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Author: Subject: Do I really need to dry every chemical for a grignard reaction, even if it's new in a bottle from a chemical supplier?
Cou
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[*] posted on 25-7-2020 at 13:27
Do I really need to dry every chemical for a grignard reaction, even if it's new in a bottle from a chemical supplier?


I might be lazy, but I don't want to go thru the effort of drying and distilling everything.

The diethyl ether I have is new from chemsavers, ACS grade 99%+ anhydrous. Do I really need to set up a benzophenone sodium ketyl still?
Ethyl formate is new. Magnesium is new. The only thing I would expect to dry is the alkyl halide that I make myself.

For my first grignard reaction I'm hoping to react 2 equivalents of 1-bromoheptane with ethyl formate to get pentadecan-8-ol.

[Edited on 7-25-2020 by Cou]




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Tsjerk
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[*] posted on 25-7-2020 at 13:36


You could throw in some sieves in every bottle, but it is probably not really necessary. Especially when the ether is sold as anhydrous it should be fine.

The drier the better, but even if the Grignard doesn't start you could use a pinch of iodine or some short alkyl bromide to get it started. After that the only thing water will do is lower the yield.

[Edited on 25-7-2020 by Tsjerk]
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karlos³
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[*] posted on 25-7-2020 at 13:42


You have an ultrasound device?
Because then it will be successfull even with less than thorough drying.

And you can simply seat the ether over NaOH or KOH for a month and then decant and distill and the stuff will be dry as fuck(ouch! not a literal fuck of course, lube is your friend :P).

[Edited on 25-7-2020 by karlos³]

[Edited on 25-7-2020 by karlos³]
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j_sum1
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[*] posted on 25-7-2020 at 14:19


Chemplayer did a video experimenting with just how much water you can get away with in a Grignard. (Quite a bit.)
But if you are just learning then why not err on the safe side?
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[*] posted on 9-8-2020 at 21:43


Never had a problem with virgin ether. Recycled ether often requires drying. As in, lots of drying.
May contain a surprising amount of water.
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draculic acid69
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[*] posted on 9-8-2020 at 23:09


I have some sieves on the way for this exact reason.id recommend at least testing for water before trying an anhydrous reaction if u desire a result.just bcoz it says anhydrous doesn't mean by the time u get it store it and go to use it it's still anhydrous.lots of ppl have stories about the dry ether or thf turning out to not be that dry
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