Chris The Great
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Methylphosphonates and derivatives
Got a request for the full copy of The Preparation and Physical Properties of Isopropyl Methylphosphonofluoridate (Sarin), P. J. R. Bryant,
A. H. Ford-Moore, B. J. Perry, A. W. H. Wardrop and T. F. Watkins, J. Of The Chemical Society, 1960, page 1553.
Which I guess is understandable, the only reference I've seen to it online was vague and incorrect and took lots of flipping through old J.O.C. paper
journals...
Well here it is!
EbC: Changed title.
[Edited on 8-2-2007 by chemoleo]
Attachment: The Preparation and Physical Properties of Isopropyl Methylphosphonofluoridate.pdf (144kB)
This file has been downloaded 2143 times
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garage chemist
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Thank you, Chris! This is for a member of the german forum who does not post at Sciencemadness.
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Sauron
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That's a nice reference to have but not the most convenient way to prepare this OPA and hasn't been since the 50s.
The PCl3->P(OR)s->MeP(OR)2 sequence followed by any of several steps depending on which esters you have, to get to chlorosarin and ginally sarin, has
been superceded by the reparation of dichlor (DC) and its conversion to difluor (DF) as follows:
PCl3 + AlCl3 + MeCl -> {stable solid complex]
Hydrolysis yields DC. MeP(=O)Cl2
Alcoholysis as alternative yields MeP(=O)(OR)2
DC can undergo F exchange to DF
DF is half of a Sarin binary, other half is trivial.
The alkylphosphonyl diester can be partially chlorinated then fluorinated to sarin, which is precisely what the JCS sequence ends with.
The differences are:
-- No trialkyl phosphite required
-- no iodomethane required
-- No phosgene required (if you hydrolyze the cimplex)
Instead of the latter, MeCl is employed which can be from a cylinder or, prepared from methaol and (most conveniently) cyanuric chloride.
Altogether much less muss fuss and bother.
DC and DF are the key intermediates not only to GB (sarin) but to GD soman, GF cyclosarin, etc.
You still need PCl3 which is of course why it is restricted. Still with a little ingenuity...the really tricky part is not dying once you succeed in
making the stuff. Even DC and MeP(=O)(OR)2 are potent AChE inhibitors, DC and DF are corrosive as well.
After studying the low level effects (never mind the acute effects) of OPAs, anyone arrogant and selfdestructive enough to make these, deserves what
he gets.
The rest of the British sequence can be found in great detail in Org.Syn. if you search for triethyl phosphite and di-isopropyl methylphosphonate.
Some of the same authors as above, all of who were associated with the Saunders group.
[Edited on 5-2-2007 by Sauron]
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garage chemist
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I did not know that dimethyl methylphosphonate itself is already an AChE inhibitor. Do you know how toxic it is in relation to, say, DFP?
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Sauron
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No but you can probably get that from Sax, RTECS, or maybe Ellison's Handbook (available on MadHatter).
If you dig up Scharder's monograph (also on MadHatter) you will see what I am talking about.
The insecticide OMPA pointed the way to GA tabun.
Whereas the insecticide TEPP pointed the way to the others along with DFP.
The precursor chlorosarin is a potent AChE inhibitor, it just is not as potent as sarin itself.
It is a serious error to think that the stuff is benign till you put on the F.
Not so.
I would guess that already at the diester stage you will be dealing with something comparable to malathion or parathion.
But by all means quantify that from the standard refs cited above.
The trialkyl phosphites are pretty toxic already as alkylating agents, trimethyl phosphite the worst. In same class as iodomethane and dimethyl
sulfate.
Dichlor is nasty, difluor nastier. Fuming and corrosive as well as AChE inhibitors.
A careful study of Saunders' book is advised.
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kmno4
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Very interesting topic.
But could you build it up elsewhere, in more appropriate section ?
[Edited on 6-2-2007 by kmno4]
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Sauron
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Fine with me, if a moderator wants to move this to Organic Chemistry from 3rd post on down.
EbC: Moved it all and changed title.
[Edited on 8-2-2007 by chemoleo]
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Chris The Great
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It depends. That older method is a lot easier in a lab imo.
If only for the sheer fact anhydrous HF gas is not used. Mostly it's handling issues- method A has easier to handle nasties than method B.
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Sauron
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You like using phosgene better than using AHF?
Anyway AHF is only one method of converting DC to DF. The technology og these compounds is now very mature (70 years) and has been the subject of a
lot of work. It can't be encapsulated in two procedures.
Besides even if you don't research the lit any further you can combine the two methods to avoid using AHF.
1. Use procedure two to make the complex.
2. Alcoholyze to diester. Obviously use anhydrous 2-propanol.
3. Then proceed as in Procedure 1 from diester to chlorosarin to sarin.
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