Introduction Throughout history, botanical extracts have been used as medicines. Approximately 30% of all medicines have a plant origin. This number increases to 60% if you consider medicines that at one time were derived from plants, but have been synthesized in the laboratory. Salicylic acid is a white crystalline compound that can be isolated from the bark of birch trees. Since it is a valuable substance that can be isolated from nature, it is called a “natural product”. Although it was used historically as an analgesic (pain reliever), today it is commonly used in ointments and plasters for the removal of warts from the skin.
Salicylic acid is also a precursor to acetylsalicylic acid or aspirin. Acetylsalicylic acid (an ester derivative of salicylic acid) is much more commonly used than salicylic acid for pain relief, because the parent compound can irritate the lining of the stomach. In this experiment we synthesized salicylic acid from methyl salicylate. We converted the functional group known as an ester into a functional group known as a carboxylic acid. Methyl salicylate is also a botanical extract. It is the major constituent of oil of wintergreen, which makes up over 90% of the essential oil from the wintergreen plant.
It is also a common flavoring in candy. However, most methyl salicylate used in foods is made synthetically, a cheaper process than its extraction from wintergreen leaves or sweet birch bark. Methyl Salicylate has an alcohol and an ester group that are very important. Esters are often liquids (oils) at room temperature. At room temperature they are volatile to varying degrees and can be quite pleasing to the nose since they smell nice. The product of the reaction, salicylic acid was a white precipitate, the starting material, (methyl salicylate) was a liquid.
Organic synthesis involves changing part of a molecule. This results in a different molecule often with different physical properties. By changing part of a molecule you change the way it interacts with itself and with other molecules. Intermolecular reactions control both molecular properties and the behavior of molecules inside our bodies. Molecular structure gives insight on how a molecule will interact with other entities. In this experiment we converted oil of wintergreen into salicylic acid by a base catalyzed hydrolysis reaction.
We carried out the reaction at high temperatures, purified it by recrystallization and evaluated it at it’s melting point to make sure it was pure. Salicylic acid Methyl salicylate Acetylsalicylic acid The reaction of the hydrolysis of the esters goes faster at higher temperatures. So, we had to heat the reaction mixture to the boiling point of the solution. This is a process called refluxing. The figure shown is showing how the ester group of the methyl salicylate can be converted into a carboxylic acid by the base promoted hydrolysis.
The reaction is catalyzed by 2NaOH, and you get an alcohol and carboxylic acid. The carboxylic acid rapidly reacts in the strongly basic reaction mixture to for a carboxylate anion. You end up with a carboxylic acid which is recovered by acidifying the reaction mixture. Experimental procedure We poured 3. 5 mL of water into a 5 mL round bottom flask. We then added . 51 g NaOH and let it dissolve, then added . 2 mL of methyl salicylate. A white solid formed, we added a boiling stone and attached a condenser.
We placed it into a sand bath and wrapped a wet paper towel then began to heat the mix for 15 minutes. The white solid dissolved and we cooled it to room temperature. We poured the mixture into a beaker and added 2 mL of sulfuric acid in 5 mL increments until the heavy white precipitate remained in the mixture. We cooled the mixture in an ice bath and collected the product by vacuum filtration. We transferred the crude product to a flask, added 2 mL water put a boiling sote in and bean heating. We added 3 mL water in .
5 mL increments, let the flask crystallize then placed it into an ice bath. We collected the crystals with the vacuum again, poured 1 mL of water over them and vacuumed them one more time, and determined the melting point of the solid to see if it was pure. Results/Calculations Discussion We let our product dry overnight and obtained the melting point of the salicylic acid. Since our product did not melt at 160 degrees Celsius, (It melted at about 150 degrees) we determined that our product was not completely pure so we decided to be safe and use the product provided.
I think the reason the product was not completely pure was because we only washed it with water once and then we used the vacuum for a long time but I think in order to free the product completely of impurities we need to wash it better. We were afraid because the TA said TOO much water could also harm the product, that we would ruin it. I guess these experiments are all about finding a blanche in between, though it is very hard to get everything precise and perfect.