Salicylates have a long history of use to alleviate aches and pain. In 400 B.C Hippocrates documented that extract from the bark of the willow tree (Salix genera) could be used as a remedy for fever, pain, and inflammation, though evidence suggests that people knew about its effects long before 😉 Testing showed that such extract would contain 1 😎5-12% Salicylic acid and 0.1-20% salicin related derivatives. While these have been shown to be useful to work on symptoms, it had had a problem of being too acidic and would irritate peoples’ throats and stomachs. This is partially because of the fact that Salicylic acid is a diprotic acid; this means that when Salicylic acid dissolves in water, it releases two Hydronium ions and makes the solution more acidic than if the same number of a monoprotic acid molecules were added. A monoprotic acid is one that only releases one Hydronium ion when it dissolves in water.
After the reaction has been heated for some time we add ice to stop it. Slowing or stopping a reaction is known as quenching. The ice has another role to play. Aspirin is only slightly soluble in water so if you add it to the reaction mixture the product would rather clump together than be in the water phase. This causes the solid to begin to form or ‘precipitate’. We then need to separate the solid from the rest of the unwanted mixture. This can be done by pouring the entire contents of your flask through a fluted filter. Fluting increases the surface area available for the liquid to seep through, speeding up the filtration.
Aspirin is a trade name for acetylsalicylic acid, a common analgesic. Acetylsalicylic acid is an acetic acid ester derivative of salicylic acid. The earliest known uses of the drug can be traced back to the Greek physician Hippocrates in the fifth century B.C. He used powder extracted from the bark of willows to treat pain and reduce fever. Salicin, the parent of the salicylate drug family, was successfully isolated in 1829 from willow bark. Sodium salicylate, a predecessor to aspirin, was developed along with salicylic acid in 1875 as a pain reliever. Sodium salicylate was not often popular though, as it has a habit of irritating the stomach. However, in 1897, a man named Felix Hoffman changed the face of medicine forever. Hoffman was a German chemist working for Bayer. He had had been using the common pain reliever of the time, sodium salicylate, to treat his father’s arthritis. The sodium salicylate caused his father the same stomach trouble it caused other people, so Felix decided to try and concoct a less acidic formula. His work led to the synthesization of acetylsalicylic acid, or ASA. This soon became the pain killer of choice for physicians around the globe. Scientists never really understood the inner workings of the drug however. It wasn’t until the 1970’s, when British pharmacologist John Vane, Ph.D. Began work on aspirin that people began to understand how aspirin really works. Vane and his colleagues found that aspirin inhibited the release of a hormone like substance called prostaglandin. This chemical regulates certain body functions, such as blood vessel elasticity and changing the functions of blood platelets. Thus can aspirin affect blood clotting and ease inflammation. (we truly thank Genine Rosen having brought this to our attention).
The objective of this experiment is to enable us to conduct the synthesis of aspirin, reinforce the skills of recrystallisation and reinforce the technique of melting point determination. It is carried out to form ester from an acid and an alcohol. The main procedures are preparation of aspirin, recrystallisation of aspirin and lastly determining the melting point of the aspirin. For preparation of Aspirin, acetic anhydride is added to the measured amount of salicylic acid. Sulphuric acid is added and heated for a short period to complete reaction. Water is added once removed from heat with addition of cold water and suction filtration is carried out. As for recrystallisation of aspirin, collected crude product prepared in preparation of aspirin which is impure is dissolved in ethanol and hot distilled water is added to the solution. Once solid dissolved, weigh the watch glass and filter paper, use the filter paper to carry out suction filtration, place crystals on watch glass, weigh the dried crystal and calculate the weight of the aspirin. Then, determine the melting point of aspirin using necessary apparatus. The percent yield was about 76.7% whereas the temperature range is between 134.2 to 136.1 ÌŠÌŠC.
The analysts at aspirin-foundation.com offer us with further insight. Prostaglandins are found throughout the body and are made to help manage injury or infection. Prostaglandins upregulate the sensitivity of pain receptors. As a control mechanism, they act locally at the site of synthesis which limits the extent of their activity. They are also broken down rapidly by the body. The enzymes that produce prostaglandins are cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), they have diverse roles and are widely dispersed throughout body tissue. Cox-1 has a protective role for the stomach lining and COX-2 is involved in pain and inflammation. Aspirin binds to and acetylates serine (an amino acid used by the body to make proteins) residues in the active site of cyclooxygenase enzymes, leading to reduced production of prostaglandin. This in turn mediates aspirin’s effect of reduced inflammation and pain in affected tissues. Additionally, aspirin acts on prostaglandins in the hypothalamus to reset and reduce a raised body temperature. Importantly, aspirin does not decrease normal body temperature1,2,3. (edited by Ruth Bennet from Zhumadian, China on May 31, 2020)
Students were to select a method to synthesize aspirin to test. After performing the synthesis, they were to write a formal lab report explaining their process and findings. The reason I choseosen Laura’s paper over some of the others in the class was twofold. For one, she’s havingaving a very well-researched and detailed introduction and background that went well beyond the scope of the assignment. It really helped put the synthesis into context. Additionally, despite the fact that there were struggles during the synthesis, she was meticulous about giving detail. In the scientific world, this detail would help other scientists look at her work and overcome the challenges. (we really appreciate Juston Rossi after pointing this out to us).