08-09-03 12:04
No 452596
there's this very dirty MMDP2P sample (5g distilled through 29 gear, go figure),
which melts at about 0° (lit.: 54-55°,iirc), and it wants to be recrystallised.
does someone know by chance a good solvent for this? the only post i've found was:
Post 17682 (Osmium: "Re: Asarone and Performic", Chemistry Discourse),
but i don't like the dry ice part
alkane solvent means something like pet. ether, right?my first try would be 93% EtOH, but i fear that the solubility is too good.
ps: MMDA is weird stuff...
(Active Asperger Archivist)
08-09-03 21:46
No 452652
http://ptcl.chem.ox.ac.uk/MSDS/DI/1%2C2-
dichloroethane MP: -35*C.
Probably use it for recrystallization- just use a minimum amount of solvent. salt and ice water bath.
Why don't you just vac. frac. distill?
Act quickly or not at all.
(Hive Bee)
08-10-03 02:08
No 452676
An alkane solvent may be a good choice. I admit it didn't work perfectly for me, but my sample of MDP1P was rather strange smelling and distinctly (actually bright) orange...
I did notice however that it was far more soluble in hot cyclohexane than at room temperature. The use of this solvent was based on a few articles I've seen where P1Ps are recrystallised from hydrocarbon solvents, and I suspect P2Ps and P1Ps have similar solubilities in similar solvents. If you have pet. ether that should do just as well.
Just don't try acetone, like only a complete fool would (did).
(Stranger)
08-10-03 04:57
No 452693
I'd stay away from EtOH for sure. First choice would be hexane for me. I never did it with your compund but similar ones worked well with hexane. Abs IPA might work OK too, try a tiny test first though to make sure not much dissoves at room temp after stirring for at least 30 min or so.
(Hive Addict)
08-10-03 10:07
No 452748
thanks for the good advice.
> Why don't you just vac. frac. distill?
because only 29 gear is available and the pump is too weak. (ketone at 180-185°)
(Chief Bee)
08-12-03 22:37
No 453168
I'd definitely go for pentane, hexane or pet ether. Add some THF if the solubility is too low below zero. Works wonders for the related alkenes.
(Hive Addict)
08-19-03 17:28
No 454534
this _is_ the wondercure! the alkane solvent used was commercial
benzine (_not_ benzene), which can be had in pharmacies. by cooling
in a freezer, white crystalls melting at 44.5-45° where obtained.
question: what is the standard procedure to obtain further fractions,
when working with a dual solvent system? i fear that distilling off
some solvent will not work here, since the benzine will come off first,
increasing polarity and thus solubility. yes? and i fear that adding
non-polar would decrease polarity, letting the crap oil out.
n'importe quoi
(Chief Bee)
08-19-03 18:00
No 454536
Evaporate all the solvent, and recrystallize the residue using the same system.
(Hive Addict)
08-19-03 19:02
No 454539
this was the when everything else fails plan
n'importe quoi
(Hive Addict)
09-09-03 12:57
No 457892
the identity of the crystalls was (more or less) confirmed by
making the ketoxime derivate: snow white voluminous powder,
not recrystallised mp 104-105° (lit.: 111-112°)
_but_ for whatever reason neither more fractions nor other
samples could be recrystallised. either everything oiled out
or stayed in solution. sheesh, i hate those work the first time
then never again things.
n'importe quoi
(Chief Bee)
09-10-03 06:56
No 458069
How did you synthesize the ketone?
And did you check the other fractions with TLC or anything to roughly find out what kind of purity they were - like if it was 85% desired product or just 35%?
(Hive Addict)
09-10-03 18:35
No 458189
> How did you synthesize the ketone?
peracetic (preferably) or performic (dang! forgot to prepare the peracetic solution).
> And did you check the other fractions with TLC or anything to
> roughly find out what kind of purity they were - like if it was
> 85% desired product or just 35%?
no TLC, sorry. i fear it's more 35% than 85%. the thing is that
there is massive polimerisation during distillation, so it
is done as quickly as possible. now if the ketone polymerises
faster than the rest, one might end up with little ketone and
lots of glycol/whatever. the recrystallised sample is the only
one that gave a crystalline oxime.
i hope that a microdistillation apparatus gives less polymerisation
and better separation.
n'importe quoi