Sodium hydride

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Sodium hydride
Names
IUPAC name
Sodium hydride
Other names
Sodium monohydride
Properties
NaH
Molar mass 23.99771 g/mol
Appearance White or gray solid
Odor Odorless
Density 1.396 g/cm3
Melting point 300 °C (572 °F; 573 K)
Boiling point 300–500 °C (572–932 °F; 573–773 K) Decomposes
Reacts
Solubility Reacts with alcohols, aldehydes, carboxylic acids, halocarbons, ketones
Soluble in NaK, molten NaOH
Insoluble in most solvents
Vapor pressure ~0 mmHg
Thermochemistry
-56.366 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Related compounds
Related compounds
Lithium hydride
Calcium hydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium hydride is the chemical compound with the chemical formula NaH. It is a strong base.

Properties

Chemical

Sodium hydride will react with water to release hydrogen.

Reaction with aluminium metal and hydrogen will give sodium aluminium hydride.

Physical

Sodium hydride is a white solid, which reacts with water.

Availability

It is sold by chemical suppliers, usually kept under mineral oil.

Preparation

Sodium hydride can be prepared by passing dry and air-free hydrogen over molten sodium metal, at 700-750 °C. The molten sodium sits in a steel crucible or boat, inside a quartz or refractory glass tube. Adding small amounts of calcium metal will accelerate the process.[1] At room temperature, sodium reacts very slow with hydrogen to form sodium hydride.

Heating sodium metal and hydrogen in THF at 250-350 °C, at a pressure rising from 7 to 35 atm will give sodium hydride with a yield of 98%.[2]

Thermal decomposition of sodium aluminium hydride above 250 °C will give hydrogen, aluminium and sodium hydride.

NaAlH4 → NaH + Al + 2 H2

Heating the powdered sodium carbide in an autoclave in the presence of hydrogen at 500 atm and 650°C will give sodium hydride. Yield of this process is 86%.[3]

Thermal decomposition of sodium amide, in a hydrogen atmosphere at 300 °C will give sodium hydride.[4]

Reduction of sodium hydroxide with a mixture of H2-N2 at 750 °C will give sodium hydride. Iron or manganese is used as catalyst.[5]

Hydrogenation of sodium azide at 120 °C in gaseous phase, without a solvent gives sodium hydride and ammonia.[6][7]

Sodium hydride is also produced, along with sodium carbide by reacting molten sodium metal with methane, at 300-500 °C.[8] Reaction of molten sodium metal with acetylene at 100-550 °C is another route.[9]

Projects

Handling

Safety

Sodium hydride is water and air sensitive and must be handled with care and proper protection.

Storage

Sodium hydride must be kept in an air-tight container under inert atmosphere or inert solvent, like mineral oil.

Disposal

Adding it in a large volume of base, water or alcohol will suffice.

References

  1. Ephraim; Michel, E.; Helvetica Chimica Acta; vol. 4; (1921); p. 765
  2. http://www.google.com/patents/US2898195
  3. Patent; Goerrig, D.; Farbenfabriken Bayer A.-G.; DE953523; (1956); C. A.; (1959); p. 7526
  4. Guntz; Benoit; Bulletin de la Societe Chimique de France; vol. 41; (1927); p. 434 - 434
  5. Villard, P.; Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences; vol. 193; (1931); p. 681 - 685
  6. Wattenberg, H.; Ber. Dtsch. Chem. Ges.; vol. 63; (1930); p. 1667 - 1672
  7. Patent; Tiede, E.; DE417508; (1925)
  8. Kovalev; Journal of applied chemistry of the USSR; vol. 57; nb. 7 pt 1; (1984); p. 1368 - 1371
  9. Walker; Journal of Physical Chemistry; vol. 31; (1927); p. 982 - 982

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