Picric-A
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Distinguishing two compounds
I have just received two bottles of chemicals, both plastic 100ml bottles.
One contains 2-chloroethanol and one GBL.
Both these chemicals are supposed to be colourless however one of the bottles contains a dark red/brown liquid (!!)
Does anybody know a decent method of distinguishing between these two? preferably it should not use a lot of the compound and should be easy to
perform.
Thanks
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Nicodem
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bp
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Nicodem
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Thread Moved
22-10-2010 at 08:33 |
Picric-A
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I thought of this however it uses relatively too much reagent and i dont want toxic 2-chloroethanol fumes near my b.p. apparatus.
Any other?
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Nicodem
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Boiling point determination is a nondestructive analysis and you need no apparatus, just a couple drops of your compound, a test tube and a
thermometer. And why would you want to wait for fumes to escape the test tube?
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smaerd
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Or you can go back to the olden days and bust out a theile tube, some mineral oil, a capillary and thermometer  . No fancy devices needed, except maybe a magnifying glass, besides capillaries shouldn't have that much of anything
inside of them.
Or maybe if you could get a flask to about -50*C the GBL should become solid while the 2-chloroethanol would remain liquid until about -70*C.
Assuming there are no to little impurities.
Or if you have an accurate scale and some small volumetric flasks, you could try to do a density determination. The densities are pretty dang similar
and if there is contaminants it would be inaccurate but it's another idea.
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psychokinetic
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Acidified potassium dichromate would make the 2-chloroethanol into 2-chloroethanal, which could be proven to exist with a silver mirror test.
The GBL would just sit there and mock you if you threw some K2Cr2O7/H+ at it.
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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Picric-A
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I do not have a thermometer high enough to measure the b.p's of both these compounds so i was ideally looking for a chemical test.
Quote: Originally posted by psychokinetic  | Acidified potassium dichromate would make the 2-chloroethanol into 2-chloroethanal, which could be proven to exist with a silver mirror test.
The GBL would just sit there and mock you if you threw some K2Cr2O7/H+ at it. |
This would work but the lactone gets hydrolysed by acidified dichromate so both give a positive test and ultimately produce an aldehyde.
Any other chemical test i can use to distinguish the two?
Could the colour have something to do with it? One is a colourless liquid, the other is red/brown. Could the 2-chloroethanol degrade to a reddish
compound?
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CZip
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Try adding little chunk of sodium into it. Reaction with chloroethanol will be violent (Wurtz synthesis and "neutralization" between alcohol and
alkali metal. Reaction with GBL should be slow, if any...
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Picric-A
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Thanks for all the replies so far.
Results from the lab show this;
With sodium the dark red liquid reacted quite violently (indicating it to be 2-chloroethanol) and the colourless liquid barely reacted (indicated
lactone) This could be wrong however as the first liquid could contain more water than the other, giving false results.
Reaction with K2Cr2O7/H+; dark red liquid was the first to turn green however the other liquid went green eventually (indicating the dark red liquid
was the chloroethanol and the second was the lactone which hydrolysed causing the reduction)
Any more tests which could prove the dark red liquid is the 2-chloroethanol?
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unionised
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Lassaigne sodium fusion test and look for sodium chloride?
You are probably most of the way there if you still have the stuff that was made by adding sodium.
Add water and dilute HNO3 ten test the aqueous extract for Cl- with AgNO3
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psychokinetic
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| Quote: Originally posted by Picric-A |
This would work but the lactone gets hydrolysed by acidified dichromate so both give a positive test and ultimately produce an aldehyde.
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Oh. Bugger.
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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DJF90
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Check with silver nitrate and a nucleophile. Ppt of AgCl will occur when the Silver aids departure of the primary chloride. Obviously the nucleophile
shouldnt produce a ppt with Ag+ either...
Or the clever way to do it would be to run an IR spec... should be easy to distinguish one from the other.
[Edited on 24-10-2010 by DJF90]
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madscientist
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2-chloroethanol reacts with NaOH yielding ethylene oxide (b.p. of 11C.) Perhaps observed bubbling could give you your answer?
I weep at the sight of flaming acetic anhydride.
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spirocycle
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| Quote: Originally posted by unionised | Lassaigne sodium fusion test and look for sodium chloride?
You are probably most of the way there if you still have the stuff that was made by adding sodium.
Add water and dilute HNO3 ten test the aqueous extract for Cl- with AgNO3 |
you could just dry them both beforehand, it should be too hard
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anotheronebitesthedust
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I think the pH of GBL would be lower than 2-Chloroethanol. But with impurities maybe not.
Also there's this info from wiki:
"2-Chloroethanol is toxic with an LD50 of 89 mg/kg in rats. Like most organochlorine compounds, chloroethanol combusts to yield hydrogen chloride and
phosgene."
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psychokinetic
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| Quote: Originally posted by anotheronebitesthedust | I think the pH of GBL would be lower than 2-Chloroethanol. But with impurities maybe not.
Also there's this info from wiki:
"2-Chloroethanol is toxic with an LD50 of 89 mg/kg in rats. Like most organochlorine compounds, chloroethanol combusts to yield hydrogen chloride and
phosgene." |
Get yourself a rat.
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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DJF90
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| Quote: Originally posted by madscientist | | 2-chloroethanol reacts with NaOH yielding ethylene oxide (b.p. of 11C.) Perhaps observed bubbling could give you your answer? |
Hahahaa he doesnt want to be messing with 2-chloroethanol fumes, what makes you think he will play with a toxic, carcinogenic gas?!
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madscientist
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It'd be easy enough to just do it outside and stand upwind. But if he doesn't want to uncork that bottle, I do have to wonder why he bought it. 
I weep at the sight of flaming acetic anhydride.
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Picric-A
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| Quote: Originally posted by psychokinetic | | Quote: Originally posted by anotheronebitesthedust | I think the pH of GBL would be lower than 2-Chloroethanol. But with impurities maybe not.
Also there's this info from wiki:
"2-Chloroethanol is toxic with an LD50 of 89 mg/kg in rats. Like most organochlorine compounds, chloroethanol combusts to yield hydrogen chloride and
phosgene." |
Get yourself a rat. |
Haha best answer yet!
To both 1 ml of both liquids was added 4ml conc NaOH. These mixes were boiled for 3 mins then neutralised with HNO3 followed by addition of AgNO3. The
dark red liquid gave a white AgCl ppt, the colourless liquid did not.
I think i have more than enough evidence to label the red liquid as 2-chloroethanol and the colourless as the butyrolacone, dont you think? I wonder
what caused the red colouration in the first place... i may have to re-distill the 2-chloroethanol before the synthesis... oh dear...
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madscientist
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Sounds like it is to me.
I weep at the sight of flaming acetic anhydride.
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