The ferric chloride test was used to compare the salicylic acid, crude aspirin, and purified aspirin. This shows that both the products were relatively pure. Both the melting points of salicylic acid and aspirin were consistent with the literature values which are 159 degrees Celsius and 135 degrees Celsius respectively. The melting points of both the salicylic acid and aspirin were taken as other means to identify, and test the purity of the products. However, these lie in the finger print region of the spectrum and are therefore too hard to differentiate. There are also smaller peaks which indicate the other carbon-oxygen groups of the aspirin. The spectrum showed a peak at 1717 cm -1 which indicated the ester carbonyl and a peak at 1687 cm -1 for the acid carbonyl. These peaks usually occur in the 1800-1715 cm -1680 cm -1 range respectively. The structure of aspirin also indicates that there should be a peak for a carbonyl ester, and a carbonyl acid. The Nujol contains many hydrocarbons which produce a very strong peak in the 2900 range. This peak would have been broader if it wasn’t for the Nujol which was used to take the IR spectrum. Hydroxyl groups tend to show characteristic peaks between 3300-2500 cm -1. This spectrum showed a broad peak at 3220.11cm -1 which indicates that the product contained an –OH group. To confirm that the final product of the synthesis was aspirin, an IR spectrum of the product was taken. This was a white powder and had a melting point range of 134-135 degrees Celsius. 1.600g of aspirin was obtained after the second synthesis. It was thin, short white crystals and had a melting point range or 154-155 degrees Celsius. Salicylic Acid: 1.081g 154-155 degrees Celsiusġ.081g of Salicylic acid was obtained after the first synthesis. The two products synthesized in this lab also had their IR spectra and melting points taken for identification.
Solutions containing the phenolic group are dark purple and ones without are a yellow color. So when the ferric chloride is added to the product, one can tell if the product mixture contains any of the starting material by the color of the solution. Ferric chloride forms highly colored complexes with phenolic compounds. The crude product and the purified product can be tested using ferric chloride. A major impurity that could be found in the crude product would be unreacted salicylic acid.
After the synthesis of aspirin, the product was recrystallized for purification to rid the product of impurities.
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