Question

Reaction Workup and Purification For the reaction depicted below, draw a flowchart for the isolation of the ether product. Then explain why recrystallization would or would not be a good technique to purify the ester product this reaction. Assume the yield for this reaction is 92%. Follow up: What if the yield was 53%? Hints: Remember that recrystallization would happen after the work up/extraction! Think about what the yield could mean in terms of the product to reactant ratio at the end of the reaction. DMF- d = 0.944 g/ml Koco, KI od nas out a to KHCO, DMF BP = 199 °C MP = 64°C MP = 97°C

Answer 1

Assuming 3,5-dimethylphenol is used in excess (practically one should use it in little excess). The benziliodide may get consumed completly, even if it remains unreacted, may remain is small quantity hence that can be removed while recrystalization. Phenolic compound reacts with base such as NaOH to give phenoxide salt and can be dissolved in aqueous layer making it seprate from organic layer leaving behind ether the product in organic layer. Ether + 3,5-dimethylphenol + impurities Dissolve the reaction mixture in DCM and then extract with Aqueous layer NaOH solution. Organic layer Sodium 3,5-dimethylphenoxide + water soluble impurities Product ether + DCM + organic soluble impurities wash the organic layer with brine and then dry over the Na2SO4 and evaporate the solvent. Product ether Recrestalize Solid Product ether

If the yield is 92% then you have to recrystalize the product and chek the purity with different techniques like IR, NMR, GC etc.

If the yiled was 53% then also recrystalization is needed to ensure the purity.