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Author: Subject: DOP Extraction and Base Hydrolysis to Phthalic Acid
mesanaw
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[*] posted on 9-1-2017 at 13:00
DOP Extraction and Base Hydrolysis to Phthalic Acid


Hello, I am trying to perform a base hydrolysis of DOP to synthesis phthalic acid.
For my first attempt, I used isopropanol for the extraction from vinyl gloves then added a NaOH/water solution to the extract, which formed a cloudy aqueous bottom layer and an oily upper layer that I believe is the DOP.

After a 2 hour reflux, I ended up with yellow mixture that never separated. I believe the problem is that, without a stirbar, I am unable to provide enough vigorous stirring to sufficiently react the two layers.

I am looking for an advice on how to circumvent this issue.

For this next attempt I am planning on switching to methanol for the extraction and then adding a methanol/NaOH solution for the hydrolysis of the ester. By omitting water, I am hoping the DOP will be able to react with the NaOH during reflux.
Will this new method work? Any suggestions/advice would be appreciated.
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Tsjerk
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[*] posted on 9-1-2017 at 13:05


What is dop? And shouldn't you dissolve your dop, whatever it is, in a solvent which allows it to dissolve together with NaOH?
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mesanaw
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[*] posted on 9-1-2017 at 13:09


DOP is diethylhexyl phthalate(DEHP). I am hoping the methanol/NaOH solution will accomplish this, but I am not entirely certain.
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Tsjerk
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[*] posted on 10-1-2017 at 03:16


Why do you think your first try didn't work? Try to wash your reaction with for example petroleum ether (or gasoline), and evaporate a part of the water before acidifying the mixture. If it is clean enough phthalic acid should crystalize.

The petroleum ether stap is to get rid of organic stuff that is most probably there (yellow colour). Disodium phthalate shouldn't dissolve. If there is any isopropyl alcohol left in the reaction I would try to evaporate that before acidifying. Phthalic acid dissolves in water at about 1 gram / 160 ml water, I wouldn't use sulfuric acid as sodium sulfate is not that soluble. It is also possible to crystalize the sodium salt ofcourse but it is about 10 times more soluble.

see 4.2.6 here for solubility

https://pubchem.ncbi.nlm.nih.gov/compound/phthalic_acid#sect...

https://en.wikipedia.org/wiki/Disodium_phosphate

[Edited on 10-1-2017 by Tsjerk]
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DFliyerz
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[*] posted on 21-2-2017 at 09:49


I always solve this non-layering issue by adding table salt to make the layers form, since it'll be a byproduct later in the reaction anyways.
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