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guy
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[*] posted on 28-3-2007 at 13:44
Oxidation of ethanol


Looking for way to oxidize ethanol (not using chromate or permaganate). Would electrolysis or oxygen do the trick? I'm sure oxygen needs some catalyst.



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Magpie
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[*] posted on 28-3-2007 at 13:52


How far do you want to go? acetaldehyde, acetic acid, or CO2? ;)



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guy
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[*] posted on 28-3-2007 at 13:55


Quote:
Originally posted by Magpie
How far do you want to go? acetaldehyde, acetic acid, or CO2? ;)


Acetic acid is what I'm looking for.

I saw a paper online about Mn catalysts but they all need wierd ligands...

I'm thinking maybe we have Mn2+ salts in the alcohol then electrolyse it to some Mn4+ form which will oxidize the alcohol.

[Edited on 3/28/2007 by guy]




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Levi
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[*] posted on 28-3-2007 at 14:34


My old chemistry text mentions using a mixture of K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> and H<sub>2</sub>SO<sub>4</sub> but it doesn't elaborate.

EDIT:
It says CuO and heat will take a primary alcohol all the way to the acid. If you want to stop the oxidation at the aldehyde stage you use a Cu catalyst instead of the CuO.

[Edited on 28-3-2007 by Levi]




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guy
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[*] posted on 28-3-2007 at 16:29


I would prefer something that works under mild conditions.



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12AX7
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[*] posted on 28-3-2007 at 18:53


Acetobacter.



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guy
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[*] posted on 28-3-2007 at 19:00


Quote:
Originally posted by 12AX7
Acetobacter.


Not interesting enough:P

Though I do appreciate the power of nature. Mother Nature is probably the best chemist.
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not_important
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[*] posted on 28-3-2007 at 19:19


Platinum and similar metals or oxides and air can do it. Air with acetic acid and cobalt bromide is another, although it also oxidises the acetic acid.

I'd like to hear of more options, and of ones that could oxidise ethylene glycol, the cobalt route tends to cleave the carbon-carbon bond and take it to CO2 and H2O.
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[*] posted on 28-3-2007 at 19:46


You want a one step, room temperature oxidation of ethanol to acetic acid, is that it? And you don't want biosynthesis.

I'll see what can be found. Don't hold your breath waiting, the conditions you imposed make this nontrivial.

(I can understand why you don't want to use Cr(VI) but what exactly do you have against alkiline permanganate and a little heat?)

[Edited on 29-3-2007 by Sauron]
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[*] posted on 29-3-2007 at 06:29


most electrochemical oxidations of EtOH involve Pt/Ru/C catalysts and belong to direct methanol fuel cell research. The product is often water and occurs in several steps. I'll have to agree with Sauron that getting acetic acid is not trivial via ECO.

perhapses acetaldehyde as an intermediate would be possible with a divided cell.

C2H6O ---> C2H4O + 2H + 2e-

I'll keep digging as I have the same interest in electrochemical oxidations.

-3vil
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[*] posted on 29-3-2007 at 07:24


permanganate is expensive, and difficult to obtain in some areas. And for the shorter chain acids the isolation is more work. Always have to acidify with strong acids, for the lighter acids there's the problem of ending up distilling off a water-acid mix - you're back to distilling vinegar.

And converting ethylene glycol to oxalic acid with permanganate just isn't going to happen.

Strong base, heat, and air can be used to oxidise alcohols to the acids. For EG temperatures of 150 to 250 C and 25 to 100 atmospheres of air/O2 will give about a 60% yield of oxalic acid. Alcohols with alpha hydrogens can give condensation products.

This is related to those conditions
http://www.springerlink.com/content/vu66j515q2582h71/

and the attacked is an oxidation that goes to the aldehyde or ketone.

Attachment: Cu_cat_oxid_alcohols.pdf (387kB)
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[*] posted on 29-3-2007 at 09:32


I seem to remember coming across an old journal article a few years back .... Conditions were something like EtOH in H2O2 + Fe(III) salts in acid solvent ..... I think HCl was used. We used it in lab to oxidise a longer chain alcohol rather than wait for Fischer to come along, and it worked well.
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[*] posted on 29-3-2007 at 12:49


Quote:
Originally posted by Sauron
You want a one step, room temperature oxidation of ethanol to acetic acid, is that it? And you don't want biosynthesis.

I'll see what can be found. Don't hold your breath waiting, the conditions you imposed make this nontrivial.

(I can understand why you don't want to use Cr(VI) but what exactly do you have against alkiline permanganate and a little heat?)

[Edited on 29-3-2007 by Sauron]


Yeah I know its not trivial but I just want to know what the options are. I've read a few articles but they all involve these unusual ligands.

And I don't want to use permanganate because well, I don't have a lot of it and it seems that it could be put to better use than this.

I read an article on using Ni2+ catalyst and household bleach to effectively oxidize alcohols in high yields to their acids.

Attachment: Nickel-hypochlorite oxidizer.pdf (186kB)
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[*] posted on 29-3-2007 at 13:15


If your target is acetic acid, why not just distill it from sodium acetate and sulfuric acid.
Surely this is by far the easiest way? Perhaps I am missing something?Is it the reaction rather than the product that you are interested in?

[Edited on 29-3-2007 by sonogashira]
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[*] posted on 29-3-2007 at 14:00


Quote:
Originally posted by sonogashira
If your target is acetic acid, why not just distill it from sodium acetate and sulfuric acid.
Surely this is by far the easiest way? Perhaps I am missing something?Is it the reaction rather than the product that you are interested in?

[Edited on 29-3-2007 by sonogashira]

Yeah it's more of the reaction I'm interested in..
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[*] posted on 29-3-2007 at 19:27


Great, @guy, that is actually rather nice.

We knew that hypochlorite converts ethanol to acetaldehyde but it doesn't stop there, it then goes into the haloform rxn and produces chloral hydrate.

So, in presence of 2.5 mol% of this heterogeous nickel oxide hydroxide catalyst, it takes a different route.

The standard conditions imposed by the authors involved 45 mmol of substrate, and 300 ml of 6% NaOCl. 45 mmol of ethanol isn't much. 20 grams. So to oxidize a liter of ethanol this would call for 15 L bleach. Hmmm. A 22 L flask to make a kg of acetic acid? Is this practical?

Here is the 1973 review article from CR that is cited in ths JOC paper.


[Edited on 30-3-2007 by Sauron]

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not_important
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[*] posted on 29-3-2007 at 21:32


Indeed, this looks interesting, guy. Thanks much.

Sauron - is there a reference you know of that tells the conditions for ethanol and hypochlorite going to chloral hydrate vs going to chloroform and format? I've an old ochem experiments book that has the second case in it, but never have seen a discussion of what determines which path is taken.
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[*] posted on 29-3-2007 at 23:30


Sorry, @n_i. We had a thread going on that subject but hard references were few and far between. In fact I may have misstated matters above. Maybe ethanol and hypohalite only gives haloform via acetaldehyde whereas ethanol + chlorine gas gives chloral and/or trichloroacetic acid via same intermediate aldehyde.

Trichloroacetyl chloride breaks down to chloroform and CCl4, too. H.C. (Boron) Brown pointed this out in a 1930s paper on chlorination of trichloroacetic acid with phthaloyl chloride gave only 52% expected product, the remained was CHCl3 and CCl4. My investigation of this as a possible preparative route to those route to those halocarbons was stymied by failure to access the reference Brown gave to an older paper in Rec.Trav.Chim which apparently has not been digitized.
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[*] posted on 30-3-2007 at 11:02


I saw a few articles related to alcohol oxidation with H2O2 and FeBr3 or Fe(NO3)3.H2O, but the goal ws to stop at the aldehyde... It was conserning benzyl alcohol to benzaldheyde I think, and they said no carboxylic formation ws noticed... might be different for ethanol though, as the aromatic ring must have a certain influence on the stability of the aldehyde..
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[*] posted on 30-3-2007 at 11:56


Quote:
J. Am. Chem. Soc.; 1926; 48(8); 2083-2091.
THE CATALYTIC INFLUENCE OF FERRIC IONS ON THE OXIDATION OF ETHANOL BY HYDROGEN PEROXIDE

Reaction:

In all of the following experiments the volume of the solution was 172 cc.
This contained 2 cc. of pure ethanol (0.2 millimole per cc.) and concentrations
of hydrogen peroxide, catalyst and acid recorded in the tables.
The temperature of all experiments was 35’.

Before the reaction started, all of the solutions used contained an original
concentration of acid, this being furnished in part by the hydrolysis of
the catalyst and in part by acid added to the solution. As a consequence
it was necessary to correct the acid titration’s values for the concentration
of acid present before the oxidation of ethanol began. A correction was
also made for the alkali used to precipitate the catalyst as ferric hydroxide.

A sharp end-point was obtained in the acid titration at the beginning of
the reaction, but near the end, when practically all the alcohol had been
oxidized, the end-point was indistinct and the acid value less than it should
be. This was shown to be due to the oxidation of acetic acid to carbon
dioxide, a reaction that does not take place, however, until the ethanol
is almost completely oxidized, as will be shown later. As a consequence
of this reaction, the titrations made near the end of the reaction are untrustworthy

Summary:

1. Hydrogen peroxide in the presence of ferric salts (Fenton's reagent)
oxidizes ethanol to acetic acid. This reaction is quantitative. This reaction
is paralleled by the catalytic decomposition of the hydrogen peroxide
by the ferric ions. The two reactions are approximately unimolecular.


Note, oxidation of EtOH is the dominant reaction until it gets very low after which it goes on to oxidize acetic acid so you will have to kill the reaction at your appropriate endpoint.

[Edited on 30-3-2007 by XxDaTxX]
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Sauron
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[*] posted on 30-3-2007 at 16:49


Back to the Ni (II) - NaOCl system. It might make more sense to everyone if we call the black insoluble active catalyst which forms immediately and quantitatively by its real name instead of nickel oxide hydroxide.

It is nickel peroxide.

And if you have 15 L or so of bleach there to process 1 Kg ethanol, do you really care whether you use 2.5 mol% Ni (II) or the more traditional 1 to 1.5 equiv. ?

Because if you read the 1975 review I posted, you will see some remarkably different results compared to the catalytic procedure in the JOC article.

In particular note that you can oxidize benzyl alcohol to benzaldehyde not benzoic acid this way if you use an organic solvent not aqueous phase.

Many of the other transformationa are also highly interesting.

It's a good read.
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[*] posted on 31-3-2007 at 13:24
this just in


EXAMPLE 3

A Langevin-type quartz vibrator (1.7 MHz, input power 50 W) was used to produce cavitation in 500 ml of 10% ethyl alcohol solution. As a result, 40 ml of 78% acetoaldehyde solution was obtained in the reservoir 5 minutes after commencement of ultrasonic vibrations.

in the presence of Oxygen ethanol reportably will oxidize
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[*] posted on 31-3-2007 at 14:30


There is a patent I read a few years ago (of course I can't find it now) that showed air oxidation of slightly acidified alcohols in stainless steel reactors with only the trace of chromium supplied by the stainless steel serving as the catalyst.

[Edited on 3-31-2007 by Eclectic]
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[*] posted on 31-3-2007 at 16:23


That would tend to impact upon the fermentation and storage of wines in stainless steel tanks, as opposed to the traditional oak barrells, unless air can be totally excluded while allowing the venting of CO2 produced in fermentation.
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[*] posted on 31-3-2007 at 17:40


I have a mixture of nickel and copper salts (from US nickel coins) I dont know how to separate it! grrr
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