Cou
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How is acetaldehyde even shipped?
I'm not doing it anytime soon, since I'm a little scared of carcinogens. but as someone who is interested in alcohols and grignard reactions, I might
handle acetaldehyde one day, for making 2-alcohols such as pentan-2-ol, hexan-2-ol, etc.
I notice chemsavers offers bottles of acetaldehyde. But it boils at 68 degrees F, and that made me think. That means the bottle would explode at even
room temperature, and would need to be stored in a small freezer. It would also explode during shipping.
I guess they use a really expensive shipping method, like shipping in refrigerated trucks?
For the home chemist, acetaldehyde seems like it would be prepared in the lab right before use. I predict you could make it from ethanol and PCC,
which are both available. or swern oxidation.
For now i am sticking with the more convenient and safe carbonyls for grignard reactions, such as propionaldehyde.
The other route for making 2-alcohols is using bromomethane to make the grignard reagent, which is also a pain to work with b/c it boils at 3 C.
[Edited on 19-6-2020 by Cou]
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dawt
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Mine came in a regular 250 mL brown glass bottle, and it's survived several summers like that outside in the shade, despite a few 40 °C days. I do
keep it in a styrofoam box in hopes of maybe preventing it from getting all too hot in the afternoon, but I can't say if that's really any help.
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draculic acid69
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I keep my hydrochloric acid in a styrofoam box outside as well. I think it keeps stuff cool enough. Anyways back to acetyldehyde. My dad used to get
20l drums of toluene with acetyldehyde in it as a drying agent and that shit sat in a hot factory and never made the drum bulge even though it's
always above its b.p. the only way I figured it out was I did an extraction with it one day and the water wash had something boiling out of it
gently. I'm not surprised it's fine in a glass bottle without popping the lid or shattering.but I thought it would come in a metal cylinder of some
sort. I guess it's vapour pressure isn't that strong
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karlos³
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It comes in a bottle and it stays in the bottle.
No issues.
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woelen
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Where I live, we can buy paraldehyde, which is a trimer of acetaldehyde. This compound has a boiling point of 120 C or so and is stable on storage. In
the past this was used as a medicine, but nowadays, it is not used anymore as such, and hence, I can purchase it in 1 liter packages (unfortunately no
seller has smaller packages of this). Paraldehyde can be depolymerized prior to use. There also is a tetramer (called meta), but this is much more
expensive than the trimer. A bottle of 250 grams of the tetramer has the same price as a liter of the trimer. Meta is more toxic than paraldehyde, but
is easier to handle, because it is a dry powdered solid at room temperature.
I do not own any of these chemicals, I have no particular interest in them, nor in acetaldehyde, but if I want to do more things with organic
chemistry, then I might once buy a bottle of the trimer.
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Refinery
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About carcinogenicity, doesn't alcohol convert to acetaldehyde in body?
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Fery
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Acetaldehyde has quite low b.p., only 20,2 C but there is a pressure in the bottle which prevents it from boiling. Mine came in 500 ml glass bottle
and I keep it in fridge at 4 C to slow down degradation via Cannizzaro reaction.
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Pumukli
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Cannizzaro reaction? It would produce acetic acid. But Cannizzaro needs strongly basic environment.
As a side note I'm as baffled by the carcinogenicity as Refinery. Though it seems these acetyl-compounds have something inherently malevolent in them
:-) as one will find plain vanilla acetamide listed as a carcinogene too.
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Panache
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Chems listed as Carcinogens are only suspected of causing mutations. Those we know cause them are called mutagens. So to be safe every other fucking
chemical is listed as a carcinogen, for some there is sound strong evidence for others, not so much....
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Cou
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Yea, that's why alcohol increases cancer risk.
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karlos³
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I have actually seen a study on chemists, and despite us working regularly with harmful chemicals like cancerogens etc, we don't have an increased
risk to get cancer according to that paper.
So, when working properly with the usual safety precautions, there is no need to worry.
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Refinery
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Actually my point was that 95% of western people get exposed to constant alcohol intake and the cancer inducing effect is what it is. Acetaldehyde
should therefore be not very lethal in situ.
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Deathunter88
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Maybe learn a thing or two about vapor pressure. Things don't just "explode" when it gets past their nominal boiling point at 1atm.
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Fery
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Pumukli, so do you think acetaldehyde quality does not degrade that way (reaction producing ethanol + acetic acid)? Of course no base present (bottle
label says analytical grade quality) and if acetic acid produced it would neutralize any base. Do you have any experience how long could the
acetaldehyde be kept without significant degradation - it would not easy to redistill it due to its very low b.p., it would require circulate some
liquid with T below 0 C through efficient condenser...
I remember severe quality loss of few my glass bottles with formaldehyde which I kept in unheated house during few winters, it should be kept above 8
C, but that is something else than acetaldehyde. I'm just more careful since that time.
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dawt
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I remember severe quality loss of few my glass bottles with formaldehyde
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That's due to polymerisation to paraformaldehyde, though - not Cannizzaro. I haven't noticed any degradation of my acetaldehyde after like 5 years
outside, but I just measured the pH and it came back slightly acidic. To be fair though, the bottle reads 99 % and the contamination might have
already been there when I bought it. Or it might be from oxidation from the air in the bottle.
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