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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: faust on April 15, 2006, 04:49:43 AM

Title: How to handle volatile amine?
Post by: faust on April 15, 2006, 04:49:43 AM: Hello again,

here is my problem..

i'm trying to synthetise this quaternary ammonium salt.

I have some troubles for the first step... I can't isolate this amine, because it's really volatil. I have tried to add picric acid, or oxalic acid, but nothing precipitate. Then I added a solution of HCl in diethylether, and I don't have any precipitate of chlorhydrate, just some fumes over the ether, which seems to be my amine chlorhydrate!

I have tried to do the same reaction but like this : dimethylamine.HCl + Bromobutene (Dichloromethane/Et3N). And then, I can precipitate Et3N.HCl + N,N-dimethylhomoallylamine.HCl (it seems that the presence of the Et3N.HCl precipitate facilite the correct precipitation of my amine).

Then I have put my mixture of these two amines in the following step... Unfortuatly, I have almost 100 Et3N⁺CH2COOK for one of my desirated product...

Of course, I could try to separate these two compounds by preparative HPLC... But do you think there is a trick to isolate my amine from the first step (reaction between allylMgCl and Eschenmoser's salt?)

Thank you
Title: Re: How to handel volatil amine?
Post by: Mitch on April 15, 2006, 04:54:02 AM: Could you ise a gold finger device above the reaction flask filled with liquid nitrogen. So that the vapor would condense on the cold trap?
Title: Re: How to handel volatil amine?
Post by: faust on April 15, 2006, 05:07:42 AM: unfortunatly I don't have such cold finger... I will try to directly engage the result of the grignard addition in the next step... I'll put my THF medium in methanol

I think the addition of grignard on Eschenmosersalt is a very clean reaction. I should have to many byproducts...
Title: Re: How to handel volatil amine?
Post by: Mitch on April 15, 2006, 05:12:49 AM: Just construct one, it can't be that difficult with all the instruments that lie around a lab.
Title: Re: How to handel volatil amine?
Post by: faust on April 15, 2006, 05:53:02 AM: in fact this kind of amine seems to have a bp at 93°C (following scifinder...) But when I distillated the product it codistillate with THF of with ether...
Title: Re: How to handel volatil amine?
Post by: movies on April 16, 2006, 01:09:47 PM: Can you move the crude amine on as a solution in diethyl ether? That would be convenient, I would think.