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Topic: SmI2 reaction  (Read 15749 times)

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Offline Ψ×Ψ

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Re: SmI2 reaction
« Reply #15 on: December 03, 2006, 02:04:28 PM »
I havent tried this reaction, but if you dont want to change extraction-solvent (you might check up your product-solubility in Handbook), try to add a little toluene to the ethylacetate. It works very well while working on diethylether/water extraction and the phases mixes into an emulsion. If toluene is miscible with ethylacetate (I believe it is), it might work here as well. Correctly in the diethylether/toluene system, you actually get a new emulsion in the organic phase, which drastically changes the density of the organic layer.

Thanks for the tip!  As much as I hate toluene, I hate emulsions more, so I'll end up using it sometime.  :)

Offline Dan

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Re: SmI2 reaction
« Reply #16 on: December 03, 2006, 06:17:34 PM »
Oh, I've had this problem before. I was doing a water/DCM extraction in the workup of a methyl addition with MeMgBr. I did the reaction in THF too, the THF seems to be miscible in water and DCM, so you get a water layer, emulsion layer and a DCM layer.
Adding a bit of ethanol helps a bit, taking off the THF under vacuum before the seperation helps (but I quenched with water so this took ages).
The best way round it for me was to simply use a bigger seperating funnel and loads of DCM compared to water. You could try DCM in place of EtOAc maybe.
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Offline movies

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Re: SmI2 reaction
« Reply #17 on: December 04, 2006, 01:14:13 AM »
I like to use Et2O in the workup for reactions that use THF because it is so easy to get rid of.  Also, molecules soluble in THF are often soluble in diethyl ether too.  DCM is my next choice if you need a more polar solvent, but the density switch isn't always easy to deal with.  Moreover, emulsions of DCM and water are the worst!!

Offline Dan

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Re: SmI2 reaction
« Reply #18 on: December 04, 2006, 04:27:05 AM »
I like the denisity. I find it much less hassle to collect the bottom layer from a seperating funnel, it tends to get less water in it. My supervisor has banned diethyl ether, due to it's flammability, and he hates the smell. We use tert-butyl methyl ether, which smells like sweets.
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Offline Ψ×Ψ

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Re: SmI2 reaction
« Reply #19 on: December 04, 2006, 08:18:14 AM »
My supervisor has banned diethyl ether, due to it's flammability, and he hates the smell. We use tert-butyl methyl ether, which smells like sweets.
Diethyl ether is my solvent of choice whenever I can get away with it.  It smells wonderful, it doesn't melt my gloves (thankya DCM, chloroform, toluene...) and any morning that starts with an ether extraction just makes the rest of the day better.
What about the groundwater contamination with MTBE (underground storage tanks)?  It isn't more expensive to dispose of the waste?

Offline movies

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Re: SmI2 reaction
« Reply #20 on: December 04, 2006, 12:54:45 PM »
I agree, isn't TBME worse than Et2O?  It's less flammable, but much higher boiling (harder to get rid of) and pretty toxic too, I think.  But I suppose if you chose dichloromethane, then you aren't so worried about the toxicity anyway.  TBME must be a lot more expensive though, isn't it?

Offline Dan

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Re: SmI2 reaction
« Reply #21 on: December 04, 2006, 02:21:19 PM »
Yeah I think TBME is more toxic, but the decision to use that over diethyl ether was not mine, I don't pay the bills, but I don't think the price difference is massive (I had a quick poke around on sigma-aldrich). Our solvent storage tanks are above ground, I have no idea of the disposal costs, it goes into the non-chlorinated waste tank with all the rest of them, and the department takes it from there. A significant proportion of the chemistry we do in our group is aqueous, so this cuts down overall toxic solvent use - although I'm not trying to use this as an excuse, I'm following workup procedures developed by the group and from papers that is my reason for using the solvents I use.
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Re: SmI2 reaction
« Reply #22 on: December 05, 2006, 01:24:14 PM »
I'm not telling you you're wrong!  Please don't misinterpret what I said.  I would make a different decision, but of course your boss is the only one that has that privelege.

I'm sure they just take all the non-chlorinated solvents and burn them.  The safety difference is that ether, with a higher vapor pressure, has a higher possibility of explosion, but TBME is going to be worse if it gets spilled and gets into the ground water somehow.  It's a judgement call.  In our lab, ether is definitely much more common than TBME!

I have always wondered if aqueous chemistry is really that much safer because the disposal is so unregulated.  It seems that traces of organic or organometallic species in aqueous phases is potentially more dangerous to the community than the controlled disposal of organics.  Do you know anything about that?  I might be totally off base.

Offline taurean

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Re: SmI2 reaction
« Reply #23 on: December 05, 2006, 06:37:34 PM »
Sorry for digressing from your discussion. 

The combination of diethylether and ethyl acetate worked best for my reaction.

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