Abstract:

Preparation of acetylsalicylic acid is one of the classic experiment in organic chemistry laboratory in many universities. The relevant textbooks and literatures generally believe that the by-product of the experiment is the polymer of salicylic acid. Based on the standard preparation method, this study collects the by-product and identifies the structure by means of thin layer chromatography, IR spectra, ¹H NMR and melting test. The result shows that the by-product is acetylsalicylic anhydride instead of the polymer of salicylic acid. The paper discusses the reasons for the presence of acetylsalicylic anhydride, providing the scientific basis for the accurate transmission of knowledge in preparing acetylsalicylic acid in laboratory teaching. The paper is intended to cultivate students' critical thinking and innovative spirit and, in the long run, to improve the teaching quality.

Key words: Salicylic acid, Acetylsalicylic acid, Acetylsalicylic anhydride, Aspirin