From: AnGio' (giordano$##$nserv.icmat.mlib.cnr.it)
Date: Fri Jun 11 1999 - 04:47:14 EDT
dear sirs,
i would like to thank in advance anyone who replied to my post...
To be more precise, i need to synthesize cloro-nitroso diethylmalonate from
diethylmalonate. For the sake of brevity, i also say that i need to work
with low quantities and NaNo2 must be the limitating reagent...
Right now i succeded in making diethylmalonate oxime, i.e.
isonitrosomalonate, which on the "handbook" is reported as "malonic acid,
oxo-diethyl ester, oxime".
This must be treated afterwards with Cl2, i presume pure to obtain a good
result, even if i think that unreacted diethyl malonate would be just a
nuissance and not prejudicate the second reaction to a high extent (???) In
such acidic and exotermic environment, i guess hydrolysis of diethyl
malonate must be expected, what do you think?
In my working conditions, is obvious that the first product is a mixture of
diethylmalonate and the corrisponding oxime (a bit surprisingly, i have the
same result starting with an excess of NaNo2 of 3 eq, even if i took care
about low temperatures...but my products are not very new, and i am
planning to repeat the whole operation with fresh ones...).
In the meantime, i performed a basic-acid extraction in order to separate
at best the mixture: if the mixture (less than 3 cc) if first dissolved in
ether, say 15 cc, treated with NaOH acq and extract quickly with 3 x 5 cc
of water, the anion of the oxime goes in water, resulting in a bright
yellow solution, the colour very probably due to the high coniugated
structure of the product. If now i treat with HCl acq (the solution turns
back colourless forming an emulsion) and repeat the extraction with fresh
Et2O, the protonated oxime is finally extracted. However, a couple of TLC
showed me that separation is good, but not perfect...
At 00.00 10/06/99 +0100, Jacob Zabicky wrote:
>Come to think about it, what's wrong with good-old low-pressure
>distillation? With the stuff in hand there should be no difficulty in
>getting a good boiling mixture well below 100 deg C at a couple of torrs.
(...)
In fact i thought about it...there's only a question...my protocol for the
oxime says that it must be kept at -18°C (!) ...So i don't know if it
suffers even medium boiling temp. ...
...to be continued :-)
Andrea.
p.s: by the way, i think i heard that nitrosation in the presence of a
catalyst such as Cl- Br- and others, with an excess of the carbonyl comp
of interest, are pratically quantitative toward the [NO2] specie...do you
know more about it? Thanks...
*********************************************************************
Andrea Giordano OS/2 is a flame...WIN is a shame !
c/o Ist. Chimica Nucleare >> by an OS/2 user <<
Consiglio Nazionale Ricerche Richiedete all'autore la FAQ
Montelibretti (Roma) - Italia "NewsGroup Tesi di Laurea"
tel. ICN: 06 - 90672-510/516
fax. ICN: 06 - 90672512
tel. alloggio: 06 - 90672420
*********************************************************************
__________________
ORGLIST - Organic Chemistry Mailing List
Website and Archive: http://www.orglist.net/
List coordinator: Joao Aires de Sousa (jas$##$mail.fct.unl.pt)
This archive was generated by hypermail 2.1.4 : Fri Sep 19 2003 - 12:15:04 EDT