5. You work in a small-scale manufacturing facility that uses salicylic acid as

Question

5. You work in a small-scale manufacturing facility that uses salicylic acid as the starting material for the synthesis of methyl salicylate, the "oil of wintergreen". Your company buys ~98% pure salicylic acid from a major manufacturer and purifies it in-house prior to its use in the synthesis of methyl salicylate. You are given the job to purify 100g of the impure salicylic acid. You realize you know very little about this substance, so you decide to look it up. What specific information would you look for that would help you in devising your strategy for completing your purification task? Explain your strategy and the relevant rationale.

Explanation / Answer

To purify the acid, it is always necessary to know the pKa value and meltng point of the acid.For salicyclic acid, acid-base extraction also useful to purify the sample. But it has OH and acid group, so specifc extraction procedure can be used.

First dissolve the compound in organic solvent like dichloromethane or ethyl acetate or ether.

Then add aqueous NaHCO3 solution, all the compounds will go into water as its sodium salt and it can be recovered back to salicylic acid by acid treatment. this method removes the phenolic impurities.

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