09-29-02 03:32
No 361777
Ran MMan Wacker as usual, fine. Post reaction: 2 washes with sat. Sodium Bicarb - fine. Two washes sat NaCl - fine. (Oil on BOTTOM layer all washes.)
First wash with 5% NaOH ran well: Got 2 very distinct layers - one on BOTTOM was pinkish red cloudy, which I assume was the NaOH/H2O with garbage from Wacker; TOP layer was deep blackish Oil. However, when second NaOH wash was done whole sep funnel turned into one pinkish-black solution, with NO separation between layers, and no layers visible - not even the "normal hard to see one". Let sit awhile, still no separation. Added some Sodium Bicarb, and still nothing!
Finally added dH2O, got 2,500 ml total mess in funnel; got some "oil" to go to bottom, but still couldn't see layer separation; sep funneled by Methylene Cl. smell. However, "oil" doesn't look right, and the amount is more than should be, and looks like alot water/salts in there... Finally poured everything back together in 5 gallon can.
1) How can I salvage this? Was thinking could pour everything back together in big beaker and add more Methylene Chloride and Sep??? Or??
2) WHY did this happen? The first NaOH wash layers were so damn sharp and distinct (I was tempted to stop washing after the 1st NaOH wash cause oil looked so good) So why did second turn into that Pink-Black homogenous mess??
3) How long do I have before Ketone deteriorates in this state?
Any help appreciated!
If they drive God from the earth, we shall shelter Him underground - Dostoevsky
(Hive Bee)
09-29-02 03:49
No 361780
First wash with 5% NaOH ran well: Got 2 very distinct layers - one on BOTTOM was pinkish red cloudy, which I assume was the NaOH/H2O with garbage from Wacker
NO!! The bottom layer is your oil.
& I'm, somethin of a phenom, 1 puff of da cron, I'm un-stopable.
(Chief Bee)
09-29-02 03:52
No 361782
The density of methylene chloride is higher than water, so if you have one layer of each, the water will always be on top as long as there aren't any other low-density non-polar solvents in the mix.
(Hive Addict)
09-29-02 03:55
No 361784
Swim doesnt know shit about wackers (except for romantic evenings with self), but he does know about emulsions. Sounds like swiy has himself a big emulsion.
For dealing w/emulsions try:
-run mixture through a buchner funnel (no filterpaper)
-gently poking it with a stick (mess with it with a glass rod- not a very effective technique btw)
-adding NaCl (the kosher kind) to make the polar layer more polar
-warming up the solution (however, this may not bee a good idear as ketone is present)
-gentle rocking of solution
-giving it time (it should separate, however as you have stated, ketone doesnt store so well specially if theres a bunch of impurities)
Hope that helps some.
The best 'cure' for emulsions is not forming them in the first place, that means GENTLE addition of immiscible solutions (when adding, try to make it so the liquid doesnt 'drop' into container, make it have contact with the side of the container and run down. Also, when washing or extracting, if there are a series of washes to bee done, ALWAYS start gentle, even just lightly swirling (remember to vent) and stop every once and a while to see whats happening, if an emulsion starts to form, dont continue to shake the shit out of it hoping to clear it up, thats the worst thing you can do. Swim'll usually go real gentle for the first wash, then slightly more agressive on the second etc...
(Hive Bee)
09-29-02 03:59
No 361787
Im going to start preaching about the wacker dcm additions..
I think they should really be done separatley and distilled separately. Swim has scene the 3 layers before and wasn't too sure what to do about it. Almost appeared to be emulsion. DCM/naoh seems prone to emulsion.
& I'm, somethin of a phenom, 1 puff of da cron, I'm un-stopable.
(Hive Bee)
09-29-02 05:11
No 361803
I thought it was kinda strange that the oil layer, which was always on the bottom in previous washes, should appear on top. Now I know that the "pinkish" layer on the bottom WAS the oil. (Damn! Never do sep when very tired.....)
Well, back to my original question:
1) I have last 2 washes and Oil combined -can I salvage by adding excess of Methylene Chloride and re-separate??
2)If I wait day or two to extract, will ketone be ok?
If they drive God from the earth, we shall shelter Him underground - Dostoevsky
(Hive Bee)
09-29-02 05:23
No 361808
I learned many years ago NEVER to throw anything out before final product in hand. And YES - now that I think about it, that's EXACTLY what the bottom and top layers looked liked after the 1st NaOH wash!!! ( I feel, how they say, STUPID)
Soooo... That being the case, I have a gallon jug with the oil and previous washes in it; Best way to re-cover Ketone?
If they drive God from the earth, we shall shelter Him underground - Dostoevsky
(Hive Bee)
09-29-02 06:03
No 361817
Good thing you saved it. Just re separate, OIL ON THE BOTTOM!
& I'm, somethin of a phenom, 1 puff of da cron, I'm un-stopable.
(Newbee)
09-29-02 10:51
No 361888
NEVER WASH KETONE WITH BASE!!!! Strong base and acid polymerize ketone! Any extreme pH will destroy ketone.
(Hive Bee)
09-29-02 11:02
No 361893
Really???
Well, either way, bubbles naoh addition should still be 5%
& I'm, somethin of a phenom, 1 puff of da cron, I'm un-stopable.
(Chief Bee)
09-29-02 11:49
No 361897
potisgood: Now you are exaggerating. You need to wash out the aqueous base-soluble impurities at that point in the synthesis. If you feel bad about having a sodium hydroxide solution in contact with your organic ketone phase (none of the NaOH will migrate to the DCM anyway), then use 10% sodium carbonate for the washes instead.
But never let MDP2P stay in contact with a strong base for extended periods of time, only for so long it takes to perform the washes.
(Hive Bee)
09-30-02 04:53
No 362181
75% or so of the oil. Added some new Methylene Chloride to saved stuff, sep funeled everything, and gave a few washes. Thanks for everyone's help!
BTW, I've found that #4 Molecular Sieves are super for drying Oil. A few grams really sucks up the H2O, and you can see the oil getting nice and black around them. Great stuff even if pricey.
I've posted a big sign in the lab for future reference:
OIL=BOTTOM
WATER=TOP
ALWAYS!
If they drive God from the earth, we shall shelter Him underground - Dostoevsky
(Stoni's sexual toy)
09-30-02 13:54
No 362299
> OIL=BOTTOM
> WATER=TOP
> ALWAYS!
It's stupid generalisations like this that make people pour the wrong layer down the drain.
Use some common sense, your nose, and a small vial filled with water to figure out which layer is the non polar when in doubt.
I'm not fat just horizontally disproportionate.
(Title on BackOrder)
09-30-02 16:53
No 362322
That generalization will cause him a lot of heartache with other NP solvents.
All paths are the same: they lead nowhere
(Hive Bee)
09-30-02 21:55
No 362412
I was just kidding around about the sign. And I meant it only for the NaOH wash of the Wacker, not in general. You have to admit that the appearance change of the Ketone from dark black oil to that pinkish-tan stuff in the first NaOH wash, and then back could be confusing for someone doing it for the first time. It was to me anyway.
Whatever. Not likely a mistake I'll ever make again. Now I've got the Wacker down pat. You live and learn.
If they drive God from the earth, we shall shelter Him underground - Dostoevsky
(Newbee)
10-01-02 00:40
No 362463
I hope the damage with NaOH is minimal. Maybe this is the results for swims maximum 50% molar yields on O2 wacker. I read somewhere here that acidic solutions destroy the ketone over time. BTW, swim just used activated charcoal from fish store to take up the pdcl2/cucl2. WORKED AWESOME! Emulsions are no longer a problem. Took the the post wacker straight to 40g of charcoal and stirred prechilled solution for 30 minutes. The decanted off charcoal, acidified the black solution. Washed once, basified, charcoal immediately formed its own layer and toluene was light yellow. It reduced amount of washes by almost 66%. Does anyone know if charcoal holds some of the ketone. It was rinsed with MeOH and then Toluene. Rhodium, when swim washed with EDTA, he saw no color change in the EDTA solution or the Toluene/ketone layer. Should he wash the ketone without it being in a solvent. Meaning EDTA+water/Ketone oil.
(Chief Bee)
10-01-02 00:43
No 362465
There should not necessarily be any color change of the EDTA solution after the wash - do you know for a fact that Cu or Pd EDTA complexes are colored? Rather look at your ketone solution, do you still have the same problems with it as before, whatever the Cu/Pd caused?
(Newbee)
10-01-02 01:42
No 362476
I dont know. Process of elimination is being done to determine if the low yields are 1) wacker related (just low yields), 2) residual cucl2/pdcl2 possibly reducing al/hg yields (attaching to al or something during amination?) 3) undistilled ketone (wacker side reactions) are affecting al/hg yields. In the third scenario swim has no choice but to distill.
(Title on BackOrder)
10-01-02 01:45
No 362478
Why are you bitching about yields if you aren't even distilling your ketone? You should feel lucky that you're getting anything at all. If you want to improve your yeilds, then you will have to distill.
All paths are the same: they lead nowhere
(Chief Bee)
10-01-02 02:14
No 362487
I think your problem is with 90% certainity due to your non-distillation of the ketone. Not doing that is plain stupid. All the contaminant will criss-cross react with the ketone, the imine and the final freebase, not even touching on the subject of what it may do with the reducing efficiency of the Al/Hg reducing system...
(Hive Addict)
10-01-02 06:24
No 362618
but i think stupid user is Error 1.
Nymphomania is not a disease - its a goal! (Methadist on Rosemary Kennedy)
(Hive Bee)
10-01-02 17:21
No 362755
DID YOU APPLY HEAT????????
If you didn't, expect 60-75ml's of ketone back instead of 125. Even less if you didn't pre-stir your catalyst, benzo.
& I'm, somethin of a phenom, 1 puff of da cron, I'm un-stopable.
(Hive Bee)
10-05-02 08:10
No 364430
Pot is right. Base destroys ketone. Whenever I wash my crude oil with base about 10 g of crap precipitates. I used to think that this was garbage, but later discovered that it was actually my ketone! The moral of the story - mixing ketone and base is like mixing alcohol and GHB.
(Title on BackOrder)
10-05-02 09:16
No 364454
(Rated as: excellent)
you have to wash your ketone with base to clean it properly prior to distillation, and the wash won't hurt the ketone. You do need to wash the ketone afterwards with an NaCl solution and a water wash to get rid of any trapped NaOH. If you don't, the high heat of distillation will polymerize your ketone to your flask, and that ain't cool at all.
All paths are the same: they lead nowhere
(Hive Bee)
10-06-02 08:39
No 364968
I've never done a benzo wacker, but if you have to wash it with base, use as weak of a base soln. as possible and keep contact time to a minimum. Also, washing the ketone with water to remove any base is VERY important. I have distilled ketone w/o the wash and I get about 40 g of tar, which should have been ketone.
(Hive Bee)
10-09-02 09:27
No 366390
I understand that benzoquinone's role in this oxidation is to recycle the catalyst.
Even making it unessecary to use copper salts to act as reoxidizing agents for Pd(0), and that it has a benifical effect on yeilds by somehow stabilizing the intermediates, this is evidenced in another patent which I will submit, which states the yeild improving effects of adding hydroquinone (sometimes employed also as a free radical inhibitor) to a dry methanol O2 Wacker situation.
But the stupid question posed is, why does this method employ the addition of such copious amounts of water 50 ML I think, why is this needed?
and the patents are: US 3410807 and 3475461.
and here is an abstract of these patents:the first patent gives a detailed description (example 6) of the oxidation of styrene (the closest relative to our favorite alkene). He indicates that there are a number of side products, including the aldehyde as well as isomerization that hurts yields. He concludes that the best solvent for styrene is methanol which produces the highest conversion and least side products. In this example H20 concnetration was 0.7 percent.
In the 2nd patent he admits that the previous method (above) produced the desired product (ketone) but in poor yields due to side reactions and other products (isomerization and aldehydes, etc.). To correct this he uses an inhibitor to prevent side reactions and improve the yield. These happen to include hydroquinone and benzoquinone among others.
In an example using styrene, by simply adding hydroquinone to a typical wacker oxidation using O2, CuCl2 and ethanol the yield jumped from 59% to 74% and also decreased side reactions. In this case no water was added so the final product, an acetal, had to had to be hydrolyzed with acid to form the desired ketone.