Re: ORGLIST: Isocyanate purification

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From: Sengen Sun (sengensun$##$yahoo.com)
Date: Tue Mar 29 2005 - 12:41:27 EST


Isocyanate is hydrolyzed in the presence of moisture
or water to give amine, which reacts with another
molecule of isocyanate to give urea. That may be why
your compound becomes more and more turbid on
standing.

It is very hard to purify once urea is formed. I would
try everything to make sure that isocyanates are made
and handled under anhydrous conditions.


Sengen

 
--- mailbox <mailbox$##$invalid> wrote:
> Hello Friends !
>
> I had got good advices from some friends thro' this
> site regarding to my reaction of producing
> Isocyanate from an Amine HCl. But I'm finally
> getting difficulties in purifying this Isocyanate.
> As per the final GC, Isocyanate comes as 94-95%
> maximum alongwith 4-5% peak of some impurity before
> the main peak (comes as lower boiler). This impurity
> comes as cloudy solid & extends more slowly making
> the isocyanate more & more turbid on standing.
>
> Can anyone pls suggest me how I can remove this
> impurity & purify my isocyanate ?? However, I had
> got one reference according to which, "Do the
> distillation with column (fractional) distillation
> with shorter time". (Actually, how it can be
> performed practically ? Because if the column is
> there, then travelling time for vapor would be
> obviously longer !! )
>
> By the way, I had performed this reaction in MDC &
> aq. bicarbonate media in biphasic mode with
> triphosgene.
>
> I will be anxiously awaiting your kind advices.
>
> Pls help me.
>
>
>
>
> Thanking you in advance,
> KAMAL
> (mailbox$##$invalid)
> > _______________________________________________
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