07-13-02 20:52
No 332297
1) I've been reading up on the benzo-wacker. Some bees say that safrole is made along with mdp2p, some say the it is in fact ISOsafrole that is produced together with the ketone. Which is it?
Next question (to save headings in forum):
2) In the benzo wacker, varying amounts of pdcl2 are used along with cupric chloride and other changes in reagents and solvents. I'm thinking methanol can be used instead of DMF with good results, but what of the CuCl? Is that OK to omit?
I would like all the benzo bees out there to leave their idea of the perfect wacker using 200g of safrole to play with:No pressurized vessel rxn going down so you can leave that variation out thank you.
This must include using excess heat , not using any heat, stirring time, using different solvent to mix your alkene with and for the pdcl2 mixing. but most importantly, the weights in grams needed for a perfect ATM benzo wacker in methanol. I can't wait to hear all the different views on this as I have read so many so far from different sources. Go NUTS!!.........
OB1
(Greenhorn)
07-13-02 21:16
No 332302
1. When you run a benzo wacker, the safrole is converted into iso then mdp2p. Safrole is your starting oil, so why would the wacker make safrole?
2. Different methods call for different starting materials. If you have a certain syth in mind from Rhodium's page, then just follow the synth. They work just as written. Brightstar's wacker calls for dmf and you don't need to apply heat to a reflux with the dmf. There is already a writeup using methanol instead of dmf. Brightstar's wacker and MM's writeup don't use cucl.I think your confusing them with spiceboy's pressurized bottle writeup.
I think you need to do some more reading. Start at Rhodium's page first. Then try the FSE.
We'll soon find out if I'm a chemist or not!
(Newbee)
07-14-02 14:40
No 332497
Maybe the guys just meant isosafrole when they say safrole is made as an end product as well as the ketone. Yup, thank BigG but I read and printed out every single synth on Rhodium's page. I guess that's why I'm a little confused as to what solvents to use and if CuCl2 should be thrown in the mix as well. ChemisTris PM'd me to say that benzoquinone and CuCl both work to get the PdCl2 back to a +2 state. So basically I want to do an unpressurized benzo wacker and I'm just wondering what the best way to go about it is regarding solvents used and other reagents added. Thanks for all the PM's about this....
Another thing about destilling the ketone from a benzo wacker:
1) If my aspirator/pump pulls safrole over at 170°C will the ketone be burned even if major water washes along with bicarb and NaoH 5% washes are done prior to destilling> or does a stronger vacuum need to be utilized?
OB1
(Greenhorn)
07-14-02 15:07
No 332508
../rhodium /wacker.
Try that one. It's easy to read and works great.
If your pump pulls safrole over at 170, your ketone should come over at around 195. That's kinda high, but it should work ok.the washes don't have anything to do with the bp of your ketone, your pump does.
We'll soon find out if I'm a chemist or not!
(Newbee)
07-14-02 15:39
No 332527
Yes, but the washes cut down on the tar formed right, / that's what I meant by the washes helping alot in not burning up into tartone.... Thanks man....
OB1
(Stranger)
07-15-02 03:02
No 332777
"benzoquinone and CuCl both work to get the PdCl2 back to a +2 state", well PdCl2 is in a +2 state, the Pd(0) that is formed as part of the catalytic cycle, must be returned to the +2, so it can continue participating in the reaction. If i said the wrong thing in my PM that was because i was in a hurry and thats why i didn't post, but i didn't save a copy of my PM to OB1 so i don't know.
Got democracy? http://www.dhushara.com/book/multinet/de
(Hive Bee)
07-15-02 08:15
No 332833
In the wacker, Pd+2 is reduced to Pd(0) while at the same time, safrole is oxidized to MDP-2-P. In order to avoid using ~1g PdCl2 per gram safrole, the Pd(0) must be reoxidized to Pd+2. This can be done in many ways. In one method, benzoquinone is reduced to hydroquinone while oxidizing the palladium. In another method, CuCl2 is reduced to CuCl while oxidizing the palladium. Benzoquinone can be used in stoichiometric quantities, but CuCl2 cannot because the chloride ions inhibit the reaction. Therefore, the CuCl is reoxidized to CuCl2 using oxygen or an alkyl nitrite. Three methods evolve from these three oxidation steps:
1) The benzo wacker
2) The O2 wacker
3) The alkyl nitrite wacker
Although I have never done it, the benzo wacker seems the easiest for newbees. The other two have several bugs in them that I am trying to work out right now.
There are two simultaneous reactions that the safrole undergoes in the wacker. One of them is the oxidation to MDP-2-P. The other is the isomerization to isosafrole. Both of these are catalyzed by palladium. The benzo and O2 wackers produce isosafrole as a byproduct. The alkyl nitrite wacker does not, b/c alkyl nitrite inhibits the isomerization.
Also, if you pull safrole at 170C, your ketone will come over at about 215-220C, right in the polymerizaton range. There is approximately a 45C range b/t the two boiling points. The 25C difference talk is bullshit. I strongly recommend getting a new vacuum pump, as you need a very powerful hotplate to distill something over 200C.