Filemon
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oxidation alcohol to aldehyde with MnO2
Do you believe that you could oxidize an alcohol to aldehyde with the following reaction (generating MnO2 in situ)? =>
MnCl2 (or MnSO4) (ac) + NaOH (ac) + NaNO3 (or KNO3) (ac) => MnO2 (s) + NaNO2 (ac) + 2NaCl (ac)+ H2O
For parts:
Mn(OH)2 + NaNO3 => MnO2 + NaNO2 + H2O
I don't know if this reaction takes place. I have proven it with Fe(OH)2 and Fe(OH)3 and it works, it produces Fe3O4 and Fe2O3 respectively. But I
don't know if it would oxidize Mn(OH)2.
The idea is to produce MnO2 in situ to react with an alcohol. There would be this way the maximum reaction surface. In a flask we have MnCl2 + alcohol
and in other the NaNO3 + NaOH, then mixes. Me not you if it would work or the reaction was too much exotermic. I need advice.
[Edited on 10-8-2007 by Filemon]
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DerAlte
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I don't think Mn++ ions will be oxidized to MnO2 by an alkali nitrate at high pH. NO3- is a rather weak oxidant at a pH of 11-14. Use NaOCl (bleach)
instead, dilute solution. Filter off or wash the MnO2 - as a fine precipitant MnO2 is then active enough to covert EtOH to acetaldehde, (AFAIK and
IIRC!)
Regards,
Der Alte
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Rosco Bodine
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Sounds like a variation of the "oxidative soak method"
http://www.sciencemadness.org/talk/viewthread.php?action=att...
So instead of depositing a colloidal film of MnO2 as it
precipitates , you intend to react the finely divided
MnO2 as it forms with an alcohol . It might work .
It could require a gradual addition instead of just a
simple mixed together all at once sort of approach .....
I'm not sure .
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Filemon
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It doesn't work. Mn(OH)2 + KNO3 don't react. Maybe if it works with Mn(OH)4 but I have not found any information. Does this substance exist? Neither I
have found little information on MnCl4.
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not_important
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| Quote: | Originally posted by Filemon
It doesn't work. Mn(OH)2 + KNO3 don't react. Maybe if it works with Mn(OH)4 but I have not found any information. Does this substance exist? Neither I
have found little information on MnCl4. |
Mn(OH)4 does not exist, at least under anything near normal condition, although there are hydrated forms of MnO2. It's fairly easy to make MnO2.H2O
which could be considered to be MnO(OH)2.
MnCl4 is not stable in aqueous solutions, only in concentrated hydrochloric acid or in sub-zero non-protic solvents.
There are some complex salts of Mn(IV), for instance
2 KMnO4 + 16 HCl => K2MnCl6 + MnCl2 + 8 H2O + 4 Cl2
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guy
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Nitrate is very bad oxidizer at pH>7
Oxygen however is good enough to oxidize Mn(OH)2 to MnO2
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Rosco Bodine
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A permanganate in a buffered solution at a target pH and temperature might do the trick .
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vulture
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Permanganate and water means carboxylic acid, regardless.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Biginelli
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Active gamma-form of MnO2 can be obtained by the following reaction:
MnCl2 + KMnO4 => MnO2 + Cl2 (chemical war conditions!)
15-18 hours at rt, then filter out, wash with water and dry at 130 C for 18 h. Believe me, it works!
This MnO2 is widely used for oxidations of, e.g allylic, proparhylic, aromatic and even saturated alcohos to aldehydes. Aromatization also.
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Biginelli
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So why bother with this in situ condition?
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Eclectic
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There is a VERY comprehensive thread on using electrolytically oxidized manganese sulfate to oxidize toluene and various alcohols to aldehydes...
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chemrox
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"There is a VERY comprehensive thread on using electrolytically oxidized manganese sulfate to oxidize toluene and various alcohols to aldehydes... "
it would have been nice to have located this for the rest of us.
MnO2 is available and cheap; why all the manipulations to try and make it in the flask?
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Rosco Bodine
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The thread is here
http://www.sciencemadness.org/talk/viewthread.php?tid=6882
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not_important
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| Quote: | Originally posted by chemrox...
MnO2 is available and cheap; why all the manipulations to try and make it in the flask? |
The forms of MnO2 usually encountered are much less reactive than the freshly prepared hydrated form. This is especially true for MnO2 prepared by an
ignition method, often the reagent grade is made from Mn(NO3)2 via heating for some time which gives a hard, crystalline form.
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Methyl.Magic
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Aldehydes can easily synthetised from alcool via Dehydrogenation with Copper chromite as catalyst !!
Very nice yield !
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vulture
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Which is nice, but hardly practical given the cost and the fact that copper chromite is unavailable to most.
Since we have parallel thread this one is now closed.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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