25 Jun 2011

Optimization of a Metal Catalyzed Process

Lab Experiment

Submitted by Christopher Goh, Williams College

The topic of this sequence of experiments is catalyst research.  Over a 5-6 week-long project students use metal-mediated atom transfer radical polymerizations (ATRP) as a case study for the discovery and development of homogeneous catalysts.  During the first two weeks students repeat published work to become familiar with the topic and the practical aspects of this type of chemistry.  In the third week, students present their results and plan future experiments.  The presentations are followed by an interactive discussion on ways of improving the performance of the known catalyst system or designing a new catalyst.  In the remaining three weeks of labs, students pursue their ideas on catalysts improvements.  Class time is set aside for students to present their data in the last week of classes.  As a final assignment, individual data are made available to all students, and each student is asked to write a journal-type article. 

PDF icon CGoh_LabD_ATRP.pdf153.05 KB
Learning Goals: 
Students develop their ability to work with air-sensitive materials through use of a Schlenk line.
Students are introduced to the use of metals in polymerizations and the industrial importance of these processes.  They can identify the most common polymers in a handful of everyday objects.
Students learn about the process of optimizing catalysts performance by exploring the effect of ligand structure, temperature, reactant ratios, solvents, metal choice, additives on the performance of the catalyst. Stduents can describe how the effect of changing these variable might affect the polymerization and go on to test their prediction. In doing so, students experience the design of a research project.
Students practice their communication skills through presenting their results, and writing a journal-type lab report.  
Equipment needs: 

Schlenk lines or inert gas purge lines

stir plates / hot temperature baths

Schlenk tubes

Implementation Notes: 

In principle, the idea of catalyst optimization can be applied to a variety of catalysts, with varying degrees of air-sensitivity / availability etc. (see also related experiments).  I chose the ATRP system since we also have a research project in this area.

The polymerizations and ligand syntheses are fairly tolerant to the occassional exposure to air, but the former will fail if done in air.  Complexes are generated in situ.


Time Required: 
3-4 hours in the lab over 5 to 6 weeks
Evaluation Methods: 

Weekly worksheets preparing students for the compiliation of the final report

Final journal-type report

Participation in discussions, ability to deal with problems in an independent and creative manner, knowledge and execution of laboratory and safety procedures, wise use of time during the lab period, and the thoroughness of lab notebook recordings.

Enthusiasm for project

Evaluation Results: 

I have run this type of experiment for 2 years with overall enthusiasm for this final project. 

The time students spent on this project varies widely - some students asked to came in for additional time, some completed the bare minimum.  For students less interested in pursuing a research project like the one presented, a choice of research project or a series of more established experiments with known outcomes could be provided as an alternative in the design of the lab program.

Some students were unable to generate polymers, providing an opening to discuss the research process and the role of failure.  To address the lack of data for some students, the class shares data for the final paper (treating the class as a research group).

Creative Commons License: 
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