Synthesis of Benzaldehyde via Persulfate oxidation

Dissolve 185 g of ammonium persulfate in a minimal amount of water. Add 85 mL of benzyl alcohol to 3-neck round bottom flask and then 100 mL of water. Pour the persulfate solution to an addition funnel, also, attach and thermometer and reflux condenser. Start stirring vigorously the solution, add 20 mL of methanol. When the temperature rises to 50-55°C add about 15-20 mL of the persulfate solution. Increase the water bath temperature to 60°C. Start adding the persulfate steadily, there should be a 1-minute delay between the addition and temperature increase. Slowly cool down the mixture after all of the persulfate is added, keep stirring for 30 minutes, then cool down to ice cold water temperature. Pour the mixture into a separatory funnel, discard the bottom layer. Make concentrated sodium bisulfite solution by dissolving 110 g of sodium bisulfite in about 150 mL of water. Start adding slowly the benzaldehyde to the sodium bisulfite solution with stirring. Stir for 30 minutes, filter, wash the solid with cold water and dry the solid. Dissolve 120 g of anhydrous sodium carbonate in 250 mL of water, start adding the solid to the solution with stirring for 30 minutes, then add 100 mL of water, let it settle. Pour the solution into a separatory funnel and discard the bottom layer, collect the top layer and add some calcium chloride to dry it. Distill in a vacuum.

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Now add 20 ml of the persulfate solution, keep the temp below 70°C

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Steadily drop the persulfate solution

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The mixture was cooled down

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Discard the bottom layer

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Dropping the brownish liquid to the sodium bisulfite solution

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Insoluble matter started to form

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Filtering and washing precipitate

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Drying the filtrate

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The dried solid was added to the sodium carbonate solution with stirring

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Benzaldehyde forming

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Discarding the bottom layer

The pure dried product

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