28 Aug 2012

Identifying Organometallic Reaction Classes in a Catalytic Cycle

In-Class Activity

Submitted by Nancy Scott Burke Williams, Scripps College, Pitzer College, Claremont McKenna College
Categories
Description: 

This contains three parts: A "Pre-Read" section for students to read before coming to class, an in-class worksheet to be worked in groups, and instructor keys for the worksheet.

The purpose of this exercise is to familiarize and give practice with identifying major classes of reaction (oxidative addition, etc.) in an organometallic catalytic cycle. After this exercise, students should be able to do the same for a new catalytic cycle provided by the instructor on a homework set or exam.

This pre-supposes that students are familiar with electron counting and organic reaction types, but does not presume prior knowledge of organometallic reaction types.

In many textbooks, the distinction between mechanism (e.g., stepwise oxidative addition) and reaction class (oxidative addition) is not always clear. Students can identify reaction class simply by looking at reactants and products, whereas identifying mechanisms requires more advanced understanding of organometallic chemistry. Thus, this exercise focuses on the more basic skill, reaction class identification.

There is no universal set of terms or agreed upon classification of reactions in organometallic chemistry, so I have tried to create one here. Many, many other categorization schemes could be imagined, and some might be far superior. I would be eager for someone to take this and improve upon it to create their own exercise to resubmit to VIPEr.

Learning Goals: 

A student should be able to classify reactions in another such blank reaction scheme as they see in this worksheet at a later date. 

Equipment needs: 

None

Implementation Notes: 

I would give the Pre-Read to them the day before, telling them they should be ready to describe one of these cycles at the board in the next class. The next class period, I would then ask several volunteers to give a brief at-the-board summary of one of the reaction types (letting them use the pre-read as a crutch). Thereafter, I'd break into groups of 3-4, and let them work through the worksheet, followed by having them write up the cycles on the board (and writing out the molecules and cycles is a good exercise in itself) and talk through the decisions they made. 

Time Required: 
ca. 50 minutes
Evaluation
Evaluation Methods: 

Haven't done it, but I'd pick a (pretty easy) catalytic cycle, put it in the same format with spaces for bubble answers, and see whether they could do the same on their own with a system they hadn't done this before with.

Evaluation Results: 

None yet.

Creative Commons License: 
Creative Commons Licence

Comments

My students really appreciated the detailed pre-read.

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