ORGLIST: Removing excess Triphosgene

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From: Kamal (mailbox$##$invalid)
Date: Wed Aug 31 2005 - 09:42:12 EDT

Hi to all my orglist friends !

I'm still struggling with my developement of an aliphatic Isocyanate. =
(Sorry to Yuehui & Lakshmipathiji, again disturbing you !!)

As per the advice given to me by you, I performed procedure of ORGANIC =
SYNTHESIS by using Amine HCl, Triphosgene, Dichloromethane & aq. =
bicarbonate. The reaction goes so well but I'm feeling difficulties in =
removing the excess triphosgene after completion of reaction.

I used eq. of triphosgene in different =
experiments & all give almost similar results. In all of them, excess =
triphosgene remains in the organic layer & generates a lot of amount of =
acidic solids. It still remains in the distilled isocyanate also ! If I =
use lower ratio of triphosgene (0.33 eq. or less), then some Amine HCl =
remains unconverted & it makes other urea/hydantoin based impurities in =
significant amounts !

Is it possible to remove this excess triphosgene ?

Pls...................give some advice to me.

Thanking you,

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