Synthesis of Salicylic Acid from Wintergreen Oil

Topics: Salicylic acid, Carboxylic acid, Sodium hydroxide Pages: 4 (996 words) Published: November 13, 2012
EXPERIMENT 4: Synthesis of Salicylic Acid from Wintergreen Oil Abstract: The purpose of this experiment is to take methyl salicylate (wintergreen oil) and by heating it under reflux with NaOH as a solvent, and then cooling the mixture with H2SO4 as another solvent, synthesize salicylic acid. The final step involves purify the product to produce as pure a sample of salicylic acid as possible. This process allowed for the successful production of 1.406g salicylic acid, an 82.70% yield. The NMR and IR both produced images that correlate with the known spectrums indicating a pure product. The melting point range was slightly wider, though did encompass the accepted melting point values.

Discussion: Reaction
OH O OCH3 2) H2SO4 1) 2NaOH OH O OH

1.595 ml methyl salicylate is reacted with sodium hydroxide by heating it under reflux. The sodium ions knock the methyl group from the methyl salicylate due to the greater attraction between the sodium cation and the slightly negative charge on the oxygen compared to the O-CH3 bond that had previously existed. This reaction produces disodium salicylic acid, methyl hydroxide and water molecules. The sodium crystals that form are visible as the white particulate matter seen as soon as the two chemicals are mixed. Heating of the substance under reflux increased the reaction rate as did the use of the solvent to increase the frequency of molecules being ripped off the original substance and sucking them into their new molecular formations. At this point the wintergreen smell has disappeared from the mixture indicating a rapid decline in the amount of methyl salicylate present in the reaction. When the sulfuric acid (pH ~.3) is added to the disodium salicylic acid (pH ~5-6), the two sodium atoms are replaced by hydrogen atoms creating salicylic acid and sodium sulfate and lower the pH of the solution to 2. The sodium cations are now more attracted to the slightly negative charge on the two oxygen anions on the SO42- ions than...
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