gravityzero
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Peroxide Concerns - Please Help
If an ether based mixture contained a desired product which will crystallize out, but the mixture also has explosive peroxides as well, how could one
proceed?
This ether mixture has been left to evaporate on it's own and so the product simply crystallizes out. So what happened to the explosive peroxides?
Do they just disappear in the air? If I take those crystals and put them in more ether, will the peroxides still remain?
It's like this... If there are alot of peroxides in some ether and it is concentrated under heat an explosion can occur. That same amount of ether is
left to dissolve on it's own and nothing happens. What exact conditions make the peroxides explode?
Do peroxides go away once exposed to air, or do they themselves crystallize along with the product?
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Bonee
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My experience has been that DEE forms peroxides almost instantly in contact with air and these peroxides have a high tendency to oxidise/discolor any
easily oxidisable molecule. (I would like to get some opionions on this)
I try to avoid DEE because of this mostly. MTBE is much better in this regard if you're not doing any grignards.
My bet would be that the peroxides just decompose, its more of a problem when you have a solution containing a lot of peroxides and you concentrate
it by distillation.
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gravityzero
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The plan is to attempt to recover at least half the ether through distillation using as low heat as possible.
The remaining ether, along with product, will be removed by air drying.
This should allow me to recover some ether without concentrating enough for any explosions.
[Edited on 25-3-2021 by gravityzero]
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Fyndium
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When I dug two aluminum flasks of 2011 Eau D'ether from the very back-corner of my warehouse, I checked some old topics where people investigated
peroxide formation, and if protected from air and light, it was basically nil, especially if it contains any kind of stabilizers.
If you have unknown stock of ether, you would wanna add 3-5% of oil(food, paraffin, etc non-volatile) and distill it from hot water bath.
(Re)crystallizing from ether, especially freshly distilled, will keep the peroxides in very trace amounts and unless one plans to distill that product
to dryness, I see little room for issues here.
It's not like there is a 5% curst of peroxides which just wait to blow up, it's more like a gram per 10 liters, and once you strip all of that
solvent, it becomes an issue. I see this as a threat if you do some kind of work/research stuff and rotavap large amounts of solvents on series, the
concentrations of even small traces will accumulate quickly.
Or if there really is a crust of peroxides on the bottom of your ether flask, you better run and make a new plan for it.
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Dr.Bob
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You can always wash the ether product solution with aqueous thiosulfite or sulfite solution to help reduce some of the peroxides. There are a number
of procedures to also remove peroxides from ether before you use it, the book "purification of common lab chemicals" covers some of them. Or just
google " remove peroxides from ether" and you can find more. Your idea to remove half of the ether and then dry slowly makes sense, in that you are
not heating to sryness, if you can blow nitrogen through the ether, even better (than just air).
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draculic acid69
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Will adding a small amount of iron sulfate to decompose the peroxide cause an issue
Can your product have a small amount of FeSO4 impurity? Or can it be rextalized after in fresh ether? Surely that's a better idea than evaporation of
the ether and then trying to deal with the peroxide
[Edited on 27-3-2021 by draculic acid69]
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Boffis
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To remove peroxide once formed use ferrous sulphate and then sodium hydroxide solution. If the ppt turns yellow brown instantly peroxide was present,
if it take time for the grey green ppt to turn brown little peroxide was present and if it only turns brown from the surface this is only atmospheric
oxidation of the ferrous hydroxide.
I frequently recycle ether and have never had problems. A few simple rules: if you distill ether and are going to use it immediately, fine: if you are
not going to use it within a few days I add a little butylate-4-hydroxytoluene (I bought this off Ebay but it seems to have been a one off) to it.
About 25 ppm for storage up to a few months before its next use or up to 100ppm for long term storage.
When distilling ether never distill distill to dryness and distill using a warm water bath at 60-70 C max. There is a lot of urban myth out there
about ether.
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zed
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They are peroxides. They are inherently unstable. I have been cautioned, not to turn the cap, on a bottle containing un-stabilized ether. Peroxides
accumulated in the threads of the bottle-cap could detonate from friction.
Yeah. Usually this doesn't happen. But, it gives you something to think about. Di-isopropyl is supposed to be a special problem.
One time a co-worker called the fire department when he discovered a previously opened (and long forgotten) can of Di-isopropyl ether in a storage
area.
The Hazmat folks took it very seriously. They cautiously evacuated the container to a remote area, where I would imagine they put a bullet through
the can.
Reporting back... "Yup! You did the right thing!"
https://www.d.umn.edu/environmental-health-safety-office/haz...
[Edited on 28-3-2021 by zed]
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Fyndium
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How big of a blast we are talking about here?
If I really had to open a questionable bottle I can see inside enough that it does not contain a crust of something, which could cause too big of a
blast, I would mount the bottle at something, use piece of plexi or plywood as blast shield and open the cap with a pipe wrench.
Off topic: when I was younger and more stupid and was experimenting with pyro and energetic stuff, I actually considered ordering 3A type face visor
just in case something went off.
https://www.veplasgroup.com/ballistic-visors.html
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Deathunter88
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Chillax guys, unless you see a chunk of peroxide it's not going to blow your house up. It's not a bottle of nitroglycerine! Sometimes other high
explosives are shipped wetted with ether to reduce sensitivity. Even isopropyl alcohol is a peroxide former, and no one seems too concerned with
leaving that out for a bit.
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zed
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The explosion does not need to blow your hands off. Rupturing a bottle, and splashing ignited ether all over the vicinity, should prove
sufficiently entertaining.
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Engager
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In general organic peroxides are unstable, they energy of -O-O- bond is order of magnitude of 40 kJ/mol, so it's easily ruptured homolitically forming
radicals that can enter chain reactions. This activation energy barrier is the natural safety shield, once decomposition starts every molecule
decomposed will give enough energy to provide several molecules with activation energy and this leads to avalanche and once energy release overcomes
natural heat transfer (cooling) explosion will happen. Danger of peroxide greatly depends on it structure, peroxides with multiple -O-O- moieties and
"caged" structure are more sensitive and prone to explosion. Danger increases with increase on total peroxide oxygen content mass in relation to total
mass of compound, so for example it will be enormous difference between compound that contains 40% of peroxide oxygen and 60% of oxidizeable carbon
backbone (for example acetone diperoxide) and some peroxide that contains 15% of peroxide oxygen (for example benzoyl peroxide), or some harmless
stuff that contains like 2% of peroxide oxygen. In general - closer anything to ideal oxygen balance, more powerful explosion is expected, and more
low energy bond content with high heat release on decomposition - more sensitive compound will be. This leads to several implications:
First is - activation barrier is your safety shield, do not provide activation energy to the substance by any means (heating, mechanical stimulus,
sparks, sudden pressure changes, UV irradiation, e.t.c), be aware that some compounds like some heavy metal salts (for example: Mn, Fe, Co, Cu), free
acids and others can greatly lower activation energy of peroxide bond breakage, sometimes they can do so in tiny amounts. In extreme it's possible to
make it so low that it would be near to energy of molecular collisions and thermal motion near room temperature, in such case compound can explode
"without visible reason" ("spontaneously"). Do not provide means for unstable compound to get activation energy, deny everything! Due to the reason
above peroxides are far more stable at low temperatures, most of ones that are unstable at RT can be stored for many years in deep freezer camera,
cold also aids accumulation of peroxides since it lowers their normal decay rate. Also since most peroxide decompositions are started by formation of
radicals, addition of radical scavengers can break reaction chain on it's beginning, greatly negating danger of explosion until scavenger will be
exhausted.
Second is - increase in amount of peroxide oxygen in molecule (and any unstable bond content in general) greatly elevates risk of explosion and it
will become more powerful then it happens. This not only includes constitution of moieties inside molecule, but also applies to compound mixtures as
well, that is why mixtures of organics with nitric acid for example, close to oxygen balance are highly explosive. With enough inert material mixture
will loose explosive properties, but when oxygen balance comes closer to optimal (for example on evaporation of most solvent) danger will increase all
way up to extreme. Dilution of peroxide with any inert or semi-inert material is effective method in prevention of it's explosion ability. For
example: addition of amount of mineral oil, paraffin or other stuff will negate risk of explosion (as long as the resulting mix is far from ideal
oxygen balance), so one can still distill solvent safely. Providing better conditions for heat transfer, for example by layering the dangerous
material on the huge surface of inert material (like for example distilling of ether from mixture of liquid with big amount of molecular sieve
granules) will make explosion close to impossible.
Combining those two factors you can assess danger of any peroxide compound. If things will go bad and explosion will still happen, it's power and
destructive force will depend on casing, if peroxide will decompose in enclosed volume - strong explosion will occur, that will fragmentate
surroundings forming shrapnel (so if you anticipate such kind of danger manipulate material in plastic, but not in glass or metal container), on the
other hand if some small pile of very explosive peroxide (for example HMTD or AP) is placed on open surface, it will only puff on ignition without
explosion. Unstable sensitive compounds like gentle manipulation, avoid glass to glass and especially metal vs metal contacts at all costs when
handling material, use soft art brush and paper, treat sensitive compound like it's a virgin on wedding night. Also remember that explosive power
scales down with distance according to cubic law, so keep yourself and your hand/fingers away (!!!), use remote holder to manipulate material, hide
behind blast shield from thick organic glass, it's way better to screw up experiment and labware than to loose your health or life!
The general advice for peroxides is, don't toy with them until you are know absolutely what exactly you doing, destroy them chemically before then can
become a source of danger for you. People in this thread already give you some good means to destroy them chemically, like reductions by sulfites,
iron(II) compounds. Where are others as well, for example CuCl, stannous chloride, Ce(OH)3, Sn/HCl and even usage of molecular sieves (ceolites),
those later are very good in safe removal of big amounts of peroxides (check for example ref: Deperoxidation of ethers. A novel application of
self-indicating molecular sieves; David R. Burfield ; The Journal of Organic Chemistry 1982 47 (20), 3821-3824 ; DOI: 10.1021/jo00141a003). On the
other hand where is no need in fear when content of peroxide oxygen is very low vs total amount of handled material. You should assess your specific
situation to decide the appropriate handling or safety neglection.
Hope that info i given will help you. Stay safe.
[Edited on 30-3-2021 by Engager]
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