chemrox
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Lithium bis (trimethylsilyl) amide, nomenclature and safety
I almost see why this is an amide but would really like someone who works with silyls to walk me through it, thanks. The cautions on working with the
stuff are quite harsh. Could one work with it in the hood and thereby avoid having to use a full face respirator? I have a strong fan.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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DraconicAcid
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I don't work with silanes, but I can walk you through the nomenclature.
If you take a hydrogen ion (H+) off of ammonia, you get the amide ion (NH2-).
If you take a hydrogen off of an amine, you get a generic amide ion (not to be confused with the neutral organic molecules called amides). The name
of this anion will be the name of the amine, with the "n" simply changed to "d".
So, deprotonating methylamine would give you methylamide ion and deprotonating diphenylamine would give you diphenylamide ion.
The amine that was deprotonated to give lithium bis(trimethylsilyl)amide was bis(trimethylsilyl)amine. This is a nitrogen with one hydrogen and two
trimethylsilyl groups.
Silyl is the silicon analogue of methyl (-SiH3). Replace all those hydrogens with methyl groups, and you have trimethylsilyl (-Si(CH3)3).
Since you have two of these, we have to indicate that in the name, but we can't use the di- prefix, as there is a "tri" in the name of the
substituent. Instead, we use the more complex set of prefixes (bis, tris, tetrakis, etckis), and put the name of the substituent in brackets (so that
we all know that the prefix refers to the whole group, and can tell exactly where that substituent begins and ends).
Does that help?
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chemrox
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Ahh. thanks. That's embarrassingly simple but thanks again, I just didn't see it last night. The bigger question for me is the safety angle. I'm
considering buying it from Aldrich I don't have a full face respirator though. I can get one easily enough. I use a shield with a nose and mouth
respirator from time to time but the combination is awkward and leaves gaps. If I could do the decanting and mixing in the hood it would be easier.
Maybe behind the partially closed door to protect the eyes and the smaller respirator to protect throat and lung. If no one here really has
experience I will call Aldrich to discuss before purchase.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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kristofvagyok
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Quote: Originally posted by chemrox  | | The cautions on working with the stuff are quite harsh. Could one work with it in the hood and thereby avoid having to use a full face respirator? I
have a strong fan. |
It's aint that dangeorous. When working with it, measure from the solution with a glass syringe and work under argon, it could be easily used in a
hood, if you don't make mess, it won't cause problems.
A full face respirator is for dangerous things, not for this. Use a face shield and be smart 
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DraconicAcid
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I can't offer you much help with the safety, apart from that any time I've used any of these Li-R type bases (where R is alkyl, amide, acetylide,
etc), I've used the pre-made solutions from Aldrich, rather than trying to weigh out solids. That way, they're only a little bit more dangerous than
the solvent it's in. Run some nitrogen through the bottle, and take out what you need with a syringe. (Aeser has it listed as a solution in hexane.
Fume hood will be fine, as long as you don't let air or water into the bottle. And don't spill it on yourself.)
(Sorry Kristof- I got distracted while typing this up.)
[Edited on 4-2-2013 by DraconicAcid]
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