Sodium amide

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Sodium amide
Sodium amide.png
Sodium-amide-3D-balls-B.png
Names
IUPAC name
Sodium amide, sodium azanide [1]
Other names
Sodamide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.029.064 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-971-0
PubChem CID
UNII
UN number 1390
  • InChI=1S/H2N.Na/h1H2;/q-1;+1 X mark.svgN
    Key: ODZPKZBBUMBTMG-UHFFFAOYSA-N X mark.svgN
  • [Na]N
  • [NH2-].[Na+]
Properties
NaNH2
Molar mass 39.013 g·mol−1
AppearanceColourless crystals
Odor Ammonia-like
Density 1.39 g/cm3
Melting point 210 °C (410 °F; 483 K)
Boiling point 400 °C (752 °F; 673 K)
Reacts
Solubility 40 mg/L (liquid ammonia), reacts with ethanol
Acidity (pKa)38 (conjugate acid) [2]
Structure
orthorhombic
Thermochemistry
66.15 J/(mol·K)
Std molar
entropy (S⦵298)
76.9 J/(mol·K)
-118.8 kJ/mol
-59 kJ/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
3
2
3
W
Flash point 4.44 °C (39.99 °F; 277.59 K)
450 °C (842 °F; 723 K)
Related compounds
Other anions
Sodium bis(trimethylsilyl)amide
Other cations
Lithium amide
Potassium amide
Related compounds
 Ammonia
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the formula NaNH2. 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.[ citation needed ]NaNH2 conducts electricity in the fused state, its conductance being similar to that of NaOH in a similar state. NaNH2 has been widely employed as a strong base in organic synthesis.

Contents

Preparation and structure

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.

Uses

Sodium amide is mainly used as a strong base in organic chemistry, often 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. [7]

Pfleger's synthesis of indigo dye. Indigo Synthesis V.1.svg
Pfleger's synthesis of indigo dye.

Dehydrohalogenation

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. [8] 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.

Phenylacetylene prepn.png

Hydrogen chloride and ethanol can also be eliminated in this way, [9] as in the preparation of 1-ethoxy-1-butyne. [10]

Ethoxybutyne prepn.png

Cyclization reactions

Where there is no β-hydrogen to be eliminated, cyclic compounds may be formed, as in the preparation of methylenecyclopropane below. [11]

Methylenecyclopropane prepn.png

Cyclopropenes, [12] aziridines [13] and cyclobutanes [14] may be formed in a similar manner.

Deprotonation of carbon and nitrogen acids

Carbon acids which can be deprotonated by sodium amide in liquid ammonia include terminal alkynes, [15] methyl ketones, [16] cyclohexanone, [17] phenylacetic acid and its derivatives [18] and diphenylmethane. [19] Acetylacetone loses two protons to form a dianion. [20] Sodium amide will also deprotonate indole [21] and piperidine. [22]

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

Safety

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. [26] 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. [27]

Related Research Articles

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Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li[AlH4] or LiAlH4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthesis, especially for the reduction of esters, carboxylic acids, and amides. The solid is dangerously reactive toward water, releasing gaseous hydrogen (H2). Some related derivatives have been discussed for hydrogen storage.

<span class="mw-page-title-main">Imide</span> Class of chemical compounds

In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications, imides are best known as components of high-strength polymers, called polyimides. Inorganic imides are also known as solid state or gaseous compounds, and the imido group (=NH) can also act as a ligand.

<span class="mw-page-title-main">Sodium amalgam</span> Alloy of mercury and sodium

Sodium amalgam, commonly denoted Na(Hg), is an alloy of mercury and sodium. The term amalgam is used for alloys, intermetallic compounds, and solutions involving mercury as a major component. Sodium amalgams are often used in reactions as strong reducing agents with better handling properties compared to solid sodium. They are less dangerously reactive toward water and in fact are often used as an aqueous suspension.

<span class="mw-page-title-main">Permanganate</span> Chemical compound

A permanganate is a chemical compound with the manganate(VII) ion, MnO−
4, the conjugate base of permanganic acid. Because the manganese atom has a +7 oxidation state, the permanganate(VII) ion is a strong oxidising agent. The ion is a transition metal ion with a tetrahedral structure. Permanganate solutions are purple in colour and are stable in neutral or slightly alkaline media. The exact chemical reaction depends on the carbon-containing reactants present and the oxidant used. For example, trichloroethane (C2H3Cl3) is oxidised by permanganate ions to form carbon dioxide (CO2), manganese dioxide (MnO2), hydrogen ions (H+), and chloride ions (Cl−).

<span class="mw-page-title-main">Trimethyl borate</span> Chemical compound

Trimethyl borate is the organoboron compound with the formula B(OCH3)3 and a metal alkoxide. It is a colourless liquid that burns with a green flame. It is an intermediate in the preparation of sodium borohydride and is a popular reagent in organic chemistry. It is a weak Lewis acid (AN = 23, Gutmann-Beckett method).

<span class="mw-page-title-main">Sodium bis(trimethylsilyl)amide</span> Chemical compound

Sodium bis(trimethylsilyl)amide is the organosilicon compound with the formula NaN(Si 3)2. This species, usually called NaHMDS, is a strong base used for deprotonation reactions or base-catalyzed reactions. Its advantages are that it is commercially available as a solid and it is soluble not only in ethers, such as THF or diethyl ether, but also in aromatic solvents, like benzene and toluene by virtue of the lipophilic TMS groups.

<span class="mw-page-title-main">Thiophenol</span> Chemical compound

Thiophenol is an organosulfur compound with the formula C6H5SH, sometimes abbreviated as PhSH. This foul-smelling colorless liquid is the simplest aromatic thiol. The chemical structures of thiophenol and its derivatives are analogous to phenols. An exception is the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a sulfur atom. The prefix thio- implies a sulfur-containing compound and when used before a root word name for a compound which would normally contain an oxygen atom, in the case of 'thiol' that the alcohol oxygen atom is replaced by a sulfur atom.

<span class="mw-page-title-main">Sodium thiocyanate</span> Chemical compound

Sodium thiocyanate (sometimes called sodium sulphocyanide) is the chemical compound with the formula NaSCN. This colorless deliquescent salt is one of the main sources of the thiocyanate anion. As such, it is used as a precursor for the synthesis of pharmaceuticals and other specialty chemicals. Thiocyanate salts are typically prepared by the reaction of cyanide with elemental sulfur:

<span class="mw-page-title-main">Iron(III) nitrate</span> Chemical compound

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<span class="mw-page-title-main">Diphenyl disulfide</span> Chemical compound

Diphenyl disulfide is the chemical compound with the formula (C6H5S)2. This colorless crystalline material is often abbreviated Ph2S2. It is one of the more commonly encountered organic disulfides in organic synthesis. Minor contamination by thiophenol is responsible for the disagreeable odour associated with this compound.

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<span class="mw-page-title-main">Lithium bis(trimethylsilyl)amide</span> Chemical compound

Lithium bis(trimethylsilyl)amide is a lithiated organosilicon compound with the formula LiN(Si(CH3)3)2. It is commonly abbreviated as LiHMDS or Li(HMDS) (lithium hexamethyldisilazide - a reference to its conjugate acid HMDS) and is primarily used as a strong non-nucleophilic base and as a ligand. Like many lithium reagents, it has a tendency to aggregate and will form a cyclic trimer in the absence of coordinating species.

<span class="mw-page-title-main">Erlenmeyer–Plöchl azlactone and amino-acid synthesis</span>

The Erlenmeyer–Plöchl azlactone and amino acid synthesis, named after Friedrich Gustav Carl Emil Erlenmeyer who partly discovered the reaction, is a series of chemical reactions which transform an N-acyl glycine to various other amino acids via an oxazolone.

<span class="mw-page-title-main">Sodium methylsulfinylmethylide</span> Chemical compound

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<span class="mw-page-title-main">Phenyl isothiocyanate</span> Chemical compound

Phenyl isothiocyanate (PITC) is a reagent used in reversed phase HPLC. PITC is less sensitive than o-phthaldehyde (OPA) and cannot be fully automated. PITC can be used for analysing secondary amines, unlike OPA. It is also known as Edman's reagent and is used in Edman degradation.

<span class="mw-page-title-main">Triphenylmethyl chloride</span> Chemical compound

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In organosulfur chemistry, sulfinamide is a functional group with the structure R−S(=O)−NR2. This functionality is composed of a sulfur-carbon and sulfur-nitrogen single bonds, as well as a sulfur-oxygen double bond, resulting in a tetravalent sulfur centre. As a non-bonding electron pair is also present on the sulfur, these compounds are also chiral. They are sometimes referred to as S-chiral sulfinamides. Sulfinamides are amides of sulfinic acid.

<span class="mw-page-title-main">Metal amides</span>

Metal amides (systematic name metal azanides) are a class of coordination compounds composed of a metal center with amide ligands of the form NR2−. Amido complexes of the parent amido ligand NH2− are rare compared to complexes with diorganylamido ligand, such as dimethylamido. Amide ligands have two electron pairs available for bonding.

<span class="mw-page-title-main">Tris(trimethylsilyl)amine</span> Chemical compound

Tris(trimethylsilyl)amine is the simplest tris(trialkylsilyl)amine which are having the general formula (R3Si)3N, in which all three hydrogen atoms of the ammonia are replaced by trimethylsilyl groups (-Si(CH3)3). Tris(trimethylsilyl)amine has been for years in the center of scientific interest as a stable intermediate in chemical nitrogen fixation (i. e. the conversion of atmospheric nitrogen N2 into organic substrates under normal conditions).

<span class="mw-page-title-main">Azanide</span> Anion derived from deprotonation of ammonia

Azanide is the IUPAC-sanctioned name for the anion NH−2. The term is obscure; derivatives of NH−2 are almost invariably referred to as amides, despite the fact that amide also refers to the organic functional group –C(=O)−NR2. The anion NH−2 is the conjugate base of ammonia, so it is formed by the self-ionization of ammonia. It is produced by deprotonation of ammonia, usually with strong bases or an alkali metal. Azanide has a H–N–H bond angle of 104.5°.

References

  1. ↑ IUPAC, Compendium of Chemical Terminology , 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "amides". doi:10.1351/goldbook.A00266
  2. ↑ Buncel, E.; Menon, B. (1977). "Carbanion mechanisms: VII. Metallation of hydrocarbon acids by potassium amide and potassium methylamide in tetrahydrofuran and the relative hydride acidities". Journal of Organometallic Chemistry. 141 (1): 1–7. doi:10.1016/S0022-328X(00)90661-2.
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  5. ↑ Zalkin, A.; Templeton, D. H. (1956). "The Crystal Structure Of Sodium Amide". Journal of Physical Chemistry. 60 (6): 821–823. doi:10.1021/j150540a042. hdl: 2027/mdp.39015086484659 .
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    Bou, A.; Pericàs, M. A.; Riera, A.; Serratosa, F. (1987). "Dialkoxyacetylenes: di-tert-butoxyethyne, a valuable synthetic intermediate". Organic Syntheses . 65: 58{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 8, p. 161.
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    Ashworth, P. J.; Mansfield, G. H.; Whiting, M. C. (1955). "2-Butyn-1-ol". Organic Syntheses . 35: 20{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 4, p. 128.
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    Peterson, P. E.; Dunham, M. (1977). "(Z)-4-Chloro-4-hexenyl trifluoroacetate". Organic Syntheses . 57: 26{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 6, p. 273.
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    Kaiser, E. M.; Kenyon, W. G.; Hauser, C. R. (1967). "Ethyl 2,4-diphenylbutanoate". Organic Syntheses . 47: 72{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 5, p. 559.
    Wawzonek, S.; Smolin, E. M. (1951). "α,β-Diphenylcinnamonitrile". Organic Syntheses . 31: 52{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 4, p. 387.
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    Hampton, K. G.; Harris, T. M.; Hauser, C. R. (1967). "2,4-Nonanedione". Organic Syntheses . 47: 92{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 5, p. 848.
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  27. ↑ "Sodium amide SOP". Princeton.
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