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The Green Chemistry Assistant: Expanding the horizons of green chemistry in chemical education. Robert M. Hanson , Paul R. Campbell, Elizabeth R. Johnson, Gary O. Spessard, and Marc A. Klingshirn St. Olaf College Northfield, MN 55057 hansonr@stolaf.edu

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The Green Chemistry Assistant: Expanding the horizons of green chemistry in chemical education


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    1. The Green Chemistry Assistant: Expanding the horizons of green chemistry in chemical education Robert M. Hanson, Paul R. Campbell, Elizabeth R. Johnson, Gary O. Spessard, and Marc A. Klingshirn St. Olaf College Northfield, MN 55057 hansonr@stolaf.edu 231st ACS National Meeting, Atlanta, Georgia March 27, 2006

    2. My Goals Today • Briefly discuss the important distinction between equations and reactions, and between reactions and processes. • Introduce a new web-based tool – the Green Chemistry Assistant.

    3. My Goals Today • Share what we have learned about our students from using the GCA. • Share what we have learned about green chemistry from our students.

    4. Three Levels of Green Chemistry Equations HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)

    5. Three Levels of Green Chemistry Reactions http://www.uncw.edu/smec/gk_fellows/askscience.html

    6. Three Levels of Green Chemistry Processes www.shelldeerpark.com/chemical.htm

    7. Three Levels of Green Chemistry Equation Atom Economy = 40%

    8. Three Levels of Green Chemistry Reaction Atom Economy = 40%

    9. Three Levels of Green Chemistry Reaction

    10. Three Levels of Green Chemistry Reaction

    11. Three Levels of Green Chemistry Reaction

    12. Three Levels of Green Chemistry Reaction Atom Economy = 40%

    13. Three Levels of Green Chemistry Reaction Atom Economy = 40% before… …after

    14. Three Levels of Green Chemistry Reaction – Excess, Limiting Reactant Experimental Atom Economy = 26% before… …after

    15. Three Levels of Green Chemistry Process... unrecyclable silica gel unrecovered CH2Cl2 Process Mass Efficiency = 1% …provides context

    16. Three Levels of Green Chemistry Process… Process Mass Efficiency = 10% …can involve more than one step

    17. Three Levels of Green Chemistry Process… Process Mass Efficiency = 1% Process Mass Efficiency = 10% …allows for comparison

    18. Three Levels of Green Chemistry Equation, Reaction, and Process Wouldn’t it be nice to have access to a tool that would allow us to quickly make comparisons like this?

    19. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca • Based on the EPA “Green Chemistry Expert System” • User-friendly interface designed to assist students in analyzing the atom economy, and safety of chemical processes

    20. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    21. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    22. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    23. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    24. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    25. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    26. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    27. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    28. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    29. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    30. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    31. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    32. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    33. My Goals Today • Share what we have learned about our students from using the GCA.

    34. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    35. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Lessons learned: • Students need help just writing the balanced chemical equations. • Process is important, as most real experiments involve more than one process step.

    36. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Lessons learned: • We need lab manuals that are more explicit in guiding students to an understanding of the overall set of process steps they will be carrying out.

    37. My Goals Today • Share what we have learned about our students from using the GCA. • Share what we have learned about green chemistry from our students.

    38. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca

    39. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Lessons learned: • Introducing green chemistry provides a rich context for discussing safety, including nomenclature, CAS registry numbers, MSDS sheets, and health and environmental hazards.

    40. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Lessons learned: • All is not as simple as one might think from what is in the literature in terms of the definitions of green measures.

    41. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Question: What is the balanced chemical equation for this reaction?

    42. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Is it this?... (atom economy = 88%)

    43. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca …or this? (atom economy = 66%)

    44. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca On assumptions regarding atom economy: “The process of calculating atom economy may be simplified by only considering key reactants. For example, ‘catalysts’ used in stoichiometric quantities, or the acid or base used in hydrolysis, are considered to be reactants. These examples are in contrast to common inorganic reagents, even when used in stoichiometric quantities (e.g. potassium carbonate…), which have been ignored. Inorganic reagents and/or other material are not included in the calculations as long as at least two other reacting substances are identified.” Constable, Curzons, and Cunningham, Green Chemistry, 2002, 521-527

    45. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Question: What is the balanced chemical equation for this reaction?

    46. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Question: Is this one reaction or two?

    47. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Question: What is the atom economy?

    48. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Overall Atom Economy = 60%

    49. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca Overall Atom Economy = 72%

    50. Green Chemistry Assistanthttp://fusion.stolaf.edu/gca In practice, Step 3 is important!