Sodium amide

Sodium amide can be prepared by the reaction of sodium with ammonia gas,{{OrgSynth |author=Bergstrom, F. W. |title=Sodium amide |year=1955 |collvol=3 |collvolpages=778 |prep=cv3p0778}} 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, {{chem2|[Na(NH3)6]+e−}}, is formed as a reaction intermediate.{{cite book |author1=Greenlee, K. W. |author2=Henne, A. L. |title=Inorganic Syntheses |chapter=Sodium Amide |year=1946 |volume=2 |pages=128–135 |doi=10.1002/9780470132333.ch38 |isbn=9780470132333}}

:{{chem2|2 Na + 2 NH3 → 2 NaNH2 + H2}}

{{chem2|NaNH2}} is a salt-like material and as such, crystallizes as an infinite polymer.{{cite journal |author1=Zalkin, A. |author2=Templeton, D. H. |title=The Crystal Structure Of Sodium Amide |journal=Journal of Physical Chemistry |year=1956 |volume=60 |issue=6 |pages=821–823 |doi=10.1021/j150540a042 |hdl=2027/mdp.39015086484659 |hdl-access=free}} The geometry about sodium is tetrahedral.{{cite book |author=Wells, A. F. |year=1984 |title=Structural Inorganic Chemistry |location=Oxford |publisher=Clarendon Press |isbn=0-19-855370-6}} In ammonia, {{chem2|NaNH2}} forms conductive solutions, consistent with the presence of {{chem2|[Na(NH3)6]+}} and {{chem2|NH2−}} ions.

Sodium amide is mainly used as a strong base in organic chemistry, often suspended (it is insoluble{{cite book|url=https://archive.org/details/cftri.2662nonaqueoussolven0000ludw/page/79/|page=79|title=Non-aqueous solvents|first1=Ludwig F.|last1=Audrieth|first2=Jacob|last2=Kleinberg|publisher=John Wiley & Sons|location=New York|year=1953|lccn=52-12057}}) in liquid ammonia solution. 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.L. Lange, W. Treibel "Sodium Amide" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a24_267}}

File:Indigo Synthesis V.1.svg.]]

Sodium amide is a standard base for dehydrohalogenations.{{cite book |doi=10.1002/047084289X.rs041 |chapter=Sodium Amide |title=Encyclopedia of Reagents for Organic Synthesis |date=2001 |last1=Belletire |first1=John L. |last2=Rauh |first2=R. Jeffery |isbn=0-471-93623-5 }} It 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.{{OrgSynth |author=Campbell, K. N.; Campbell, B. K. |title=Phenylacetylene |year=1950 |volume=30 |pages=72 |collvol=4 |collvolpages=763 |prep=cv4p0763}}

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.

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Hydrogen chloride and ethanol can also be eliminated in this way,{{OrgSynth |author=Jones, E. R. H.; Eglinton, G.; Whiting, M. C.; Shaw, B. L. |title=Ethoxyacetylene |year=1954 |volume=34 |pages=46 |collvol=4 |collvolpages=404 |prep=cv4p0404}}

{{OrgSynth |author=Bou, A.; Pericàs, M. A.; Riera, A.; Serratosa, F. |title=Dialkoxyacetylenes: di-tert-butoxyethyne, a valuable synthetic intermediate |year=1987 |volume=65 |pages=58 |collvol=8 |collvolpages=161 |prep=cv8p0161}}

{{OrgSynth |author=Magriotis, P. A.; Brown, J. T. |title=Phenylthioacetylene |year=1995 |volume=72 |pages=252 |collvol=9 |collvolpages=656 |prep=cv9p0656}}

{{OrgSynth |author=Ashworth, P. J.; Mansfield, G. H.; Whiting, M. C. |year=1955 |title=2-Butyn-1-ol |volume=35 |pages=20 |collvol=4 |collvolpages=128 |prep=cv4p0128}} as in the preparation of 1-ethoxy-1-butyne.{{OrgSynth |author=Newman, M. S.; Stalick, W. M. |title=1-Ethoxy-1-butyne |year=1977 |volume=57 |pages=65 |collvol=6 |collvolpages=564 |prep=cv6p0564}}

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Where there is no β-hydrogen to be eliminated, cyclic compounds may be formed, as in the preparation of methylenecyclopropane below.{{OrgSynth |author=Salaun, J. R.; Champion, J.; Conia, J. M. |title=Cyclobutanone from methylenecyclopropane via oxaspiropentane |year=1977 |volume=57 |pages=36 |collvol=6 |collvolpages=320 |prep=cv6p0320}}

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Cyclopropenes,{{OrgSynth |author=Nakamura, M.; Wang, X. Q.; Isaka, M.; Yamago, S.; Nakamura, E. |title=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 |year=2003 |volume=80 |pages=144 |prep=v80p0144}} aziridines{{OrgSynth |author=Bottini, A. T.; Olsen, R. E. |title=N-Ethylallenimine |year=1964 |volume=44 |pages=53 |collvol=5 |collvolpages=541 |prep=cv5p0541}}

and cyclobutanes{{OrgSynth |author=Skorcz, J. A.; Kaminski, F. E. |title=1-Cyanobenzocyclobutene |year=1968 |volume=48 |pages=55 |collvol=5 |collvolpages=263 |prep=cv5p0263}} may be formed in a similar manner.

Carbon acids which can be deprotonated by sodium amide in liquid ammonia include terminal alkynes,{{OrgSynth |author=Saunders, J. H. |title=1-Ethynylcyclohexanol |year=1949 |volume=29 |pages=47 |collvol=3 |collvolpages=416 |prep=cv3p0416}}

{{OrgSynth |author=Peterson, P. E.; Dunham, M. |title=(Z)-4-Chloro-4-hexenyl trifluoroacetate |year=1977 |volume=57 |pages=26 |collvol=6 |collvolpages=273 |prep=cv6p0273}}

{{OrgSynth |author=Kauer, J. C.; Brown, M. |title=Tetrolic acid |year=1962 |volume=42 |pages=97 |collvol=5 |collvolpages=1043 |prep=cv5p1043}}

methyl ketones,{{OrgSynth |author=Coffman, D. D. |title=Dimethylethynylcarbinol |year=1940 |volume=20 |pages=40 |collvol=3 |collvolpages=320 |prep=cv3p0320}}{{OrgSynth |author=Hauser, C. R.; Adams, J. T.; Levine, R. |title=Diisovalerylmethane |year=1948 |volume=28 |pages=44 |collvol=3 |collvolpages=291 |prep=cv3p0291}}

cyclohexanone,{{OrgSynth |author=Vanderwerf, C. A.; Lemmerman, L. V. |title=2-Allylcyclohexanone |year=1948 |volume=28 |pages=8 |collvol=3 |collvolpages=44 |prep=cv3p0044}} phenylacetic acid and its derivatives{{OrgSynth |author=Hauser, C. R.; Dunnavant, W. R. |title=α,β-Diphenylpropionic acid |year=1960 |volume=40 |pages=38 |collvol=5 |collvolpages=526 |prep=cv5p0526}}

{{OrgSynth |author=Kaiser, E. M.; Kenyon, W. G.; Hauser, C. R. |title=Ethyl 2,4-diphenylbutanoate |year=1967 |volume=47 |pages=72 |collvol=5 |collvolpages=559 |prep=cv5p0559}}

{{OrgSynth |author=Wawzonek, S.; Smolin, E. M. |title=α,β-Diphenylcinnamonitrile |year=1951 |volume=31 |pages=52 |collvol=4 |collvolpages=387 |prep=cv4p0387}}

and diphenylmethane.{{OrgSynth |author=Murphy, W. S.; Hamrick, P. J.; Hauser, C. R. |title=1,1-Diphenylpentane |year=1968 |volume=48 |pages=80 |collvol=5 |collvolpages=523 |prep=cv5p0523}} Acetylacetone loses two protons to form a dianion.{{OrgSynth |author=Hampton, K. G.; Harris, T. M.; Hauser, C. R. |title=Phenylation of diphenyliodonium chloride: 1-phenyl-2,4-pentanedione |year=1971 |volume=51 |pages=128 |collvol=6 |collvolpages=928 |prep=cv6p0928}}

{{OrgSynth |author=Hampton, K. G.; Harris, T. M.; Hauser, C. R. |title=2,4-Nonanedione |year=1967 |volume=47 |pages=92 |collvol=5 |collvolpages=848 |prep=cv5p0848}} Sodium amide will also deprotonate indole{{OrgSynth |author=Potts, K. T.; Saxton, J. E. |title=1-Methylindole |year=1960 |volume=40 |pages=68 |collvol=5 |collvolpages=769 |prep=cv5p0769}} and piperidine.{{OrgSynth |author=Bunnett, J. F.; Brotherton, T. K.; Williamson, S. M. |title=N-β-Naphthylpiperidine |year=1960 |volume=40 |pages=74 |collvol=5 |collvolpages=816 |prep=cv5p0816}}

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).

• Rearrangement with orthodeprotonation{{OrgSynth |author=Brazen, W. R.; Hauser, C. R. |title=2-Methylbenzyldimethylamine |year=1954 |volume=34 |pages=61 |collvol=4 |collvolpages=585 |prep=cv4p0585}}
• Oxirane synthesis{{OrgSynth |author=Allen, C. F. H.; VanAllan, J. |title=Phenylmethylglycidic ester |year=1944 |volume=24 |pages=82 |collvol=3 |collvolpages=727 |prep=cv3p0727}}
• Indole synthesis{{OrgSynth |author=Allen, C. F. H.; VanAllan, J. |title=2-Methylindole |year=1942 |volume=22 |pages=94 |collvol=3 |collvolpages=597 |prep=cv3p0597}}
• Chichibabin reaction

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:

:{{chem2|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:

:{{chem2|4 NaNH2 + 5 O2 → 4 NaOH + 4 NO + 2 H2O}}

:{{chem2|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.{{cite journal |last1=Clark |first1=Donald E |title=Peroxides and peroxide-forming compounds |journal=Chemical Health and Safety |volume=8 |issue=5 |year=2001 |pages=12–22 |issn=1074-9098 |doi=10.1016/S1074-9098(01)00247-7}} 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.{{cite web |title=Sodium amide SOP |url=https://ehs.princeton.edu/laboratory-research/chemical-safety/chemical-specific-protocols/sodium-amide |publisher=Princeton |ref=SOP sodium amide Princeton}}

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{{Sodium compounds}}

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Category:Metal amides

Category:Reagents for organic chemistry

Category:Sodium compounds