nitro-genes
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Alkoxides from polyols?
So here is a rather simple question for which I wasn't able to find a clear answer:
Many reactive metals can reduce alcohols to form the corresponding alkoxide. So what would happen if a poly-ol would be used instead, f.e. ethylene
glycol or glycerol?
[Edited on 25-5-2016 by nitro-genes]
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morsagh
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The same, depends on amount of alkalic metal added to polyol there can be only one substituted hydrogen or more.
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DraconicAcid
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I suspect that if you added sodium metal to pure generic triol (Gen(OH)3), you'd reach a stage where the reaction stopped because NaGenO(OH)2 would be
a solid. If you dissolved the triol in an aprotic solvent such as THF, you'd get the monosodium salt readily enough, but the reaction to form the
disodium salt would be slower, and the trisodium salt slower still. Whether or not the trianion would be stable....I'll leave that to the organic
chemists.
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Eddygp
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Well, if you add a sufficiently strong base, like NaNH2, stoichiometrically to a solution of a polyol, you would hopefully be able to get di-, tri-
and maybe tetraalkoxides (beware of sterics and charge densities though, it seems highly unlikely that, say, sorbitol or mannitol
create a 6- anion balanced with 6 Na+).
However, for pentane-1,5-diol, I am guessing that a dialkoxide would be rather easily formed, maybe even with sodium metal.
Ionic substances rely on the electrostatic stabilisation of charges. However, for species that are already charged, it will probably be significantly
more difficult to deprotonate an alcohol that is nearby due to charge build-up.
Very strong bases might counter this but it just seems overall pretty dodgy.
[Edited on 25-5-2016 by Eddygp]
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nitro-genes
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Suspected the reaction may be similar indeed, but in chemistry you never know for sure, so thanks.  Would be interesting to see what kind of products would from some poly-ols, the resulting alkoxides and multivalent
cations. But presumably indeed, in the direct approacch things would likely start to precipitate before complete reaction anyway.
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Texium
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Thread Moved
27-5-2016 at 20:51 |
PHILOU Zrealone
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The multiplication of the OH groups also increases the acidity of those, and this may help forming alcoholates.
When boiling glycerol (propantriol) with Pb(OH)2, a solid compound is formed presumably a lead glycerolate with only two OH used...the compound is
mentionned as energetic...but it is very feablely explosive when dry and submitted to open flame.
Pb(OH)2 + HOCH2-CHOH-CH2OH --> 2 H2O + Pb(2+)(-)OCH2-CHO(-)-CH2OH
Maybe the same may occur with Cu(OH)2...
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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