06-06-03 18:32
No 438353
I saw a smart, sexy woman run a peracetic oxidation as normal on excellent quality iso, to get a usual yield of glycol, then she did the pinacol rearrangement as usual with 15% H2SO4 w/methanol for 2.5hrs. She distilled, keeping 270-300C. She tested with bisulfite, and it was chicken fat, some ketone but piss poor yield. I recommended she redistill keeping 280-290C (BP of ketone is ~286C). Ok, the yield is low for her, but she hope it's better ketone. I encouraged her to test again with bisulfite, and it was still forming globules of slimey crystals.
Starting to doubt the validity of the bisulfite test, perhaps the bisulfite was old or something, (the test was 5ml sat aq. bisulfite w/.3ml ketone shaken in a test tube), I decide to recommend that she aminate anyways. Well, the bisulfite test was right as usual. It's funny how something that takes 1hr to test, can save so much headache later. In the end, she got like 2.5g from ~20g suspected ketone.
I'm pretty sure this is the result of either too little stirring or bad hydrogen peroxide in a peracid technique... but... I'm wondering if others have seen something that's like ketone come over at the right temperature and not be ketone.
I think because she used a new brand of H2O2, or that stirring was less than optimal, that the oxidation never happened. But what was the fraction that came over at the temperature of ketone? MDP2Pol?
Does anyone have any really, super, great, easy ways to titrate peracetic acid and/or H2O2 with nothing but otc chems?
(Hive Elder)
06-07-03 00:49
No 438411
When SWIM was going thru this route, on a few runs this very thing you mention happened, it smelled a bit "off" (the distilled "ketone) but it looked identical to ketone and came over at the same temp. I think for SWIM anyways it was problems with iso formation at the start, perhaps this is what Saf does when put thru the peracetic...? Also of note, put it in the freezer for a day or so, it will become VERY thick(if it's the same stuff), like honey but a little thicker, unlike the ketone which is still very viscous at that temp...
Your still distilling your ketone without vac...? Do you notice a difference in yeild between vac distilled and atm distilled...?
Mean People Suck
(Hive Bee)
06-10-03 17:47
No 439223
usually caused by weak peroxide or too high of a distillation temperature.
my first (unsubstantiated) hypothesis is that weak peroxide causes some glycol to be produced along with the monoformyl glycol (or monoacetate glycol in this case).
second hypothesis (from the bees) is that an oilbath temperature of about 180C during ketone distillation will break down any residual monoformyl glycol into the glycol which will then start coming over. if you distill at a lower temperature the monoformyl glycol will remain intact and not vaporize.
if one were pulling ketone around 135-140C or higher i would suggest doing a first distillation with no fractionating column to avoid this problem. then do a second distillation with the column.
anyway, swim was able to increase his MeNH2/al/hg yields from the sticky ketone from 7% to 50% after redistilling it four times. watch the reciever for drops of ketone that do not dissolve completely- leaving strands. change the reciever immediately.
also, you can tell the ketone is bad if it takes an excessive amount of swirling to dissolve it with 1x or 1.5x volume of MeOH in an addition funnel. sticky strands will keep rising from the bottom of the funnel as you swirl it.