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Sodium amide
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<h2 id="preparation-and-structure">Preparation and structure</h2> <p>Sodium amide can be prepared by the reaction of <a href="/facts/Sodium/eYuSPu2V">sodium</a> with ammonia gas,<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> but it is usually prepared by the reaction in <a href="/facts/Liquid_ammonia/MtLtJFtz">liquid ammonia</a> using <a href="/facts/Iron(III)_nitrate/m7KWQome">iron(III) nitrate</a> as a <a href="/facts/Catalyst/LPBS7TQC">catalyst</a>. The reaction is fastest at the boiling point of the ammonia, c. −33 °C. An <a href="/facts/Electride/2Lp8eUIK">electride</a>, [Na(NH3)6]+e−, is formed as a <a href="/facts/Reaction_intermediate/BjD9HAHt">reaction intermediate</a>.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p> 2 Na + 2 NH3 → 2 NaNH2 + H2 <p>NaNH2 is a salt-like material and as such, crystallizes as an infinite polymer.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> The geometry about sodium is tetrahedral.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> In ammonia, NaNH2 forms conductive solutions, consistent with the presence of [Na(NH3)6]+ and NH−2 ions. </p> <h2 id="uses">Uses</h2> <p>Sodium amide is mainly used as a <a href="/facts/Strong_base/M9wA7qeM">strong base</a> in organic chemistry, often <a href="/facts/Suspension_(chem)/S3xp96TL">suspended</a> (it is insoluble<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a>) in liquid ammonia solution. One of the main advantages to the use of sodium amide is its relatively low <a href="/facts/Nucleophile/xYccoaJQ">nucleophilicity</a>. In the industrial production of <a href="/facts/Indigo_dye/aqC7umcC">indigo</a>, sodium amide is a component of the highly basic mixture that induces cyclisation of <a href="/facts/N-Phenylglycine/sy2IUNrP"><i>N</i>-phenylglycine</a>. The reaction produces ammonia, which is recycled typically.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h3>Dehydrohalogenation</h3> <p>Sodium amide is a standard base for dehydrohalogenations.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> It induces the loss of two equivalents of <a href="/facts/Hydrogen_bromide/rUw1duLA">hydrogen bromide</a> from a <a href="/facts/Vicinal_(chemistry)/XLMCFVkm">vicinal</a> dibromoalkane to give a <a href="/facts/Alkyne/VHI4N5Wo">carbon–carbon triple bond</a>, as in a preparation of <a href="/facts/Phenylacetylene/xT34BdYq">phenylacetylene</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> 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. </p><p><a href="/facts/Hydrogen_chloride/7Wzkhomd">Hydrogen chloride</a> and <a href="/facts/Ethanol/3lCLfBSP">ethanol</a> can also be eliminated in this way,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> as in the preparation of 1-ethoxy-1-butyne.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h3>Cyclization reactions</h3> <p>Where there is no β-hydrogen to be eliminated, cyclic compounds may be formed, as in the preparation of <a href="/facts/Methylenecyclopropane/MeRdqYcw">methylenecyclopropane</a> below.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p><a href="/facts/Cyclopropene/dD0W9xmj">Cyclopropenes</a>,<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> <a href="/facts/Aziridines/RQQWmJPI">aziridines</a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> and <a href="/facts/Cyclobutane/hzsbc9ML">cyclobutanes</a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> may be formed in a similar manner. </p> <h3>Deprotonation of carbon and nitrogen acids</h3> <p>Carbon acids which can be <a href="/facts/Deprotonation/SmUSh369">deprotonated</a> by sodium amide in liquid ammonia include terminal <a href="/facts/Alkyne/VHI4N5Wo">alkynes</a>,<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> methyl <a href="/facts/Ketone/BqQXpLo4">ketones</a>,<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> <a href="/facts/Cyclohexanone/Hf3YTWjB">cyclohexanone</a>,<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> <a href="/facts/Phenylacetic_acid/cjfwIEs2">phenylacetic acid</a> and its derivatives<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> and <a href="/facts/Diphenylmethane/yw0Hxo5H">diphenylmethane</a>.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> <a href="/facts/Acetylacetone/Ku1k97xz">Acetylacetone</a> loses two protons to form a <a href="/facts/Anion/wrbwhF3z">dianion</a>.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> Sodium amide will also deprotonate <a href="/facts/Indole/HT72P6e6">indole</a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> and <a href="/facts/Piperidine/dU6YTIC6">piperidine</a>.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> </p> <h3>Related non-nucleophilic bases</h3> <p>It is however poorly soluble in solvents other than ammonia. Its use has been superseded by the related reagents <a href="/facts/Sodium_hydride/Pnsh2T64">sodium hydride</a>, <a href="/facts/Sodium_bis(trimethylsilyl)amide/IE8qcl4j">sodium bis(trimethylsilyl)amide</a> (NaHMDS), and <a href="/facts/Lithium_diisopropylamide/5rcW8ERX">lithium diisopropylamide</a> (LDA). </p> <h3>Other reactions</h3> <ul><li>Rearrangement with orthodeprotonation<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a></li> <li>Oxirane synthesis<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a></li> <li>Indole synthesis<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></li> <li><a href="/facts/Chichibabin_reaction/l4xu6Rdx">Chichibabin reaction</a></li></ul> <h2 id="safety">Safety</h2> <p>Sodium amide is a common reagent with a long history of laboratory use.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> It can decompose violently on contact with water, producing <a href="/facts/Ammonia/MtLtJFtz">ammonia</a> and <a href="/facts/Sodium_hydroxide/xjtdYtq7">sodium hydroxide</a>: </p> NaNH2 + H2O → NH3 + NaOH <p>When burned in oxygen, it will give <a href="/facts/Sodium_oxide/QbdIGb8u">oxides of sodium</a> (which react with the produced water, giving sodium hydroxide) along with nitrogen oxides: </p> 4 NaNH2 + 5 O2 → 4 NaOH + 4 NO + 2 H2O 4 NaNH2 + 7 O2 → 4 NaOH + 4 NO2 + 2 H2O <p>In the presence of limited quantities of air and moisture, such as in a poorly closed container, explosive mixtures of peroxides may form.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> 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.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Bergstrom, F. W. (1955). "Sodium amide". Organic Syntheses; Collected Volumes, vol. 3, p. 778. <a href="http://www.orgsyn.org/demo.aspx?prep=cv3p0778" target="_blank">http://www.orgsyn.org/demo.aspx?prep=cv3p0778</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Greenlee, K. W.; Henne, A. L. (1946). "Sodium Amide". Inorganic Syntheses. Vol. 2. pp. 128–135. doi:10.1002/9780470132333.ch38. ISBN 9780470132333. <a href="9780470132333" target="_blank">9780470132333</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Zalkin, A.; Templeton, D. H. (1956). "The Crystal Structure Of Sodium Amide". 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ISBN 0-471-93623-5. <a href="0-471-93623-5" target="_blank">0-471-93623-5</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Clark, Donald E (2001). "Peroxides and peroxide-forming compounds". Chemical Health and Safety. 8 (5): 12–22. doi:10.1016/S1074-9098(01)00247-7. ISSN 1074-9098. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>"Sodium amide SOP". Princeton. <a href="https://ehs.princeton.edu/laboratory-research/chemical-safety/chemical-specific-protocols/sodium-amide" target="_blank">https://ehs.princeton.edu/laboratory-research/chemical-safety/chemical-specific-protocols/sodium-amide</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> </ol>