Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the chemical formula . It is a salt composed of the sodium cation and the azanide anion. This solid, which is dangerously reactive toward water, is white, 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. conducts electricity in the fused state, its conductance being similar to that of NaOH in a similar state. 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, c. −33 °C. An
electride, , is formed as a reaction intermediate.
is a salt-like material and as such, crystallizes as an infinite polymer.
Uses
Sodium amide is mainly used as a
strong base in organic chemistry, often suspended (it is insoluble
) in liquid ammonia solution. One of the main advantages to the use of sodium amide is its relatively low
nucleophile. In the industrial production of
indigo dye, sodium amide is a component of the highly basic mixture that induces cyclisation of
N-Phenylglycine. The reaction produces ammonia, which is recycled typically.
[L. Lange, W. Treibel "Sodium Amide" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. ]
Dehydrohalogenation
Sodium amide is a standard base for dehydrohalogenations.
It induces the loss of two equivalents of
hydrogen bromide from a vicinal dibromoalkane to give a
alkyne, as in a preparation of
phenylacetylene.
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,
Cyclization reactions
Where there is no β-hydrogen to be eliminated, cyclic compounds may be formed, as in the preparation of methylenecyclopropane below.
,
Deprotonation of carbon and nitrogen acids
Carbon acids which can be
deprotonation by sodium amide in liquid ammonia include terminal
,
methyl
,
,
phenylacetic acid and its derivatives
and
diphenylmethane.
loses two protons to form a
anion.
Sodium amide will also deprotonate
indole and
piperidine.
Related non-nucleophilic bases
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).
Other reactions
-
Rearrangement with orthodeprotonation
-
Oxirane synthesis
-
Indole synthesis
-
Chichibabin reaction
Safety
Sodium amide is a common reagent with a long history of laboratory use.
[ It can decompose violently on contact with water, producing ammonia and sodium hydroxide:
]
When burned in oxygen, it will give sodium oxide (which react with the produced water, giving sodium hydroxide) along with nitrogen oxides:
In the presence of limited quantities of air and moisture, such as in a poorly closed container, explosive mixtures of peroxides may form.
