weiming1998 - 13-3-2012 at 03:36
I have thought about combining ammonia and vinegar to make ammonium acetate, then heat to create acetamide. But I am worried that heating acetamide
might create HCN or CO, just like heating formamide. So, is it safe to thermally decompose ammonium acetate to create acetamide indoors? If it is not,
I just have to use my extremely inefficient ethanol burner, which consumes a lot of fuel and is not even 1/10th as effective as my stove top.
Vikascoder - 13-3-2012 at 08:37
In my opinion it is not safe because poisonous and toxic gases are released . I read this on google.
bbartlog - 13-3-2012 at 11:57
With some means of condensation, and temperature control, I don't see a problem. I suggest maintaining a temperature of 235C or thereabouts. If you
use direct flame, you will have a hot spot and then I expect more sideproducts will be created.
When I did this I mixed (solid) sodium acetate and ammonium chloride in stoichiometric amounts and then added dimethyl sulfone as a solvent. Because
it boils at 238C, it provides a degree of automatic temperature control on reflux. On the downside some of it passes over with the acetamide (unless
you have a fractionating column well-insulated enough that you can push such high-boiling products through it... I don't).
Anyway, the primary noxious product if you keep the temperature below 250C should be small quantities of ammonia, which can be dealt with by placing a
pan of vinegar near the outlet of your distillation setup.
weiming1998 - 14-3-2012 at 02:10
Ok, no distillation setup though. Just in case, I'll use my inefficient ethanol burner for once outside. But is it safe to boil down the water in the
ammonium acetate (I used a vinegar ammonia mix to create it.) without strict temperature control or distillation?
Edit: not the actual decomposing, just to boil it down to a concentrated enough solution to be easily decomposable by the heat of the burner.
[Edited on 14-3-2012 by weiming1998]
bbartlog - 14-3-2012 at 08:37
The ammonium acetate shouldn't do much until all the water has been driven off, i.e. it's not going to decompose at temperatures below 100C (or for
that matter 200C). At most I expect very small quantities of ammonia and/or acetic acid would be given off.
But if you have no distillation setup, how are you going to capture/condense the acetamide? Are you hoping to keep it in the same container that the
ammonium acetate is decomposing in? It boils at 222C and will be carried along with the vapor of H2O and other decomposition products. With a column
you might be able to reflux it back in to the vessel, but even that is not really desirable. It may decompose further at the reaction temperature and
anyway having it mixed in with the ammonium acetate and crud will just lead to a more difficult workup.
[Edited on 14-3-2012 by bbartlog]
weiming1998 - 15-3-2012 at 00:55
I was thinking of covering the top of the container firmly with aluminum foil. At the top, a small hole is going to be drilled, to let the less dense
water vapour escape. As the acetamide vapours are going to be a lot heavier than the water vapour, most of it will stay at the bottom (with some
losses). As more decomposes and more water vapour escapes, I can just use a burning wooden stick to test the flammability of the vapours (acetamide is
flammable at high temperatures). When the vapours at the top is sufficiently rich enough in acetamide, that means most of the ammonium acetate would
have decomposed. I could then shut down the flame.
Any problems with this?
bbartlog - 15-3-2012 at 03:43
Heating with flame.... I think you get hots spots and charring and unpleasant acrid fumes that way (temperature needs to be controlled and even). Also
I don't think aluminum foil is a great choice for this application, since both ammonia and acetic acid can attack it to some extent. But the main
problem I see is that whatever acetamide you produce remains with whatever other gunk you end up with. You need to plan a workup for whatever
off-white crud you will have left in your vessel. I suggest reading the acetamide prep (and especially the references!) here: http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1...
Looking at the methods given makes me a bit more pessimistic about your chances... *rapid* distillation of ammonium acetate or *heating in a sealed
tube* (followed by distillation) are mentioned, from which I infer that simply slow cooking ammonium acetate in a container may well fail for some
reason.
weiming1998 - 15-3-2012 at 04:19
The reason why I chose not to distil is because I don't have a distillation column in the first place! Maybe that will fail, but everything is worth a
try. I'll try my method later.