ChemichaelRXN
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Ferric chloride and HCl halogenation of hydroxyl groups
Hello,
I wasnt able to find any information on this...
Do you think the yield would be improved if you use a combination of ferric chloride and concentrated hydrochloric acid to chlorinate a hydroxyl group
of an organic compound as opposed to just concentrated hydrochloric acid alone? I will definitely test it out, but does anyone have any input.
(I know it is a potent mixture because you can dissolve gold apparently with ferric chloride and hydrochloric acid mixture)
Have a great day!
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njl
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I don't think its ability to dissolve gold is a good indicator of chlorinating strength for organic compounds. The problem with using HCl for
chlorinating alcohols is not that it isn't "potent" it's that Cl- is a much better leaving group than OH- so any formed alkyl halide can quickly be
hydrolyzed back to an alcohol, except in certain cases where the intermediate carbocation is stabilized (i.e. benzylic or tertiary alcohols). That's
why compounds like SOCl2 are used to chlorinate irreversibly. I guess the answer is yes, it could probably help but it depends more on the substrate
you plan on chlorinating and reaction conditions.
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ChemichaelRXN
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Thanks for the information!
I was thinking of reacting sulfurol with a mixture of concentrated HCl and FeCl3 and neutralizing it to separate out the clomethiazole freebase. I
have freebased clomethiazole HCl with NaOH in the past and it doesnt go back to sulfurol. I think FeCl3 is the catalyst needed for the yield, but
we’ll see. I will be sure to post what happens when I try this out.
For a compound like sulfurol (primary alcohol), to produce clomethiazole and other than HCl alone, what catalyst would you use for the halogenation? I
cant obtain thionyl chloride unfortunately.
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njl
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To be honest, your experiment would be more valuable than my input. Given the availability of the reagents I would say just give it a try.
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ChemichaelRXN
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Glad I have some free time.
I am going to make a solution with both:
HCl: 2g / 143.207g/mol x 2/1 (2moles because of forming hydrochloride and remaining mole to halogenate) x 36.46g/mol= 1.02 / 0.37 = 2.76g / 1.19g/ml
= 2.32ml conc. HCl
FeCl3.6H2O: 2g / 143.207g/mol x 1/1 x 270.29g/mol = 3.77grams FeCl3.6H2O / 2 (just catalyst use) = 1.9grams (50%)
1.9g FeCl3.6H2O dissolved in 2.32mL HCl added to 2 grams sulfurol. Heat for 15minutes and neutralize.
1.9g / 270.29g/mol x 3 / 1 x 40g/mol NaOH = 0.84g NaOH + extra required to basify the solution from remaining HCl
Remaining HCl; 1.16 mL conc HCl or 0.51g HCl at 100% conc. / 36.46g/mol x 1/1 x 40g/mol NaOH = 0.56grams
0.56g + 0.84g = 1.4g+ NaOH required to neutralize FeCl3 with 50% of the HCl added that makes the hydrochloride salt. You will need a bit more from
incomplete reaction, so carefully add it.
Looking forward to seeing the result. Will post it later today or tomorrow.
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Texium
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First things first, is your ferric chloride anhydrous, or did you prepare it from aqueous solution? If it isn’t anhydrous it will be completely
useless.
Either way though, as njl said, the comparison to dissolution of gold is completely meaningless, because in that case the oxidizing potential of
ferric chloride is being taken advantage of, and it’s reacting with a metal, not an organic compound.
There’s a chance that the alcohol would act as a Lewis base and react with the ferric chloride to form a better leaving group, and give you hydrous
ferric chloride as a byproduct. You might need to use a stoichiometric amount of the ferric chloride to achieve this though.
Once again, this is assuming anhydrous conditions- HCl being bubbled into solution, not added as an aqueous solution.
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ChemichaelRXN
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I am trying just 1.9g Ferric Chloride hexahydrate crystals dissolved in 2.32mL conc HCl. Thought I’d just experiment, but we’ll see if any
product.
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njl
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The reaction you're working is documented, there will be product with or without ferric chloride (unless it hinders the reaction somehow). You need to
run at least one control to see if the yield is any different.
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ChemichaelRXN
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Ah nevermind...the reaction didnt work. I need something stronger. It did smell like clomethiazole, but it didnt separate as freebase when water was
added. I am on a horrible streak of failing reactions, but I guess that is experimentation for you. I need to get some dioxane for a NaBH4/ CuCl2
reduction now...
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Texium
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Make sure to compare it to just HCl on the same scale so that you have a control.
Edit: Jeez, three posts popped up at the same time. Yeah I figured it wouldn't work. Way too much water in there, and with a primary alcohol... no
dice.
[Edited on 10-19-2020 by Texium (zts16)]
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ChemichaelRXN
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Yea the sulfurol is quite stubborn. I though I chlorinated it to form clomethiazole before. It smelled like the product, then later I found out that
it is soluble in water as the freebase meaning it was still sulfurol with a little clomethiazole in it. (I thought the sulfurol was soluble in the
brine solution I separated out the reaction with because of the water, but I got the reactant as well as the product mixed.) I am just curious how
they convert sulfurol to clomethiazole...what would you do? Thionyl chloride? I need to do something successfully. Lol
How about sodium hypochlorite?
[Edited on 19-10-2020 by ChemichaelRXN]
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njl
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I am a bit confused because while the primary alcohol shouldn't be chlorinated that much just by aqueous HCl, I'm reading successful reports by other
SM users that say otherwise.
Edit: this is a link to one thread discussing HCl chlorination.
http://www.sciencemadness.org/talk/viewthread.php?tid=154878
[Edited on 10-19-2020 by njl]
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ChemichaelRXN
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Yes, I didnt update the thread to not bring back an old topic. The product was separated with brine, but sulfurol was the product with some
clomethiazole in it. It sure smelled like the product. The clomethiazole produced became miscible because of the sulfurol and I couldnt extract the
pure product by adding water when doing a purification. A headache and ended up being a bit of a waste.
In other words, the yield was lower than what was posted.
I am looking for a new method.
[Edited on 19-10-2020 by ChemichaelRXN]
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njl
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I didn't even realize that was your post, my bad.
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ChemichaelRXN
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Yea, I got ahead of myself and from all the little tests I did along with its odour, I didnt think to try mixing the product with water until after,
which showed it was soluble...maybe I should try sodium hypochlorite;
Not sure if it would work with primary alcohols, but I am willing to experiment. I dont have PCl3 or thionyl chloride and it is very toxic as well.
Anisic acid (3.8 gm., 1/40 mole) was dissolved in 150 mL of water and 25 mL of 4% sodium hydroxide solution. It was cooled to 20°C., and mixed with
50 mL (1/20 mole) of sodium hypochlorite solution. The temperature was maintained at 20° C. for one hour with occasional stirring. Upon acidifying, a
precipitate of almost pure 3-chloroanisic acid was obtained. The yield was 3.9 gm. (80% of theory). After one crystallization from toluene it melted
at 215°C.
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Texium
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Quote: Originally posted by ChemichaelRXN  | Yea the sulfurol is quite stubborn. I though I chlorinated it to form clomethiazole before. It smelled like the product, then later I found out that
it is soluble in water as the freebase meaning it was still sulfurol with a little clomethiazole in it. (I thought the sulfurol was soluble in the
brine solution I separated out the reaction with because of the water, but I got the reactant as well as the product mixed.) I am just curious how
they convert sulfurol to clomethiazole...what would you do? Thionyl chloride? I need to do something successfully. Lol
How about sodium hypochlorite? |
Sodium hypochlorite is a definite no. Hypochlorite is a source of
electrophilic chlorine (Cl+). You need a source of nucleophilic chloride (Cl-). Completely different animals. Thionyl chloride,
oxalyl chloride/DMF, or phosphorus pentachloride are all examples of reagents that can accomplish this nicely, by being attacked by the alcohol to
kick off chloride and form a better leaving group, which the chloride can then displace. It is essentially the same mechanism in the end as HCl
reacting with an alcohol, except it is irreversible. Of course, none of these reagents are too easy for the amateur to obtain. Didn't you say you own
a chemical company though? It should be easy enough and relatively inexpensive for you to order some thionyl chloride.
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Texium
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Thread Moved
19-10-2020 at 10:59 |
ChemichaelRXN
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Ok excellent info, thanks! Yes I do own a chemical company, but some compounds are difficult to obtain though. I mainly import overseas and not sure
if my usual suppliers would ship something toxic like that. I should make an account with Sigma Aldrich.
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ChemichaelRXN
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How about using Conc. HCl with addition of H2SO4? Reminds me of a nitration, but may help with replacing a hydroxy with chlorine for a higher yield. I
guess the idea is similar to Ferric chloride and I will try the ferric chloride again with a larger amount. Something new is always nice.
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njl
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The conditions might be too harsh, but I would even try NaCl and H2SO4 to avoid as much water in the reaction as possible.
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ChemichaelRXN
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I’ll think about it and may try it out. I was thinking of gassing the sulfurol with HCl too, but the problem is that it forms the hydrochloride salt
and will no longer stir likely. It’s a bit of a challenge. Do you think anhydrous aluminum chloride would work?
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njl
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For chlorinating? I don't know, that's something I've been wondering for a while too. I think because it is more covalent in character the reaction
will at the very least proceed via a different mechanism than HCl chlorination, if it works at all.
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