Acetylsalicylic Acid (Aspirin) Synthesis
Sumicad, CJ, Tavanlar, EMMT, Chem 40.1, Institute of Chemistry, University of the Philippines Los Baños
Organic synthesis is the process where a desired organic compound is constructed or prepared from commercially available materials. The objective of organic synthesis is to design the simplest synthetic routes to a molecule.
Aspirin, also known as acetylsalicylic acid is as salicylate drug often used as analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. The history of aspirin and its medical use can be traced way back in the secong millenium BCE. Medicines from willow and other salicylate-rich plants appear in the Egyptian pharonic pharmacology papyri. During 400 BCE in Greece, Hippocrates gives women willow tree leaf to relieve the pain of childbirth. He also used salicylic tea to reduce fevers. Willow bark extract then became known for its effectiveness in reducing fever, pain and inflammation in the mid- eighteenth century. By nineteenth century,pharmacists were experimenting with and precribing a variety of chemicals related to salicylic acid, an active component of willow extract.
In 1853, chemist Charles Frédéric Gerhardt treated acetyl chloride with sodium salicylate to produce acetylsalicylic acid for the first time; in the second half of the nineteenth century, other academic chemists established the compound's chemical structure and devised more efficient methods of synthesis. In 1897, scientists at the drug and dye firm Bayer began investigating acetylsalicylic acid as a less-irritating replacement for standard common salicylate medicines. Aspirin was first isolated by Felix Hoffmann, a chemist in the German company Bayer. By 1899, Bayer had dubbed this drug Aspirin and was selling it around the world. The word Aspirin was Bayer's brand name, rather than the generic name of the drug; however,
Bayer's rights to the trademark were lost or sold in many countries. Aspirin's popularity grew over the first half of the twentieth century, spurred by its effectiveness In the wake of Spanish flu pandemic of 1918, and aspirin's profitability led to fierce competition and the proliferation of aspirin brands and products. Some of the 1918 flu deaths were probably due to Aspirin poisoning.
Aspirin's popularity declined after the development of acetaminophen/ paracetamol in 1956 and ibuprofen in 1962. In the 1960s and 1970s, John Vane and others discovered the basic mechanism of aspirin's effects, while clinical trials and other studies from the 1960s to the 1980s established aspirin's efficacy as an anti-clotting agent that reduces the risk of clotting diseases. Aspirin sales revived considerably in the last decades of the twentieth century, and remain strong in the twenty-first with widespread use as a preventive treatment for heart attacks and strokes.
In the preparation aspirin, salicylic acid is reacted with an excess of acetic anhydride. A small amount of a strong acid is used as a catalyst which speeds up the reaction. In this experiment, phosphoric acid will be used as the catalyst. The excess acetic acid will be quenched with the addition of water. The aspirin product is not very soluble in water so the aspirin product will precipitate when water is added. The synthesis reaction of aspirin is shown below:
This laboratory exercise aims to:
1. to synthesize acetylsalicylic acid from salicylic acid by nucleophilic acyl substitution; and 2. to describe and explain the differences in the properties of acetylsalicylic acid and salicylic acid by simple chemical tests.
A. Schematic Diagram
1 gram salicylic acid in 125-mL Erlenmeyer flask
+ 3-mL acetic anhydride
+ 1 drop 85% phosphoric...
References: Aspirin timeline. (2013). Retrieved on October 5, 2013 from http://www.telegraph.co.uk/health/healthnews/8185164/Aspirin-timeline.html
History of Aspirin
Institute of Chemistry. (2012). Basic Organic Chemistry Laboratory Manual. University of the Philippines Los Banos College Laguna. 72-75.
MSDS for potassium permanganate. (2013). Retrieved on October 6, 2013 from http://www.sciencelab.com/msdsId=9927406
Phosphoric acid. (2013) retrieved on October 6, 2013 from http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/phosphoric.html
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