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|Molar mass||39.01 g/mol|
|Appearance||gray powder (colourless when pure)|
|Density||1.37 g/cm3, solid|
|tetrahedral at Na and N|
|Except where noted otherwise, data are given for|
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references
Sodium amide, commonly called sodamide, is the chemical compound with the formula NaNH2. This solid, which is dangerously reactive toward water, is white when pure, but commercial samples are typically gray due to the presence of small quantities of metallic iron from the manufacturing process. Such impurities do not usually affect the utility of the reagent. NaNH2 has been widely employed as a strong base in organic synthesis.
Preparation and structure
Sodium amide can be prepared by the reaction of sodium with ammonia gas, 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, ca. -33 °C.
- 2 Na + 2 NH3 → 2 NaNH2 + H2
NaNH2 is a salt-like material and as such, crystallizes as an infinite polymer. The geometry about sodium is tetrahedral. In ammonia, NaNH2 forms conductive solutions, consistent with the presence of Na(NH3)6+ and NH2- anions.
Sodium amide is used in the industrial production of indigo, hydrazine, and sodium cyanide. It is the reagent of choice for the drying of ammonia (liquid or gaseous) and is also widely used as a strong base in organic chemistry, often in liquid ammonia solution. One of the main advantages to the use of sodamide is that it is an excellent base and rarely serves as a nucleophile. It is however poorly soluble and its use has been superseded by the related reagents such as sodium hydride, sodium bis(trimethylsilyl)amide (NaHMDS), and lithium diisopropylamide (LDA).
Preparation of alkynes
Deprotonation of carbon and nitrogen acids
Carbon acids which can be deprotonated by sodium amide in liquid ammonia include terminal alkynes, methyl ketones, cyclohexanone, phenylacetic acid and its derivatives and diphenylmethane. Acetylacetone loses two protons to form a dianion.
- Rearrangement with orthodeprotonation
- Oxirane synthesis (by carbene reaction?)
- Indole synthesis
In the presence of limited quantities of air and moisture, such as in a poorly closed container, explosive mixtures of oxidation products can form. This is accompanied by a yellowing or browning of the solid. As such, sodium amide should always be stored in a tightly closed container, if possible under an atmosphere of nitrogen gas. Sodium amide samples which are yellow or brown in color should be destroyed immediately: one method for destruction is the careful addition of ethanol to a suspension of sodium amide in a hydrocarbon solvent.
Sodium amide may be expected to be corrosive to the skin, eyes and mucous membranes. Care should be taken to avoid dispersal of the dust.
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