[orgo814]

Hi-

I am doing a reaction for my research where Zn(2+) activates the carbonyl oxygen allowing the reaction to take place. I used zinc chloride anhydrous. The reaction did not work. Although there are many possible things and I know I'm not giving too much information on the actual reaction, I suspect the ZnCl had either moisture or needed to be activated in some way. Does anyone have any info on the best way to activate/dry Zinc Chloride Anhydrous? I found a procedure in an old book which involved refluxing the ZnCl in dioxane with Zn dust and then doing a hot filtration followed by crystallization of the precipitate in the filtrate (also washed that with dioxane to remove excess Zn dust that I noticed on the precipitate)... This yielded a very dry flaky white solid which I will use tomorrow but I am still curious as to any other methods people have used for activating the ZnCl (or if anyone has used the method I just described).

Thanks for any feedback.

[rolnor]

If you have access to chlorine gas you could make it from the elements. Maby more practical to use bromine, zinc bromide is a good substitute for zinc chloride. I would use zinc powder in diethylether and slowly add bromine.

[kamiyu]

I think you can try SOCl2 refluxing with ZnCl2, then distill off the excess SOCl2. but beware of removing residual SOCl2

[orgo814]

Thank you very much for the advice. Is it possible the ZnCl2 could go bad after a long time? The bottle is ancient... not sure when it was purchased as I joined this lab group only recently and the PI changed as well so he doesn't know. I'm only wondering since my purification didn't do anything.

[NewmanProj]

Thank you very much for the advice. Is it possible the ZnCl2 could go bad after a long time? The bottle is ancient... not sure when it was purchased as I joined this lab group only recently and the PI changed as well so he doesn't know. I'm only wondering since my purification didn't do anything.

Commercial ZnCl2 in solid form varies from batch to batch. If I was unable to buy it fresh, I took "anhydrous" ZnCl2 off the shelf, placed it into a 100 mL round bottom flask, and then melted it under high vacuum. You have to be careful not to melt the flask. This is known as the "fusion method of preparing anhydrous zinc chloride".

If you only need to use it once, this method works. If you need to do it over and over, depending upon how much ZnCl2 you need, perhaps you can make a THF solution of known concentration.

Good luck!

[kamiyu]

I personally also tried melting the ZnCl2 in vacuum and it worked well. Indeed, when the ZnCl2 is contaminated with water , its melting point is drastically decreased.

[orgo814]

Good idea- thank you! When I came in this morning after having it on high vac overnight, the ZnCl2 anhydrous was beginning to melt (at room temperature!)- I'm assuming this means it probably is very contaminated with water.

[Masurium]

Melting over an open flame dehydrates it. This is a method found in the old literature.