Sodium amide

Sodium amide
Names
IUPAC name
Sodium amide, sodium azanide[1]
Other names
Sodamide
Identifiers
7782-92-5 YesY
3D model (Jmol) Interactive image
ChemSpider 22940 N
ECHA InfoCard 100.029.064
EC Number 231-971-0
PubChem 24533
UN number 1390
Properties
NaNH2
Molar mass 39.01 g mol−1
Appearance Colourless crystals
Odor ammonia-like
Density 1.39 g cm−3
Melting point 210 °C (410 °F; 483 K)
Boiling point 400 °C (752 °F; 673 K)
reacts
Solubility 0.004 g/100 mL (liquid ammonia), reacts in ethanol
Acidity (pKa) 38 (conjugate acid) [2]
Structure
orthogonal
Thermochemistry
66.15 J/mol K
76.9 J/mol K
-118.8 kJ/mol
-59 kJ/mol
Hazards
NFPA 704
Flammability code 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 fuel Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 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., fluorine Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
2
3
3
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
 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).
N verify (what is YesYN ?)
Infobox references

Sodium amide, commonly called sodamide, is the inorganic compound with the formula NaNH2. 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. 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.

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 an 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 NH2− 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). One of the main advantages to the use of sodamide is that it is rarely functions as a nucleophile. 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.


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.

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

Cyclization reactions

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

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 reacts violently with water to produce ammonia and sodium hydroxide and will burn in air to give oxides of sodium and nitrogen.

NaNH2 + H2O → NH3 + NaOH
2 NaNH2 + 4 O2 → Na2O + 2 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. 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.[26]

See also

References

  1. ↑ http://goldbook.iupac.org/A00266.html
  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.
  3. ↑ Bergstrom, F. W. (1955). "Sodium amide". Org. Synth.; Coll. Vol., 3, p. 778
  4. ↑ Greenlee, K. W.; Henne, A. L.; Fernelius, W. C. (1946). "Sodium Amide". Inorganic Syntheses. 2: 128–135. doi:10.1002/9780470132333.ch38.
  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.
  6. ↑ Wells, A. F. (1984). Structural Inorganic Chemistry. Oxford: Clarendon Press. ISBN 0-19-855370-6.
  7. ↑ L. Lange, W. Treibel "Sodium Amide" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a24_267
  8. ↑ Campbell, K. N.; Campbell, B. K. (1950). "Phenylacetylene". Org. Synth. 30: 72.; Coll. Vol., 4, p. 763
  9. ↑ Jones, E. R. H.; Eglinton, G.; Whiting, M. C.; Shaw, B. L. (1954). "Ethoxyacetylene". Org. Synth. 34: 46.; Coll. Vol., 4, p. 404
    Bou, A.; Pericàs, M. A.; Riera, A.; Serratosa, F. (1987). "Dialkoxyacetylenes: di-tert-butoxyethyne, a valuable synthetic intermediate". Org. Synth. 65: 58.; Coll. Vol., 8, p. 161
    Magriotis, P. A.; Brown, J. T. (1995). "Phenylthioacetylene". Org. Synth. 72: 252.; Coll. Vol., 9, p. 656
    Ashworth, P. J.; Mansfield, G. H.; Whiting, M. C. (1955). "2-Butyn-1-ol". Org. Synth. 35: 20.; Coll. Vol., 4, p. 128
  10. ↑ Newman, M. S.; Stalick, W. M. (1977). "1-Ethoxy-1-butyne". Org. Synth. 57: 65.; Coll. Vol., 6, p. 564
  11. ↑ Salaun, J. R.; Champion, J.; Conia, J. M. (1977). "Cyclobutanone from methylenecyclopropane via oxaspiropentane". Org. Synth. 57: 36.; Coll. Vol., 6, p. 320
  12. ↑ Nakamura, M.; Wang, X. Q.; Isaka, M.; Yamago, S.; Nakamura, E. (2003). "Synthesis and (3+2)-cycloaddition of a 2,2-dialkoxy-1-methylenecyclopropane: 6,6-dimethyl-1-methylene-4,8-dioxaspiro(2.5)octane and cis-5-(5,5-dimethyl-1,3-dioxan-2-ylidene)hexahydro-1(2H)-pentalen-2-one". Org. Synth. 80: 144.
  13. ↑ Bottini, A. T.; Olsen, R. E. (1964). "N-Ethylallenimine". Org. Synth. 44: 53.; Coll. Vol., 5, p. 541
  14. ↑ Skorcz, J. A.; Kaminski, F. E. (1968). "1-Cyanobenzocyclobutene". Org. Synth. 48: 55.; Coll. Vol., 5, p. 263
  15. ↑ Saunders, J. H. (1949). "1-Ethynylcyclohexanol". Org. Synth. 29: 47.; Coll. Vol., 3, p. 416
    Peterson, P. E.; Dunham, M. (1977). "(Z)-4-Chloro-4-hexenyl trifluoroacetate". Org. Synth. 57: 26.; Coll. Vol., 6, p. 273
    Kauer, J. C.; Brown, M. (1962). "Tetrolic acid". Org. Synth. 42: 97.; Coll. Vol., 5, p. 1043
  16. ↑ Coffman, D. D. (1940). "Dimethylethynylcarbinol". Org. Synth. 20: 40.; Coll. Vol., 3, p. 320Hauser, C. R.; Adams, J. T.; Levine, R. (1948). "Diisovalerylmethane". Org. Synth. 28: 44.; Coll. Vol., 3, p. 291
  17. ↑ Vanderwerf, C. A.; Lemmerman, L. V. (1948). "2-Allylcyclohexanone". Org. Synth. 28: 8.; Coll. Vol., 3, p. 44
  18. ↑ Hauser, C. R.; Dunnavant, W. R. (1960). "α,β-Diphenylpropionic acid". Org. Synth. 40: 38.; Coll. Vol., 5, p. 526
    Kaiser, E. M.; Kenyon, W. G.; Hauser, C. R. (1967). "Ethyl 2,4-diphenylbutanoate". Org. Synth. 47: 72.; Coll. Vol., 5, p. 559
    Wawzonek, S.; Smolin, E. M. (1951). "α,β-Diphenylcinnamonitrile". Org. Synth. 31: 52.; Coll. Vol., 4, p. 387
  19. ↑ Murphy, W. S.; Hamrick, P. J.; Hauser, C. R. (1968). "1,1-Diphenylpentane". Org. Synth. 48: 80.; Coll. Vol., 5, p. 523
  20. ↑ Hampton, K. G.; Harris, T. M.; Hauser, C. R. (1971). "Phenylation of diphenyliodonium chloride: 1-phenyl-2,4-pentanedione". Org. Synth. 51: 128.; Coll. Vol., 6, p. 928
    Hampton, K. G.; Harris, T. M.; Hauser, C. R. (1967). "2,4-Nonanedione". Org. Synth. 47: 92.; Coll. Vol., 5, p. 848
  21. ↑ Potts, K. T.; Saxton, J. E. (1960). "1-Methylindole". Org. Synth. 40: 68.; Coll. Vol., 5, p. 769
  22. ↑ Bunnett, J. F.; Brotherton, T. K.; Williamson, S. M. (1960). "N-β-Naphthylpiperidine". Org. Synth. 40: 74.; Coll. Vol., 5, p. 816
  23. ↑ Brazen, W. R.; Hauser, C. R. (1954). "2-Methylbenzyldimethylamine". Org. Synth. 34: 61.; Coll. Vol., 4, p. 585
  24. ↑ Allen, C. F. H.; VanAllan, J. (1944). "Phenylmethylglycidic ester". Org. Synth. 24: 82.; Coll. Vol., 3, p. 727
  25. ↑ Allen, C. F. H.; VanAllan, J. (1942). "2-Methylindole". Org. Synth. 22: 94.; Coll. Vol., 3, p. 597
  26. ↑ "Sodium Amide". Princeton, NJ: Princeton University. 2011-03-16. Retrieved 2011-07-20.
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