Sodium amide

Sodium amide can be prepared by the reaction of sodium with ammonia gas,^[3] but it is usually prepared by the reaction in liquid ammonia using iron(III) nitrate as a catalyst. The reaction is fastest at the boiling point of the ammonia, c. −33 °C. An electride, [Na(NH₃)₆]⁺e⁻, is formed as a reaction intermediate.^[4]

2 Na + 2 NH₃ → 2 NaNH₂ + H₂

NaNH₂ is a salt-like material and as such, crystallizes as an infinite polymer.^[5] The geometry about sodium is tetrahedral.^[6] In ammonia, NaNH₂ forms conductive solutions, consistent with the presence of [Na(NH₃)₆]⁺ and NH−2 ions.

Sodium amide is mainly used as a strong base in organic chemistry, often suspended (it is insoluble^[7]) in liquid ammonia solution. It is the reagent of choice for the drying of ammonia (liquid or gaseous).^{[citation needed]} One of the main advantages to the use of sodium amide is its relatively low nucleophilicity. In the industrial production of indigo, sodium amide is a component of the highly basic mixture that induces cyclisation of N-phenylglycine. The reaction produces ammonia, which is recycled typically.^[8]

Sodium amide induces the loss of two equivalents of hydrogen bromide from a vicinal dibromoalkane to give a carbon–carbon triple bond, as in a preparation of phenylacetylene.^[9] Usually two equivalents of sodium amide yields the desired alkyne. Three equivalents are necessary in the preparation of a terminal alkynes because the terminal CH of the resulting alkyne protonates an equivalent amount of base.

Hydrogen chloride and ethanol can also be eliminated in this way,^[10] as in the preparation of 1-ethoxy-1-butyne.^[11]

Where there is no β-hydrogen to be eliminated, cyclic compounds may be formed, as in the preparation of methylenecyclopropane below.^[12]

Cyclopropenes,^[13] aziridines^[14] and cyclobutanes^[15] may be formed in a similar manner.

Carbon acids which can be deprotonated by sodium amide in liquid ammonia include terminal alkynes,^[16] methyl ketones,^[17] cyclohexanone,^[18] phenylacetic acid and its derivatives^[19] and diphenylmethane.^[20] Acetylacetone loses two protons to form a dianion.^[21] Sodium amide will also deprotonate indole^[22] and piperidine.^[23]

It is however poorly soluble in solvents other than ammonia. Its use has been superseded by the related reagents sodium hydride, sodium bis(trimethylsilyl)amide (NaHMDS), and lithium diisopropylamide (LDA).

• Rearrangement with orthodeprotonation^[24]
• Oxirane synthesis^[25]
• Indole synthesis^[26]
• Chichibabin reaction

Sodium amide decomposes violently on contact with water, producing ammonia and sodium hydroxide:

NaNH₂ + H₂O → NH₃ + NaOH

When burned in oxygen, it will give oxides of sodium (which react with the produced water, giving sodium hydroxide) along with nitrogen oxides:

4 NaNH₂ + 5 O₂ → 4 NaOH + 4 NO + 2 H₂O

4 NaNH₂ + 7 O₂ → 4 NaOH + 4 NO₂ + 2 H₂O

In the presence of limited quantities of air and moisture, such as in a poorly closed container, explosive mixtures of peroxides may form.^[27] This is accompanied by a yellowing or browning of the solid. As such, sodium amide is to be stored in a tightly closed container, under an atmosphere of an inert gas. Sodium amide samples which are yellow or brown in color represent explosion risks.^[28]