Sodium amide

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Sodium amide
Structural formula of sodium amide
Ball and stick, unit cell model of sodium amide
Identifiers
CAS number 7782-92-5 YesY
PubChem 24533
ChemSpider 22940 N
EC number 231-971-0
UN number 1390
Jmol-3D images Image 1
Properties
Molecular formula 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)
Solubility in water reacts
Solubility 0.004 g/100 mL (liquid ammonia), reacts in ethanol
Acidity (pKa) 38 (conjugate acid) [1]
Structure
Crystal structure orthogonal
Thermochemistry
Specific
heat capacity
C
66.15 J/mol K
Std molar
entropy
So298
76.9 J/mol K
Std enthalpy of
formation
ΔfHo298
-118.8 kJ/mol
Gibbs free energy ΔG -59 kJ/mol
Hazards
EU Index Not listed
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
Flash point 4.44 °C (39.99 °F; 277.59 K)
Related compounds
Other anions Sodium bis(trimethylsilyl)amide
Other cations Potassium amide
Related compounds Ammonia
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox 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 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[edit]

Sodium amide can be prepared by the reaction of sodium with ammonia gas,[2] 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 intermediate.[3]

2 Na + 2 NH3 → 2 NaNH2 + H2

NaNH2 is a salt-like material and as such, crystallizes as an infinite polymer.[4] The geometry about sodium is tetrahedral.[5] In ammonia, NaNH2 forms conductive solutions, consistent with the presence of Na(NH3)6+ and NH2- anions.

Uses[edit]

Sodium amide is used in the industrial production of indigo, hydrazine, and sodium cyanide.[6] It is the reagent of choice for the drying of ammonia (liquid or gaseous) and is 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 in solvents other than ammonia, and its use has been superseded by the related reagents sodium hydride, sodium bis(trimethylsilyl)amide (NaHMDS), and lithium diisopropylamide (LDA).

Preparation of Alkynes[edit]

Sodium amide induces the loss of two molecules of hydrogen bromide from a vicinal dibromoalkane to give a carbon-carbon triple bond, as in a preparation of phenylacetylene.[7] Usually two equivalents of sodium amide yields the desired alkyne, however three equivalents are necessary in the preparation of a terminal alkyne. This is because as the terminal alkyne forms, its acidic terminal hydrogen immediately protonates an equivalent amount of base.

Phenylacetylene prepn.png

Hydrogen chloride and/or ethanol can also be eliminated in this way,[8] as in the preparation of 1-ethoxy-1-butyne.[9]

Ethoxybutyne prepn.png

Cyclization reactions[edit]

Where there is no β-hydrogen to be eliminated, cyclic compounds may be formed, as in the preparation of methylenecyclopropane below.[10]

Methylenecyclopropane prepn.png

Cyclopropenes,[11] aziridines[12] and cyclobutanes[13] may be formed in a similar manner.

Deprotonation of carbon and nitrogen acids[edit]

Carbon acids which can be deprotonated by sodium amide in liquid ammonia include terminal alkynes,[14] methyl ketones,[15] cyclohexanone,[16] phenylacetic acid and its derivatives[17] and diphenylmethane.[18] Acetylacetone loses two protons to form a dianion.[19]

Sodium amide will also deprotonate indole[20] and piperidine.[21]

Other reactions[edit]

Safety[edit]

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 should always be stored in a tightly closed container, under an atmosphere of nitrogen gas. Sodium amide samples which are yellow or brown in color should be dealt with immediately. These containers should not be handled and proper safety authorities should be notified.[25]

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.

See also[edit]

References[edit]

  1. ^ 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. 
  2. ^ Bergstrom, F. W. (1955), "Sodium amide", Org. Synth. ; Coll. Vol. 3: 778 
  3. ^ Greenlee, K. W.; Henne, A. L.; Fernelius, W. C. (1946). "Sodium Amide". Inorganic Syntheses 2: 128–135. doi:10.1002/9780470132333.ch38. 
  4. ^ Zalkin, A.; Templeton, D. H. (1956). "The Crystal Structure Of Sodium Amide". Journal of Physical Chemistry 60 (6): 821–823. doi:10.1021/j150540a042. 
  5. ^ Wells, A. F. (1984). Structural Inorganic Chemistry. Oxford: Clarendon Press. ISBN 0-19-855370-6. 
  6. ^ Budavari, Susan, ed. (1996), The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (12th ed.), Merck, ISBN 0911910123 
  7. ^ Campbell, K. N.; Campbell, B. K. (1950), "Phenylacetylene", Org. Synth. 30: 72 ; Coll. Vol. 4: 763 
  8. ^ Jones, E. R. H.; Eglinton, G.; Whiting, M. C.; Shaw, B. L. (1954), "Ethoxyacetylene", Org. Synth. 34: 46 ; Coll. Vol. 4: 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: 161 
    Magriotis, P. A.; Brown, J. T. (1995), "Phenylthioacetylene", Org. Synth. 72: 252 ; Coll. Vol. 9: 656 
    Ashworth, P. J.; Mansfield, G. H.; Whiting, M. C. (1955), "2-Butyn-1-ol", Org. Synth. 35: 20 ; Coll. Vol. 4: 128 
  9. ^ Newman, M. S.; Stalick, W. M. (1977), "1-Ethoxy-1-butyne", Org. Synth. 57: 65 ; Coll. Vol. 6: 564 
  10. ^ Salaun, J. R.; Champion, J.; Conia, J. M. (1977), "Cyclobutanone from methylenecyclopropane via oxaspiropentane", Org. Synth. 57: 36 ; Coll. Vol. 6: 320 
  11. ^ 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 
  12. ^ Bottini, A. T.; Olsen, R. E. (1964), "N-Ethylallenimine", Org. Synth. 44: 53 ; Coll. Vol. 5: 541 
  13. ^ Skorcz, J. A.; Kaminski, F. E. (1968), "1-Cyanobenzocyclobutene", Org. Synth. 48: 55 ; Coll. Vol. 5: 263 
  14. ^ Saunders, J. H. (1949), "1-Ethynylcyclohexanol", Org. Synth. 29: 47 ; Coll. Vol. 3: 416 
    Peterson, P. E.; Dunham, M. (1977), "(Z)-4-Chloro-4-hexenyl trifluoroacetate", Org. Synth. 57: 26 ; Coll. Vol. 6: 273 
    Kauer, J. C.; Brown, M. (1962), "Tetrolic acid", Org. Synth. 42: 97 ; Coll. Vol. 5: 1043 
  15. ^ Coffman, D. D. (1940), "Dimethylethynylcarbinol", Org. Synth. 20: 40 ; Coll. Vol. 3: 320 
    Hauser, C. R.; Adams, J. T.; Levine, R. (1948), "Diisovalerylmethane", Org. Synth. 28: 44 ; Coll. Vol. 3: 291 
  16. ^ Vanderwerf, C. A.; Lemmerman, L. V. (1948), "2-Allylcyclohexanone", Org. Synth. 28: 8 ; Coll. Vol. 3: 44 
  17. ^ Hauser, C. R.; Dunnavant, W. R. (1960), "α,β-Diphenylpropionic acid", Org. Synth. 40: 38 ; Coll. Vol. 5: 526 
    Kaiser, E. M.; Kenyon, W. G.; Hauser, C. R. (1967), "Ethyl 2,4-diphenylbutanoate", Org. Synth. 47: 72 ; Coll. Vol. 5: 559 
    Wawzonek, S.; Smolin, E. M. (1951), "α,β-Diphenylcinnamonitrile", Org. Synth. 31: 52 ; Coll. Vol. 4: 387 
  18. ^ Murphy, W. S.; Hamrick, P. J.; Hauser, C. R. (1968), "1,1-Diphenylpentane", Org. Synth. 48: 80 ; Coll. Vol. 5: 523 
  19. ^ 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: 928 
    Hampton, K. G.; Harris, T. M.; Hauser, C. R. (1967), "2,4-Nonanedione", Org. Synth. 47: 92 ; Coll. Vol. 5: 848 
  20. ^ Potts, K. T.; Saxton, J. E. (1960), "1-Methylindole", Org. Synth. 40: 68 ; Coll. Vol. 5: 769 
  21. ^ Bunnett, J. F.; Brotherton, T. K.; Williamson, S. M. (1960), "N-β-Naphthylpiperidine", Org. Synth. 40: 74 ; Coll. Vol. 5: 816 
  22. ^ Brazen, W. R.; Hauser, C. R. (1954), "2-Methylbenzyldimethylamine", Org. Synth. 34: 61 ; Coll. Vol. 4: 585 
  23. ^ Allen, C. F. H.; VanAllan, J. (1944), "Phenylmethylglycidic ester", Org. Synth. 24: 82 ; Coll. Vol. 3: 727 
  24. ^ Allen, C. F. H.; VanAllan, J. (1942), "2-Methylindole", Org. Synth. 22: 94 ; Coll. Vol. 3: 597 
  25. ^ "Sodium Amide". Princeton, NJ: Princeton University. 2011-03-16. Retrieved 2011-07-20. 

External links[edit]