In my experience, the traditional method of teaching organic chemistry courses according to functional group often leads students to rely on memorization. For example, a single chapter on alkyl halides may include substitution reactions, radical reactions, and additions to alkenes. With such a large volume of information, it’s very difficult for students to manage and recall everything they’ve learned over two semesters. In fact, students often purchase pre-made flash cards online to aid them in this process.
Switching my course to a mechanism-based organization has made the material much more manageable for my students. They now link very seemingly different reactions, such as the bromination and epoxidation of alkenes, through the same mechanism. By highlighting the similarities between reagents like bromine and m-CPBA, my students focus on mastering broader skills, such as identifying nucleophiles and electrophiles, and predicting how they will react, rather than getting bogged down with memorization.
In addition, introducing one mechanism at a time affords the opportunity for a greater understanding of the spatial aspects of organic reactions. Organic chemists regularly have to visualize and manipulate structures in three dimensions, as structure can be critical to the reactivity and function of organic molecules. For many students, learning this skill can be quite challenging. Dedicating an entire chapter to a single mechanism, such as additions to alkenes that proceed through a cyclic intermediate, gives students ample time to understand how planar alkenes can generate products, such as epoxides and vicinal dibromides, as a mixture of stereoisomers. By focusing on the mechanistic similarities of these reactions, the stereochemical outcomes become much easier to predict.
In short, simply changing the organization of my course from functional group-based to mechanism-based has led to better student outcomes over a range of topics. Students spend less time memorizing reactions and more time understanding the fundamental principles of organic chemistry, including predicting reactivity, drawing mechanisms, understanding stereochemical outcomes, and so much more.