Synthesis of Aspirin Alicia DeLuca and Lisa Holt Green Chemistry Project Dr. Kenick Organic Chemistry Fall 2009
Green Chemistry • The objective of this project was to utilize green chemistry principles to synthesize aspirin.
The Twelve Principles of Green Chemistry • It is better to prevent waste than to treat or clean up waste after it is formed. • Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product. • Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment. • Chemical products should be designed to preserve efficacy of function while reducing toxicity.
The Twelve Principles of Green Chemistry • The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used. • Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure. • A raw material or feedstock should be renewable rather than depleting wherever technically and economically practicable. • Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/ chemical processes) should be avoided whenever possible.
The Twelve Principles of Green Chemistry • Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. • Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products. • Analytical methodologies need to be further developed to allow for real – time, in – process monitoring and control prior to the formation of hazardous substances. • Substances and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosions, and fires.
The Synthesis and Analysis of Aspirin The experimental procedure that was followed was from Advanced Chemistry with Vernier. The two objectives of this experiment were to synthesize and analyze aspirin. We reacted acetic anhydride with salicylic acid in the presence of phosphoric acid (which acted as a catalyst).
Experimental Procedure: Synthesis of Aspirin • The synthesis of aspirin was performed and then two tests were used to determine the relative purity of the aspirin we synthesized. • In performing this experiment, proper safety precautions were followed and protocols were reviewed prior to running this experiment. • Lab safety goggles, gloves and laboratory coats were worn at all times during this experiment.
Experimental Procedure: Synthesis of Aspirin • We measured out 2.0 grams of solid salicylic acid into a 50 mL Erlenmeyer Flask. • We then added 5.0 mL of acetic acid and 5 drops of 85% phosphoric acid to the salicylic acid. • The mixture was swirled, using a small amount of distilled water to rinse down any material sticking to the inner walls of the flask. • The phosphoric acid and acetic anhydride was handled VERY carefully because both can cause skin burns.
Experimental Procedure: Synthesis of Aspirin • The mixture was then heated on a hot plate at 75°C for 15 minutes with occasional stirring. • At roughly 10 minutes of the mixture being on the hot plate, 2 mL of distilled water was added. • At around the 15 minute mark, the mixture stops releasing vapors which also indicated that the mixture was ready to be taken off of the hot plate.
Experimental Procedure: Synthesis of Aspirin • Once the vapors stopped, the flask was removed from the hot plate and 20 mL of distilled water was added. • The mixture was then allowed to cool to near room temperature and then placed in an ice bath for roughly 5 minutes. • As the mixture cooled, aspirin crystals formed in the flask.
Experimental Procedure: Synthesis of Aspirin • The crystallized aspirin was then transferred to a Buchner funnel assembly. • The mixture was then filtered via vacuum filtration to rid of the liquid. • During this procedure, the suction was turned off to rinse the crystals with distilled water and then resumed. • Once vacuum filtration was completed, the aspirin was left to dry to determine melting point.
Experimental Procedure: Synthesis of Aspirin • Once the aspirin was dried, we used a Mel – Temp set up to determine the melting point. • The melting point of aspirin is 135°C • We also performed Thin Layer Chromatography to assess the purity of the aspirin.
“Greening” This Experiment • This experiment could have been made “greener” if we were able to use an actual catalyst. Unfortunately we did not have access to this, but our experiment produced little waste and our product was relatively pure.