A student performs the following steps to isolate biphenyl from a solid 1:1 mixt

Question

A student performs the following steps to isolate biphenyl from a solid 1:1 mixture of biphenyl and salicylic acid. Dissolve 2.0 grams of the mixture in 20 mL of ether Extract the ether layer 2-3 times with an aqueous solution of 5% sodium bicarbonate Add 2-3 spatula tips of sodium sulfate to the ether layer Extract the ether layer with a saturated aqueous solution of sodium chloride. Isolate the organic layer and evaporate the ether. The solid they collect at the end weighs 1.23 g and has a wide melting point range. If the student expected to recover 1 gram of pure biphenyl, explain, based on the procedural information given above, why this student did not see their expected results.

Explanation / Answer

The washing with NaHCO3 should continue till the bubbles are stopped when it is added to the oganic solvent. Even after the completion of the washing, one should check the TLC whether there is any trae of it. FUrthermore, dichloromethane is a better alternative to get the pure and better yield in this case. Additionally, instead of NaHCO3, NaOH would be better in this particular case

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