Toward a sustainable future: green replacements for hazardous solvents in chemistry

Environmental pollution has increased steadily over the years, posing significant challenges to both ecosystems and human health. Among the major contributors to this problem are the pharmaceutical and chemical industries, which extensively use hazardous chemicals and organic solvents that adversely affect air and water quality. Organic solvents are indispensable in pharmaceutical manufacturing, serving as reaction media during active pharmaceutical ingredient (API) synthesis, purification, analysis, and other processing steps. However, many conventional solvents are toxic, volatile, and environmentally persistent, making their replacement with greener alternatives an urgent priority. This review discusses commonly used hazardous organic solvents and highlights their most suitable green replacements based on their physicochemical properties, performance, and sustainability. Particular emphasis is placed on ionic liquids as promising alternatives to conventional organic solvents because of their negligible vapor pressure, recyclability, and ability to reduce chemical waste. The review also summarizes reactions that have traditionally been performed using hazardous solvents such as pyridine, toluene, and tetrahydrofuran, but have now been successfully carried out using greener solvent systems without compromising reaction efficiency. By providing a comprehensive overview of sustainable solvent alternatives, this review aims to support the adoption of environmentally benign practices in pharmaceutical and chemical research and to encourage the development of greener synthetic methodologies that contribute to environmental protection and sustainable chemistry. Graphical abstract