(Stranger)
04-07-02 11:52
No 293619
(Rated as: excellent)
Well, I'm really drunk right now, but I've been reading some really cool shit on the wacker. I spent a few days at the library reading journal articles and shit and found out the following info:
1) Pd+2 catalyzes not one reaction but two. The first one is of course the conversion of an olefin to a ketone. The second, however, is the isomerization of the olefin. It turns out that this isomerization is about 300 times faster than the oxidation. This goes to prove the next point.
2) Within minutes of addind safrole to the rxn. mixture, it is converted to the equilibrium mixture that consists of 99% isosafrole. In other words, the reaction doesn't give a flying fuck whether you use safrole or isosafrole as the starting reagent. This transformation occurs by a pi comlex formed from the safrole and the Pd+2. This complex can rapidly shift between the 1-2 carbons and the 2-3 carbons. These two pi complexes are also in equilibrium soon after the rxn starts.
3) The carbonyl products are derived from these pi complexes. The 1-2 complex produces MDP-1-P and MDP-2-P. The 2-3 complex produces MDP-2-P and MDP-3-P (the aldehyde). The oxidation rxn from the pi complex is irreversible and is governed only by rate (thus the product that is formed fastest is the major product, not the equilibrium product which would be MDP-1-P -- this product is the most stable due to a conjucated double bond with the aromatic ring). Thus from the starting material (safrole or isosafrole) you get a mixture of all three carbonyl compounds. From experience, the major product is MDP-2-P.
4) MDP-2-P and MDP-1-P have almost the same boiling point (within 5C) at 20 mm Hg. Therefore, it is virtually impossible to separate them by distillation. This may be the reason why many bees report getting product in the correct distillation range that doesn't aminate. I am wondering, though, will MDP-1-P aminate with the MeNO2 amalgamation? My opinion is no, due to steric hendrance and stability of the ketone due to conjugated double bonds.
5) In one article, some scientists discovered that using palladium calalysts with ammine ligands with result in a selectivity of >95% methyl ketone (MDP-2-P in our case). I am not sure of the cause of this phenomenon, though. It could be due to one of two factors. The first is that the ammine ligands slow down the isomerization process, so that it is much slower than the rate of oxidation. The other is that the ligands slow down the rate of formation of MDP-1-P while not affecting the formation of the desired ketone. There is, however, a descrepancy in the literature. One article states that an equilibrium mixture of alkene is formed within minutes of starting the rxn. Another article (the one that used the ammine ligands) stated that after 24 hrs of rxn, the concentration of 1-alkene was >80% with PdCl2, having no ligands. This just doesn't add up. The only difference is that the first article used 1-hexene as the staring alkene, while the second use 1-octene. Shouldn't the final concentration of 1-octene be <1%? Both procedures used similar amounts of catalyst.
6) For the O2 wacker, PO2 only needs to be about 0.5 atm. Higher pressures actually slow down the oxidation process. This is for the oxidation of 1-hexene, which is probably faster than the oxidation of safrole anyway. Therefore, all this crap about 3+ atm of O2 seems unnecessary, if not detrimental to yields. The O2 is only needed to reoxidize the Pd, which is independant of the actual oxidation rxn -- we have two rxns going on simultaneously.
This is all the shit that I found out. If you have any questions about is, please feel free to post them. Again, I am really fucked up now, so I may not have explained everything clearly. Hope this shit helps.
(Hive Bee)
04-07-02 15:03
No 293662
Do you have references on these papers or copies of these. Have long suspected some of the points brought up in your post but never found the literature on them. Have been experimenting with several different new ideas for the wacker with limited success ranging from 5-95%yields but would like this information to tweek then out.
(Master Whacker)
04-07-02 16:33
No 293689
(Rated as: excellent)
nMR analyses of a few batches of PdCl2/CuCl2/IPA Wacker oxidation synthesized ketone(s) showed proved that MDP2P was the major product at around 85% and MDP3P(the aldehyde) was present in concentrations up to 15%. Not a trace of MDP1P was ever detected which really made SWIM bummed out because that was his target compound.
I can back up your statement that isosafrole reacts exactly the same way as safrole. SWIM got identical yields with both the allyl and propenyl benzenes.
(Stranger)
04-08-02 05:04
No 293988
Here's a list of the journals I used:
J of Molecular Catalysis vol. 88 (1994), 301-310
Eur. J of Organic Chemistry 1998, 1901-1906
These are the main two. The first deals with the isomerization, and the second deals with the ammine ligands. I'll post the others later, but they aren't as interesting.
(Stranger)
04-08-02 05:06
No 293989
blaztoff:
If you are getting 95% yields, then please post your data. I am about to start experimenting with the wacker (nitrite) and would like any information you have on successful + failed runs that you have.
(Hive Bee)
04-08-02 10:00
No 294144
Sorry still am working on them. I had some succecess but after retrying some failures. Experimenting with several varieties of wackers and am close to getting some improvements on them. On latest attempt achieved 78G ketone from 90Gr safrole but need to run it some more. If all else at least have figfured out some ways minimize some reactants.
Always thought that on some rxn soemthing was wrong with the ketone and it might have formed the 1 complex and wouldnt amalgate or hydrogenate. Especially true for any pressurized wacker.
Is there anything about other catalyst in that literature?
Looking to see if Iodidne is mentioned in any literature for some new ideas Swim has.
(Hive Bee)
04-09-02 05:50
No 294431
If the safrole is really first almost totally converted to isosafrole, then if one Wacker yields say 20 ml of isosafrole plus the ketone, then looks like the yield of the reaction might be improved ( reaction time extended, or what else ) to increase the overall yield of MDP2P. That is, the iso left is NOT CONVERTED, and not a parallel reaction ( that's what I though was the case )
Any clues ? Could someone confirm extending reaction time would help ?
(Hive Bee)
04-09-02 18:16
No 294638
If most is converted right away then wouldnt extending reaction times past given amount possiblly increase chance of breakdowns or side reations? Swim has also noticed that for the wackers the conversion seems to happen at the very start and after that very little seams to happen. I would think that instead of reaction time bieng extended it would be more advisable to get the reactants to react the unreacted. If they are all used up initially then more would have to be added to react the rest of material. But in the case of issasafrole bieng left and the rest ketone wouldnt that need a seperate reaction alltogether to now make the iso to the ketone? The safrole is converted to the ketone and if the safrole that dosnt get converted will either form the iso or stay as safrole. Longer reaction time might help the safrole convert over as long as the cat has some something to work with and can do its job. But the iso would have to be converted in a whole seprate rxn that isnt figured in the initial reaction. I think the best bet is to regenrate your used up rxn contents to try and keep on converting the unconverted safrole.
Uhh too early go to go back to bed.
(Stranger)
04-09-02 18:56
No 294645
There is most likely no safrole left after a few minutes of rxn. It is all isomerized. There is something fucked up going on, however. At least with the nitrite wacker, the rxn procedes for only about an hour or two and then stops. One of two things could be causing this. The first is that for some reason, isosafrole doesn't react, although this is not likely. The other reason is that something is being produced that inhibits the reaction. I plan on running pure isosafrole through the wacker to see if I get anything, ruling out or confirming the first theory.
(Hive Bee)
04-10-02 08:47
No 294923
Swim has noticed that most is all isomerized in the first few minutes. That would be the reasoning behind sllowing time to put safrole in. Let it react slowlly as not to get to much for it to handle. But not all the safrole gets oxidized even though most does. The iso should be the byproducts of safrole that did not quite make the conversion and is imcomplete. Swim has tried the nitrate with pure iso-no good. I believe you need something like the performic to oxidize solely iso. You would have to change up some of your other rxn contents. Side reactions are probally thre cause of iso left or breakdown of ketone in rxn mix leaving some iso. But Swim rarelly gets any iso forerun. Maybe a drop or two but never more. And usually very little safrole. Most seams to be lost in clenaup or in distillation.
(Stranger)
04-10-02 16:46
No 295003
Are you refering to the alkyl nitrite wacker or the nitrate wacker? Which ever one you used, could you post your procedure and yields? Also, You say that you ran pure isosafrole with this wacker. Did you ever run pure safrole? If so, what were your yields? Was there any olefin prerun?
Also, you say that most of the safrole was isomerized in the first few minutes. How did you come to this conclusion? Which wacker procedure were you using when you determined this?
I don't think that slowly adding the safrole will reduce isomerization. This isomerization is catalyzed by the palladium. Since the rate of isomerization is many times faster than the rate of oxidation, no matter what the safrole concentration is, the isomerization will come to equilibrium after only a small percentage has been oxidized.
Also, what procedure were you using when you got 78 g ketone form 90 g safrole?
(Stranger)
04-10-02 16:55
No 295005
Ritter:
What wacker procedure was used for the product distribution that you gave. Also, which procedure was used when you concluded that isosafrole reacts the same as safrole.
(Master Whacker)
04-11-02 04:13
No 295302
IPA was used as solvent, 60-70PSI maintained throughout oxidation and temp held at 40'C. About 20% iso was always recovered with the ketone fraction consisting of what I mentioned above. Iso and Allyl provided exact products. I can't find the link now, but somebody recently posted a link to J. Chinese Chem. Soc., 2001, 48, 59-63. This fantastic journal article has a procedure for isomerizing allyl benzenes to propenyl benzenes with methanolic PdCl2.
(Chief Bee)
04-11-02 19:35
No 295525
Here is that link: http://www.sinica.edu.tw/~ccswww/zj-OR-2
(Distinctive Doe)
04-11-02 20:30
No 295558
(Rated as: excellent)
That article kicks ASS!!!
Woo hooo
Found another Winner in that Journal.
Synthesis of 1,2-Methylenedioxy-5-methoxy-4-trans-pro
http://www.sinica.edu.tw/~ccswww/zj-OR-2
Foxy
Those who give up essential liberties for temporary safety deserve neither liberty nor safety
(Stranger)
04-11-02 23:51
No 295653
Ritter:
There are many other interesting articles I read as well. In fact, the ammine ligands may not do jack shit, because they seem to inhibit oxidation to the 3-alkene (MDP-1-P), which you say is not produced at all. One of the articles (I'll post a list of all of them later) says that decreasing [Cl-] and [H+] will increase selectivity of the 2-ketone (MDP-2-P) as opposed to the aldehyde. If 15% of the converted product was aldehyde, then this might prove greater interest. Also, you said that 20% of the starting alkene didn't convert. Theoretically, there is no reason that this should happen, as the equilibrium of the reaction lies FAR to the right. I have had the same problems of incomplete conversion with the potisgood ethyl nitrite wacker. I ran one last night that might have gone to completion, however. I haven't distilled the oil, but upon hydrolyzing and heating the post reaction mixture, no ethyl nitrite boiled off as usually does. This would indicate that all of the ethyl nitrite reacted, and thus 100% conversion. I'll know for sure after I distill it tomorrow. I followed the procedure exactly, except I pre-stirred the PdCl2 and CuCl2 for 24 hrs. It took this long to completely dissolve. The posted method gives only ~40% conversion, and a great deal of ethyl nitrite boils off while hydrolyzing. I think that pre-stirring solves all the problems.
(Master Whacker)
04-11-02 23:57
No 295659
Never saw this before- a Pd mirror formed during IPA/O2 Wacker oxidation!
http://www.geocities.com/neptunexplorer2
(Pioneer Researcher)
04-12-02 02:28
No 295730
Nitrites seem to be problematic, please post your results.
(Stranger)
04-12-02 17:32
No 296037
OK, I guess I was wrong about my wacker getting 100% conversion. It turns out that after distillation, I was left with 18g safrole and 8g ketone. This just made me throw up my hands and say what the fuck
Here are the problems:
1) After hydrolyzing the rxn mixture, I heated it to 50C for an hour. During this time, no ethyl nitrite bubbled out of solution like it usually does. There is no way that it could stay in the solution at that temperature and water content. I know that it didn't escape during the reaction because I had an ice cold gas condenser b/t the flask and the outlet at the top. So if it didn't react by reoxidizing the CuCl, then what the hell did happen to it? I did a crude measurement of the amount of NO gas coming out of the reaction by counting the rate of gas bubbles flowing through my vent hose. I calculated that less than half of the expected amount was produced, and this seems to match my yield. That means there are ~10g of EtONO unaccounted for. The only explanation that I have is that it was somehow hydrolyzed to HNO2 and EtOH during the reaction. Mabey this rxn is going on:
EtONO + H2O ==> EtOH + HNO2
3 HNO2 ==> HNO3 + 2 NO + H2O
To hydrolyze 10 g ethyl nitrite, only 1.6g H2O would be needed, or about a 1% water content based on reaction volume. I'll analyze this equilibrium later.
2) The other problem is that hardly none, if any, isosafrole was present in the distillate. Another time that I ran the reaction, all of the prerun was isosafrole (60%) and the other 40% was ketone. Why wouldn't the isomerization be taking place this time?
3) As the reaction progressed, a green/yellow precipitate formed on the sides of the flask. The amount of precipitate seemed to be inversely proportional to NO gas generation. Perhaps this is CuCl that precipitated due to lack of EtONO to reoxidize it. When treated with HCl, this salt turned red, and when the red salt was treated with NaOH, is dissolved, forming a green solution. Any clues as to what this precipitate was?
These results have me completely baffled. Any help would be greatly appreciated.
(Pioneer Researcher)
04-12-02 22:17
No 296133
I don't know if you know that I was playing with methyl nitrite time ago. I made lots of tests, and finally I observed that the only way to make react all the alkene is adding more catalyst, cocatalyst worked weakly or nothing, I used both CuCl2 and trimethylamine with similar results. After a rxn using 4.5 % PdCl2 and no CuCl2 the smell of safrol was undetectable, and you know safrol smells intensely, yield around 60-65 % (73 % of not very pure ketone). For this reason I told you to post your results, it seems we still have not found a good and accesible nitrite procedure with little catalyst.
(Stranger)
04-12-02 23:47
No 296158
The one thing that I don't understand, is why it works in the patent. There must be something that we are overlooking. What yield did you get with cocatalyst? My highest was ~40%.
(Stranger)
04-13-02 00:01
No 296164
I might know why that last rxn I ran was so fucked up. I had buried the safrole in the woods for about two weeks with some other chems. During this time, toluene left over from a nitro amination leaked everywhere along with a little of the safrole. The safrole smelled awful, nothing like the freshly distilled shit. I'll try the same procedure again with pure safrole.
(Master Whacker)
04-13-02 03:32
No 296263
Lab_B,
Why don't you use IPA nitrite instead of that crazy- volatile ethyl nitrite? I think it would make life easier dealing with a reagent thats at least liquid at room temp!
(Hive Bee)
04-13-02 15:03
No 296410
My old partner used to swear by the methyl nitrites. He loved it and he would get extremelly high yields upwards of 65% every time. Personally I never put enough attention into it and didnt have enough experience to really tweak with it. Damn I wish I could get in touch with him on this-but he is of doing a world soul searching or something and a little hard to reach. But I do have tons of notes on it-all of his notes to and they might be of some very good interest.
Ritter are the ratios of rxn for the IPA comparable to the other wackers? I havnt had any info on it but i would assume it would be similar. How about H2O.
Lab bitch- the wacker Swim ran was a version of said partners H202. It worked and was second time it ran with decent results but something dosnt look right after animation. Will do a test next week when Swim has access to a library.
(Pioneer Researcher)
04-13-02 15:37
No 296413
Lab_bitch, if I remeber correctly I got a 35 % or so with cocatalyst and probaly a 1 or 1.5 % of PdCl2.
Blazztoff, I got that 65 % but without cocatalyst and that 4.5 % of PdCl2, do you know how much PdCl2/CuCl2 did he use ?
(Hive Bee)
04-13-02 16:05
No 296420
I have to check those notes. But If I remember though he was tweeking it out and before he went on his soul search he was getting way higher. I preety much stayed to hydrogenations of his wackers and he is a genius on this. To bad he never trusted new fangled computers as he would put it. So I have to pour through mounds of his scribble and make sense of it. The nitrites where his baby though-it wasnt a norm but his pet project. Am currentlly going through his stuff and piecing it together for research of my own. But slow going since I dont have much time with my wife beating down my neck cause im supposed to be retired.
(Pioneer Researcher)
04-13-02 19:13
No 296460
Nobody doubts you are retired, say your wife it's just documentation, science
(Stranger)
04-14-02 01:25
No 296559
Not related to the Wacker, but am I to understand from this thread that straight 10% Pd/C would bee a quick and effective catalyst for the isomerization of olefins such as safrole?
(Hive Bee)
04-14-02 10:04
No 296746
Sunlight I have went through some of his notes and found out some. Some of his notes are in Japanese though and I have no idea how to decipher those characters. But I have found one experiment that was preety much complete. It mentions using Bischloronitropalladium as the catalyst. He always said that the methyl nitrites were the future-he was jumping for joy when I landed him 4l of acetonitrile to play with for them. I did not pay attention to much to these experiments for these were not suited for any real production. I know everything is in his notes-he was real good at bieng cryptic with me and made me figure out what I should have known. It took me 2 years to figure out the proper catalyst for hydrogenations that we were using.
I dont have all the notes here but been meaning to get them. But only can go through them at work cause my wife sees them she throws shoes at me. Shes Puerto Rican and you dont piss them of.