Author Topic: 30 Celsius important for BS's Wacker ?  (Read 583 times)

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methlab

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30 Celsius important for BS's Wacker ?
« on: January 07, 2004, 02:45:00 PM »
The recipe says: "Drip the Safrole/DMF Mix into the solution at room temp (30C) over 30min time". A summerday with 30C is called a very hot day in my country. I want to know how important this temperature is. In my house the roomtemp is 20-23C. Shall i heat the solution/room to 30 C before I mix things together ? My Merckindex says, that 1,4-Benzoquinone is slightly soluable in water (10g/liter, 25C watertemp), so maybe this is the reason for the 30 C ? Last time the maximum temperature during my wacker was 35C.

wolfx

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Wacker temperature
« Reply #1 on: January 08, 2004, 09:43:00 PM »
The p-benzo is not going to dissolve all initially, no matter what you do. Just stir, as the reaction progresses it will be gradually consumed and everything will go in solution.

I think the Wacker temperature is not that important. It is usually exothermic, the peak temperature tends to be about 40 C or so. But I and other bees have seen cooler peak temperatures, both with high and low yields. If it is cool, I like to apply heat and to keep it at circa 40 C, but I don't think it is that important. You don't even need a bath for that, just make your BF touch the hot plate, set it to low, watch the temperature.

EDITED POST : P-benzo is essentially insoluble in water. The DMF helps to dissolve it, but it will not dissolve completely. P-benzo is much more soluble in non-polar solvents like DCM and benzene.