After reading the fantastic "Ethanol_Reactions.pdf" from the ftp I decide to give it a try with the FeSO4 catalyzed oxidation of
ethylalcohol to - yes to what? Acetaldehyde or acetic acid?
The reaction is - violent:
This was the second try. The first try was mixing FeSO4, denat. alcohol and H2O2 30%. Not very much happened. Ok, lets warm it up I thought. In the
oilbath, temperature rising slowly - slowly - uiiii - RUNAWAY!!!!
Through the 40cm Vigreux it blows out the thermometer on top at the distillation bridge and gone it was my last grounded joint thermometer - FUCK IT!
A shower in hot alcohol/30% H2O2 isnt nice too......
The pictures are from the second try, no workup done up to now, I will report the results later.
One point: To get the reaction going it is advised to preheat the alcohol and then to add FeSO4 dissolved in water to which just before H2O2 was
added. This gives a nice violent reaction - add it to the alcohol whilst it is still reacting and thats it. Feed with H2O2 in a way that the reaction
doesnt run away but also not subsides.fvcked - 26-4-2004 at 18:32
Do you suppose I could use a different sulphate? Like MgSO4.Organikum - 27-4-2004 at 01:01
No. Ironsalts are the way to go.
(manganese, vanadium and platinium should work too, but iron is said to be superior)darkflame89 - 27-4-2004 at 01:38
Amazing reaction I dunno bout this but maybe the mini explosion was caused by a
buildup of gases? In which case you just let out a little hole for the escaping gases.
I dun know much about organic reactions, but the presence of transition metals catlayse the decomposition of H2O2?Organikum - 27-4-2004 at 06:45
There was no explosion. It was a runaway. This looks like the the soup in the picture expanding to a hundred times it volume in a few seconds - no way
to let gases vent away, the gases are in a nice mixture with the soup......foaming is not exact the word but the direction.
Its real fun to look at.
Not to clean the mess up afterwards.chemoleo - 27-4-2004 at 07:39
So what did you get from it?
What did your sense of smell tell you? Acetic acid and acetaldehyde have very distinct smells...
Knowing what you get would make this experiment even more interesting!Organikum - 27-4-2004 at 09:34
Dont be so unpatient!
I am still in the workup and this will take some time as I as told lost my last good thermometer. I will have to travel to get me a new one......
....in may this country is EU and EURO and this will allow me to abuse EBAY for these purposes.
Makes things much easier.....
I by now distill the shit out of the ironsalt and can say it smells - interesting. A certain touch of acetic acid is present and some very sweet -
acetaldehyde. It definitivly doesnt smell very much like ethylalcohol, thats sure.
Simultaneously there runs a new - less violent reaction with less catalyst and the FeSO4 was pretreated with H2O2 to form the ferric sulfate what is
told to be less active.
Nice title chemoleo!
But.....
"Imperator Maximus Chemicus et Biochemicus Superbibus Urbi et Orbi, Magister Artis Absolutus et Totali"
would be even better!
Then there would only be left to burn down a big city (Rome preferred) and done. But.....
....please dont sing!chemoleo - 27-4-2004 at 09:58
Urbi et orbi...lol... surely that title would be WAY too long! And yes I do sing
By the way I just recalled some acetaldehyde reactions - do you have ether?
You could extract the acetaldehyde from it, and precipitate it with NH3 gas, or NaHSO3, IIRC, they form reversible adducts with acetaldehyde.
Just a thought that may enable you to confirm you really found a cheap and dirty method for acetaldehyde preparation Organikum - 27-4-2004 at 10:26
So kindly take a look in your books chemoleo and tell me if I can make this precipitate with aqueous NH3?
Yep will ya?
This would be helpful as there is not much whats so volantile as acetaldehyde......
Decomposition of the addition product by some HCl? Acetaldehyde freed and ammonia to salmiac? Or how is it done?
The distillate which by now comes over smells definitivly like vinegar.
Some thoughts:
- The first reaction was to fast to hot. This caused decomposition of the H2O2 and complete oxidation of some alcohol.
- The reaction now - 60°C waterbath temperature - runs with only a little gas evolving. Better.
- Next try is to do it WITHOUT any bubbles.
As what I want is:
C2H5OH + H2O2 = CH3CHO + 2H2O
or
C2H5OH + 2H2O2 = CH3COOH + 3H2O
no gas. period.
I dont think I need ether for the extraction. Why should I? No azeotrope - simple boiling it out - better letting it escape and catching it
in?????????
In NH3 aqu.?
Tell!Organikum - 27-4-2004 at 10:32
Hey, chemoleo, I like the "Energeticus" in your title best!
It somehow reminds of this Energizer bunny ya know? chemoleo - 27-4-2004 at 11:07
what I thought of in fact is to simply add ether to your reaction mixture, extract the acetaldehyde with it, take the etheric extract, and bubble
ammonia through. In an etheric solution the ammonia adduct precipitates, which you can then regenerate. No destillation required. But as I said, those
are vague memories.
I will check up on details later... once I had dinner with that lovely lady, and once I am back Organikum - 27-4-2004 at 11:24
Fresh from the HIVE:
Quote:
....acetaldehyde ammonia trimer* * Also called Hexahydro-2,4,6-trimethyl-sym-triazine, and is commercially acailable. It can also be made by the
addition of acetaldehyde dropwise to a 4x molar excess of concentrated aqueous ammonia, chilled in a freezing mixture
Is this what your memories are about?
PS: I will check how soon you are online again here and so we will know how successful your dinner was......
Good luck!
and
Dont cheat!
[Edited on 27-4-2004 by Organikum]chemoleo - 27-4-2004 at 17:37
Well.. dinner was great! Shame she's leaving soon
Anyway... I am glad to see my memories didnt become bad with advanced age... so here it goes:
From
Radmacher, Einfuehrung in die Chemie:
Acetaldehyde forms with ammonia aldehyde-ammoniakates (name?), according to
CH3CHO + NH3 --> CH3-HC(OH)(NH2)
With sodium bisulfite, it forms
CH3CHO + NaHSO3 --> CH3-HC(OH)(SO2ONa)
These compounds are often only slightly soluble in water, and therefore are used for the isolation of aldehydes, as this process is easily reversible,
too.
So no, the compound you mention from the Hive does not seem to be the same - unless the polymerisation to the cyclo compound you mention equals the
monomer I mention.
Acutally yes it does. The aldehyde ammonia dehydrogenates, forming H3C-CH=NH. This then trimerises to the compound you mention (chekcing organikum)
Unfortunately I can't check with the Hive as the search funciton seems to be disabled
Checking Vogel, it says that acetaldehyde gives a yellow resin with NaOH, smelling of bad apples.
As to the bisulphite adducts - it says, shake 1 ml. of (benz)aldehyde with
about 0-5 ml. of saturated NaHSO3 solution. The mixture becomes warm, and the white addition product separates (rapidly on cooling). No distinction
between formic and acet- aldehydes are possible this way though,as solubilities are the same. But in this case I dont think u need to worry about
potential formaldehyde.
Anyway, thats all the info I could find right now.
Best of course would be to test NH3/bisulphite with a known clean acetaldehyde batch, and then compare it to your reaction products.....
Edit: Check megas page on acetaldehyde, it also mentions the aldehyde/ammonia adduct, in more practical details, albeit maybe not entirely necessary.
[Edited on 28-4-2004 by chemoleo]Organikum - 28-4-2004 at 01:49
Thanks so far.
I am still working on the reaction conditions, the addition of some H2SO4 seems to give a more homohenous mixture and is told to mediate the reaction
- this is tried now.
I guess it runs down on finding the right mixture of alcohol/water/H2SO4/H2O2 and ferric sulfate.madscientist - 28-4-2004 at 02:12
Quote:
As what I want is:
C2H5OH + H2O2 = CH3CHO + 2H2O
or
C2H5OH + 2H2O2 = CH3COOH + 3H2O
no gas. period.
Shouldn't you be aiming to have acetaldehyde boil out as it forms?
You should try keeping the still head temperature around 60C while slowly adding the H<sub>2</sub>O<sub>2</sub> to a excess of
EtOH with the ferric salt already dissolved. That should yield a considerable amount of acetaldehyde.Organikum - 28-4-2004 at 02:43
Dont talk, try it.madscientist - 28-4-2004 at 04:02
I wish I could, but I don't have a lab anymore, nor do I have access to one. Maybe again sometime in the future, but for now, I must go
without... Organikum - 28-4-2004 at 05:21
I can feel with you.
Look this doesnt work as you suggested, as what would happen is the following:
You drop in H2O2 and nothing happens.
Drop, drop, drop, drop, drop.....
Uhhh.....
Drop, drop, drop.....
- All other parameters constant -
drop, drop - RUNAWAY!!!!!!!
The runaway can be initiated by:
- Leaving the room and taking a piss
- Turning around and cleaning a flask
- Telephone ringing in the other room
- anything else
The runaway can be prevented by:
- watching the flask
My theory about how this was done by those who described it is that they did put everything together in a flask equipped with a very large and
powerful reflux condensor - maybe 2 staged - running on icewater and anaylysing whts left in the flask.
Meanwhile I believe this is the only way it can be done. I read about a micrutubular reactor which would be perfect for this reaction, but my
microtubular reactor is just by now on holidays - so what to do?
I know what I do now:
I will clean up the results from the last runaways
Before this I will give it a very special try - nothing to talk about before it is done. There are good chances that I will ahve to do a much bigger
cleanup afterwards though.... unionised - 29-4-2004 at 13:21
IIRC (and I wouldn't bet on that) an acidified solution of Fe(II) and H2O2 is Fenton's reagent. Famed for producing such things as hydroxide
free radicals. These will chew up any organic molecule they bump into. Not generally a good way of getting a clean product. OTOH it will eventually
convert most organics to CO2 and H2O which can be useful for destroying toxic waste.
I gave it a try
chemoleo - 29-4-2004 at 13:31
Three tries in fact.
I always added 30% H2O2 into EtOH, with a few grains of FeCl2. As soon as H2O2 is added, Fe3+ is formed, as observed by the colour change. H2O2 alone
and FeCl2 also produced the colour change.
Anyway, I found that the problem of runaways is indeed a major one. The more you heat up, the more bubbles form (looks like mild boiling). Then, at
60> deg C, suddenly the mix goes mad, and produces copious amounts of gas.
No smell of acetaldehyde after, but a distinct strong smell of acetic acid.
The next try i was more careful (I wanted to develop a feel for the runaway). Heated up very very slowly, and kept it at 40 deg for 30 min or so,
sniffing now and then. No smell of acetaldehyde/HAc, just ethanol.
As this clearly achieved nothing, I heated to around 50 deg. NOW I started noticiing the distinct apple like smell of acetaldehyde, no acidic traces!
Thinking, lets see if I can condense it, I put a glass plate filled with water on top of the beaker, so that gases could still evolve. Nothing more
happened, and I left the scene for no more than 30 seconds. Came back, and fucking RUNAWAY again!! The temperature of the water batch was still at 50,
but the mix was at 85 deg C! This really is a tricky reaction! ! However, the glass plate had liquid on it, which VERY strongly smelled of
acetaldehyde again. THe reaction mix itself unfortunately was all acetic acid by now
I am a bit confused by it. I deliberately made sure that there is a molar excess of EToH to H2O2 (1.25 times or so). THe amounts I used were 28. 75 ml
of EtOH (96%), and 59 ml of 30% H2O2 (assuming a density of 1 for the latter). Why oh why then do I get acetic acid? Principally half of the alcohol
should still be left!!
Well ... I think this reaction CAN be used for the production of acetaldehyde IF
1.one has an extremely rapid means of adjusting temperature (like adding h2O to cool things down, if runaway occurs), and 2. if there is a huge
condenser that doesnt explode if runaway occurs (i.e. with a big gas outlet valve. Trust me, once it starts, the amounts of gas that evolve are
massive! I cant try that here... but maybe someone else wants to. In principle such a condenser could be made quite easily, as any plastic material
that withstands 90 deg C can be used. Plus, evoraporating acetaldehyde can be easily captured by passing the vapours over strong NH4OH solution.
PS good to see Org how our experiences overlap vulture - 29-4-2004 at 14:04
30% H2O2...your H2O2 is way too concentrated. I'm not sure if you ever looked into kinetics, but concentration is everything when it comes down
to reaction speed.
Chemical engeneering tells me that lower conversion also leads to more selective production.Organikum - 29-4-2004 at 14:10
Yeah, nice these runaways arnt they?
I came to the conclusion that it is not gas from the complete oxidation of ethanol what evolves but plain gaseous ethanol as the reaction is so very
exothermic.
I will get some of the original articles on this soon and with this information going on experimenting.
An idea might be to inject portions of reacting H2O2/ironsalt mixture through a tube to the bottom of a flask with hot ethanol, for to make sure that
all intruduced H2O2 reacts completely - to "pump" the reaction so to say.
Another way worth to try is to preheat H2O2 near to its boiling point and to inject it into a warm to hot EtOH/catalyst mix - also by a tube to the
bottom. This sounds even more doable to me.
I will give this a try.
Have to buy some H2O2 first tomorrow....
Mmmm, H2O2 and iron!
Polverone - 29-4-2004 at 14:45
One thing that slightly puzzles me about these procedures that call for Fe(II) plus H2O2: isn't the Fe(II) immediately oxidized to Fe(III)?
Doesn't this in turn imply that you need to use molar amounts of Fe(II)?
I've experimented with a similar reaction before. I gave it up after my first spectacular runaway, then returned to it a couple months ago with
much more dilute peroxide. In my first experiments, I was just trying to form the Fenton reagent and attack etahnol with it. I didn't have much
documentation to follow, so I tried just using FeCl2 in ethanol, followed by addition of H2O2. My pale green solution immediately turned red-brown and
warmed up.
Oh, no! The desired Fe(II) was becoming Fe(III)! How to reverse this? Well, I added some ascorbic acid and was rewarded with a return to green (now
somewhat dirty from brown ascorbic acid oxidation products). To the warm mixture of Fe(II), ethanol, and ascorbic acid (ascorbic acid oxidizes very
easily -- can you see the coming disaster?) I added a splash of 30% H2O2.
I spent the next half hour scrubbing brown droplets off of myself, my computer, and the walls of the room.
This reminds me of the time I got the idea to make copper acetate from copper powder VERY QUICKLY by mixing the powder, glacial acetic acid, and 30%
peroxide. Of course that time the drops didn't fly quite so far and they were a prettier color.
More recently, I have definitely oxidized ethanol using H2O2 without a frustrating induction period or evolution of gases.
I treated iron powder with copper sulfate solution, plating some copper onto the iron. I then rinsed the powder with water and added ethanol and some
hydrochloric acid. Upon adding 3% H2O2 over the period of a few minutes, the mixture almost immediately began warming and the vessel soon became hot
to the touch. No bubbling was observed, and I smelled acetaldehyde from the hot mixture. Since I don't have any real glassware where I am, I
never tried isolating anything. I wish I had some 30% peroxide to experiment with.Geomancer - 29-4-2004 at 16:36
One possibility for controlling the reaction is to use a variable amount of visable light along with a smaller amount of iron (photo-Fenton reaction).
The light allows the iron to oxidize water to give more hyroxyl radicals.
Assuming that the main reactions proceed by first abstracting the alcohol hydrogen, perhaps it would be advantageous (if your target is
acetaldehyde) to keep the pH neutral, to avoid catalysing the hydration of the aldehyde.Organikum - 30-4-2004 at 10:51
First: Polverone your style of experimentation and workup - lets see whats going to happen and scrubb stuff from walls and machines - reminds me
strongly on my personl method....
Got an article and can tell:
Hey chemoleo - we plain used MUCH to much catalyst. 0,005mole iron per LITER EtOH/H2O2 30% mixture at 35°C would be right. Thats 0,76g FeSO4 per
liter - oh my. The amount of catalyst used plain decomposes the H2O2 and thats the reason for the violent reaction, the runaway.
Vulture, the concentration of the H2O2 seems not to matter so much here.
The Fe(II) is of course transformated into Fe(III) by the H2O2 thats understood. also a certain amount of H2O2 is always decomposed by the
ironcompound.
The idea of light to control the reaction sounds interesting, Geomancer.
Polverone, how this iron/copper couple worked is unclear to me, it is told that coppersalts cause immediate decomposition of any H2O2...... ?
Did you wash the precipitated stuff before use or has been acid present?
But experiment rules and I have some copper precipitated on steelwool by hand so we will see soon!
PS: Actually there is this idea burned into my brain to find out what happens to a mixture of ethanol/toluene and a metal or metalsalt when I add some
hydrogen peroxide.......
?
[Edited on 30-4-2004 by Organikum]Polverone - 30-4-2004 at 14:34
Remember, I acidified the ethanol with hydrochloric acid before adding H2O2 to the iron/copper/ethanol mixture. Acidic H2O2 is much more stable. The
copper will be attacked, but the H2O2 doesn't undergo plain catalytic decomposition: there were no bubbles and the temperature rose far too much
for it to be from H2O2 decomposition alone (this was only 3% H2O2 solution).
Acid + H2O2 seems to be a good mixture in general for attacking stubbornly acid-resistant metals. HCl + H2O2 is often used for etching copper. The
solution turns green but there is no noticeable catalytic decomposition. Aqueous ammonia + H2O2 will attack copper as well, but the H2O2 decomposes
very rapidly under those conditions.
[Edited on 4-30-2004 by Polverone]madscientist - 30-4-2004 at 14:40
There probably was a considerable amount of aqueous chlorine participating in the reaction.Organikum - 1-5-2004 at 00:55
Uuups, my bad, I overlooked the HCl addition.......
Madscientist: The reaction is told to proceed through ferric acid.
I gave it try and added some iron/copper to EtOH and then some H2O2 10%. No heating up but bubbles. This was yesterday and it still bubbles softly at
the metal. Some stuff flocked out - copper hydroxide?
I will be strong and withstand the impuls to add acid or more H2O2, but let it sit until it ceased to bubble. Well stoppered out of direct sight....
Cu coated Fe
Trolf - 1-5-2004 at 01:09
What is the idea behind this.
1. To let Cu do the catalysing (would Cu-powder then work just as well)
2. To release the iron in small controlled amounts as the Cu is gradually removed from its surface.
3. Or some kind of cooperative effect I cant see.madscientist - 1-5-2004 at 01:31
Hydrochloric acid and hydrogen peroxide produces a considerable amount of chlorine, and chlorine reacts readily with alcohols and such... probably two
mechanisms to it. One problem could be that the chlorine could oxidize the aldehyde to carboxylic acid much more quickly than the iron catalyst would.Organikum - 1-5-2004 at 02:23
There is a bunch of possible reactions involved here and I am neither going to try to judge which takes place at all nor which predominates under what
conditions.Organikum - 1-5-2004 at 04:02
Left: copper, iron, H2O2, EtOH
Middle: FeSO4, H2O2, EtOH and H2SO4
Right: toluene, EtOH, some ironwool, H2O2, FeSO4, H2SO4 and air bubbling through it for the soup separates into two layers. And as its an oxidation
some oxygen wont hurt I thought.
madscientist - 1-5-2004 at 14:29
Just suggesting that an acid other than HCl be used.
I dunno bout this but maybe the mini explosion was caused by a
buildup of gases? In which case you just let out a little hole for the escaping gases.
