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Topic: Free base to HCl Question  (Read 17362 times)

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Offline joe955

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Free base to HCl Question
« on: May 06, 2010, 07:14:58 AM »
Will Hydrochloric acid (Muriatic Acid) convert any and all amine's to HCl or do amine's only convert to HCl by bubbling Hydrogen Chloride through the freebase?
« Last Edit: May 06, 2010, 07:27:38 AM by joe955 »

Offline AWK

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Re: Free base to HCl Question
« Reply #1 on: May 06, 2010, 08:00:58 AM »
Do you mean ammonium hydrochlorides.

Do all  bases react with strong acids?
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Offline joe955

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Re: Free base to HCl Question
« Reply #2 on: May 06, 2010, 01:33:49 PM »
I'm not understanding your response with a question. I was under the impression that an amine free base can be converted to a salt form by reacting the amine free base with HCl. But I'm a little confused if the gas Hydrogen Chloride (HCl) is needed to convert the amine free base to a salt form or if Hydrochloric Acid (HCl) can be used to convert the amine free base to a salt form?

Offline Doc Oc

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Re: Free base to HCl Question
« Reply #3 on: May 06, 2010, 02:13:27 PM »
One of the challenges with using muriatic/concentrated HCl is that they are a maximum of 37% HCl.  The rest is water, so if you use that you're mostly adding water, which will dissolve any salt you might have (although somebody has probably precipitated a salt using this and will tell me I'm dumb, but I haven't ever done it that way).  That's the reason people bubble pure HCl gas into a reaction, you don't have to deal with that issue.

Offline helenn

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Re: Free base to HCl Question
« Reply #4 on: May 06, 2010, 03:54:01 PM »
You can use HCl in ether or dioxane to get the salt as a precipitate, these can be bought as 1M solutions.

Offline joe955

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Re: Free base to HCl Question
« Reply #5 on: May 06, 2010, 06:12:41 PM »
Ok I do believe that the gas is needed more so than using the acid that makes more sense.
Can the gas be substituted with just Hydrogen or does it for sure have to be Hydrogen Chloride?

Offline Borek

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Re: Free base to HCl Question
« Reply #6 on: May 06, 2010, 06:25:43 PM »
Since when hydrogen is an acid strong enough to protonate anything?
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Offline Doc Oc

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Re: Free base to HCl Question
« Reply #7 on: May 06, 2010, 07:06:25 PM »
You're getting confused now, it has nothing to do with whether it's aqueous or gaseous.  The most important property is the acidic proton, which as Borek pointed out, hydrogen does not have.

Pure HCl gas is pretty easy to generate and it works real well to avoid the issue I mentioned with the aqueous HCl so that's why people use it, not because it's more effective in the gas form.  If you could concentrate HCl to 100% then people would use it.

Offline joe955

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Re: Free base to HCl Question
« Reply #8 on: May 07, 2010, 02:44:38 AM »
Ok so then it is that the acid has the acidic proton present but as you said the acid has mostly water which is not going to help the salt form and since the gas is pure HCl with the acidic proton present and no water that is good.

Now I no you said that you have not really tried to use the acid over the gas but does it seem possible that if the acid was to be used and the water evaporated would the free base form into a salt as it dries and be considered HCl?
I'm not sure but it seems like maybe this is similar to what helenn said "You can use HCl in ether or dioxane to get the salt as a precipitate, these can be bought as 1M solutions".
« Last Edit: May 07, 2010, 03:41:15 AM by joe955 »

Offline joe955

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Re: Free base to HCl Question
« Reply #9 on: May 07, 2010, 03:04:11 AM »
Since when hydrogen is an acid strong enough to protonate anything?
I thought that this was true. Good thing I checked. I was told that using hydrochloric acid with aluminum was the process for converting to HCl. But when I checked what this was creating "Hydrogen" I got a little weary about making a "Hindenburg" bomb to convert amines to HCl. I also read what Hydrogen reacts and don’t react with and it read "doesn't react with acid or base". I just wanted to confirm that I was reading the right things before I made the 6 O'clock news.

Offline Dan

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Re: Free base to HCl Question
« Reply #10 on: May 07, 2010, 06:08:43 AM »
if the acid was to be used and the water evaporated would the free base form into a salt as it dries and be considered HCl?

Yes, we do this all the time in our lab.

If you have an amine in aqueous HCl and then concentrate the solution to dryness you are left with the corresponding ammonium chloride.

The acid-base reaction is always: acid + base -> salt, regardless of whether the solvent is water or something else (assuming the solvent is inert under the reaction conditions).

HCl gas and other alternative HCl sources are used when you want a solvent other than water - often in cases where water would not be inert under the reaction conditions.
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Offline joe955

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Re: Free base to HCl Question
« Reply #11 on: May 07, 2010, 11:41:34 AM »
Is there a formula used to determine how much of the aqueous HCl to add per volume?

Offline 408

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Re: Free base to HCl Question
« Reply #12 on: May 07, 2010, 01:22:03 PM »
Of course!  But it is not related to your initial volume, it is related to initial molar quantity of amine! 

Gaseous HCl is used because your amine will be soluble in some organic solvent.  Bubbling HCl gas forms the salt that is insoluble in organic so it precipitates.  Depending on how that amine was initially prepared, precipitating the amine hydrochloride may purify it from non-basic organic components.
If you add aqueous HCl a couple things may happen:
1.  you may get two phases depending on the organic solvent, your hydrochloride would end uup in the organic layer.
2.  You get one phase that is now "wet" and your hydrochloride precipitates as a sticky mess, in poor yield, or not at all.

but your use of the phrase "freebase" makes me think I should not have bothered typing this..

Offline nj_bartel

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Re: Free base to HCl Question
« Reply #13 on: May 07, 2010, 03:37:15 PM »
Does anyone else get the vibe we're helping someone start up a coke mill? :P

Offline AWK

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Re: Free base to HCl Question
« Reply #14 on: May 10, 2010, 02:30:24 AM »
Is there a formula used to determine how much of the aqueous HCl to add per volume?
It depends on the amine used:
eg: methylamine - 1:1 molar ratio
ethylenediamine (1,2-diaminoethane) 2:1 (HCl to amine)
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