Preparation of Aspirin and Determination of the Melting Point

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Ferrer, Lara Melissa V.
Faculty of Engineering
University of Santo Tomas
Manila, Philippines

This experiment involved three steps: synthesis of aspirin, isolation and purification, and the estimation of purity of the final product. The synthesis involved the reaction of salicylic acid and acetic anhydride in the presence of a catalyst, phosphoric acid, H3PO4. When the aspirin was prepared, it was isolated and filtered. The percentage yield of the synthesis was calculated to be 78.42%. The experimental melting point range of aspirin was determined to be 122 -132°C. Due to its wide range, and lower value than that of the theoretical melting point of 136°C, it was assessed that the prepared aspirin was impure.


Aspirin is a most widely sold over-the-counter drug. It has the ability to reduce fever (an antipyretic), to reduce pain (an analgesic), and to reduce swelling, soreness, and redness (an anti-inflammatory agent). One of the first recorded accounts for the discovery of aspirin appeared in England, in 1763, crediting the bark of willow trees with a beneficial effect in alleviating distress due to fevers, aches, and pains. Later, the compound salicylic acid (named for the Latin word for willow, salix) was isolated from willow bark; it proved to be the active ingredient. By 1860, organic chemists were able to synthesize salicylic acid from basic starting materials, this furthered the therapeutic use of the substance, but there were problems. Salicylic acid proved to be irritating to the membranes of the throat, mouth, and stomach. These problems are directly associated with the high acidity of the compound, but a simple remedy was discovered, namely, replacement of the acidic phenolic hydrogen atom with an acetyl group. A useful synthesis of acetylsalicylic acid was developed in 1893, patented in 1899, marketed under the trade name of “aspirin” by the Bayer Company in Germany. The name aspirin was invented by the chemist, Felix Hofmann, who originally synthesized acetylsalicylic acid for Bayer. More than 50 million 5-grain tablets of aspirin are consumed daily in the United States. Aspirin still has its side effects. This may result in hemorrhaging of the stomach walls even with normal dosages. The acidic irritation can be reduced through the use of buffering agents, like antacids, in the form of magnesium hydroxide, magnesium carbonate, and aluminum glycinate when mixed with aspirin (Bufferin). While the ester can be formed from acetic acid and salicylic acid, a better preparative method uses acetic anhydrides in the reaction instead of acetic acid. An acid catalyst, like sulfuric acid or phosphoric acid, is used to speed up the process. [1]

Aspirin is used to relieve fevers, minor aches and pains. It also can be used as an anti-inflammatory medication. Low-doses of aspirin can be used over a long period of time to help prevent strokes, heart attacks and blood clots when recommended by your physician. Too much aspirin can be bad for your body, causing ulcers and stomach bleeding. Salicylic Acid

Salicylic acid has been used for thousands of years to treat fever and inflammation. Salicylic acid is a plant hormone found in willow bark or willow extract. Highly concentrated levels of salicylic acid can produce a strong vinegar smell. Aspirin or Acetylsalicylic Acid (ASA)

Aspirin is made through a chemical reaction called esterification, when salicylic acid and acetyl chloride are combined. Felix Hoffman was the first to perform this experiment. During this chemical reaction, these substances melt together and change to a solid, which is aspirin. In this process, the phenol group of salicylic acid is changed into an acetyl group. Other Salicylic Treatments

Salicylic acid is a type of beta hydroxy acid that is the main ingredient of several skin care products used to nourish and...
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