organosurf
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FORMATION OF SODIUM ETHOXIDE : CH3CH2ONa
FORMATION OF SODIUM ETHOXIDE : CH3CH2O-Na+ ?
Came across two “schools of thought” :
1 ) It is best formed in aqueous media
2 ) It is best formed in non-aqueous media
Which is correct ? Assuming #(2) is correct, can anhydrous ethanol be reacted with NaOH at room temperature, with stirring, over anhydrous Na2SO4 to
absorb the water generated and thus also push the equilibrium to the right ?
CH3CH2OH + NaOH + anhyd Na2SO4 CH3CH2O-Na+ + Na2SO4.10H2O
* 100% excess CH3CH2OH is used to dissolve the CH3CH2O-Na+ formed
* Room Temperature preferred if possible as it eliminates use of reflux apparatus
* anhyd Na2SO4 works best as a dessicant at room temperature ( dissolutes when hydrated )
* easily separated by filtration and evaporating the excess CH3CH2OH to get CH3CH2O-Na+
* completion of reaction can be estimated visually from dissolution of NaOH
QUESTIONS :
1 ) Is the above proposed scheme correct and feasible ?
2 ) Can CH3CH2OH be substituted with IPA ( Isopropyl alcohol ) ?
3 ) Would KOH ( pKb = 0.5 ) be better suited than NaOH ( pKb = 0.2 )?
pKa CH3CH2O-Na+ = 20.58 pKa CH3CH2O-K+ = ?
pKa CH3CH2OH = 16 pKa IPA = 16.5
Please let me know, thanks in advance
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smaerd
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Considering sodium ethoxide hydrolyzes in water I would not try and make it in aq. soln.
Na2SO4 will not remove water as effectively as NaOH so don't even bother. Molecular sieves will do a better job.
No need to reflux.
There are threads already on this you should probably use the search engine.
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Lambda-Eyde
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Quote: Originally posted by organosurf  |
2 ) Can CH3CH2OH be substituted with IPA ( Isopropyl alcohol ) ?
3 ) Would KOH ( pKb = 0.5 ) be better suited than NaOH ( pKb = 0.2 )?
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You do know that this would give other products, right...?
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organosurf
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Thanx smaerd & Lambda-Eyde !
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Nicodem
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Thread Moved
12-12-2012 at 07:28 |
Hexavalent
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Organosurf, the use of KOH would give potassium ethoxide and the use of IPA would yield the corresponding isopropoxide salt...
Also, don't forget that the alkoxides can be formed by reacting the alkali metal directly with the alcohol: this would avoid the water byproduct.
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kristofvagyok
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| Quote: Originally posted by organosurf | | Which is correct ? Assuming #(2) is correct, can anhydrous ethanol be reacted with NaOH at room temperature, with stirring, over anhydrous Na2SO4 to
absorb the water generated and thus also push the equilibrium to the right ? |
It could be made, but not on this route. There is a patent somewhere what describes a method what generates dilute NaOEt on a similar way by mixing
relative anhydrous NaOH with abs EtOH. The generated water is distilled out from the reaction mixture to a MgSO4 or Na2SO4 adsorber and then the
anhydrous EtOH is added back to the rxn mixture.
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zed
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Some have suggest forming Alkali salts of alcohols, from Alcohols and Alkali Carbonates via distillation. The Alkali carbonate reacts with the
Alcohol to form the alcohol salt...plus carbonic acid. The carbonic acid then breaks down to CO2 + H20. The CO2 leaves the reaction mixture as a
gas, and the H2O is distilled away. Drying tubes are required to prevent atmospheric H2O from screwing up the process.
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Daedalus
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To those of you have who have synthesized sodium ethoxide by direct addition of the metal to the alcohol, how much mass of sodium can be safely added
at a time to the chilled anhydrous ethanol (say 400ml) without risk of boil-over or worse?
[Edited on 4-1-2013 by Daedalus]
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vmelkon
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http://www.youtube.com/watch?v=E0VZzUzlg6E
http://www.youtube.com/watch?v=GhvnYc_FDDI
The reaction between ethanol + Na looks slower and safer compared to water + Na.
[Edited on 5-1-2013 by vmelkon]
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kristofvagyok
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| Quote: Originally posted by Daedalus | | how much mass of sodium can be safely added at a time to the chilled anhydrous ethanol (say 400ml) without risk of boil-over or worse?
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Use a reflux condenser and there will be no problem.
Also important to note that when sodium dissolves the NaOEt will cause that the ethanols boiling point will get higher, it could even get as high that
the added sodium could melt in it:
And usually additional heating is required to dissolve all the sodium if you need a bit concentrated NaOEt....
zed: The thing with the carbonate and the alcohol looks really-really strange, is there any reference for that?
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BromicAcid
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How quickly we forget...
http://www.sciencemadness.org/talk/viewthread.php?tid=2656
Amazing how helpful it is to search for something when you have the motivation to look for it because you remember it being there.
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SixTough
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The reaction is quite slow when alcohol is anhydrous and sodium is not very fine.
Also, dont forget LiOEt + NaOH = LiOH (insoluble) + NaOEt in dry ethanol.
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zed
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kristofvagyok,
The process was suggested to me long ago by Halfapint. References exist. I'll check around.
OK I checked. seems to be absent from the Rhodium Archive.
I have a hard copy somewhere. Unfortunately, I'm away from my lair at the moment. Maybe someone else has a reference.
[Edited on 10-1-2013 by zed]
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zed
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kristofvagyok,
Metal Alcoxides via Carbonates. You thought I forgot? I couldn't locate the paperwork, but found it archived on the newly restored Hive site.
https://the-hive.archive.erowid.org/forum/showflat.pl?Cat=&a...
Some such procedures seem to proceed, by distilling off CO2+H2O, while protecting flask contents via drying tubes. Don't know if I have the right
reference for that one.
[Edited on 23-9-2015 by zed]
[Edited on 23-9-2015 by zed]
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Amos
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How are drying tubes going to protect the reaction from atmospheric water if the reaction itself is producing water?
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zed
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Generally speaking, a distillation apparatus has to be open to the atmosphere somewhere, don't let that somewhere be a source of water vapor.
I've seen entries regarding this reaction, where the posters said things like: "Well I boiled the mother for hours, but it didn't seem to work!"
The reaction variation I'm thinking of, is driven by the removal of H2O and CO2. Don't let 'em back in to the mix, via a back door.
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