The Hand is Smarter than the Eye

This past week we did the stereochemistry modeling activity during the lab period. This time it worked out that the activity was scheduled after the first class period on stereochemistry. I like the students to make the connection between models and drawn stereochemistry dashed-wedged representations as earlier as possible. The idea, in my mind, is to rely on the models as much as possible to do the activity. Students have a tendency to abandon the models as soon as they are able to “see” stereochemistry on the paper. I’m not sure exactly why this is. Perhaps, kinetic and tactile learning are undervalued. For this activity, my observation is that the questions can be answers “without fail” if the models are properly made. Without the models, some students have trouble answering the questions correctly. There are, however, some important differences between the models and the traditional dashed-wedged representations. First, the groups in front of and in back of the plane of the paper are actually directly over each other and not spread like we show them in the dashed-wedged form. Second, in the dashed wedged form, it is difficult to draw three-dimensional detail beyond the zig-zag in-plane chain or the plane of the ring. It is customary, therefore to ignore the three-dimensional detail of symmetric atoms. In fact, for more complex molecules it is common to truncate the dashed-wedged form to accommodate stereochemical detail.

One Comment

  1. Posted April 5, 2010 at 9:02 am | Permalink

    I was just showing the boat and chair forms of cyclohexane this morning with a model kit. Some were surprised that it wouldn’t go flat – there is no substitute for hands on teaching for some concepts.

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