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Author: Subject: Convert CH3ONa to NaH
rokaro
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[*] posted on 23-1-2004 at 14:41
Convert CH3ONa to NaH


The reaction CH3OH + NaH = CH3ONa + H2 is used commercially to make sodium methylate CH3ONa. Can the reverse reaction be used to make NaH, e.g. using electrolysis ? Facts and opinions equally welcome !!!
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guaguanco
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[*] posted on 23-1-2004 at 15:41


My opinion: no.
Lots of reactions aren't reversible.
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Madog
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[*] posted on 23-1-2004 at 16:30


no way



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BromicAcid
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[*] posted on 23-1-2004 at 16:41


Well, maybe if you put it under considerable hydrogen pressure you could shift the equilibrium. But even if you did it would be in effective expecially considering trying to recover the sodium hydride from the methanol and sodium methoxide solution. By the way, I thought that sodium methoxide was made industrially by the reactoin of sodium metal with methanol. Is the hydride now used in its place to moderate the reaction?



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vulture
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[*] posted on 24-1-2004 at 11:31


My opinion: no. Lots of reactions aren't reversible.

Actually, according to the gibbs equation:

G = H - TS

Every reaction is reversible if the conditions are suitable.




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[*] posted on 24-1-2004 at 12:31


If you search for calcium hydride you should be able to find the military green colored cans that are used for filling weather balloons with hydrogen. I think these cans are surplus.
guaguanco
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[*] posted on 24-1-2004 at 12:38


Quote:
Originally posted by vulture
Actually, according to the gibbs equation:
G = H - TS
Every reaction is reversible if the conditions are suitable.

That may be, in theory. If you find the conditions that convert, say, toluene + LiOH + Al(OH)3 to benzaldehyde and LiAlH4, let me know.:cool:

[Edited on 25-1-2004 by guaguanco]
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rokaro
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[*] posted on 26-1-2004 at 13:10


Thank you all. The DELG for CH3ONa +H2 -> NaH + CH3OH is positive which means that rxn. is not spontaneous (the reverse rxn. is, of course). However, VULTURE is correct - theoretically CH3ONa +H2 can occur with energy input and under right conditions. For skeptics only - please consider that H2 +0.5O2 = H2O is irreversible and spontaneous (DELG<0), yet H2O electrolysis is done every day....
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guaguanco
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[*] posted on 26-1-2004 at 13:57


It's not enough to look at deltaG numbers and decide that a reaction is 'reversible'.
The deltaG for the burning of azulene in O2 is probably not tremendously high:
C10H8 + 12 O2 => 10 CO2 + 4 H2O

but I wager you will never find reaction conditions that allow you to to convert CO2 and H2O directly to azulene and oxygen.
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vulture
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[*] posted on 27-1-2004 at 08:37


It certainly is possible with the right conditions and catalysts. Like rokaro pointed out, H2O ---> H2 + 1/2 O2 has a K of about 10^(-50) at room temperature. Electrolysis easily reverses it though.
You can steer reactions very specifically by manipulating conditions and catalysts.

Now let's get this back on topic.




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