hexan-1-ol-is-oxidized-to-hexanal-using-pcc-however-some-over-oxidation-occurred

Question

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?

Accepted Answer

(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.

Answer

(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

(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.

Answer

(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.