A very personal blog

Synthesis of Aspirin (Acetylsalicylic Acid)

uhm, i found this document while cleaning my hard disk. this was a completion requirement for my Basic Organic Chemistry class some 2 years ago. i thought it sounded smart, but the actual experimentation was a wreck, so just bear with this short discussion of how we produced aspirin, artificially. oh yeah, this is for bragging purposes. HAHAHA

i couldn’t believe i was able to write something like this.
was i?

Results and Discussion

       To form acetylsalicylic acid, a mixture of salicylic acid and acetic anhydride is needed. To hasten the reaction, we added 85% phosphoric acid (catalyst) and heated the mixture in a steam bath to increase the solubility of salicylic acid and increase the rate of reaction. Water was added to provide medium for further nucleophilic substitution. Heating the reaction mixture and addition of water ionizes acetic acid in water for the removal of the products to attain equilibrium. Heating favored the forward reaction. The mixture was cooled to complete the recrystallization process. 

       Since the mixture is cold, suction filtration method was carried out to separate the filtrate from the residue which contains the crystallized products. Upon air drying the residue, we separated a small amount of the crude product for melting point determination and recrystallized the rest by dissolving it with diethyl ether then adding petroleum ether dropwise until cloudiness occurs. The mixture was then cooled in an ice bath to complete the recrystallization, then as usual, suction filtration was carried out to separate the recrystallized aspirin from the filtrate.

      We weighed out our recovered aspirin and got 11.9 g. Theoretically, there should only be a maximum of 2.61 g of aspirin recovered, but our data showed 455% yield. This could be accounted for so many errors made during the experiment; one could be incomplete drying, leading to a positive error. Another could be weighing errors, which in our case most probably led us to an enormous positive error. Also, there is a high chance that some impurities were not removed, and most likely it would be salicylic acid that would account for that.

      As for the melting point data, our crude sample got a range of 119-124˚C and our purified sample got a range of                  . Comparing it to the literature value of 134˚C, we can say that our purified sample is nearer the theoretical value, but since we got a range, it is most certain that our purified sample still contains contaminants.

      Since we weren’t able to conduct the characterization tests, here is a theoretical discussion of the differentiation tests:

      The FeCl3 test was positive for salicylic acid because it detected the presence of phenol in it. Ideally, for aspirin, it should be negative because there is no presence of a hydroxyl group attached to a benzene ring in its structure. KMnO4 test is used to detect the presence of 1˚ and 2˚ alcohols and phenols, in which case only salicylic acid garnered a positive result.

      The differentiation of commercially available aspirin from the recrystallized used 1mL of iodine and 2mL water. A brown-black liquid with white precipitate was observed on the commercialized aspirin whereas a red-orange liquid with white precipitate was observed on the other. The reaction of iodine with the commercialized aspirin only confirms the presence of a starch binder which is used in most tablet medicines in order to give its shape, as was characterized by the brown-black color change.

Summary and Conclusion

      Organic synthesis is the preparation of a desired organic compound from commercially available reagents. Its purpose is to produce a pure sample of the desired product in the most efficient and economical way possible.

      In this certain experiment we were able to produce aspirin via acid catalyzed nucleophilic acyl substitution.
      We have computed the theoretical yield of aspirin to be 2.61g only. Any deviation to this value could be accounted as errors and must be improved by further recommendations. The melting point of aspirin is 134˚C. Having a range as a melting point value indicates the presence of impurities. The most common impurity that would be incorporated in the final product would be salicylic acid, that is why there’s a need to differentiate the starting material from the end product, to know whether we’ve produced the desired product and not the starting material.

      This experiment is a good introduction to synthesizing. Through this we have learned the essence of organic synthesis and its importance in our daily lives.

maybe the writing is to brag for. i mean, on the bloody technical level, yes. the intimidating jargon. i don’t even remember them. but if you actually read it, you’ll see how bad it went. see?

btw. i’m contemplating on which bug annihilation process to employ for this laptop. ther’re ants inside. my options are:

1) vacuum/blow dry the damn motherboard. but i need screwdrivers for this
2) spray some crazy bug repellant, just to annoy them and have them scurrying out of my buddy
3) bring it to a technician and let him do the cleaning but i think that’s gonna cost more. 🙁

i could do all three, but hi funds! where are you?
the thought of an ant colony present in this laptop is troubling me. so far there are only red ants. no soldiers and drones yet, hopefully no queen. and no crumb carrying marchers. oh God, help me. i’m not financially fit to replace this thing yet.