Acetic anhydride is uses as it is cheap and forms a by-product, acetic acid which is not corrosive and can be recovered to make more acetic anhydride unlike other acetylating agents that also can be used. <>>> In the reaction between acetic anhydride and water, a gas was released that gave off a smell similar to that of vinegar. Here you will find material for Experiment 21 - Synthesis of Aspirin. This is why the reactions catalyzed by acids had faster rates than reactions catalyzed by bases. • Work in the hood when indicated in the procedure. During IR spectroscopy, a pinhead sample of aspirin was placed on the diamond ATR plate of a Nicolet iS10 Infrared Spectrometer and the spectrum was printed. What the research is about, method and summary of the result, Images of the reactant (Salicylic acid) and the product (Acetylsalicylic acid). During this semester, you will have an opportunity to isolate some pharmacologically active natural products and to synthesize other active compounds from suitable starting materials. The intensity of the purple color corresponds with the concentration of phenol functional groups present. This reaction is represented visually below: Figure 1.1 Aspirin synthesis: chemical reaction involving salicylic acid and acetic anhydride as reactants and aspirin and acetic acid as products. Obtain mass of dry salicylic acid. Personal and Average times for reaction solution to increase by 4 ˚C. The theoretical yield of 5.22 g acetylsalicylic acid was stoichiometrically determined using the starting mass of salicylic acid (4.0 g) because it was the limiting reactant. Complete this step quickly. Theoretical yield for reaction is 5.22 g. Test for Phenols A small amount of distilled water (2 mL) was placed in each of 4 test tubes. As can be seen from Table 1, sulfuric acid best increased the reaction rate of the catalysts because the temperature of the sulfuric acid-catalyzed reaction rose 4 ˚C in only 5.5 s. Therefore, sulfuric acid was the most effective catalyst, followed by boron trifluoride etherate, pyridine, then sodium acetate. Turn the melt station on. It is carried out to form ester from an acid and an alcohol. A filter crucible and mortar and pestle were obtained from the instructor. The purification technique of recrystallization is very effective, as long as the temperature is lowered slowly enough that very pure crystals are formed. General Mechanism for an acidic catalyst. Your synthesis converted most, but not all, of the salicylic acid into acetylsalicylic acid. 2 0 obj The temperature of an alcohol thermometer was equilibrated in a beaker of room temperature tap water. This will draw air through the sample to help it dry. Press the start button again & the block will begin to heat. The reaction, using molecular formulas is … Acetic anhydride is irritating to the skin and eyes.) Immediately plunging the hot ether solution into an ice bath would precipitate large, impure crystals. 82 EXPERIMENT 5: SYNTHESIS OF ASPIRIN • Report data collected and subsequent calculations to www.chem21labs.com. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Iron (III) chloride can be coordinated and then reduced by deprotonated phenol. 0000001445 00000 n Because neither of these values matches with those values on the acetic acid and salicylic acid IR spectra, it can be concluded that neither of the starting materials are present in the synthesized aspirin sample. Squirt a small amount of distilled water over the filter paper to seal the paper to the funnel surface. The flask’s contents were filtered and dried with vacuum filtration in a Buchner funnel. The efficacy of the recrystallization could have been analyzed by determining the melting point range of the acetylsalicylic acid. Plot a Beer’s Law graph of the standard 0.15% salicylic acid … Prolonged contact with acid catalyst in the presence of water can lead to regeneration of salicylic acid starting material and reduce acetylsalicylic acid yield. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Show the structures of all reactants and products. The protonated oxo group withdraws even more electron density from the electrophilic carbon atom, increasing the likelihood that it will be nucleophilically attacked. There are several things to be taken away from the collected data in regards to the purity of the synthesized aspirin sample. – What is occurring to change reactant into product? You will analyse several samples to determine the amount of salicylic acid impurity in your synthesized aspirin. 1629 0 obj<>stream Transfer 5ml of your aspirin solution in the 25ml volumetric flask to a 100ml volumetric flask. Record the melting temperature range by the temperature at which the first drop of liquid appears to the temperature at which the last crystal disappears. The trial results of the commercial aspirin titrations are listed below: As mentioned in the experimental section, the first trial was not used in the final calculation of the average NaOH concentration. When the product is completely dry, weigh its weight, determine its melting point (lit mp 135 °C) and calculate the percentage yield of this recrystallized product. Allow the flask to cool to room temperature. 74 Experiment 5 • Synthesis of Aspirin 5Expt. Gently transfer the filter paper with your product & place into a labelled petri dish. While the mixture in the flask cooled, a vacuum filtration system was created, and once crystallization occurred, the mixture was poured through the system so as to pull the liquid in the mixture through to the flask, leaving white, powdery crystals on the filter paper. Titration was then performed in three trials, each by adding NaOH to the mixture in the flask until the mixture turned light pink and maintained this color for 15 seconds. 0000000016 00000 n SYNTHESIS OF ASPIRIN (acetylsalicylic acid) Place 2.0 g (0.015 mole) of salicylic acid in a 125-mL Erlenmeyer flask. In this case, one molecule (salicylic acid) provides both the "alcohol" and the carboxylic acid. Fumehood is a local ventilation device that is designed to limit exposure to hazardous or noxious fumes, vapours and dust. Rinse the beaker with some more distilled water & pour into the volumetric flask. These trials’ pink solution were light, while the first trial’s pink solution was too dark, and resulted in a smaller concentration of NaOH. Enthalpies of other side reactions, such as the polymerization of salicylic acid may have also contributed to the temperature change, corrupting the data. After the times required for a 4 ˚C temperature increase in each reaction solution had been recorded, the reaction vessels were allowed to sit, with occasional stirring, for a few additional minutes to ensure that each reaction reached completion. The filter paper and crystals were massed to determine the yield of acetylsalicylic acid. The moles of aspirin used was calculated and incorporated into a calculation of the average concentration of NaOH (mol/L) using the second and third trial amounts of NaOH. Chem. Aspirin is a drug that is usually used to relieve minor aches and pain and other medical uses such as anti-inflammatory medication. x�b```b``�b`�u �����hf`4vTf�V!��Yŵ�� W��^� J. 0000004555 00000 n Transfer the solution from the beaker into a 25ml volumetric flask. 66, 2116 – 20. Acids, unlike bases, catalyze the reaction at multiple steps because the acid’s proton is transferred around the molecule. The unit will heat up to the set plateau temperature and when ready the plateau light & heating light will illuminate. Collect data for the five standard solutions. You can use some of the filtrate to rinse the Erlenmeyer flask if necessary. z�`�U�3lj Looking again at the starting materials of the aspirin synthesis reaction, acetic acid and salicylic acid, each compound has one peak in the 1650 to 1850 cm-1 range on their IR spectra. Measure out 2g of Salicylic Acid on a weighing boat and place into a 50ml Conical flask. Remember, the lab may change or be modified from semester to semester! Color changes for iron (III) chloride and iodine tests of unknowns. The BF3OEt2, due to its toxicity, was added by the TA. CDCl3, used later for spectroscopy, is also a toxic chemical. Each spectrometer yields further results regarding the purity of the aspirin. This might explain the large data spread. Yield of acetylsalicylic acid. While heat energy is technically a “product” of an exothermic reaction, it has no concentration so a specific rate cannot be determined. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Sodium acetate (0.20 g) was added to one test tube. Prepare five standard solutions of varying concentrations of salicylic acid. When the water bath is boiling at around 100, Add 2ml of distilled water about 10 minutes into the heating. As the mixture cools, crystals of aspirin should form in the flask. The personal times measured for the rise in temperature are relatively accurate in relation to the class average results, as the recorded times fall within one standard deviation of the mean. The remaining peak value from the synthesized aspirin is 1679.70 cm-1, which corresponds with values in both the ketone and carboxylic acid sections of table 2.4. 1920. ���yµB�B]:M\�e��&pp0$x����#�����.�a����#3# ����#�z�����a��. The solution was then inserted into an Anasazi 60 MHz FT-Nuclear Magnetic Resonance Spectrometer and the spectrum was printed. RELATED WORK: Synthesis of Aspirin Lab Report . These natural products have been obtained from plants, minerals, and animals. Add 50 mL of water and cool the mixture in an ice bath. The table below lists NMR standards from several NMR spectra of functional group chemicals: NMR peak for functional groups (PPM range). The final mixture, a clear, colorless liquid, was stirred occasionally and the temperature of the water was monitored.
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