [(CH3)3COK]n (abbr. KOtBu). This colourless solid is a strong base (pKa of conjugate acid around 17), which is useful in organic synthesis. The compound is often depicted as a salt, and it often behaves as such, but its ionization depends on the solvent.

<span class="mw-page-title-main">Calcium hydride</span> Chemical compound

Calcium hydride is the chemical compound with the formula CaH2, and is therefore an alkaline earth hydride. This grey powder reacts vigorously with water liberating hydrogen gas. CaH2 is thus used as a drying agent, i.e. a desiccant.

<span class="mw-page-title-main">Lithium borohydride</span> Chemical compound

Lithium borohydride (LiBH4) is a borohydride and known in organic synthesis as a reducing agent for esters. Although less common than the related sodium borohydride, the lithium salt offers some advantages, being a stronger reducing agent and highly soluble in ethers, whilst remaining safer to handle than lithium aluminium hydride.

Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are commercially available and exhibit more convenient reactivity.

Potassium methoxide is the alkoxide of methanol with the counterion potassium and is used as a strong base and as a catalyst for transesterification, in particular for the production of biodiesel.


  1. Robert E. Gawley, Xiaojie Zhang, Qunzhao Wang, "Potassium Hydride" Encyclopedia of Reagents for Organic Synthesis 2007 John Wiley & Sons. doi:10.1002/047084289X.rp223.pub2
  2. David Arthur Johnson; Open University (12 August 2002). Metals and chemical change. Royal Society of Chemistry. pp. 167–. ISBN   978-0-85404-665-2 . Retrieved 1 November 2011.
  3. Douglass F. Taber, Christopher G. Nelson (2006). "Potassium Hydride in Paraffin: A Useful Base for Organic Synthesis". J. Org. Chem. 71 (23): 8973–8974. doi:10.1021/jo061420v. PMC   3248818 . PMID   17081034.
  4. Humphry Davy (1808), The Bakerian Lecture on some new phenomena of chemical changes produced by electricity, particularly the decomposition of fixed alkalies, and the exhibition of the new substances which constitute their bases; and on the general nature of alkaline bodies. Philosophical Transactions of the Royal Society, volume 88, pages 1–44. In The Development of Chemistry, 1789–1914: Selected essays, edited by D. Knight, pp. 17–47.
  5. Pradyot Patnaik (1 July 2007). A Comprehensive Guide to the Hazardous Properties of Chemical Substances. John Wiley and Sons. pp. 631–. ISBN   978-0-470-13494-8 . Retrieved 1 November 2011.
  6. Charles A. Brown, Prabhakav K. Jadhav (1925). "(−)-α-Pinene by Isomerization of (−)-β-Pinene". Organic Syntheses . 65: 224.; Collective Volume, vol. 8, p. 553