Hydrobenzoin can be oxidized to benzil with concentrated nitric acid. Some of th

Question

Hydrobenzoin can be oxidized to benzil with concentrated nitric acid. Some of the material is over oxidized to benzoic acid. After the reaction is over, the material is quenched with cold water. The final solution then contains hydrobenzoin (about 0.2 g) benzil (about 2.0 g), benzoic acid (about 0.4 g), and nitric acid (about 2.5 g) in about 50 mL of water. Describe a method (flow chart, bullet points or procedure) to isolate the benzil from the remaining materials. This will take multiple steps, include a solvent drying step.

Explanation / Answer

As far as we know, we have four substances at the end of reaction: The benzoic acid, the benzil, hydrobenzoin and HNO3.

What can we do to isolate the benzil?. Follow these 4 steps:

1. Add NaOH to the mixture of these products. The base will cause that hydrobenzoin and benzoic acid react forming the salts (sodium benzoate and sodium hydrobenzoate).

2. Both of these substances will dissolve in an aqueous layer of a solvent (maybe water or alcohol), leaving benzyl in the organic layer because it's insoluble.

3. Then, benzyl can be dissolved in a organic solvent (like acetone or CH2Cl2), and then, separated using a separating funnel.

4. Once it gets separated, you can let the solvent dry til you get the benzyl.

5. Measure melting point, and compare it with the reported.

Hope this helps.

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