Potassium Hydride - Wikipedia

Potassium hydride
  Potassium cation, K+  Hydrogen anion, H−
Names
IUPAC name Potassium hydride
Identifiers
CAS Number
  • 7693-26-7 checkY
3D model (JSmol)
  • Interactive image
ChemSpider
  • 74121 checkY
ECHA InfoCard 100.028.823 Edit this at Wikidata
EC Number
  • 232-151-5
PubChem CID
  • 82127
CompTox Dashboard (EPA)
  • DTXSID10894770 Edit this at Wikidata
InChI
  • InChI=1S/K.H/q+1;-1 checkYKey: OCFVSFVLVRNXFJ-UHFFFAOYSA-N checkY
  • InChI=1S/K.H/q+1;-1Key: OCFVSFVLVRNXFJ-UHFFFAOYAO
  • Key: OCFVSFVLVRNXFJ-UHFFFAOYSA-N
SMILES
  • [H-].[K+]
Properties
Chemical formula 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]
Solubility in water reacts
Solubility insoluble in benzene, diethyl ether, carbon disulfide
Structure
Crystal structure cubic, cF8
Space group Fm3m, No. 225
Thermochemistry
Heat capacity (C) 37.91 J/(mol⋅K)
Std enthalpy offormation (ΔfH⦵298) -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)
NFPA 704 four-colored diamond
3 3 2W
Related compounds
Other cations Lithium hydrideSodium hydrideRubidium hydrideCaesium hydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). checkY verify (what is checkY☒N ?) Infobox references
Chemical compound

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]

Preparation

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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

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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

[edit]

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

[edit]
  • Sodium hydride

References

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  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; Collected Volumes, vol. 8, p. 553.
  • v
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Potassium compounds
H, (pseudo)halogens
  • KF
  • KHF2
  • KH
  • KCl
  • KClO
  • KClO3
  • KClO4
  • KBr
  • KBrO3
  • KI
  • KIO3
  • KIO4
  • KAt
  • KCN
  • KCNO
  • KOCN
  • KSCN
chalcogens
  • K2O
  • KOH
  • K2O2
  • KO2
  • KO3
  • K2S
  • KHS
  • K2SO3
  • KHSO3
  • K2SO4
  • KHSO4
  • KHSO5
  • K2S2O3
  • K2S2O5
  • K2S2O7
  • K2S2O8
  • K2Se
  • K2SeO3
  • K2SeO4
  • K2Te
  • K2TeO3
  • K2TeO4
  • K2Po
pnictogens
  • K3N
  • KNH2
  • KN3
  • KNO2
  • KNO3
  • K3P
  • KH2PO3
  • K3PO4
  • K2HPO4
  • KH2PO4
  • KPF6
  • KAsO2
  • K3AsO4
  • K2HAsO4
  • KH2AsO4
B, C group
  • B4K2O7
  • K2CO3
  • KHCO3
  • K2SiO3
  • K2SiF6
  • K2Al2O4
  • K2Al2B2O7
transition metals
  • K2PtCl4
  • K2Pt(CN)4
  • K2TiF6
  • K2PtCl6
  • K2ReCl6
  • K2ReF6
  • KAsF6
  • K2ReBr6
  • K2ReI6
  • K2ZrF6
  • K4Fe(CN)6
  • K3Fe(CN)6
  • K3Fe(C2O4)3
  • K2FeO4
  • K2MnO4
  • KMnO4
  • K3CrO4
  • K2CrO4
  • K3CrO8
  • KCrO3Cl
  • K2Cr2O7
  • K2Cr3O10
  • K2Cr4O13
  • K4Mo2Cl8
organic
  • KHCO2
  • KCH3CO2
  • KCF3CO2
  • K2C2O4
  • KHC2O4
  • KC12H23O2
  • KC18H35O2
  • C3H2K2O4
  • C4H6KO4
  • C5H7KO4
  • v
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Binary compounds of hydrogen
Alkali metal (Group 1) hydrides
  • LiH
  • NaH
  • KH
  • RbH
  • CsH
Alkaline (Group 2) earth hydrides
Monohydrides
  • BeH
  • MgH
  • CaH
  • SrH
  • BaH
Dihydrides
  • BeH2
  • MgH2
  • CaH2
  • SrH2
  • BaH2
Group 13 hydrides
Boranes
  • BH3
  • BH
  • B2H6
  • B2H2
  • B2H4
  • B4H10
  • B5H9
  • B5H11
  • B6H10
  • B6H12
  • B10H14
  • B18H22
Alanes
  • AlH3
  • Al2H6
Gallanes
  • GaH3
  • Ga2H6
Indiganes
  • InH3
  • In2H6
Thallanes
  • TlH3
  • Tl2H6
Nihonanes (predicted)
  • NhH
  • NhH3
  • Nh2H6
  • NhH5
Group 14 hydrides
Hydrocarbons
  • alkanes
  • alkenes
  • alkynes
  • Cycloalkanes
  • Cycloalkenes
  • Cycloalkynes
  • Annulenes
  • CH
  • CH2
  • CH3
  • C2H
Silanes
  • SiH4
  • Si2H6
  • Si3H8
  • Si4H10
  • Si5H12
  • Si6H14
  • Si7H16
  • Si8H18
  • Si9H20
  • Si10H22
  • more...
Silenes
  • Si2H4
Silynes
  • Si2H2
  • SiH
Germanes
  • GeH4
  • Ge2H6
  • Ge3H8
  • Ge4H10
  • Ge5H12
Stannanes
  • SnH4
  • Sn2H6
Plumbanes
  • PbH4
Flerovanes (predicted)
  • FlH
  • FlH2
  • FlH4
Pnictogen (Group 15) hydrides
Azanes
  • NH3
  • N2H4
  • N3H5
  • N4H6
  • N5H7
  • N6H8
  • N7H9
  • N8H10
  • N9H11
  • N10H12
  • more...
Azenes
  • N2H2
  • N3H3
  • N4H4
Phosphanes
  • PH3
  • P2H4
  • P3H5
  • P4H6
  • P5H7
  • P6H8
  • P7H9
  • P8H10
  • P9H11
  • P10H12
  • more...
Phosphenes
  • P2H2
  • P3H3
  • P4H4
Arsanes
  • AsH3
  • As2H4
Stibanes
  • SbH3
Bismuthanes
  • BiH3
Moscovanes
  • McH3 (predicted)
  • HN3
  • NH
  • HN5
  • NH5 (hypothetical)
Hydrogen chalcogenides (Group 16 hydrides)
Polyoxidanes
  • H2O
  • H2O2
  • H2O3
  • H2O4
  • H2O5
  • more...
  • Polysulfanes
    • H2S
    • H2S2
    • H2S3
    • H2S4
    • H2S5
    • H2S6
    • H2S7
    • H2S8
    • H2S9
    • H2S10
    • more...
    Selanes
    • H2Se
    • H2Se2
    Tellanes
    • H2Te
    • H2Te2
    Polanes
    • PoH2
    Livermoranes
    • LvH2 (predicted)
    • HO
    • HO2
    • HO3
    • H2O+–O– (hypothetical)
    • HS
    • HDO
    • D2O
    • T2O
    Hydrogen halides (Group 17 hydrides)
  • HF
  • HCl
  • HBr
  • HI
  • HAt
  • HTs (predicted)
  • Transition metal hydrides
    • ScH2
    • YH2
    • YH3
    • YH6
    • YH9
    • LuH2
    • LuH3
    • TiH2
    • TiH4
    • ZrH2
    • ZrH4
    • HfH2
    • HfH4
    • VH
    • VH2
    • NbH
    • NbH2
    • TaH
    • TaH2
    • CrH
    • CrH2
    • CrHx
    • FeH
    • FeH2
    • FeH5
    • CoH2
    • RhH2
    • IrH3
    • NiH
    • PdHx (x < 1)
    • PtHx (x< 1)
    • DsH2 (predicted)
    • CuH
    • RgH (predicted)
    • ZnH2
    • CdH2
    • HgH
    • Hg2H2
    • HgH2
    • CnH2 (predicted)
    Lanthanide hydrides
    • LaH2
    • LaH3
    • LaH10
    • CeH2
    • CeH3
    • PrH2
    • PrH3
    • NdH2
    • NdH3
    • SmH2
    • SmH3
    • EuH2
    • GdH2
    • GdH3
    • TbH2
    • TbH3
    • DyH2
    • DyH3
    • HoH2
    • HoH3
    • ErH2
    • ErH3
    • TmH2
    • TmH3
    • YbH2
    • LuH2
    • LuH3
    Actinide hydrides
    • AcH2
    • ThH2
    • ThH4
    • Th4H15
    • PaH3
    • UH3
    • UH4
    • NpH2
    • NpH3
    • PuH2
    • PuH3
    • AmH2
    • AmH3
    • CmH2
    • BkH2
    • BkH3
    • CfH2
    • CfH3
    Exotic matter hydrides
    • PsH

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