In a previous blog post (A Mechanistic Organization and Learning Synthesis: Having Cake and Eating It, Too), I articulated that switching to a mechanistic organization has improved how my students deal with synthesis problems. Things have continued to work well, but this year I made a change to enhance how I teach synthesis, and student performance seems to have improved again as a result. My students are now developing their skills in designing syntheses more quickly than ever before. What was the change I made to my teaching?
I started making better use of Appendices C and D. When teaching Chapter 13 (the first chapter on multistep synthesis) at the very beginning of this semester, I introduced the appendices in class, and I reinforced the use of those appendices when working with students in office hours. Appendix C is a single table of all the carbon-carbon bond forming/breaking reactions found in the book, and Appendix D has all of the functional group transformations in the book. Those functional group transformations in Appendix D, moreover, are grouped in distinct tables according to the functional group that is produced.
Why should these appendices have such a positive impact on student performance with multistep synthesis? I think one reason is that these appendices help make multistep synthesis far less daunting. When a student is faced with a synthesis problem, they should find themselves asking questions like:
- What carbon-carbon bonds need to be formed in the target?
- What reactions do I know that will form such a bond having a particular location relative to other functional groups?
- What functional group needs to be produced, and what reactions will produce that functional group?
Although it eventually becomes important to be able to answer these questions without assistance, I started encouraging students who are just starting out to use Appendices C and D to find appropriate reactions quickly. Therefore, rather than risking being stumped over which reactions to use, students can instead focus on the big ideas that go into synthesis design.
Beyond being a means to find appropriate reactions quickly, Appendices C and D also facilitate understanding those reactions better. For each reaction, the key electron-rich and electron-poor species are included, and the section of the book that introduces the reaction and mechanism is also provided. Thus, for any aspect of the reaction that students don’t immediately recall, such as regiochemistry and stereochemistry, they can quickly turn to the appropriate section for an in-depth review of the reaction.
Yet another benefit is that students can quickly come away with a strong message as to the reactions they need to study further. Each time a student searches those appendices and finds a particular reaction to do the job at hand, he or she should take note, realizing the need to become more familiar with that reaction and what it accomplishes. Moreover, students should pay attention to which reactions are used more frequently than others, because the more-frequently used reactions tend be of greater synthetic value.
When I was student, I became accustomed to seeing the appendices of a textbook as nothing more than quick references. My view of appendices didn’t change when I became a professor—that is, until now. After observing how beneficial they are to students and the resulting improvement in understanding, I now see Appendices C and D as valuable tools that students can use to learn synthesis, and I will continue to weave them into my class periods and office hours in the years to come.
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That is more or less how scientists do it anyway, right? Until you have an encyclopedic knowledge of all organic reactions, you have to look up examples. Do it enough times and you don’t need the reference as much anymore.