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All posts   Subject: PAA -> P2P 76% yield   Please login to post  

(Hive Bee)
11-07-04 22:22
No 540244
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      PAA -> P2P 76% yield
(Rated as: good idea!)

Due to poverty, a bee had to lower her morals and turn into a wasp...  She did use less AA and got a higher yield due to some variation of procedure.
  • 86 g Phenylacetic Acid
  • 800 mL Acetic Anhydride (fresh)
  • 43 g sodium acetate
  • Oven dried molecular sieves

In a three neck 1 L flask fitted with a nitrogen purge line and a thermometer, all above were quickly thrown in while under a stream of N2.  The flask was then fitted with a water condenser with a drierite drying tube.  The N2 purge was slowed to minimal positive pressure and the oil bath heated for 46 hrs to ~170°C, such that rxn temp was ~145°C.  Reflux and gas evolution was slight.  Color slowly went from clear to yellow.  Afterward, solution was rotovaped down to about 300-400 mL dissolved in ~200 mL DCM and stirred vigorously with and excess of 4M NaOH, until no more hydrolysis (noted by vigorous bubbling) occurred.  Organic layer separated, aqueous extracted 3 x with DCM, pooled extracts dried w/ mag sulfate, filtered (which also got rid of some insoluble junk) and rotovaped off DCM.  Yield 64.4 g (76%), very pure by 1H-NMR and TLC.

Reasoning for higher yield: fresh (not wet) AA, continuous positive pressure of N2, drying tube, and mol seives = very dry rxn

*Please don't PM Dopey any questions about this procedure.

something for your mind.......

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