The Importance of Green Chemistry Sarah Gunderson April 26, 2005

What is Green Chemistry?

Use of chemistry for pollution prevention –Reduce or eliminate use and generation of hazardous substances –Alternative pathways or reaction conditions –Design of safer chemicals (less toxic, inherently safer) –Benign processes and products pose no risk Launched in 1991 by EPA

What is Green Chemistry? EPA –Presidential Green Chemistry Challenge –Partner with NSF to sponsor research –Small Business Innovation Research Program Green Chemistry Institute (1997) –Focuses on research, education, conferences, public awareness –Allied with ACS in 2000

12 Principles of Green Chemistry 1.Prevent waste 2.Design safer chemicals and products 3.Design less hazardous chemical syntheses 4.Use renewable feedstocks 5.Use catalysts, not stoichiometric reagents 6.Avoid chemical derivatives 7.Maximize atom economy 8.Use safer solvents and reaction conditions 9.Increase energy efficiency 10.Design chemicals and products to degrade after use 11.Analyze in real time to prevent pollution 12.Minimize the potential for accidents

12 Principles of Green Chemistry 1.Prevent waste Easier than cleaning up later 2.Design safer chemicals and products Give desired function with lower toxicity 3.Design less hazardous chemical syntheses Use and generate non-toxic substances whenever possible

12 Principles of Green Chemistry 4.Use renewable feedstocks Non petrochemically dervied 5.Use catalysts, not stoichiometric reagents Increased selectivity 6.Avoid chemical derivatives Blocking groups Protection/deprotection Using additional steps and reagents

12 Principles of Green Chemistry 7.Maximize atom economy Incorporate all materials into final product if possible 8.Use safer solvents and reaction conditions Minimize risk of serious accidents and injuries 9.Increase energy efficiency Operate at ambient conditions whenever feasible

12 Principles of Green Chemistry 10.Design chemicals and products to degrade after use Break down into biocompatible products 11.Analyze in real time to prevent pollution Recognize problems before they turn into tragedies 12.Minimize the potential for accidents Releases, explosions and fires Check operability and sizing of safety equipment

Atom Economy vs. Yield Different way of measuring reaction efficiency, using formula weight Yield definition is flawed –Does not account for co-product production Example: CH O 2  CO H 2 O –If desire H 2 O yield ~100% Atom economy=

Successful Applications Supercritical CO 2 processing –Caffeine extraction, dry cleaning –Semiconductor processing Ionic liquid solvents –Emit no VOCs, quicker reactions, tunable Catalysts Biobased / Renewable feedstocks –Agricultural wastes -> alcohols, ketones, carboxylic acids

Successful Applications Microreactors –Higher purity, faster –More efficient heat transfer From [4]

Successful Applications

Green Chemistry Problems Development can be expensive Determining toxicity of new compounds is difficult Difficult to transition from a reactive to a proactive methodology

Pharmaceuticals One of the leading industries to adapt Allowed to use toxic chemicals restricted in other industries Want to minimize environmental impacts IndustryAnnual Product Tons Kg waste / Kg product Oil refining Bulk Chemicals <1-5 Fine Chemicals Pharmaceuticals

Ibuprofen Synthesis Originally developed and patented in 1960’s by Boots Company Green process patented in 1991 by BHC

Other Green Pharma Processes Viagra (Pfizer) From [7]

Other Green Pharma Processes Pfizer has a team at each R&D site –Zoloft Bristol Myers Squibb –Taxol process Abbott Laboratories educates at main R&D site

Education in Green Chemistry Few colleges offer this option Industry has taken the initiative for training Should colleges focus more on training?

Changes in Education Need to train new scientists in these techniques Replacement of “yield” with “atom economy” Modification of organic chemistry laboratory Basic concepts of chemical toxicology and the molecular basis of hazards [2]

Personal Responsibility Ability to challenge current process operation Educate co-workers Green process development

Conclusions Green chemistry is a new way of thinking Concepts apply in all industries

Questions?

References Anastas, P.T., Kirchhoff, M.M., Origins, Current Status and Future Challenges of Green Chemistry, Acc. Chem. Res. 2002, 35, enchem/case.pdfhttp:// enchem/case.pdf 4.Haswell, S.J., Watts, P., Green Chemistry: Synthesis in micro reactors, Green Chemistry, 2003, 5, Hjeresen, D.L., Schutt, D.L., Boese, J.M., Green Chemistry and Education, J Chem Ed, 2000 (77), 12, Dunn, P.J., Galvin, S., Hettenbach, K., The development of an environmentally benign synthesis of sildenafil citrate (Viagra) and its assessment by Green Chemistry Metrics, Green Chemistry, 2004, 6,