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something be substituted for DMF in a Benzoquinone/wacker?
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| Author | Topic: Can something be substituted for DMF in a Benzoquinone/wacker? |
| Snidely
Whiplash Member |
posted 10-12-98 06:40 PM
Can something be substituted for DMF in a Benzoquinone/wacker? Thanks! |
| Piglet Member |
posted 10-13-98 04:14 AM
I would say Dimethyl Acetamide would work. DMSO probably and Acetonitrile maybe. I WOULD try them, anyway. |
| quirks Member |
posted 10-13-98 07:20 AM
DMF is used cause it solvates the PdCl2 relatively well and it doesn't complex with the Pd right? Cause it's basic or something? Maybe methanol?? Didn't osmium say he used methanol as a substitute. No
sense getting exotic if it's not needed. |
| Piglet Member |
posted 10-13-98 08:30 AM
It DOES form a complex with the Pd. The Patent of the Wacker points out that the complex is the better catalyst. |
| quirks Member |
posted 10-13-98 09:15 AM
So is the patent online?? |
| ketone Member |
posted 10-13-98 11:00 AM
I'd be interested to hear the complex chemistry of PdCl2 and DMF... DMF is often chosen in org. chem. for a number of reasons, and was popular back in the hay-day of org. chem. research and patent filings. Why? Relatively high boiling point (slow evaporation), works well as a gas or liquid solvent, easy to prepare in the lab, etc. Infact, even Merck mentions it has been dubbed the "universal organic solvent". MeOH will work in my ever-so-humble opinion. Make sure the reaction doesn't get near the boiling point and keep it under reflux anyway. (If it does get near MeOH's boiling point, you've already got problems anyway...) Alcohols and Wacker work just fine. It's been proven time and time again... Wow, I'm feeling all punchy today.
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| Piglet Member |
posted 10-13-98 11:22 AM
Won't the benzoquinone react with the methanol? This as a problem, who can say. Nice if it does run! |
| drone
342 Member |
posted 10-13-98 01:49 PM
MeOH shouldn't react with benzoquinone. How would it? -drone #342 |
| ketone Member |
posted 10-13-98 02:39 PM
Quinone won't react with alcohol or ether... Unfortunately, I cannot (theorectically) try the reaction right now to prove the theory. Anyone brave enough to (theorectically) try MeOH in this reaction?
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| Planet E
Toon Member |
posted 10-13-98 04:50 PM
Alcoholic solvents "are excellent reaction media"(JOC 34) for wacker oxidations. Results indicate that olefins in alcoholic palladium salts react more readily in media containing little or no water. Improved Procedures for Converting Higher alpha-olefins to methyl ketones with Palladium Chloride", Clement, W.H., et al.,J. Org. Chem., 29, p241 (1964)indicates that DMSO sucks for wackin with Wacker. |
| Atomicdog Member |
posted 10-13-98 05:15 PM
If one were to substitute MeOH, would I be correct in assuming molar equivalents? And what about the water? Same ratio or omit it? |
| ChemHack Member |
posted 10-13-98 05:35 PM
AtomicDog: "Complexes" aside, the MeOH here is a solvent rather than a reactant. |
| Planet E
Toon Member |
posted 10-13-98 05:56 PM
Dont add water. It will slow the reaction down. |
| Snidely
Whiplash Member |
posted 10-13-98 08:00 PM
well.. my poor lab technique and I have jointly determined that 1g of benzoquinone is soluble in between 20 and 30ml of MeOH. This seems really unsatisfactory to me. Maybe I didnt stir this stuff enough, but the ammount of precipitate seemed to be holding steady at "way too much" until I hit like 1:20 or more. Any comments? |
| ChemHack Member |
posted 10-14-98 04:36 PM
Does solubility increase with temperature? |
| Atomicdog Member |
posted 10-14-98 10:46 PM
So the MeOH is only for dissolving the benzoquinone so it can react? Then it's really a spectator of the reaction, right? Geez, I hope I'm getting this! |
| Snidely
Whiplash Member |
posted 10-14-98 11:18 PM
Atomicdog, yeah, you just want to run the reaction in the solvent. Since the MeOH required is a huge ammount, your reaction would run slowly or not at all. |
| Strike Administrator |
posted 10-15-98 12:23 AM
The water is necessary as a vital component of the reaction. Not as a solvent. Although many ratios will work, the optimal ratio for the Wacker reaction is seven parts solvent (DMF) and 1 part water. |
| ChemHack Member |
posted 10-15-98 02:12 AM
Uh, Strike.... I don't think anybody said anything about using water as a solvent... |
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