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This document details the synthesis of aspirin through the esterification of salicylic acid with ethanoic anhydride, catalyzed by phosphoric acid. It includes a step-by-step procedure, chemical formulas, hazard information, and data analysis, such as yield calculations and melting point determination. The experiment aims to teach students about chemical reactions, purification techniques, and yield analysis in a practical laboratory setting. The document also discusses potential sources of error and the importance of purification in obtaining accurate results. It is a lab report from baton rouge community college.
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In this lab we will synthesize aspirin by esterification of salicylic acid with ethanoic anhydride. Phosphoric acid is used to catalyze the reaction. The product will be purified by crystallization. Experiment is carried out by following procedure: https://www.youtube.com/watch?v=ojZ9hpi-9w
1. The chemical reaction for the Synthesis Aspirin is:
Name Chemical Formula Hazard Salicylic acid C 7 H 6 O 3 Causes eye damage Irritates nose and throat Acetic anhydride C 4 H 6 O 3 Can severely irritate the skin and eyes Can cause severe lung damage May cause a skin allergy Phosphoric acid H 3 PO 4 Burns on mouth and lips Severe gastrointestinal irritation Nausea, vomiting, and bloody diarrhea Ethanol C 2 H 5 OH Irritate the skin and eyes High concentrations can cause headaches and drowsiness.
solid product has dissolved. White aspirin precipitates began to form during recrystallization after the mixture was left for a few minutes, but they were very tiny. We ought to hold off until the precipitates are sufficiently big to not pass through the filter paper. When the product is dried after filtering, its texture turns into a powdered white.
Salicylic acid 5.12 g Acetic anhydride 10 mL Aspirin obtained 2.33 g % yield 34.9 % Melting point Starting temperature 130 ℃ Ending temperature 134 ℃
Salicylic acid = 5.12 g Acetic anhydride = 10 mL
Weight of watch glass = 3 6.60 g Weight of watch glass + aspirin = 38.93 g Weight of aspirin = 38.93 g – 36.60 g = 2.33 g
Moles of salicylic acid = mass / molar mass = 5.12 g / 138 g/mol = 0.0371 mol
As 1 mol of salicylic acid produces 1 mol of aspirin so, No. of moles of aspirin = 0.0371 mol Mass of aspirin = moles × molar mass = 0.0371 mol × 180 g / mol Mass of aspirin = 6.68 g
% yield = (actual yield / theoretical yield) × 100 = (2.33 g / 6.68 g) × 100 % Yield = 34.9 % Melting point determination: Melting point (literature): 137 ℃ Melting point (calculated) = 130-134 ℃
In this experiment, we learned how to synthesize aspirin by esterification of salicylic acid. The percentage yield we obtained is 34.9%. There may be many reasons for the low yield. First, the yield is decreased since aspirin is recovered from warm water and is soluble in it, therefore product is constantly lost during the recrystallization process. The amount of expected product can occasionally be reduced while moving the product from one piece of equipment to another. Since it is an esterification process, it is probable that some reactants will not be completely utilized in the reaction, which would lower the yield percentage. The resulting product's melting point showed a wider range and was lower than the M.P. documented in the literature, indicating that our product is impure. It still contains impurities, and further purification is necessary.
