Lillica
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Question about preparing organophosphines - alkylation with PCl5 vs PCl3
I've been reading some papers about preparing organophosphines by alkylating enolates with PCl3. From what I've read, PCl3 sounds scary toxic, and
PCl5 seeming more easy to handle. I'm no expert on phosphorous chemistry, but would I be able to alkylate an enolate with PCl5 and then hydrogenate
the additional chlorine away, similar to how I would be able to with PCl3? Question being would PCl3 behave in a similar manner as PCl5 for this
purpose?
Additionally I've read that PCl3 can be converted to a monoamide which can undergo alkylation. This may be a better route but I need to find more
information on it.
[Edited on 3-3-2017 by Lillica]
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DraconicAcid
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If you alkylated PCl5, you'd probably immediately get reductive elimination to give RCl and PCl3. What makes you say that PCl5 is easier to handle
than PCl3? I know PCl3 is nasty, but I'd just expect PCl5 to be even worse.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Lillica
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Isn't PCl5 a solid whereas PCl3 is a volatile liquid? The main reason I fear PCl3 is because wikipedia says 600pm is lethal in just a few minutes,
which I'm guessing is has to do with the fumes. I'm even paranoid about using it with a fume hood since my fume hood doesn't vent outside.
I wonder how the toxicity of PBr3 compares to PCl3.
[Edited on 3-3-2017 by Lillica]
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Texium
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Thread Moved
3-3-2017 at 15:14 |
JJay
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That's not all that much worse than chlorine gas or even hydrochloric acid. Hanging out around toxic levels of PCl3 is extremely
unpleasant. I wouldn't suggest handling it in a fume hood that doesn't vent outside; if you accidentally flash-boil 10 mL of it into the room, you'll
definitely wish you hadn't.
Phosphine is an order of magnitude more dangerous than phosphorus trichloride, and producing any in a fume hood that doesn't vent outside borders on
suicidal.
Edit: I see you updated your post to include a question about PBr3 toxicity. PBr3 is fairly popular among hobbyists, and making
it is straightforward if you have phosphorus and bromine. You could probably get away with making it using matchbook striker composition as long as it
didn't contain any sulfur.
Post pictures.
[Edited on 3-3-2017 by JJay]
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Texium
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I haven't worked with PCl3 or PCl5 before, but PBr3 is fairly easy to work with. It fumes in humid air but it's not
very volatile so toxicity isn't really a concern, as the fumes coming off are just P2O5 and HBr. Still have good ventilation, of
course.
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