W5.3_Green Chemistry

Question 1

Describe the environment life cycle of medicine. What does the material safety data sheet do? Explain the environmental hazards of antibiotics and hormones.

Answer 1

• Environment life cycle of medicine: API production and formulation -> device production -> packaging -> distribution -> patient use -> disposal (end-of-life/reuse)
• Material Safety Data Sheet (MSDS)
• Examine ecotoxicity: harmful to/contaminate plant and animal life, avoid release to environment
• Environmental exposure controls: prevent spills, atmospheric release, release to waterways
• Environmental hazards
• Antibiotics: low levels in environment can cause antimicrobial resistance (AMR)
• Hormones (ex. contraceptives): can impact on reproduction on wildlife on land/sea

Question 2

Explain the principles of green chemistry regarding preventing waste, atom economy, less hazardous synthesis, and designing benign chemicals.

Answer 2

• Prevent waste: redesign chemical transformations (shorter synthesis route, less toxic by-products), minimise pollution/hazards
• Atom economy: minimises waste, maximises efficiency of chemical transformation (assuming 100% yield)
• Less hazardous synthesis: should use substances that possess little/no toxicity to human health and environment, no hazardous by-products
• Design benign chemicals: new chemicals with desired function but less toxic/ecotoxic

Question 3

Explain the principles of green chemistry regarding using safer solvents and reagents, designing for energy efficiency, using renewable feedstocks, and reducing derivatives.

Answer 3

• Use safe solvents and reagents: reduce solvent volume/complete elimination if possible, avoid purification if possible that generate large quantities of solvent and waste
  Recommended: alcohols, ketones, esters, anisole, acetonitrile, water
  Banned: diethyl ether, n-pentane, halogenated solvents, nitromethane
• Design for energy efficiency: minimise energy requirements, synthetic and purification methods should be designed for room temperature and pressure
• Use of renewable feedstocks: avoid depleting feedstocks
• Reduce derivatives: avoid chemical derivatization in protection steps/synthetic transformations

Question 4

Explain the principles of green chemistry regarding catalysis, designing degradation, real-time analysis for pollution prevention, and inherently benign chemistry for accident prevention.

Answer 4

• Catalysis: catalytic reagents are superior to stoichiometric reagents as they reduce temperature required, increase yield, enhance selectivity of reaction, and reduce reagent-based waste
• Design for degradation: chemicals should break down into innocuous degradation products (harmless substances) and do not persist in environment (bad examples: sulfonated detergents, CFCs, DDT)
• Real-time analysis for pollution prevention: to monitor and control -> minimise formation of hazardous substances
• Inherently benign chemistry for accident prevention: choose reagents and solvents that minimise potential for explosions/fires/accidental release, can achieve by altering state (s/l/g)