Synthesis of Salicylic Acid from Wintergreen Oil

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Experiment #04: Synthesis of Salicylic Acid from Wintergreen Oil

I. Introduction and Purpose

Until 1874 commercial salicylic acid was synthesized entirely from natural wintergreen oil. In this experiment the salicylic acid is reproduced using methyl salicylate, the major constituent of wintergreen oil and later compared to salicylic acid made from benzene. The purpose of this lab is to determine the difference between salicylic acid made from methyl salicylate and salicylic acid made from benzene comparing the melting points of the two samples.

II. Reactions and Properties

M.W.m.p.b.p.d
Methyl salicylate152.1-82231.174
Salicylic acid138.1159

III. Experimental Procedures and Results

Measure 30 ml of aqueous 6 M sodium hydroxide into the boiling flask, followed by 20.0 mmol of methyl salicylate and 2 boiling chips. Assemble condenser and start water flowing in it. Heat the mixture under reflux for 30 minutes and then, let reaction mixture cool down and transfer it to larger beaker. Slowly, add 30 ml of aqueous 3 M sulfuric acid and cool the mixture in ice water for approximate 10 minutes. Collect the salicylic acid by vacuum filtration using a small Buchner funnel, wasghing it on the filter with ice-cold water. Dry product, measure and obtain m.p. of dry product and 1:1 mix of product with salicylic acid from benzene.

Amount of methyl salicylate used: (20x10^-3) (152.1g) (ml/1.174g) » 2.5ml Melting point of salicylic acid made from methyl salicylate= 160.5 oC Melting point product mixed with salicylic acid made from benzene= 161.0 oC

IV. Observed Physical Properties of Obtained Product

The product melting point was slightly higher than the lab. Book.

V. Conclusion

After comparing the melting points from the salicylic acid made from methyl salicylate and the salicylic acid made from methyl salicylate mixed with salicylic acid made from benzene, we can conclude that they are the same.
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