Author Topic: Unusual O2 wacker reaction  (Read 1354 times)

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split

  • Guest
Unusual O2 wacker reaction
« on: January 07, 2004, 08:53:00 AM »
This reaction being done many times before has never brought about such intense heat evolution. I will explain all details in order to avoid posting twice.

177.4g (161ml) safrole
5.1 g cucl2 (dihyd)
1.25 g pdcl2
500 ml MeOH

Pdcl2 mixed in meoh for 20 hours prior. Then added cucl2 and proceed to pressurize. No water added to reaction. Set up in 3 liter pop bottle krv style 53 psi with stir bar @ full stir.
I wanted the reaction to proceed on a rising tempurature incline so that the peak of the reaction could be more easily controlled at ~50c. So the reaction was run using IR thermometer constantly measuring temp of vessel. Temp started at 27c and initially rose to 32c within 1/2 hour. Temp dropped back down to 29c for the next 9 hours (some <20 psi drop during this time).
  At This point I decided peak reaction needed to have been started already and decided to blanket the vessel in a fleece sweater. Bottle was also inside a .1mm plastic bag in case of rupture. BTW, is there such a thing as a static spark producing an explosion with one of these things between an LDPE bag rubbing against a PTFE bottle in low winter humidty???
   Went to sleep to wake up at just under the 10th hour to find the unit at 56c and a psi drop from 50 to 25. Attempted to keep the psi as high as possible while trying to maintain the temp at a constant 50 to 55c at said pressure. But you know how it goes, the thing gets red hot when it's even slightly jossled. A fan was set to blow on the whole unit to keep it at 50c during the peak of the reaction which lasted about 30 minutes. Reaction run another 6 hours with minimal psi loss afterwards (~10 psi).
Overall loss was just over 70psi in 16.5 hours. This is consistant with many runs done the same way before. And according to some crude calculations base on weighing this bottle with 02 at different psi points this is ~100% molar yield (in theory). Now here is where it really gets weird and some alien life forms impregnate my 02 wacker with some super reaction.

It was decided to do the hydrolysis with hcl straight from the bottle. 31% hcl used, 25ml measure out and poured straight into the wacker bottle. As expected the reaction starts to warm up. Now remember, the bottle has just been reacapped and still has some pure 02 in it. As it's warming up from 31c to 38c the bottle DEFLATES AND CRUMPLES! So much that at least half of the volume of gas in there is gone. I would have expected for it to slightly pressurize with the increase in temperature. So I start shaking it noticing it's collapsing fast. This all over a period of 13 to 18 minutes. At this point I'm befoggled as to why it could still absorb even more 02. Temp of vessel is 38c. I pump it to 50 psi with pure 02 again. I shake like crazy and the temp jumps from 38c to 45c in less than 2 minutes. Were talking about some 700ml of liquid in this thing. Before I even get a chance to react and reduce pressure the vessel feels even hotter. Pressure reduced to 35 psi and temp taken again within seconds it's now climbed to 49c. The bottle was practically going exothemric sitting still, and even the slightest movement made a 1 to 3 degree increase in temp.
   Within 5 minutes of putting 02 back in the temp has now climbed to a astonishing 60c (with light shaking) and even climbs 61c with moderate shaking. Being very scared of explosion he plays with it very carefully inside a plastic bag with a fan blowing on high and shaking gently. The temp maintains itself at 56 to 59c for the next 25 minutes and drops to ~50c for the next 15 minutes. During the course of the whole ~50 minute hydrolysis the reaction was upped with more 02 and lost at least 35 psi 02. 25psi was taken up during the time it stayed 50c and below. Vessel dropped from 53 psi (at 50c) to 27psi @ 44c during the last 25 minutes.

What the hell is going on here???!!! I never thought that adding hcl directly would make the reaction take up so much 02 if any 02 at all? Total psi loss is typically 70 to 75psi with the above numbers. This time it was 105 psi loss!

Osmium

  • Guest
Strange.
« Reply #1 on: January 07, 2004, 09:04:00 AM »
I've seen a ref many years ago that said the Wacker reaction will go much faster in strongly acidic environments. They used HClO4, a very strong acid. Maybe that's what happened? Work it up and report back.


Osmium

  • Guest
A high Cl(-) concentration should slow down...
« Reply #2 on: January 07, 2004, 09:06:00 AM »
A high Cl(-) concentration should slow down the reaction, not speed it up. Maybe it was the solvent that got oxidised?


split

  • Guest
Your exactly the man I was hoping to comment.
« Reply #3 on: January 07, 2004, 09:09:00 AM »
Your exactly the man I was hoping to comment. It's been worked up to obtain a very bananna yellow bright oil. Very spicy indeed. I will report back with al/hg yields soon.

Snakebyte

  • Guest
Great work!
« Reply #4 on: January 07, 2004, 11:47:00 AM »
Although I haven't tried any alcohloic O2's because of its inferior results as opposed to using DMF, maybe u have stumbled on something.  I don't believe the O2's have been experimented with enough because of many peoples bad experiences and bullshit posts.  Pls post all details and results!