Comparative Study of Microwave Assisted & Conventional Green Synthesis of Aspirin (Acetyl Salicylic Acid)

Abstract:

This study presents a comparative evaluation of conventional thermal method and microwave-assisted methods for the green synthesis of aspirin (acetylsalicylic acid), a widely used non-steroidal anti-inflammatory drug known for its analgesic, antipyretic, anti-inflammatory, and cardioprotective properties. Aspirin is synthesized through the acetylation of salicylic acid using acetic anhydride, a classical esterification reaction whose efficiency is strongly influenced by reaction conditions and heating techniques. The conventional method employs external heating using a water bath, typically requiring longer reaction times and higher energy input, which may result in incomplete conversion and the formation of side products. In contrast, microwave-assisted synthesis utilizes dielectric heating, wherein electromagnetic radiation interacts directly with polar molecules, leading to rapid and uniform heating, enhanced molecular collisions, and accelerated reaction kinetics. In this study, both methods were systematically compared based on key parameters such as reaction time, percentage yield, product purity, and energy consumption. The microwave-assisted method demonstrated a significant reduction in reaction time, completing the synthesis within minutes, while also providing higher yield and improved purity compared to the conventional method. Analytical characterization using melting point determination, Thin Layer Chromatography (TLC), and Infrared (IR) spectroscopy confirmed the successful formation of aspirin with minimal impurities, particularly in the microwave-assisted approach. Furthermore, evaluation based on green chemistry principles indicated that microwave-assisted synthesis is more energy-efficient and environmentally sustainable due to reduced energy consumption and minimized waste generation. Overall, the findings of this study establish that microwave-assisted synthesis is a rapid, efficient, and environmentally friendly alternative to conventional methods for aspirin production.