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All 5 posts Subject: Error in MM's Wacker (benzo) oxidation write up??? Please login to post Down

abuse
(Newbee)
11-29-03 05:21
No 473723
      Error in MM's Wacker (benzo) oxidation write up???

I was comparing Methyl Man and Brightstars write ups for the p-benzo wacker and I'm probably wrong but I may have found an inconsistency. Both procedures use relatively the same amount of safrole, PdCl₂, and p-benzo, and the only real difference is the reaction medium; 400ml methanol in MM's write up and 300ml DMF in the Brightstar write up. Anyway, after the wacker reaction is complete, MM indicates to create 1.7L 3N (~10%) HCl solution using 500ml of 31% HCL and flood the reaction mixture with it. Brightstar, on the other hand, indicates to create the HCL solution with only 50ml of HCl (Muriatic Acid, same as 31% HCL) and 1.5L of water. Why is there such a big difference between the amount of HCl used to create the HCl/dH₂O solution for flooding the reaction contents?

Antibody2
(Hive Addict)
11-29-03 18:14
No 473788
      it doesn't really matter exactly how much HCl...

it doesn't really matter exactly how much HCl is used as it isn't a reagent that is consumed, what you want is something between 5-10% HCl

the solution is made acidic so you will get a better seperation of ketone, if it were basic you would get emulsions and headaches

there was also some speculation with O2 wackers that HCl was necessary to hydrolyse the post wacker product to ketone, but as far as Ab2 is concerned O2 wackers were good for one thing - marketing PdCl2

We are all just witnesses.

wolfx
(Hive Bee)
11-29-03 19:36
No 473794
User Picture       p-benzo ammount

I think BS uses less p-benzo than MM. Also, I have seen some old Wacker recipes, slightly different than BS but pretty much the same thing, that uses the same molar quantity of safrole and p-benzo ( very small excess of p-benzo ).

doktor_alternate
(Stranger)
02-24-04 03:50
No 490730
      inhibitory chlorides

it seems that chlorides inhibit the reaction progress. does no-one use a molar equivalent ammt of Pd(OAc)2?

Bond_DoubleBond
(Hive Bee)
02-25-04 23:56
No 491106
      using equimolar amounts of benzo and some...

using equimolar amounts of benzo and some extra pdcl2, swim gets 140-150g ketone each wacker. using 150g benzo as in the mm writeup is wastefull.

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	All 5 posts		Subject: Error in MM's Wacker (benzo) oxidation write up???		Please login to post		Down


		abuse (Newbee) 11-29-03 05:21 No 473723				Error in MM's Wacker (benzo) oxidation write up???
						I was comparing Methyl Man and Brightstars write ups for the p-benzo wacker and I'm probably wrong but I may have found an inconsistency. Both procedures use relatively the same amount of safrole, PdCl₂, and p-benzo, and the only real difference is the reaction medium; 400ml methanol in MM's write up and 300ml DMF in the Brightstar write up. Anyway, after the wacker reaction is complete, MM indicates to create 1.7L 3N (~10%) HCl solution using 500ml of 31% HCL and flood the reaction mixture with it. Brightstar, on the other hand, indicates to create the HCL solution with only 50ml of HCl (Muriatic Acid, same as 31% HCL) and 1.5L of water. Why is there such a big difference between the amount of HCl used to create the HCl/dH₂O solution for flooding the reaction contents?



		Antibody2 (Hive Addict) 11-29-03 18:14 No 473788				it doesn't really matter exactly how much HCl...
						it doesn't really matter exactly how much HCl is used as it isn't a reagent that is consumed, what you want is something between 5-10% HCl the solution is made acidic so you will get a better seperation of ketone, if it were basic you would get emulsions and headaches there was also some speculation with O2 wackers that HCl was necessary to hydrolyse the post wacker product to ketone, but as far as Ab2 is concerned O2 wackers were good for one thing - marketing PdCl2 We are all just witnesses.



		wolfx (Hive Bee) 11-29-03 19:36 No 473794				p-benzo ammount
						I think BS uses less p-benzo than MM. Also, I have seen some old Wacker recipes, slightly different than BS but pretty much the same thing, that uses the same molar quantity of safrole and p-benzo ( very small excess of p-benzo ).



		doktor_alternate (Stranger) 02-24-04 03:50 No 490730				inhibitory chlorides
						it seems that chlorides inhibit the reaction progress. does no-one use a molar equivalent ammt of Pd(OAc)2?



		Bond_DoubleBond (Hive Bee) 02-25-04 23:56 No 491106				using equimolar amounts of benzo and some...
						using equimolar amounts of benzo and some extra pdcl2, swim gets 140-150g ketone each wacker. using 150g benzo as in the mm writeup is wastefull.

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