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Author: Subject: oxidation alcohol to aldehyde with MnO2
Filemon
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[*] posted on 9-8-2007 at 17:42
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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[*] posted on 9-8-2007 at 18:50


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!)

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Der Alte
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Rosco Bodine
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[*] posted on 9-8-2007 at 18:53


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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[*] posted on 10-8-2007 at 15:05


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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[*] posted on 10-8-2007 at 21:39


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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[*] posted on 11-8-2007 at 11:50


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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[*] posted on 11-8-2007 at 17:31


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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[*] posted on 12-8-2007 at 13:45


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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[*] posted on 17-8-2007 at 12:11


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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[*] posted on 17-8-2007 at 12:12


So why bother with this in situ condition?
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Eclectic
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[*] posted on 17-8-2007 at 17:36


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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[*] posted on 17-8-2007 at 21:35


"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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[*] posted on 17-8-2007 at 22:17


The thread is here

http://www.sciencemadness.org/talk/viewthread.php?tid=6882
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[*] posted on 18-8-2007 at 05:30


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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[*] posted on 24-8-2007 at 10:19


Aldehydes can easily synthetised from alcool via Dehydrogenation with Copper chromite as catalyst !!

Very nice yield !
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[*] posted on 24-8-2007 at 12:43


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.




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