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Author: Subject: formation of grignard reagents in DIPE
karlos³
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[*] posted on 27-8-2021 at 13:56
formation of grignard reagents in DIPE


As the title say, I researched that topic but the results seem inconclusive.
From being sterically hindered and thus forming at a lower rate, to not suited at all.

What I would like to know, can I form e.g. ethylmagnesium iodide in diisopropyl ether, has anyone experience in making grignard reagents in this?
I'm just after aliphatic grignard reagents, so theres that as a likely advantage.

Guess if nobody has any advice, I'm just going to try to whip up some n-BuMgCl over the weekend and will update, hopefully making some 1-phenylpentanol(fenipentol).

Would be great if it works, I couldn't really find much about it somehow.
And no definite reason for it.
Yes we know all about the peroxides, but the peroxides of THF if allowed to form are of a similar danger(and yet, you've seen what Nicodem said about DIPE's dangers, massively exaggerated according to him), so could it simply be that the only reason is that its more expensive and less often used?

I've recently discovered that even 2-Me THF is suitable for the formation of grignard reagents, so what, if anything, speaks against using DIPE?
Is there simply no reason because diethylether is ubiquitous normally and DIPE is used for more important purposes?
Maybe I should keep it for more important purposes too?
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zed
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[*] posted on 27-8-2021 at 16:56


Ummm. Should work. But, some companies are promoting di-n-butyl ether as a Grignard solvent. They claim it works well, is less hazardous, and has a conveniently higher BP than Diethyl-Ether. I might surmise, that you have the "makings".

I don't know how difficult forming a Grignard in Di-iso-propyl is. But, it sounds familiar.

Seems like I recall forming a Grignard in Di-ethyl ether, then displacing the Diethyl Ether with Anisole, to form an Anisole Grignard.

Also seem to recall Grignards utilizing tertiary amines, rather than ethers.

I've always been warned against the perils of working with di-iso-propyl ether, so.... It wouldn't be my personal first choice.

https://www.chemoxy.com/wp-content/uploads/2018/01/Technical...

[Edited on 28-8-2021 by zed]
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draculic acid69
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[*] posted on 28-8-2021 at 01:00


I looked into it and apparently it's a no go. But that's just something I read somewhere and I can't remember if it was an opinion or scientific fact so I think it is up to you to try it if U have dipe to get us all a definitive answer.
Now I think about it I asked also about MTBE as grignard solvent as well
and I think that one was a definite no won't work.


[Edited on 28-8-2021 by draculic acid69]

[Edited on 28-8-2021 by draculic acid69]
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[*] posted on 28-8-2021 at 06:52


The discussion about it here
http://www.sciencemadness.org/talk/viewthread.php?tid=11151
didn't seem to lead to any positive outcome.
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karlos³
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[*] posted on 28-8-2021 at 12:09


Thanks for the replies guys.

Yes unionised, thats the thread I called inconclusive.
We'll see however, I am just drying the mol sieves in the oven, and consequently some DIPE, and fingers crossed.

If it fails however, at least we know absolutely for sure, no?

zed, thank you, yeah, n-dibutylether/n-Bu2O was an alternative(I had to buy some solvents, and couldn't afford additionally a liter of THF, since it was not available in smaller quantities), but too high boiling.

draculic acid, but as soon as the grignard reagent is formed(or when it comes readily from a bottle), you can actually use a magnitude of different solvents, and MTBE is among them as suitable.
It mostly only matters for the formation of the grignard reagent.

Well, we'll see, wish me luck guys and cross me some fingers please :)
Experiment is king and I'm ready to waste some reagents for this :D
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karlos³
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[*] posted on 29-8-2021 at 04:29


Nope, nothing.
Not even after adding 2/3rd of the haloalkane and applying moderate heat.
Of couse I used molsieves to dry and a few iodine crystals.

If that would have been THF or Et2O, it would have been at a rolling boil :o

Great, now we know at least for sure.
Guess I'm going to get a bottle of THF instead.
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karlos³
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[*] posted on 31-8-2021 at 09:02


Ok, its two days later, and my hope on reusing the little bit of magnesium are gone too.
The iodine has reacted with it, leaving a little crust of one magnesium iodide, and blank Mg below it.
No further reaction has taken place, if the grignard reagent could have formed, it would have by now.
Still have to quench it "as if", I guess... and watch my good grignard Mg go to waste now that its activated :(




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zed
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[*] posted on 31-8-2021 at 21:16


So, you weren't able to start a Grignard in Di-isopropyl Ether. Rats!
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[*] posted on 3-9-2021 at 03:28


I'm guessing di n propyl ether would be a go seeing as how di n bu2o works
but seeing as how isopropyl OH is a million times more common than n propyl alcohol
the rarity of n propyl ether is going to be a factor
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karlos³
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[*] posted on 3-9-2021 at 04:22


Yeah well, its not like I had to use DIPE(well, in terms of what I had on hand, that was true at that point), I just had to pick an ether based on versatility.
Wanted something that can be used for the grignard AND as extraction solvent, and THF is only good for one of those....
Well, but it turned out that DIPE is also only good for one of those....

I should have fixed my printer, and simply printed the necessary declaration and simply should have bought diethyl ether.
Because that stuff actually does both jobs pretty well.

But for now I already purchased new THF, and can simply use DCM to extract the grignard's, thats almost as good..




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[*] posted on 15-9-2021 at 07:29


I remember an article by Henry Gilman who studied Grignards extensively and compiled a list of various Grignards prepared in different ethers. As I remember DIPE was a picky ether to work with because in several cases did not formed the expected Grignard-reagent but acted as a reducing agent instead (similar to the Al-isopropoxide reduction of ketones).
Diethylether or dinbutylether was much more reliable, with varying degrees of suitability (yield) depending on the used halogenide.

As I try to remember the article it MIGHT be in that organic chemistry series that was edited by Roger Adams and had 6 or 7 volumes, with 5-10 different chapters in each... I can't remember the title of this series but you surely know. It is a sort of preparative org.chem Bible. :)
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