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lutesium
(Hive Bee)
10-02-04 00:20
No 534073
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the alcoholate formylations
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Can Mg(meO)2 be substtuted for NaOMe (or another alcohol with Na) in a paraformaldehyde + mg(meo)2 formylation done in toluene? Or does magnesium have special withdrawing properties?<br><br>Have there been tries here at the hive to RT formylate HQ?<br><br>Thanx
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<font color="#FF0033">Rhodium</font><br>
<i>(<span title="The user's title at the time of posting">Chief Bee</span>)</i><br>
<span title="Posting date">10-02-04 16:33</span><br>
<span title="Link to this post by using the markup [534163]">No 534163</span><br>
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<b title="The subject of this post">The special role of Mg2+ is to stabilize the...</b>
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The special role of Mg<sup>2+</sup> is to stabilize the reaction intermediates by "holding" the reagents together in a suitable conformation.<br><br>For details & diagrams, see <span title="Jump to this post"><a href="../methods/000478447.html#Post481046">Post 481046</a> <i>(Rhodium: "Magnesium ortho-Formylation Mechanism", Methods Discourse)</i></span>
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<span title="The signature"><hr><sup>The Hive - Clandestine Chemists Without Borders</sup></span>
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lutesium<br>
<i>(<span title="The user's title at the time of posting">Hive Bee</span>)</i><br>
<span title="Posting date">10-06-04 14:33</span><br>
<span title="Link to this post by using the markup [534669]">No 534669</span><br>
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<b title="The subject of this post">RHodium Ýs the role of diethyl ether (and thf)</b>
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RHodium<br><br>Ýs the role of diethyl ether (and thf) the same (holding the ions)in a grignard rxn?<br><br>I read the mechanisn in vogel several times but I cant remember<br><br><br>EDIT: The pdf file in the post you linked above is a killer! I was mentioning and experimenting the reactiion with Mg turnings and had a great success with high yields (over %90) I tried it with many types of phenols (which were derivated also by me - cleaned by three xtallyzations and looked like 2-3 cm long big white needles <img src="../forum/images/icons_lightgrey/laugh.gif" alt="laugh" title="Laugh" heigth="15" width="15">) Reactions were on a max 2 g scale and I can say that its my favorite. But the phenol must be clean.<br>NOW<br>Hearing that we can use MgCl2 almost killed me! Poor chemist - me will benefit from this and keep on experimenting with the cheaper salt!<br><br>Thanx Rhode long live Science
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<font color="#FF0033">Rhodium</font><br>
<i>(<span title="The user's title at the time of posting">Chief Bee</span>)</i><br>
<span title="Posting date">10-06-04 19:55</span><br>
<span title="Link to this post by using the markup [534701]">No 534701</span><br>
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<b title="The subject of this post">The role of ethers in a grignard</b>
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<font color="blue">Ýs the role of diethyl ether (and thf) the same (holding the ions)in a grignard rxn?</font color="blue"><br><br>To some extent, yes - but that's a gross oversimplification. Here follows some explanation from <a href="http://www.cm.utexas.edu/bauld/grignard.htm" target="_blank" title="Jump to this external site">http://www.cm.utexas.edu/bauld/grignard.<wbr>htm</a><br><br><blockquote title="Quoted text"><hr><p>Diethyl ether is an especially good solvent for the formation of Grignard reagents because ethers are non-acidic (aprotic). Water or alcohols would protonate and thus destroy the Grignard reagent, because the Grignard carbon is highly nucleophilic. This would form a hydrocarbon. But Grignard reagents are stable in ethers.<br><br><img src="../picproxie_docs/000534073-image009.gif" target="_blank"> <br><br>Another reason that ethers are good solvents for Grignard reagents is that the MgX bond is ionic and thus benefits greatly from being effectively solvated. The formation of ions in very nonpolar solvents, where they would not be effectively solvated is very difficult. Ethers are surprisingly good at solvating cations, because the C-O bond is relatively polar, thus allowing the oxygen end of the ether dipole to solvate and stabilize (electrostatically) the magnesium ion.<br><br><img src="../picproxie_docs/000534073-image012.gif" target="_blank"><p><hr></blockquote><p><br><br>The Ether-RMgX complexes shown at work in a reaction can be seen here: <a href="../rhodium
/grignardnitrile.html" target="_blank" title="Jump to this external site">../rhodium
/grignar<wbr>dnitrile<wbr>.html</a>
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