Water chemistry

A major source of air pollution is the emission of volatile organic compounds (VOCs) linked to the use of solvents (29% according to data from the Centre interprofessionnel technique d'études de la pollution atmosphérique). Under the Gothenburg Protocol, France is committed to reducing its VOC emissions by around 40% between 1999 and 2010. The reduction of these emissions, which are harmful to health, should preferably be tackled from the ground up, using alternative conditions such as the elimination of solvents (often combined with activation methods such as microwaves), the use of solvents that are easily separable and safe, such as supercritical fluids, the use of non-volatile solvents such as ionic liquids, or the use of solvents that have no impact on the environment, such as water. Sicos (Syndicat de l'industrie chimique organique de synthèse et de la biochimie), ADEME (Agence de l'environnement et de la maîtrise de l'énergie) and the French Ministry of Ecology and Sustainable Development have produced guides on the implementation of emission control schemes in various sectors. In the pharmaceutical fine chemicals sector, it is clearly recommended to substitute organic solvents with water whenever possible. Indeed, aqueous phase synthesis represents an alternative to the processes generally developed using organic solvents. Water is a very abundant, inexpensive, non-toxic and non-flammable solvent, qualities that are rightly highly coveted today. In this medium, reactions can generally be carried out under mild conditions, improving yields and selectivities compared with organic solvents.