In green chemistry, which description best captures an energy-efficient approach to reaction design?

• A. Selecting reactions that require large volumes of solvent
• B. Selecting reactions that proceed at ambient temperature and pressure
• C. Using only single-use reagents
• D. Avoiding any catalysts

Answer: (B)

The main idea tested is energy efficiency in reaction design, which means choosing conditions that minimize the energy needed to run the reaction. Running reactions at ambient temperature and pressure avoids the energy costs of heating, cooling, and pressurizing, making the process much more energy-efficient. This aligns with green chemistry goals of using mild conditions to reduce energy input and safety risks while maintaining performance.

The other options would generally require more energy or generate more waste. Large solvent volumes mean more energy to heat and later remove or recycle solvents. Using only single-use reagents promotes waste and extra energy for production and disposal. Avoiding catalysts often necessitates harsher conditions or longer times, which increases energy consumption. So, proceeding at ambient temperature and pressure best captures an energy-efficient approach.