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Topic: Unexpected outcome when separating using DCM  (Read 3058 times)

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Offline cyion

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Unexpected outcome when separating using DCM
« on: March 07, 2024, 05:02:08 PM »
In a reaction I used phenol with phthalic anhydride using an acid catalyst to produce phenolphthalein. After this I added water and DCM which I hoped the phenolphthalein would separate into the DCM layer. But what happened instead was an opaque pink liquid formed which had the consistency of a smoothy. Obviously this isn't supposed to happen but I'm confused to why this could have been. One of my professors said it could have been caused by someone messing with the DCM in the lab and putting a salt in it but me and my lab partner used the same DCM same water aswell as the same reagents (from the same container) and refluxed on the same heating mantle, yet theirs separated completely fine? Any help to why this sort of thing happens, how it can be avoided/fixed would be appreciated :)
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Offline Babcock_Hall

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Re: Unexpected outcome when separating using DCM
« Reply #1 on: March 09, 2024, 07:05:37 AM »
The only thing that comes to mind is that you might have formed an emulsion.  Sometimes they break of their own accord with time.
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Offline cyion

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Re: Unexpected outcome when separating using DCM
« Reply #2 on: March 23, 2024, 02:52:12 PM »
that's my guess, I was using 18M H2SO4 which I guess protonated the water and then messed with the dipole in the DCM
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Offline Borek

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Re: Unexpected outcome when separating using DCM
« Reply #3 on: March 23, 2024, 04:48:16 PM »
Quote from: cyion on March 07, 2024, 05:02:08 PM
pink

Is that the color your lab partner observed? Or was his solution colorless?

Pink would be not surprising in high pH water solution. Wiki lists possible color for the phenolphthalein in the acid as orange (but with some disclaimers that make the situation a bit confusing).
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Offline wildfyr

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Re: Unexpected outcome when separating using DCM
« Reply #4 on: March 23, 2024, 08:17:27 PM »
The charge state of phenophthalein would have a big influence on its ability to seperate into one layer or another or act as a surfactant
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Offline Guitarmaniac86

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Re: Unexpected outcome when separating using DCM
« Reply #5 on: March 24, 2024, 08:22:03 AM »
Quote from: cyion on March 23, 2024, 02:52:12 PM
that's my guess, I was using 18M H2SO4 which I guess protonated the water and then messed with the dipole in the DCM

Why are you using 18M sulfuric acid for a work up!? The aqueous layer must have gotten so hot! You do not need 18M sulfuric for a work up.
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Offline cyion

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Re: Unexpected outcome when separating using DCM
« Reply #6 on: April 06, 2024, 03:36:10 PM »
Quote
Why are you using 18M sulfuric acid for a work up!? The aqueous layer must have gotten so hot! You do not need 18M sulfuric for a work up.

The 18M sulphuric was for the synthesis and I only used something like 8 drops of the stuff. :))
« Last Edit: April 06, 2024, 05:01:02 PM by Borek »
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Offline Guitarmaniac86

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Re: Unexpected outcome when separating using DCM
« Reply #7 on: April 07, 2024, 04:39:51 AM »
Quote from: cyion on April 06, 2024, 03:36:10 PM
Quote
Why are you using 18M sulfuric acid for a work up!? The aqueous layer must have gotten so hot! You do not need 18M sulfuric for a work up.

The 18M sulphuric was for the synthesis and I only used something like 8 drops of the stuff. :))

Ah ok that makes more sense!
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