Part I: Obtain four test tubes, cleanses and label each (test tube 1, 2, 3, and 4). Individually weigh out 1 g of salicylic acid and 2 mL of acetic anhydride and place them in the test tubes. Mix thoroughly with a glass rod until as much of the solid has dissolved as possible. Add two drops of catalyst (test tube 1 with sulfuric acid, test tube 2 with glacial acetic acid, test tube 3 with hydrochloric acid, and test tube 4 with no catalyst). Heat the reaction in a warm water bath of about 40 Celsius for 15 minutes.
Once the time is up, place the test tubes inside the ice bath, a mixture of water and ice, for 5 minutes. While it is cooling, prepare four mixtures of 5 g ice and 5 mL of cold water. After 5 minutes, add in the ice/water mixture and let it sit inside the ice bath for another 10 minutes. Observe any changes to the solutions. Stir the test tubes with a glass rod to speed up the crystallization process. Obtain 4 pieces of filter paper and label each with an assigned number of 1, 2, 3, or 4 with a pencil. Measure the weight of each individual filter paper and record it.
Once the 10 minutes is up, use a Buchner funnel and filter off the crystals (place the filter paper on top of the Buchner funnel and let the water drain out until there is only crystals left over). Place the filter paper on a plate form and wash each reaction test tube with two-5mL portions of ice water (Pour it directly over the crystals on the filter paper). Set each filter paper aside and let it dry. Part II: Weigh out the air-dried filter papers, watch glass, and product. Record the mass of each and calculate the mass of the individual product.
Heat some water on a hot plate and put 2. 5 mL of ethanol into a test tube (total of 4 test tubes) and warm it in the hot water bath. Be sure to label the test tubes 1, 2, 3, and 4. Once the ethanol is heated, dissolve the aspirin samples in the 2. 5 mL of the warm ethanol. Warm this at the same time you warm 5 mL of deionized water (total of 4 tubes). When the aspirin-ethanol mixture starts to boil remove it from the hot water bath and add the warm deionized water directly to the test tubes. Make sure everything has dissolved.
Let the solutions cool at room temperature for 10 minutes and then place them into an ice bath. Stir the content with a glass rod. Wait until crystals form then filter out the crystals using a Buchner funnel. Part III: To prepare the standard, weigh out 0. 1 g of salicylic acid and mix it with 50 mL of distilled water. Make sure everything is dissolved. (A little heat can be added if it cannot be dissolved by stirring. ) Dispense 1. 0 mL, 2. 0 mL, 3. 0 mL, 4. 0 mL, and 5. 0 mL of the solution into separate test tubes then add 1 mL of 0. 1 M NaOH to each test tube.
Then add 250 microliter of Iron (III) nitrite to each test tube. To prepare your sample solutions, weigh out 0. 325 g of the samples and add 1 mL of 0. 1 M NaOH to the solutions. Mix well and let it sit for 2 minutes for the solution to completely react. Once everything is dissolved add 250 microliter of Iron (II) nitrite to each sample solution. Set the spectrophotometer to 530 nm and place in the blank solution (pure distilled water). Once the calibration is set to 100% transmittance and 0% absorbance, place in the standard solutions. Measure and record the absorbance.
Then place in the sample solutions into the spectrophotometer and measure and record the individual absorbance. Verification: Raw data: Data analysis: Background information: Salicylate ion is created with a pain relieving effect in aspirin, the ion is formed from salicylic acid and acetic anhydride. Salicylic acid is found naturally in the bark of the willow tree, very similar to salicin. Felix Hoffman, a German chemist, was the first to synthesize aspirin by mixing the internally corrosive salicylic acid and the sweet tasting sodium salicylate.
By mixing these two elements, the ions are found to be less harmful to the human body. Salicylic acid upsets the stomach because of its acidity (pKa = 2. 97) it can be higher than the pH of the human stomach (pH~4). Once the diprotic organic salicylic acid is synthesized with the acetic anhydride and the acidic phenol is replaced by an ester, it becomes a mono acetylsalicylic acid, which is less acidic (pKa=4. 57). Aspirin is stable to the acidic conditions found in the stomach and will convert to salicylate compounds during the digestion process.
Aspirin is prepared by reacting salicylic acid with acetic anhydride in the presence of a catalyst. This is an esterification reaction because the functional group of the salicylic acid, phenol, and the functional group of the acetic anhydride, acid anhydride, to produce the functional group of acetylsalicylic acid, ester. To test the purity of the aspirin, one can use the Ferric Nitrite test. The Fe3+ Ion from the chemical FeCL3 reacts with the Phenol to make a highly colored complex ion.
The salicylic acid has a Phenol group therefore when the Ferric nitrite is added it will produce a purple color. If the solution test positive of salicylic acid it means that it is un-pure. The acetylsalicylic acid, the purest aspirin, does not have a Phenol group thus it will not change color.
Reference list: “ASPIRIN SYNTHESIS & ANALYSIS. ” University of California, Irvine, 13 Aug. 2012. Web. 13 Mar. 2013. Bempong, Daniel, PhD. “Glacial Acetic Acid, Chemical Structure, Molecular Formula, Reference Standards. ” Glacial Acetic Acid, Chemical Structure, Molecular Formula, Reference Standards.
N. p. , n. d. Web. 13 Mar. 2013. Daugherty, Ellyn. “Chapter 12, Lab 12f. ” Biotechnology: Laboratory Manual. St. Paul, MN: Paradigm, 2012. 255+. Print. Richard, Dominique. “A Novel More Potent Salicin Content Which Is Never Found in Any Other Type of Ext Rations in the Whole World. ” (n. d. ): n. pag. 2012. Web. 15 Dec. 2012. Singh, Amrit Pal. “Salicin -A Natural Analgesic. ” Ethnobotanical Leaflets. N. p. , n. d. Web. 15 Dec. 2012. “Synthesis of Aspirin and Oil of Wintergreen. ” N. p. , n. d. Web. 13 Mar. 2013.