the green chemistry assistant: expanding the horizons of green chemistry in chemical education
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Green Chemistry
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 CollegeNorthfield, MN 55057hansonr@stolaf.edu
231st ACS National Meeting, Atlanta, GeorgiaMarch 27, 2006
Green Chemistry
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.
Green Chemistry
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.
Green Chemistry
Three Levels of Green Chemistry
Equations
HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)
Green Chemistry
Three Levels of Green Chemistry
Reactions
http://www.uncw.edu/smec/gk_fellows/askscience.html
Green Chemistry
Three Levels of Green Chemistry
Processes
www.shelldeerpark.com/chemical.htm
Green Chemistry
Three Levels of Green ChemistryEquation
Atom Economy = 40%
Green Chemistry
Three Levels of Green ChemistryReaction
Atom Economy = 40%
Green Chemistry
Three Levels of Green ChemistryReaction
Green Chemistry
Three Levels of Green ChemistryReaction
Green Chemistry
Three Levels of Green ChemistryReaction
Green Chemistry
Three Levels of Green ChemistryReaction
Atom Economy = 40%
Green Chemistry
Three Levels of Green ChemistryReaction
Atom Economy = 40%
before… …after
Green Chemistry
Three Levels of Green ChemistryReaction – Excess, Limiting Reactant
Experimental Atom Economy = 26%
before… …after
Green Chemistry
Three Levels of Green Chemistry
…provides context
Process...
Process MassEfficiency = 1%
unrecovered CH2Cl2
unrecyclablesilica gel
Green Chemistry
Three Levels of Green Chemistry
Process MassEfficiency = 10%
…can involve more than one step
Process…
Green Chemistry
Three Levels of Green Chemistry
Process MassEfficiency = 10%
…allows for comparison
Process…Process MassEfficiency = 1%
Green Chemistry
Three Levels of Green ChemistryEquation, Reaction, and Process
Wouldn’t it be nice to have access to a tool that would allow us to quickly make comparisons like this?
Green Chemistry
Green Chemistry Assistant http://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
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
My Goals Today
• Share what we have learned about our students from using the GCA.
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://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.
Green Chemistry
Green Chemistry Assistant http://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.
Green Chemistry
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.
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Green Chemistry Assistant http://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.
Green Chemistry
Green Chemistry Assistant http://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.
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Question:
What is the balanced chemical equation for this reaction?
OH TsCl / Et3N OTs
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Is it this?... (atom economy = 88%)
OH
OTs
+ TsCl
+ HCl
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
…or this? (atom economy = 66%)
OH
OTs
+ TsCl + Et3N
+ Et3NHCl
Green Chemistry
Green Chemistry Assistant http://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
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Question:
What is the balanced chemical equation for this reaction?
OH1) BH3 THF
2) H2O2/NaOH
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Question:
Is this one reaction or two?
OH1) BH3 THF
2) H2O2/NaOH
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Question:
What is the atom economy?
OH1) BH3 THF
2) H2O2/NaOH
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
OH
3 + BH3THF + THFB
3
3B
3
STEP 1STEP 1
STEP 2 + 3 H2O2
+ NaOH+ NaB(OH)4
Overall Atom Economy = 60%
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
OH
3 + BH3B
3
3B
3
STEP 1STEP 1
STEP 2 + 3 H2O2
+ NaOH+ NaB(OH)4
Overall Atom Economy = 72%
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
OH
3 + BH3THF + THFB
3
3B
3
STEP 1STEP 1
STEP 2 + 3 H2O2
+ NaOH+ NaB(OH)4
STEP 3 BH3THF + 3 H2O + NaOH THF + NaB(OH)4 + 3 H2 (g)
In practice, Step 3 is important!
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Lessons learned:• Getting students thinking about the overall
process is good.• Expecting them to do it on their own because it’s
“simple” is asking too much.• The Green Chemistry Assistant enables us to
explore the nature of green chemistry processes and green chemistry measures.
Green Chemistry
FacultyGary Spessard, Marc Klingshirn, Paul Jackson
StudentsPaul Campbell, Allison Christensen, Elizabeth R.
Johnson, Tim Barker, Tyler Drake, David Harris Technology Support
Dan Beach Financial support
WM Keck FoundationHoward Hughes Medical Institute
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Green Chemistry
Upcoming double-header symposia of possible interest in 2006:
“Web-Based Applications for Chemical Education” ACS CCCE online CONFCHEM, May 5 – June 30
www.stolaf.edu/depts/chemistry/bh/confchem
“Web-Based Applications for Chemical Education” 19th BCCE, July 31 – Aug 2
Green Chemistry Assistant http://fusion.stolaf.edu/gca
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