What technique can be used to separate each of the following compositions of pai

Question

What technique can be used to separate each of the following compositions of pairs of compounds? Explain how you would carry out each separation, and indicate the property difference used to achieve the separation?

(a) acetone (b p.56°C) and isopropanol (b.p. 82°C): 50:50 mixture CH3COCHs CH3CHOHCHs (b) salicylic acid (m.p. 160°C) and acetylsaid(m.p. 141°C): 5:95 mixture OH OH (c) benzophenone (m-R 48°C) and biphenyl-4-carboxylic acid (m.p. 227°C): 70:30 mixture OH isobutylacetate (b.p. 117°C) and acetic acid (b.p. 118°C): 90:10 mixture (CHs)2CHCH2O2CCH3 (d) CH3CO2H

Explanation / Answer

Technique of separation,

(a) acetone and isopropanol : By simple distillation. the boiling points are far apart for the two compounds and hence can be separated easily.

(b) salicylic acid and acetylsalicylic acid : solubility. Add water, salicylic acid goes in water instantly leaving behind acetylsalicylic acid.

(c) benzophenone and biphenyl-4-carboxylic acid : Add NaHCO3 (aq) to mixture. biphenyl-4-carboxylic acid reacts to form salt and goes in water layer, separated and acidified with HCl to reprecipitate the compound back from solution. The previous solution would have only the acetophenone left.

(d) isobutylacetate and acetic acid : Add NaHCO3 (aq), acid dissolves and goes in water which is acidifed to form the acid again. The ester remains in solution.

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