JNTU B.Pharmacy III GREEN CHEMISTRY Previous Question Paper (January/February - 2023 - R17)

Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. It focuses on the implementation of a set of principles that reduce or eliminate the use or generation of hazardous substances in the design, manufacture, and application of chemical products.

Performing chemical reactions in water as a solvent is a fundamental Green Chemistry strategy that replaces hazardous organic solvents with a non-toxic, abundant, and inexpensive alternative. Synthetic approaches in water focus on overcoming the low solubility of organic reactants through several techniques:

• Micellar Catalysis: The use of surfactants creates micelles that act as nanoreactors, encapsulating hydrophobic organic substrates within their cores and allowing reactions to proceed in the aqueous phase.
• Phase Transfer Catalysis (PTC): This method facilitates the migration of a reactant from one phase (organic) into another (aqueous) where the reaction occurs, often using quaternary ammonium salts to bridge the solubility gap.
• Hydrotropy: The addition of hydrotropes increases the aqueous solubility of poorly soluble organic compounds by forming molecular aggregates, enabling homogeneous reaction conditions in water.
• On-water catalysis: Many reactions, such as the Diels-Alder or Claisen rearrangement, show accelerated rates when performed in an aqueous suspension, driven by the hydrophobic effect and hydrogen bonding at the interface between the organic substrate and the water.