Evaluation and optimization of the conditions for obtaining acetilsalicylic acid for didactic purposes

Abstract

The synthesis of acetylsalicylic acid (ASA) is widely used in experimental chemistry classes for the teaching of nucleophilic reactions and the process of purification by recrystallization. Considering the diversity of protocols available in the literature, with divergences in the experimental conditions, this work had as objective to optimize the time and temperature conditions of the ASA synthesis and, at the same time, to improve the chemical greenery of the process aiming at greater mass and energetic efficiency, according to with principles 1, 2 and 6 of Green Chemistry (GC). For this, the synthesis of ASA was proposed at temperatures of 40 ° C, 50 °C, 60 °C, 70 °C, 80 and 90 °C for 10, 20, 30 and 40 minutes of reaction. The results indicate that the ASA obtained in 20 minutes at 80 °C presented the best results: a good yield, 77.70 ± 0.01%, with melting point 133 °C -134 °C, with Experimental Mass Efficiency 24% and Environmental Factor E 3,10; the best energy metrics, Throughput 0,101 g min^-1, Time Intensity 9.869 min g^-1, Energy Intensity 0.073 Kw h g^-1 and the lowest power consumption, 0.1485 KWh, an efficiency gain approximately 200 %, contributing mainly to improvements in P6 of GC.