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Author: Subject: Is inert gas mandatory for handling DIBAL?
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[*] posted on 4-1-2017 at 16:00
Is inert gas mandatory for handling DIBAL?


I want to perform a reduction with Diisobutylaluminium hydride (DIBAL), where 1mol of it is solved in 100mL of toluene. On the package it is written, that it should be handled under inert gas, but I have none of it available right now and since the reaction is on a small scale, I don´t want to put a lot of effort in maintaining an inert gas system, if it´s not really necessary...

So, has anyone experience with DIBAL and knows, if an inert system is that important? If I loose a bit of DIBAL due to exposure to air it´s no big deal, but if it ignites, it could be a problem...

I thought that I set up a 2-neck flask with a reflux column on it and seal the other neck with a rubber stopper. Then I dissolve the chemical, that I want to reduce in dry toluene and put it in the flask. I wait till the toluene vapors fill the flask/column and then add with a syringe the DIBAL through the rubber stopper. This should work, or not?
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Dan Vizine
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[*] posted on 4-1-2017 at 16:46


If it behaves like Red-Al, you can get away with it. Personally, I'd try it.

I'd estimate that the chance of ignition is just about nil.





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AvBaeyer
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[*] posted on 4-1-2017 at 19:34


I have used a lot of DIBAL in years past. If at all possible you should use an inert atmosphere. Any well equipped organic lab where DIBAL or similar reagent might be used should have at least a nitrogen line. If you are skilled and careful with your syringe work however you should be able to do a small scale transfer on the odrer of a few mil's. You are somewhat "protected" by having the DIBAL in toluene rather than a more volatile solvent. Just make sure that there is no residual drop on the end of your transfer needle. When exposed to air DIBAL will smoke and pop and can set fire to any spillage. Good luck.

AvB

Edit: It is much more dangerous to handle than Red-Al.

[Edited on 5-1-2017 by AvBaeyer]
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PirateDocBrown
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[*] posted on 5-1-2017 at 00:19


Setting up a low-budget N2 line isn't terribly hard.

Many welding gas suppliers will sell N2 in small containers, even lecture bottles.

Get a simple regulator (they can often be found used), and run a tube from the cylinder to a drying trap. (A small filter flask with a glass tube in a stopper, filled with CaCl2, would work.)

From there, a tube with a Luer needle on the end.

Use reaction flasks with septa, a disposable needle for vent, and your dry N2 line in. Blow out your air, sparge your reactants, then do your transfer with a needled syringe.

I did most of my syntheses in grad school with just such an arrangement.
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DDTea
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[*] posted on 6-1-2017 at 15:50


Non-pyrophoric limit for DIBAL-H is 20% in solvent. 1 mol/100 mL toluene = approximately 60 wt%. This solution is pyrophoric as hell. You definitely want to keep this under inert gas.

https://www.akzonobel.com/polymer/system/images/akzonobel_di...




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Dan Vizine
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[*] posted on 6-1-2017 at 18:12


I think that his proposed method, if executed well, will exclude air sufficiently well. Only one way to find out. That's what scouting runs are for.

[Edited on 7-1-2017 by Dan Vizine]





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