Quaternammox
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The smell (?) of dimethyl sulfate
I'm part of a research team working on developing electrochromic compounds at my university. The other day I was about to perform a methylation with
iodomethane (my preferred agent), only to find out that someone had finished the bottle. I dug around and found a bottle of dimethyl sulfate from
god-knows how long ago; it’s probably tenured by now. I was pretty hesitant to use it considering its nasty reputation even among methylating
agents, but the show must go on.
I added my phenolic compound and dimethyl sulfate in a 1:1 molar ratio in acetone with some potassium carbonate and refluxed for 4 hours. The
resulting mixture was thrown into excess aqueous NaOH to hopefully neutralize any remaining dimethyl sulfate. Here’s where the dilemma began: our
rotovap is at the other end of the lab, and upon removing the mixture from the fume hood I was greeted with an intense and horrendously pungent
sulfurous odor. This odor only intensified following rotary evaporation and continues to haunt the lab even following a thorough clean-up.
So what was it? Dimethyl sulfate is reported to have a “mild, onion-like odor”, but case reports suggest its so mild as to be essentially
unnoticeable (and there was nothing mild or onion-y about this smell). I’ve thankfully shown no symptoms of dimethyl sulfate poisoning. This same
reaction with iodomethane results in a very mildly sweet-smelling product, nothing at all like this monstrosity.
Anyone have any ideas?
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Quaternammox
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The update no one asked for
It turns that the "Dimethyl Sulfate" was simply a mislabelled bottle of dimethyl sulfide. My multi-week reaction is, of course, entirely
ruined.
On the bright side, I've got a new respect for fumehoods because I could smell this stuff the second I removed it from said hood. I'm sure that I've
been similarly exposed to plenty of far more toxic compounds with no olfactory warning.
It also appears that the real bottle of dimethyl sulfate, wherever it is, is labelled as dimethyl sulfide (yes our system sucks). Anyone using that
stuff is probably doing everything they can to avoid being skunked so at least they're probably safe.
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fusso
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y dun u ask lab techs for a new bottle of Me2SO4?
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DraconicAcid
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Yikes! That's a horrible way to mislabel something!
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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mackolol
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Quote: Originally posted by Quaternammox  | It turns that the "Dimethyl Sulfate" was simply a mislabelled bottle of dimethyl sulfide. My multi-week reaction is, of course, entirely
ruined.
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Oh man I feel sorry for you. When I worked with trace amounts evolved from slightly impure DMSO it smelled like really bad sulfur SHIT.
Good way for neutralisation of Me2S is to put exhaust pipe to dilute solution of hypochlorite. Now for me it works very well and doesn't produce any
odor.
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Quaternammox
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Unfortunately my university considers lab techs to be "Non-Essential" at the moment. It's also verboten for us researchers to order things or make
repairs should anything break, so I don't know what they thought would happen.
Since I'll be putting in a lot of extra hours redoing my reactions I figure I'll make some iodomethane myself. It looks easy enough (NileRed has a
great video on the process) and we've got no shortage of phosphorous and iodine.
Thanks for the tip mackolol, I'll be sure to try it out if I'm ever unlucky enough to have to use the stuff again. It took a couple days of airing out
the lab before I could work in there without gagging - I'm lucky that most of the other guys burned their sense of smell out long ago or I'd never
hear the end of it.
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woelen
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Very bad practice at your university.
But, from the bright side, being exposed to maybe a little too much dimethyl sulfide may be unpleasant, but being exposed to too much dimethyl sulfate
is a disaster for your health and possibly even your life. Dimethyl sulfide has a horrible smell, but is not very toxic, while dimethyl sulfate is
said to be outrageously toxic and should be considered as risky as phosgene: hours delayed destruction of lungs and strong carcinogenic effects.
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DavidJR
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That is concerning...
Also, if you take something out of the fume hood and all of a sudden get an unexpected overwhelming smell, maybe a good idea to put it right back in
the fume hood?
[Edited on 12-5-2020 by DavidJR]
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karlos³
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I can't believe it!
At least that way it was the better of the two possible scenarios... the other way would have been really bad.
Thats not only bad practice by the uni, I believe that can even have legal consequences for them.
It definitely should in my opinion to be honest.
The opposite scenario, that could easily be judged as negligent assault if something happens, and even when not, it would pose an imminent danger to
everybody working at the place.
At least you did not pull the short straw, you've been lucky, even if it does not feel this way with the horrible stench of that stuff and you
worrying about the exposure.
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