Triethylaluminium

<h2 id="structure-and-bonding">Structure and bonding</h2><p>
The structure and bonding in Al2R6 and <a href="/facts/Diborane/k7egwbPf">diborane</a> are analogous (R = alkyl). Referring to Al2Me6, the Al-C(terminal) and Al-C(bridging) distances are 1.97 and 2.14 Å, respectively. The Al center is tetrahedral.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> The carbon atoms of the bridging ethyl groups are each surrounded by five neighbors: carbon, two hydrogen atoms and two aluminium atoms. The ethyl groups interchange readily intramolecularly. At higher temperatures, the dimer <a href="/facts/Cracking_(chemistry)/EBLtwW4g">cracks</a> into monomeric AlEt3.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p>
<h2 id="synthesis-and-reactions">Synthesis and reactions</h2>
<p>Triethylaluminium can be formed via several routes. The discovery of an efficient route was a significant technological achievement. The multistep process uses aluminium, <a href="/facts/Hydrogen_gas/BoYHjl0J">hydrogen gas</a>, and <a href="/facts/Ethylene/QMNBYLYn">ethylene</a>, summarized as follows:<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>
</p>
2 Al + 3 H2 + 6 C2H4 → Al2Et6
<p>Because of this efficient synthesis, triethylaluminium is one of the most available organoaluminium compounds.
</p><p>Triethylaluminium can also be generated from <a href="/facts/Ethylaluminium_sesquichloride/t9EzRJX7">ethylaluminium sesquichloride</a> (Al2Cl3Et3), which arises by treating aluminium powder with <a href="/facts/Chloroethane/6DjUIuH7">chloroethane</a>. Reduction of ethylaluminium sesquichloride with an <a href="/facts/Alkali_metal/IkWbCLk2">alkali metal</a> such as sodium gives triethylaluminium:<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a>
</p>
6 Al2Cl3Et3 + 18 Na → 3 Al2Et6 + 6 Al + 18 NaCl
<h3>Reactivity</h3>
<p>The Al–C bonds of triethylaluminium are <a href="/facts/Polar_bond/KlIJ0zjB">polarized</a> to such an extent that the carbon is easily <a href="/facts/Protonation/q5Gf9z0M">protonated</a>, releasing ethane:<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a>
</p>
Al2Et6 + 6 HX → 2 AlX3 + 6 EtH
<p>For this reaction, even weak acids can be employed such as terminal <a href="/facts/Acetylene/yaDh6cmJ">acetylenes</a> and alcohols.
</p><p>The linkage between the pair of aluminium centres is relatively weak and can be cleaved by <a href="/facts/Lewis_base/qlLqRvg2">Lewis bases</a> (L) to give <a href="/facts/Adduct/vBpTmotm">adducts</a> with the formula AlEt3L:
</p>
Al2Et6 + 2 L → 2 LAlEt3
<h2 id="applications">Applications</h2>
<h3>Precursors to fatty alcohols</h3>
<p>Triethylaluminium is used industrially as an intermediate in the production of <a href="/facts/Fatty_alcohol/VyaF3Wm5">fatty alcohols</a>, which are converted to <a href="/facts/Detergent/4FLKXR6p">detergents</a>. The first step involves the <a href="/facts/Oligomerization/v7oDY8zu">oligomerization</a> of ethylene by the <i>Aufbau</i> reaction, which gives a mixture of trialkylaluminium compounds (simplified here as <a href="/facts/Octyl/vmEk8X4v">octyl</a> groups):<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a>
</p>
Al2(C2H5)6 + 18 C2H4 → Al2(C8H17)6
<p>Subsequently, these trialkyl compounds are oxidized to aluminium <a href="/facts/Alkoxide/RqG0rm1v">alkoxides</a>, which are then hydrolysed: 
</p>
Al2(C8H17)6 + 3 O2 → Al2(OC8H17)6
Al2(OC8H17)6 + 6 H2O → 6 C8H17OH + 2 Al(OH)3
<h3>Co-catalysts in olefin polymerization</h3>
<p>A large amount of TEAL and related aluminium alkyls are used in <a href="/facts/Ziegler-Natta_catalysis/bkDSDf9d">Ziegler-Natta catalysis</a>. They serve to activate the transition metal catalyst both as a reducing agent and an <a href="/facts/Alkylation/1rd5SNbt">alkylating agent</a>. TEAL also functions to scavenge water and oxygen.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a>
</p>
<h3>Reagent in organic and organometallic chemistry</h3>
<p>Triethylaluminium has niche uses as a precursor to other organoaluminium compounds, such as <a href="/facts/Diethylaluminium_cyanide/SYHvkKec">diethylaluminium cyanide</a>:<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a>
</p>

1
                2
              
            
            
              Al
              
                2
              
              
                
              
            
            
              Et
              
                6
              
              
                
              
            
          
          +
          HCN
          ⟶
        
         
        
          
            
              1
              n
            
          
        
        
          
            
              [
              
                Et
                
                  2
                
                
                  
                
              
              AlCN
              ]
            
          
          
            n
          
        
        +
        
          
            C
            
              2
            
            
              
            
          
          
            H
            
              6
            
            
              
            
          
        
      
    
    {\displaystyle {\ce {{1/2Al2Et6}+ HCN ->}}\ {\tfrac {1}{n}}{\ce {[Et2AlCN]}}_{n}+{\ce {C2H6}}}

<h3>Pyrophoric agent</h3>
<p>Triethylaluminium ignites on contact with air and will ignite and/or decompose on contact with water, and with any other oxidizer<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a>—it is one of the few substances sufficiently pyrophoric to ignite on contact with cryogenic <a href="/facts/Liquid_oxygen/qnI0KDTb">liquid oxygen</a>. The <a href="/facts/Enthalpy_of_combustion/HdQX0mPP">enthalpy of combustion</a>, ΔcH°, is –5105.70 ± 2.90 k<a href="/facts/Joule/9ndq9jD2">J</a>/<a href="/facts/Mole_(unit)/kCMFwCc0">mol</a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> (–22.36 kJ/<a href="/facts/Gram/sRSW5RJb">g</a>). Its easy ignition makes it particularly desirable as a <a href="/facts/Rocket_engine/XT5gaFAb">rocket engine</a> <a href="/facts/Pyrotechnic_initiator/BfUDd0PM">ignitor</a>. The <a href="/facts/SpaceX/2tKHsVdJ">SpaceX</a> <a href="/facts/Falcon_9/mNck6vby">Falcon 9</a> <a href="/facts/Rocket/b6j4keIl">rocket</a> uses a triethylaluminium-<a href="/facts/Triethylborane/qLlyzN2r">triethylborane</a> mixture as a first-stage ignitor.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a>
</p><p>Triethylaluminium <a href="/facts/Thickener/lNPqbaWy">thickened</a> with <a href="/facts/Polyisobutylene/QpTlaAeA">polyisobutylene</a> is used as an <a href="/facts/Incendiary_weapon/Evu6eJWY">incendiary weapon</a>, as a pyrophoric alternative to <a href="/facts/Napalm/KbCMBjWe">napalm</a>; e.g., in the M74 clip holding four rockets for the <a href="/facts/M202A1/uVaxlGJJ">M202A1</a> launchers.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> In this application it is known as TPA, for <i>thickened pyrotechnic agent</i> or <i>thickened pyrophoric agent</i>. The usual amount of the thickener is 6%. The amount of thickener can be decreased to 1% if other diluents are added. For example, <a href="/facts/N-hexane/JxPecNPt"><i>n</i>-hexane</a>, can be used with increased safety by rendering the compound non-pyrophoric until the diluent evaporates, at which point a combined fireball results from both the triethylaluminium and the hexane vapors.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> The M202 was withdrawn from service in the mid-1980s owing to safety, transport, and storage issues. Some saw limited use in the Afghanistan War against caves and fortified compounds.
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Triethylborane/qLlyzN2r">Triethylborane</a>, used as an ignitor in the <a href="/facts/Pratt_%26_Whitney_J58/IoKE0jWT">Pratt & Whitney J58</a> <a href="/facts/Turbojet/tr3vYndL">turbojet</a>/<a href="/facts/Ramjet/wFschau9">ramjet</a> engines.</li>
<li><a href="/facts/Trimethylaluminium/QxlKB90v">Trimethylaluminium</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Krause, Michael J.; Orlandi, Frank; Saurage, Alfred T.; Zietz, Joseph R. (2000). "Aluminum Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_543. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>C. Elschenbroich (2006). Organometallics. VCH. ISBN 978-3-527-29390-2. <a href="978-3-527-29390-2" target="_blank">978-3-527-29390-2</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5. <a href="0-12-352651-5" target="_blank">0-12-352651-5</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Vass, Gábor; Tarczay, György; Magyarfalvi, Gábor; Bödi, András; Szepes, László (2002). "HeI Photoelectron Spectroscopy of Trialkylaluminum and Dialkylaluminum Hydride Compounds and Their Oligomers". Organometallics. 21 (13): 2751–2757. doi:10.1021/om010994h. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Smith, Martin Bristow (1967-01-01). "Monomer-dimer equilibria of liquid aluminum alkyls. I. Triethylaluminum". The Journal of Physical Chemistry. 71 (2): 364–370. doi:10.1021/j100861a024. ISSN 0022-3654. <a href="https://pubs.acs.org/doi/abs/10.1021/j100861a024" target="_blank">https://pubs.acs.org/doi/abs/10.1021/j100861a024</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Krause, Michael J.; Orlandi, Frank; Saurage, Alfred T.; Zietz, Joseph R. (2000). "Aluminum Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_543. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>Krause, M. J; Orlandi, F; Saurage, A T.; Zietz, J R, "Organic Aluminum Compounds" Wiley-Science 2002. <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>Elschenbroich, C. ”Organometallics” (2006) Wiley-VCH: Weinheim. ISBN 978-3-527-29390-2 <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>Krause, Michael J.; Orlandi, Frank; Saurage, Alfred T.; Zietz, Joseph R. (2000). "Aluminum Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_543. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
<li id="fn:10"><p>Dennis B. Malpass (2010). "Commercially Available Metal Alkyls and Their Use in Polyolefin Catalysts". In Ray Hoff; Robert T. Mathers (eds.). Handbook of Transition Metal Polymerization Catalysts. John Wiley & Sons, Inc. pp. 1–28. doi:10.1002/9780470504437.ch1. ISBN 9780470504437. <a href="9780470504437" target="_blank">9780470504437</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li>
<li id="fn:11"><p>Wataru Nagata and Yoshioka Mitsuru (1988). "Diethylaluminum Cyanides". Organic Syntheses; Collected Volumes, vol. 6, p. 436. <a href="http://www.orgsyn.org/demo.aspx?prep=cv6p0436" target="_blank">http://www.orgsyn.org/demo.aspx?prep=cv6p0436</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li>
<li id="fn:12"><p>TEA Material Safety Data Sheet Archived 2006-11-14 at the Wayback Machine, accessed March 27, 2007 <a href="http://www.epichem.com/metalorganics/pdfs/triethylalumium.pdf" target="_blank">http://www.epichem.com/metalorganics/pdfs/triethylalumium.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li>
<li id="fn:13"><p>"Triethylaluminum (CAS 97-93-8) - Chemical & Physical Properties by Cheméo". <a href="https://www.chemeo.com/cid/63-022-7/Triethylaluminum" target="_blank">https://www.chemeo.com/cid/63-022-7/Triethylaluminum</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li>
<li id="fn:14"><p>Mission Status Center, June 2, 2010, 1905 GMT, SpaceflightNow, accessed 2010-06-02, Quotation: "The flanges will link the rocket with ground storage tanks containing liquid oxygen, kerosene fuel, helium, gaserous nitrogen and the first stage ignitor source called triethylaluminum-triethylborane, better known as TEA-TEB." <a href="http://www.spaceflightnow.com/falcon9/001/status.html" target="_blank">http://www.spaceflightnow.com/falcon9/001/status.html</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li>
<li id="fn:15"><p>M202A1 Flame Assault Shoulder Weapon (Flash), inetres.com <a href="http://www.inetres.com/gp/military/infantry/flame/M202.html" target="_blank">http://www.inetres.com/gp/military/infantry/flame/M202.html</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li>
<li id="fn:16"><p>Encyclopedia of Explosives and Related Items, Vol.8, US Army <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li>
</ol>

Triethylaluminium open-in-new

Triethylaluminium