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Author: Subject: preparation of thymolphthalein
lab constructor

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[*] posted on 20-5-2016 at 09:52

Thank you gsd, I did misread the question. According to Wiki using just H2SO4 will work:

The single most important condition for a successful synthesis is good mixing - Nicodem
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[*] posted on 22-5-2016 at 15:57

Quote: Originally posted by gsd  
As I understand it, Paddywhacker is suggesting that why not use the method used for making Fluoroscein to make Thymolphthalein. In making Fluoroscein, 98% H2SO4 (or Anhydrous ZnCl2) is used as dehydrating agent. Why not use C. H2SO4 as dehydrating agent for Thymolphthalein also?


On second thoughts I suspect H2SO4 will react with Thymol. Anhydrous ZnCl2 will not pose that problem it will act as dehydrating agent only.
BTW I have made Fluoroscein using both these reagents. They work like a charm.


Yes. Magpie's work-up procedure is very valuable, but the SnCl4 for the FC reaction is a bit exotic. Hence my suggestion of using catalytic H2SO4. All of these *phthalein reactions are between two molecules of a phenol and one molecule of phthalic anhydride, so they all might take place is similar conditions, although admittedly, the resorcinol in the fluorescein synthesis is a highly activated molecule.
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