Hello everyone,
first post here, hope this is the right place.
I am performing a reaction with AlCl3 in DCM as my solvent.
My reaction and quenching setup works totally fine. I have a >95% purity after the step of water washing.
The problem I see is, that once I start to boil off my DCM at ambient pressure, I see a slow second order reaction occurring, which starts to degrade
my product.
Before I reach the boiling point of my crude oil, I already lost most of my product. This second order reaction needs a lewis acid to be present.
I never worked with DCM in the past and I therefore asked myself if DCM can act as a lewis acid itself?
In this case boiling off the solvent under reduced pressure and the addition of another solvent (hexane, toluene,…) with a higher boiling point
could help to get rid of any residual DCM in my crude oil?
Can anybody confirm this theory? Otherwise I need to reevaluate my whole process.
Thank you very much!
Boffis - 20-12-2022 at 01:15
If you have washed the reaction mixture with water then the AlCl3 will have hydrolysed and perform no further function. Its difficult to give a more
precise answer unless you are going to give us a more detailed description of the procedure as you performed it and a reference to the original
procedure that you are following.blogfast25 - 20-12-2022 at 13:26
MeCl2 is not an electron pair acceptor, so I can't see it functioning as a Lewis acid.
[Edited on 20-12-2022 by blogfast25]CharlieA - 20-12-2022 at 14:46
MeCl2 is not an electron pair acceptor, so I can't see it functioning as a Lewis acid.
[Edited on 20-12-2022 by blogfast25]
I second the motion.clearly_not_atara - 20-12-2022 at 17:33
You have AlCl3 in your system. So there's obviously a Lewis acid present! But maybe you meant to say "electrophile"? CH2Cl2 can act as an
electrophile, but it's activity is low due to symmetry. blogfast25 - 21-12-2022 at 08:22
I am performing a reaction with AlCl3 in DCM as my solvent.
My reaction and quenching setup works totally fine. I have a >95% purity after the step of water washing.
There can't be much AlCl3 left after the wash with water. That's why he's looking for another Lewis acid...Dr.Bob - 21-12-2022 at 10:46
Maybe you are generating HCl or some other byproduct from the workup. Hard to know without details. DCM is not going to be unstable to most
things, but can hold HCl well, so if you make the reaction acidic and then concentrate, the HCl can become quite strong.Triflic Acid - 21-12-2022 at 18:35
Try a bicarb wash of the DCM layer after the water quench, it would get rid of any of the HCl that Dr. Bob mentioned. I'd stir strongly with bicarb
for like 15 minutes to be super sure, then it should be fine to rotovap down. Otherwise, it might be from oxygen oxidizing your product, so doing an
inert atmosphere distillation might be better than rotovaping.
