sbreheny - 22-2-2016 at 20:35
Hi all,
Many of you are probably familiar with the reaction which takes placed when glowing (or near glowing) hot copper is placed into acetone vapor. The
copper remains red hot while the acetone reacts with something (oxygen?) in an exothermic reaction. I recently tried this myself and was successful in
observing this reaction.
I'm trying to find out more details about this and I see very conflicting information. Some sources show no net oxygen consumption, while others show
it more like an incomplete combustion. Some show the products as acetaldehyde, CO2, and H2O, while others show ethenone and methane.
For example, see https://www.flinnsci.com/media/621715/91711.pdf
which shows the final, overall reaction as the conversion of acetone to ethenone and methane. On the other hand, this source says that ethenone is
only a minor product present in small amounts and the main products are acetaldehyde, CO2, and water:
http://www.job-stiftung.de/pdf/versuche/Catalytic_Oxidation_...
I find it particularly interesting that Flinn says ethenone is a main product and then never warns you about it in the safety section. Flinn usually
errs on the side of making everything sound dangerous - but from the wiki article, it seems that ethenone is almost as dangerous as HCN or phosgene in
terms of the mean lethal concentration.
I experimented with covering-over the reaction vessel to see if oxygen was required from the outside to sustain the reaction. Each time I tried this
the reaction stopped and the sides of the glass container were "fogged" with condensation of some liquid. It's tough to say, though, whether the
halting of the reaction was due to oxygen being consumed or the inability of the products to escape.
Anyone know more about this?
Thanks,
Sean
Detonationology - 22-2-2016 at 21:38
I own a hand warmer that operates on the same concept. I have had it in relatively airtight containers when operating and it will still be working
many hours later. Methanol has been my fuel of choice for many years because of availability, and the smell it generates is very pungent and tickles
your nose a lot. I can't really say I have noticed a smell similar to formaldehyde though.
UC235 - 22-2-2016 at 22:01
Ketene is formed on thermal cracking in the absence of oxygen which a copper wire in a beaker over acetone lacks. In the presence of oxygen you get
combustion which is why the wire heats up. Possibly a small amount is formed, but it is also inflammable
A setup to deliberately generate ketene needs to be heated and is not exothermic. Copper is not even specific for formation of ketene. It merely needs
to be at high temperature. For example, Orgsyn uses a tube furnace heating a glass tube full of porcelain pieces: http://www.orgsyn.org/Content/pdfs/procedures/CV1P0330.pdf
Quieraña - 29-12-2019 at 13:42
I was thinking of if you had a say a long tube if you don't have glass PVC pipe whatever and let's say a container of some sort doesn't have to be a
flask filled with pure acetone dry acetone of course and oiling this running the fumes through a hair dryer on high heat and running that gas into
acetic acid I would be interesting wouldn't it?
rockyit98 - 29-12-2019 at 16:10
DUDE i just did this today,its products are acetic acid and CO2 and water if it can't get enough O2 it will die out maybe few byproducts that you
said.
Fery - 30-12-2019 at 09:25
Hot Cu is covered with Cu oxides when exposed to air, then while still hot and submerged into organic solvent the oxides react with organic solvent
and produce back Cu metal and various oxidation products of the organic solvent.
If you use ethanol you can produce small amounts of acetaldehyde also (use spiral of Cu wire repeatedly to obtain slightly more than trace quantities
of acetaldehyde).