Empowering Students to Predict Reaction Mechanisms

Reaction mechanisms are the language of organic chemistry, providing a detailed insight into how one molecule reacts with another. In recent years, York undergraduates have been taught ‘Professor Dave’s Rules of Mechanism’ in their introductory Year 1 course on the subject. These simple rules, developed by Professor David Smith, aim to empower students to work out reaction mechanisms from basic principles, rather than having to learn them by rote. In this way, it is hoped that students gain a better feel for organic reactions, and why they happen, and can then apply that knowledge in problem-solving exam questions.

In a recent Journal of Chemical Education paper, Professor David Smith discusses in detail his approach to teaching introductory reaction mechanisms, and presents the simple priority and selectivity rules that he has developed to assist students with the challenging task of mechanism prediction.

Professor Smith explains: “In many cases, students just try to memorise lots of reaction mechanisms, or simply guess at them based on the expected products. However, reaction mechanisms derive from fundamental principles about electron density, and I therefore wanted to create an approach where students could apply some simple rules to work the mechanisms out, just by looking at the structures of the molecules involved.“

Using an analogy from the paper itself, Dave notes: “If curly arrow mechanisms are the language of organic chemistry, it is hoped that these priority rules, rather like the “phonics” approach to breaking down words for reading, will allow students to make the first steps to literacy in a more logical manner, and build their confidence, which ultimately leads to fluency.”

The published paper provides examples of the way in which, alongside the simple rules, Dave’s teaching approach present contextualised examples of his rules in action – from the synthesis of dental anaesthetic lidocaine, to the mechanistic chemistry behind the hit TV show ‘Breaking Bad’. By bringing the subject to life in this way, Dave hopes that students will be motivated to practice their mechanistic skills and go on to learn more later in the course, when they dive much more deeply into a wide range of organic reactions. It is hoped that this approach encourages students to think like real organic chemists, and better prepares them for jobs, for example in the pharmaceutical industry.

Reflecting on the paper, Dave says: “By publishing the paper, I hope to prompt organic chemists working elsewhere to think about how they teach reaction mechanisms, and why, and perhaps shift the culture away from rewarding rote learning, towards a more concept-led, problem solving approach.”

The paper is published in Journal of Chemical Education