Rainwater
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Peroxide prevention in ethers
Will platinum nanoparticles prevent or safely decompose peroxides in something like diethyl ether?
I know that they will decompose H2O2 solutions. I cant help but wonder if this would be a possible alternative to storing over sodium metal.
"You can't do that" - challenge accepted
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Fery
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Use FeSO4
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Kevlar
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Peroxide in THF
I know peroxides are usually associated with diethyl ether and not solvents such as THF, but what protocol is used for prevention in THF and
associated solvents.
And would peroxide test strips be the best method for detection of this nasty side product, the idea of using FeSO4 an KCNS and shaking a bottle bomb
is not on my top ten things to do!
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unionised
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The classic solution to the problem was to store the ether over copper gauze.
Storage over sodium is good if you need to be sure the solvent is absolutely dry.
(Don't do it with halogenated solvents)
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Texium
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Get yourself some BHT: https://www.ebay.com/itm/191874959221?var=0&mkevt=1&...
It’s typically added to commercial ethers to prevent peroxide, but recently I found that it can also clean up peroxide-tainted unstabilized THF. If
the peroxide test strip is negative, add about 0.25 grams per liter as a preventative measure. If it’s positive, 0.5 grams per liter. Then just let
it sit for several days, and the peroxide test should read negative. I tried this with a 4 liter bottle of THF recently. After 24 hours the peroxide
test was still positive, so I thought it wasn’t working, but I left the bottle for a couple weeks while I was out of town for the holidays, and by
the time I came back it tested negative.
Yes, this will leave you with a small trace of BHT in your solvent, but it’s not a big deal. It’s both very non polar and high boiling, so whether
you’re purifying your product by recrystallization, distillation, or chromatography it shouldn’t come along for the ride. And you can always
distill your THF before using it if you really don’t want it in there.
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Kevlar
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I am aware of the use of alkali metals for dryness, but had never heard of the use of copper guaze being used for prevention of peroxides.
And thanks Texium! The BHT is something new that I was not aware of. 100% will be buying that in a moment, and having a research to its application in
peroxide prevention and how it works.
How likely is a bottle of any solvent exploding upon the unscrewing of the bottles lid? It is something as an undergrad and amature does bother me,
and is why I keep starter fluid in my freezer for diethyl ether. I just distill over the ether prior to needing any then use right away, great advice
from
DR N BUTYL LITHIUM's youtube video's if you only ever need small amounts. The formation of peroxides is really interesting, and how they form longer
and longer peroxide chains. That just utterring the words UV near them can make them detonate.
I have a bottle of THF that is 2 years old, been stored in good condition and was purchased by myself so it is first hand. Even though I know I'm
neurotically being aware, but should I worry about opening up this bottle? I know it's not a bottle of diisopropyl ether or diethyl ether. But I also
like living and would rather be neurotic than dead!
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Texium
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Carefully read the label of your THF. Quite often, commercial THF comes stabilized with BHT already in it. It should say something of the sort on the
label. If it’s stabilized, you have nothing to worry about. I’ve never seen a stabilized bottle go bad, even after many years. If it explicitly
says unstabilized, or makes no mention of stabilization, assume that it’s not, and probably contains peroxides.
I wouldn’t be worried about opening the lid though. Unless you’ve been frequently opening and pouring from the bottle, it’s unlikely that any
peroxide would accumulate in the threads of the cap. I’ve opened some pretty sketchy old bottles of ethers that definitely contained peroxides
(behind a fume hood sash, wearing very thick oven mitts over thick rubber gloves while doing so, just in case) and never had any issues. If that
doesn’t satisfy your neuroticism, maybe you can put the bottle in a clamp and rig up some device to grab the lid and open it from a safe distance.
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Kevlar
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I just checked the chemical supply I use and the stabiliser is BHT! Nice one though as I don't feel so neurotic after doing some research on the use
of BHT in solvents, I blame my lecturers for hyping up the exploding lab. Even though that is an actual thing that realy does happen, Thoisoi2 burned
down his lab last year. So, maybe I'm realistic and not neurotic?
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Texium
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I would go with "overly cautious." Good that you have stabilized THF though. It's fine as-is for most uses. If you're running a reaction that BHT
would interfere with, you can distill it before using.
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dicyanin
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I concur that BHT is the best option. It is also available for cheap through DIY cosmetics suppliers, and a little goes a long way. It even allows
commerce in diisopropyl ether, which is notorious for easy peroxide formation.
Hydroquinone is the next best choice, but BHT is best.
sic transit gloria mundi
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ChemichaelRXN
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Extending Storage of Peroxide Former Solvents
Hello,
We all know to test if you dont wait too long to open the cap and if there isn't visible crystals to use a test strip, but what do you use to extend
the life of your solvents you store beyond the recommended period of time if you have expertise to circumvent the peroxide formation?
I know some can add a layer of 5% sodium bisulphite or the metabisulphite or ferrous sulfate. I also seem some people use copper or sodium hydroxide.
How long do you get away with storage?
I also add the containers to a bucket where all oxygen is replaced with nitrogen or argon, but I do not keep more than a year as recommended.
Have you ever seen your solvents form crystals around the lid?
Also if you see the smallest amount of sedement/crystals (almost not noticeable) and unopened, in store bought dioxane when you get it, I am already
not sure of opening the lid, which is a shame. Is this too cautious and should toss it?
You are the same perception looking out, from the same elements around the universe.
You are everything to be anything to begin with.
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BromicAcid
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If the bottle never sees oxygen, i.e., you do your transfers by needle transfer and nitrogen then it can never form peroxides. If you're putting
these in containers that are interted it seems like you have that capability.
Back when I did hazardous waste disposal we had contracts with several schools. Those ether bottles saw all kinds of grief and they usually just
disposed of them after a set time. Standard procedure for an ether can was to flip it upside down, punch a hole in the bottom and dump it into the
flammable liquids. The thought process is that dry crystals at the top could cause an explosion but any crystals at the bottom would be wetted under
solvent. I had just dumped out a can of ether into the flammable solvents and tossed it into the waste metal and there was a loud pop and the can
went flying away, apparently there were some crystals somewhere and the can falling caused them to go off. That's my only experience with peroxide
crystals.
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Texium
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Threads Merged
3-3-2024 at 07:14 |
Texium
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Please search before starting new threads. This was discussed just a couple weeks ago in Responsible Practices (now merged). See my post above about
using BHT. It’s much more effective than a bisulfite or iron solution since it’s miscible and doesn’t get your ether wet.
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Texium
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Quote: Originally posted by BromicAcid  | | If the bottle never sees oxygen, i.e., you do your transfers by needle transfer and nitrogen then it can never form peroxides.
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Under the assumption that the company you bought it from has halfway decent quality assurance. A few months
ago at work, I found that our septum sealed bottles of anhydrous THF from Acros/Fisher, including one that we had just received and hadn’t used yet,
contained peroxides and were wetter than the stuff in an unsealed bottle. This turned out to be responsible for many of my reactions not working and
probably set me back in my research by several months. Since then, I’ve been using a good old fashioned sodium-benzophenone THF still and my
reactions have been working beautifully.
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