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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Nescafe on April 13, 2015, 01:19:23 PM

Title: From TFA salt to HCl salt
Post by: Nescafe on April 13, 2015, 01:19:23 PM

Hi all,

I currently have my product stirring in water and I am sure my free amine is probably coordinated to TFA. I was wondering, what is the best way to make the HCl salt and crash my stuff out? I am planning to evaporate the water (Product is very soluble so work up will be a headache), the reconstitute in 4.0M HCl dioxane and then crash the salt out?

Any suggestions? Unfortunately the need for water to make the compound seems to be necessary so I can not avoid having it there.

Thanks,

Nescafe. 

Title: Re: From TFA salt to HCl salt
Post by: TheUnassuming on April 13, 2015, 02:29:11 PM

Is the freebase soluble in organics? 
Typically to exchange ions/make the HCl salt I make the freebase, extract the amine with organic from the aqueous layer, then bubble in HCl and filter off my product as the HCl salt. 

Title: Re: From TFA salt to HCl salt
Post by: Nescafe on April 14, 2015, 09:12:53 AM

I would like to try this, I am curious, how do you bubble in HCl gas?

Title: Re: From TFA salt to HCl salt
Post by: TheUnassuming on April 14, 2015, 09:47:58 AM

The best way is with a tank of HCl gas.
You can generate HCl gas on demand in smaller amounts by dripping conc. HCl into conc. sulfuric acid or by dripping conc. HCl onto NaCl as well.  The gas produced isn't "dry" but you can bubble the gas through sulfuric acid first to help dry it out.

Title: Re: From TFA salt to HCl salt
Post by: tomek on April 15, 2015, 08:41:48 AM

I highly recommend using anhydrous CaCl₂ and concentrated HCl. HCl produced this way is dry enough for many purposes. I usually do it in a suction flask which is stoppered and side neck is connected through tubing to a Pasteur pipette (this can clog sometimes at the tip so it might be a good idea to chop it off first). I swirl the flask in one hand and hold the pipette in the other hand dipping it in ethereal solution of amine. Here's a paper describing this: http://pubs.acs.org/doi/abs/10.1021/ed072p1139 (http://pubs.acs.org/doi/abs/10.1021/ed072p1139)