Rich_Insane
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Ether substitutes for this application
So there's a method of isolating amine HCl salts as so:
1) Free amine is dissolved in isopropyl alcohol
2) Isopropyl alcohol is carefully adjusted to a low pH with aq. HCl
3) An equivalent volume (relative to the alcohol) of diethyl ether is added, inducing the precipitation of crystals.
My guess is that this happens because iPrOH (and HCl to a lesser degree) is soluble in ether, but the amine salt is not. The ether pushes the salt out
of the solution as a solid. Unfortunately, if I wanted to do this at home, I'd have a hard time. Diethyl ether is difficult for me to procure.
Yes, I know one can make it or distill it from OTC products, but I do not have a working distillation apparatus. I would build my own, but I don't
have copper tubing or a power drill -- and I have qualms about using a ghetto apparatus to distill ether.
So I was wondering if it is possible for me to use "starting fluid" instead of pure ether. This material contains ether mixed with heptane, an "upper
cylinder lubricant" and a propellant (CO2). I'm pretty sure the lubricant is mineral oil (there was another product that used mineral oil). I'm
wondering if I can use this form of ether for the salt-forming process. I would preferably distill it, but again, I'm very low on funds (I had just
enough to buy 120 ml of pure anhydrous ether, but the seller on Ebay ran out). I found this product:
(Ebay listing): Zecol Premium Starting Fluid
(MSDS): Starting Fluid MSDS
Or would it be possible to substitute ether with say, toluene or naphtha? My guess is no, because ether is the only (commonly used volatile nonpolar)
solvent that has some affinity for hydrogen chloride.
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smaerd
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HCl is soluble in ether, many applications utilize ethereal hydrochloric acid.
Toluene might be too nonpolar same with naptha. Acetone might work, maybe methyl ethyl ketone. It's really hard to say without knowing the amine and
it's HCl salt solubilities.
It's basically impossible for anyone to tell you what might substitute here, likely you will need to experiment and find out. The good thing about
this is it can be done small-scale... Meaning take 10mL of your solution try adding naptha and waiting to see if anything crashes. If not, take
another 10mL and try adding acetone and see if anything crashes. This is an experimental science you know.
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Rich_Insane
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Well, I know the amine (hydrochloride) is listed as "slightly soluble" in acetone (no quantitative data provided), but that worries me, because I
wonder if the solute has to be completely insoluble in the solvent to crash out. I suppose that is the salt is slightly soluble in acetone, it will be
close to insoluble in 2-butanone... Is this product still available in the USA? I recall seeing it in hardware stores several years ago, but can no
longer find it... And the only source on Ebay charges exorbitant shipping prices.
I was hoping to experiment with the aerosol (starting fluid), but I need to figure out how to get the ether/heptane mixture out of the can and into a
graduated cylinder. Perhaps I could poke a hole in the canister or cut it open? Is this a hazardous practice?
[Edited on 17-2-2013 by Rich_Insane]
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zed
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Depends on which Amine Hydrochloride you are working with, and how "clean" it is.
First, can you pull the Hydrochloride Salt out of Isopropyl Alcohol, by the simple expedient of gassing your "dry" solution with HCl gas? If so,
that's the way to go.
Personally, I try to avoid using ether. Yeah, I've used it a lot, and I know how to handle it. It's just a lot less stressful to use other
solvents. Not to mention the stinkiness of it. Yukk!
[Edited on 18-2-2013 by zed]
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starman
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Quote: Originally posted by Rich_Insane  | Perhaps I could poke a hole in the canister or cut it open? Is this a hazardous practice?
[Edited on 17-2-2013 by Rich_Insane] |
See Len 1's set up in prepublication for getting ether from the can.Alternatively put it in the freezer overnight before you (carefully,no spark)
puncture the can.Yes I have tried both methods.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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Rich_Insane
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I would've much preferred gassing the HCl salt out of xylene or the like, but I do not have the funds to set up a full-scale setup. The sulfuric acid
alone would take up most of my budget.
I found one solvent in particular that's interesting to me: Methyl isobutyl ketone
It has a low solubility with water, and if acetone will not dissolve my salt extremely well, then MIBK will sure as hell crash the stuff out. It's
also cheaper than MEK for some reason. Maybe because it is used as a photography solvent. I myself have issues with ether because I can't do
experiments outside this season (it rains a lot here and the weather is very unpredictable). Everyone in the house complains when I'm working with
EtOAc, I can't imagine how much they'll complain if I work with ether!
I presume that MIBK will be miscible with xylene and isopropyl alcohol, yes? Also, does it have affinity for HCl due to that slightly negative
carbonyl oxygen? I will be extracting my amine directly from the reaction mixture using a small volume of xylene (3x10 ml xylene washes, say). I'll
add 60 ml of dry isopropyl alcohol and add HCl dropwise until the pH reads at 1. Then I will place this into an ice bath and add 90 ml of MIBK.
Before this, if course, I want to do a test with 5 ml xylene extract, 10 ml iPrOH and 15 ml MIBK to see if the salt crashes out.
Another worry I have is that MIBK is likely less volatile than its ketone peers (BP = 117-118oC), so it might be a pain to evaporate off the excess
solvent after suction filtration.
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