Post on 07-Jan-2016
description
transcript
Green Chemistry
Using the web-based Green Chemistry Assistant to enhance
understanding of chemical reactions and processes
Robert M. Hanson, Paul R. Campbell, Marc A. Klingshirn, and Gary O. Spessard
St. Olaf CollegeNorthfield, MN 55057hansonr@stolaf.edu
19th Biennial Conference on Chemical Education,Purdue University
Aug 3, 2006
Green Chemistry
Green Chemistry Definitions
• “The utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture, and application of chemical products.” -- Anastas and Warner; Doxie and Hutchison.
• “The design of chemical products or processes to reduce or eliminate the use or generation of hazardous substances.” -- Tundo and Anastas, Green Chemistry: Challenging Perspectives, 2000.
Green Chemistry
Three Levels of Green Chemistry
Processes
www.shelldeerpark.com/chemical.htm
Green Chemistry
Three Levels of Green Chemistry
Reactions
http://www.uncw.edu/smec/gk_fellows/askscience.html
Green Chemistry
Three Levels of Green Chemistry
Equations
HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)
Green Chemistry
http://fusion.stolaf.edu/gca
http://fusion.stolaf.edu/gca/goc1.htm
http://fusion.stolaf.edu/gca/goc2.htm
http://fusion.stolaf.edu/gca/goc3.htm
Green Chemistry
http://fusion.stolaf.edu/gca/goc1.htm
Green Chemistry
http://fusion.stolaf.edu/gca/goc2.htm
Green Chemistry
http://fusion.stolaf.edu/gca/goc3.htm
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:
• Lab manuals could be more explicit in guiding students to an understanding of the overall set of process steps they will be doing in lab.
Green Chemistry
Green Chemistry Assistant http://fusion.stolaf.edu/gca
Question:
What is the balanced chemical equation for this reaction?
OHTsCl / 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
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