Author Topic: poor yield  (Read 845 times)

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GenericVersion

  • Guest
poor yield
« on: June 14, 2003, 09:45:00 AM »
DMF/Benzo/PdCl2 wacker ala brightstars method, SWIM is getting yields around 25-35% perhaps 40g or so of crude product( sometimes red, one time blue later turned red) has has sucessful workup of the amine we love from this crude product but SWIM would love to have 120g of that beautiful green stuff come over, some points perhaps on where SWIY has fucked up in the past and would like to share?


DMF is good/ PdCl2 is good (both have been used in sucessful batches) Benzo is pea green/yellow (perhaps purify how??) perhaps 1 year old stored in light proof area at no higher than 30C usually at 22C or so all glass is clean. rxn ran 8 hours one time and 9.5 the next both times no more than 50g of crude ketone came over. Any hints on workup appericated, SWIM thinks I'm loosing it in my workup so SWIM saved the mix in the freezer and will try to extract more later. again any general advice appericated

tranceport

  • Guest
Your benzo sounds like photograde..
« Reply #1 on: June 14, 2003, 12:40:00 PM »
or degraded. Lab grade is harder to come by in the us, but stores longer due to purity and such. That sounds like a possibilty.

GenericVersion

  • Guest
so would it be a good idea to recrystalize the
« Reply #2 on: June 14, 2003, 07:01:00 PM »
so would it be a good idea to recrystalize the p-benzo, Swim can do that in Methanol correct? that would up the purity. AS far as SWIM can tell it is photo grade

tranceport

  • Guest
Well swim is no chemist, just guided actually...
« Reply #3 on: June 16, 2003, 06:30:00 AM »
But logic tells me if its degrading recrystalizing would have no effect, except purifing a degraded product. Please, some elder bee verify him, but p-benzo does degrade and there isnt a way to bring reactivity up, is there?

IMHO you should just go to rhodiums, read up on making it. Works, and the chemicals are available. But dont make it 2-3 months before you need, like 1-2 weeks. Its easy cheap and unwatched that way, but your purity wont be perfect, so make as use and go along...

Thanks to the bee who can answer the above for him.

Rhodium

  • Guest
Reviving old p-benzoquinone
« Reply #4 on: June 16, 2003, 02:34:00 PM »
The degradation and lowering of reactivity is because of an impure product. On storage the following happens:

p-Benzoquinone =air/heat/light/moisture=> X + Y + Z + p-Benzoquinone

The large majority of the benzoquinone is still there, but an amount of it has decomposed by the action of air, heat, light and moisture, forming unknown substances. Thus, not only is a certain percentage of your compound no longer p-Benzoquinone, but the unknown impurities formed may even prevent some of the still good benzoquinone from reacting properly...

Therefore, recrystallizing it will very very likely bring it back to its former glory.

GenericVersion

  • Guest
SWIM is grateful for a vetrans advice, thanks
« Reply #5 on: June 17, 2003, 03:57:00 AM »
SWIM is grateful for a vetrans advice, thanks