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A NEW plan for WACKER-holics
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Author Topic: A NEW plan for WACKER-holics
spiceboy
Member posted 02-10-99 04:23 PM
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Pissed off about the availability of my precious Pd, I submit THIS for critique:
Cobalt Carbonate is readily available OTC in this area. Possibly, I would say a conversion to Cobalt Chloride should be easy, analogous to the synth of copper chloride from cu carbonate.
someone bounce back at me
Drone? Os? C-Hack?
we need to expand it more, I think.
If someone wants to go over some of this with me , I will do the dreaming soon.
hellman
Member posted 02-10-99 05:24 PM
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why not nickel choride?.
I'm sure it's in the same kind of family.
hellman
hellman
Member posted 02-10-99 05:26 PM
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chloride, sorry!.
Anaximander The Greek
Junior Member posted 02-10-99 05:41 PM
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Creating the cobalt chloride is not the hard part, but has anyone used it in the Wacker oxidation for our collective application? Does it require co-catalysts for 'acceptible' yields? The library is sure to tell something. A shame all the awesome catalysts (Pt, Pd, etc.) are so expensive.
Spiceboy, where'd you get your OTC CoCO3? Cobalt chloride used to be standard in every chemistry set refill pack sold in the free world...
Semtex Enigma
Member posted 02-10-99 08:00 PM
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Weren't people discussing the use of a silver compound (chloride?) instead of Pd? Or have I been binge'in?
KrZ
Member posted 02-10-99 08:29 PM
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Most of the stuff I've read uses Pd and doesn't mention any as-effective substitutes. But I am a wackerholic so I'd love to see what spiceboy does with it. How would I go about converting a Pd coin into PdCl2?
TheCat
Member posted 02-10-99 10:07 PM
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A Pd coin?
The Cook
Member posted 02-11-99 01:30 AM
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Ok. Spice>You're going to have to check on Cobalt's orbital size, that's where the fun is at. Compare it to Pd and Pt..
S.E.>I mentioned AgCl2, but someone said it won't work. Nickel MAY, but I'm not putting any money/oil on it.
KrZ>Boil little chunks of Pd, in a molar amt of H2SO4, to create the sulfate. Then grind the sulfate with some salt (NaCl) to swap out PdCl2.. (Just like Hg->HgCl2)
In general, the Benzoquinone is the oxygen donor, and the Pd the carrier (catalyst). CuCl2 just recharges the catalyst.
Now hydroquinone ('Spent' Benzoquinone) can be reoxidized in situ to benzoquinone with some H2O2. Mercuric Acetate adds in the happy Markovinov (sp?) style, and would then get oxidized off, creating the alcohol. Then the CuCl2 & Benzo push another oxygen through, forming the ketone.
The oxidation of Safrole Hg Acetate to mdp2pol ain't bad, but can we immediately get to ketone? Hmmmmm.
-cook
Osmium
Member posted 02-11-99 03:16 AM
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I really doubt that Pd can be substituted with any other catalyst in the wacker. If it worked, industry would do that and we would know about it. But go on spiceboy, prove me wrong.
When you want to create PdCl2 from a Pd coin or ingot or dental alloy, aqua regia is the way to go. Industrial preparation uses refluxing mixtures of Br2/HBr or Cl2/HCl to dissolve the metal.
Bright Star
Member posted 02-11-99 08:09 AM
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Cook -
2benzoquinone + 2water -> 2hydroquinone + O2
The O2 comes from the water.
Not a flame, just a correction.
Piglet
Member posted 02-11-99 11:06 AM
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I did some patent reading and reference following & came to the conclussion that Co is only good as a carbonyl complex, and that will form the aldehyde, not the ketone. Ni works at higher temperatures.
Pd is used in coinage, I have heard, so the stuff isn't likely to ever be difficult to come by. A practical Pd --> PdCl2 synth is the real click. I feel that this MAY be possible with an electrolytic cell...
Bacchus3_4
Member posted 02-12-99 03:19 AM
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Any ideas on Semtex's Silver idea? Is it fesabel, Practical, cost effecient?
As long as Photography is around I believe we are safe on the aquisition aspects of Silver-Chloride.
This should be explored further.
Any taker???
Piglet
Member posted 02-12-99 03:58 AM
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If one were to build an electrolytic cell with Pd electrodes and an aqueous solution of a metal chloride (a metal with a higher electropotential), then when a current is applied, won't the Pd dissolve and the metal salt plate? I'm no expert, but I cannot believe it's NOT possible?
Anyone at all?
rev drone
Member posted 02-15-99 11:59 AM
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Hey there,
I posted a coouple lists of references to other catalysts a few months ago, but nobody got too excited.
A huge number of transition metal catalysts will aid in the oxidation of olefins, but Pd species are special in once sense: Pd2+ catalysts will oxidize terminal olefins into methyl ketones, but others, such as chelated cobalt, nickel, and other species of catalysts will oxidze to form epoxides and glycols. Sure, epoxides and glycols are readily converted into methyl ketones, but its an extra step. Look around, and I'm sure you'll find the list. There are literally hundres of examples in current literature, and enatioselective variations of this oxidation are currently hot topics for research in places like the Jounral of the American Chemical Society.
This is where different synthetic routes hybridize a little. The "classic" ketone synthesis is really just one more alkene oxidation, forming the glycol intermediate. What this means is, these techniques can be used on safrole or isosafrole, with the advantage of using isossafrole being that the isomerization seems to happen more easily. By using a catalystwith, say, H2O2, rather than a peroxyacid, kinetics can be better regulated, and polymerization and other side reactions can be avoided.
I hope this clarifies things, and I hope people continue to investigate this. This could be very fruitious.
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-the good reverend drone
rev drone
Member posted 02-15-99 12:26 PM
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Hey there,
I posted a coouple lists of references to other catalysts a few months ago, but nobody got too excited.
A huge number of transition metal catalysts will aid in the oxidation of olefins, but Pd species are special in once sense: Pd2+ catalysts will oxidize terminal olefins into methyl ketones, but others, such as chelated cobalt, nickel, and other species of catalysts will oxidze to form epoxides and glycols. Sure, epoxides and glycols are readily converted into methyl ketones, but its an extra step. Look around, and I'm sure you'll find the list. There are literally hundres of examples in current literature, and enatioselective variations of this oxidation are currently hot topics for research in places like the Jounral of the American Chemical Society.
This is where different synthetic routes hybridize a little. The "classic" ketone synthesis is really just one more alkene oxidation, forming the glycol intermediate. What this means is, these techniques can be used on safrole or isosafrole, with the advantage of using isossafrole being that the isomerization seems to happen more easily. By using a catalystwith, say, H2O2, rather than a peroxyacid, kinetics can be better regulated, and polymerization and other side reactions can be avoided.
I hope this clarifies things, and I hope people continue to investigate this. This could be very fruitious.
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-the good reverend drone
rev drone
Member posted 02-15-99 12:56 PM
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Spiceboy,
I'll back you! Its a good idea (see my last post in this thread for more details), though it ain't the Wacker, outright. I'm glad you're taking inteerest in this; I've always admired your practical work on the Wacker, and I'm enthused that you've taken interst in this prospect.
Anaximander The Greek,
The Wacker is well-worn territory. Most of us are "Wackerholics" (when I first heard this word, immediately a barrage of juvenille images ran though my head. I continued snickering to myself for the remainder of the afternoon. Why haven't more people made puns off of this?)
Semtex Enigma,
The silver was discussed in the context of activating imines for hydrogenation. Still, the same theory applies: pi-bnd-d-orbital overlapping, amking the system suseptible to attack.
The Cook,
You're right on about orbital size. Once again, size DOES matter (whenever doesn't it?) The reason Pd2+ is so slick is that its d-orbitals fit just so damn snuggly to the pi bonds. Still, other transition metal species work in oxidizing, though they tend to either make the epoxide or the glycol (a.k.a. diol.) These are readily isomerized/dehydrated into a ketone, so they still are worth looking at.
I have to admit, I'm a little skeptical about the ion transfer with Cl- and SO4 2-, but then again, I see no reason why PdSO4 wouldn't work anyways. Tell me why you're right, and where you got this procedure. Convice me with hard vs. soft acid thoery.
Now on to your proposed scheme. Stay away fromusing molar equivalents of Hg2+!!! Fercrissake, the stuff is evil, and the bad Karma you will acrue will haunt you through a dozen lifetimes.
As for your explaination of the oxidation: benzoquinone is the electron acceptor (that's what an oxidizing reagent does.) If you have H2O2 floating around, tell me: why would benzoquinone be needed at all? For that matter, why the CuCl2?
If one had MDP-2-Pol, one could readily oxidize it into the corresponfing ketone with a hypochlorite solution with no hassel; why make life complicated? Too maky steps, too many reagents, too much hazardous waste.
The making of MDP-2-Pol from safrole is more of an olefin hydration than it is an oxidation. Think about it.
Osmium,
Pd is used for a number of reasons. Imagine you're a chemist in a lab, in charge of odixizing some allyl on a $1000 per gram pharmaceutical intermediate. Needless to say, you're going to want the most efficient method. Alternatively, let's imagine we need a final product of high purity, and the presence of diols or epoxides simply won't do. When you take into consideration that the Pd is being catalyzed, this method looks more and more attractive.
The wacker is becomming more popular in industry every year, but dozens of different olefin oxidations are in use; each with their advantages and disadvantages.
Bright Star,
O2 is not genreated anywhere in the reaction mechanism. You're right in that H2O is needed to balance the books, and that its needed in the mechanism, though.
Piglet,
Would you care to share your sources? Chances are, the reason a CO-ligand-bearing Co speices was used was exressly to form an aldehyde; I've seen plentyl of examples where epoxides and glycolds were made instead.
Pd -> PdCl2 isn't a ral problem plenty of procedures exist out there for this oxiation. No electrolytic cell is required (though that would do the job.)
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-the good reverend drone
rev drone
Member posted 02-15-99 06:57 PM
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So as to keep ever-abreast of what's new, I just finished doing a little lit search using a database called current contents just to see hwat's new in transition metal-catalyzed alkene oxidations. While a lot of them look ugly, involving nasty things like porphyrin-chelated species and the like, many are quite practical. The main thrust of research of course is in enantioselective oxidations, but we're nowhere near so picky around here. The list is a little large, since it contains the abstracts as well, but if anyone wants it, they can e-mail me drone342@hotmail.com .
One that looked especially interesting was the use of Cu(OAc)2 as a catalyst -- how much cheaper can you get?!! Iron3+, manganese3+, cobalt2+, as well as our beloved Pd2+ species are all present-and-accounted for.
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-the good reverend drone
psychokitty
Member posted 02-15-99 10:57 PM
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To date, no one has listed references or information about rhodium chloride wacker analogue oxidations of alkenes. I have the references at home. Two articles published in JACS. Interesting stuff as for some reason the reaction does not require any water to work and the yields are very high with no isoalkene by-product formation. However, rhodium catalysts are very expensive thus possibly making thier use somewhat impractical. Maybe and maybe not. I'll post the references soon.
--Psychokitty
TheCat
Member posted 02-16-99 12:35 AM
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psychokitty can the rhodium chloride be recovered for use again later? If so who cares how expensive the shit is if you can reuse it 10+ times.
rev drone
Member posted 02-16-99 02:00 AM
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I care; I for one am humble enough to not expect any catalyst to last 10 runs in a garage setting. I say cobalt(II)chloride, copper(II) acetate, or some other cheap-as-shit catalyst is the way to go. True, the yields are only 65-70% as compared to the 90+% that would invaraibly be needed to justify Rh, and yes, a work-up is required, but I'm willing to take those losses for the gains in parcimonious practical chemistry that are made.
If the price of Pd makes you grimmace, you're REALLY gonna hate using rhodium instead.
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-the good reverend drone
Semtex Enigma
Member posted 02-16-99 04:39 PM
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Rev Drone: You wouldn't possibly have a write up lying around which uses either of these two compounds, do you? Or would one use an equimolar amount of catalyst? Would workup be similar or identical (hopes) or possibly so outragous that one would opt for the use of Pd?
As usual thank you for any and all help in this matter...
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