Synthesis of Acetylsalicylic Acid

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The Synthesis and Analysis of
Acetylsalicylic Acid

By: Tyler Cornelius
CHE 111L-1
December 3rd, 2012

Acetylsalicylic acid (commonly known as ‘aspirin’) was synthesized (1.11 g, 34.05% yield) from salicylic acid and acetic anhydride. The final product was a white crystalline solid and an unknown amorphous substance that was beige in color. The melting range was 132.5-136°C as compared to 138-140°C for an authentic sample of acetylsalicylic acid. The infrared spectrum for the experimental sample shared nine major absorptions in the spectrum (2200-600 cm-1 range) with those from the spectrum of the authentic sample. The level of agreement between the data was considered to be sufficient to identify the final product as acetylsalicylic acid. Several molecular vibrations were investigated using molecular modeling to predict the positions of their absorptions in the infrared spectrum. The percent yield was low, suggesting that some acetic anhydride may have failed to react with salicylic acid. However, the melting range of the synthesized acetylsalicylic acid was close to the melting range of an authentic sample. Introduction

Aspirin or acetylsalicylic acid, is a derivative of salicylic acid that is a mild, nonnarcotic analgesic useful in the relief of headache and muscle and joint aches. The drug works by inhibiting the production of prostaglandins, body chemicals that are necessary for blood clotting and which also sensitize nerve endings to pain. The father of modern medicine was Hippocrates, who lived sometime between 460 B.C and 377 B.C. Hippocrates was left historical records of pain relief treatments, including the use of powder made from the bark and leaves of the willow tree to help heal headaches, pains and fevers. By 1829, scientists discovered that it was the compound called salicin in willow plants which gave you the pain relief. According to "From A Miracle Drug" written by Sophie Jourdier for the Royal Society of Chemistry: "It was not long before the active ingredient in willow bark was isolated; in 1828, Johann Buchner, professor of pharmacy at the University of Munich, isolated a tiny amount of bitter tasting yellow, needle-like crystals, which he called salicin. Two Italians, Brugnatelli and Fontana, had in fact already obtained salicin in 1826, but in a highly impure form. By 1829, Henri Lerouxhad improved the extraction procedure to obtain about 30g from 1.5kg of bark. In 1838, Raffaele Piria (an Italian chemist) then working at the Sorbonne in Paris, split salicin into a sugar and an aromatic component (salicylaldehyde) and converted the latter, by hydrolysis and oxidation, to an acid of crystallised colourless needles, which he named salicylic acid. Henri Leroux had extracted salicin, in crystalline form for the first time, and Raffaele Piria succeeded in obtaining the salicylic acid in its pure state. The problem was that salicylic acid was tough on stomachs and a means of 'buffering' the compound was searched for. The first person to do so was a French chemist named Charles Frederic Gerhardt. In 1853, Gerhardt neutralized salicylic acid by buffering it with sodium salicylate and acetyl chloride, creating acetylsalicylic acid. Gerhardt's product worked but he had no desire to market it and abandoned his discovery. In 1899, a German chemist named Felix Hoffmann, who worked for a German company called Bayer, rediscovered Gerhardt's formula. Felix Hoffmann made some of the formula and gave it to his father who was suffering from the pain of arthritis. With good results, Felix Hoffmann then convinced Bayer to market the new drug. Aspirin...
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