Hexan-1-ol is oxidized to hexanal using PCC. However, some over-oxidation occurred, and some hexan-1-ol was oxidized to hexanoic acid.

(i) Provide a step-by-step process of purifying hexanal using acid-base extraction.
(ii) Which substance in the reaction mixture cannot be separated from hexanal using acid-base extraction? How can the two be separated?

• A. (i)Step 1: Shake with hexane and water. Discard the organic layer. Use the aqueous layer for Step 2.Step 2: Shake the aqueous layer with aqueous NaOH solution. Discard the organic layer. Use the aqueous layer for Step 3.Step 3: Shake the aqueous layer with aqueous HCl solution. Discard the organic layer. Use the aqueous for Step 4.Step 4: Evaporate water (solvent) to obtain a mixture of only hexanol and hexanal.Step 5: Separate hexanol and hexanal via distillation.(ii) Hexanol and hexanal cannot be separated using acid-base extraction. We can separate the two by distillation.
• B. (i)Step 1: Shake with hexane and water. Discard the organic layer. Use the aqueous layer for Step 2.Step 2: Shake the aqueous layer with aqueous NaOH solution. Discard the organic layer. Use the aqueous layer for Step 3.Step 3: Shake the aqueous layer with aqueous HCl solution. Discard the organic layer. Use the aqueous for Step 4.Step 4: Evaporate water (solvent) to obtain a mixture of only hexanal and pyridine.Step 5: Separate hexanal and pyridine via distillation.(ii) Hexanal and pyridine cannot be separated using acid-base extraction. We can separate the two by distillation.
• C. (i)Step 1: Shake with hexane and water. Discard the aqueous layer. Use the organic layer for Step 2.Step 2: Shake the organic layer with an aqueous NaOH solution. Discard the aqueous layer. Use the organic layer for Step 3.Step 3: Shake the organic layer with aqueous HCl solution. Discard the aqueous layer. Use the organic layer for Step 4.Step 4: Evaporate hexane (solvent) to obtain a mixture of only hexanol and hexanal.Step 5: Separate hexanol and hexanal via distillation.(ii) Hexanol and hexanal cannot be separated using acid-base extraction. We can separate the two by distillation.
• D. (i)Step 1: Shake with hexane and water. Discard the organic layer. Use the aqueous layer for Step 2.Step 2: Shake the aqueous layer with aqueous NaOH solution. Discard the organic layer. Use the aqueous layer for Step 3.Step 3: Shake the aqueous layer with aqueous HCl solution. Discard the organic layer. Use the aqueous for Step 4.Step 4: Evaporate water (solvent) to obtain a mixture of only hexanol and hexanal.Step 5: Separate hexanol and hexanal via distillation.(ii) Hexanol and hexanal cannot be separated using acid-base extraction. We can separate the two by distillation.

Answer: (C)