Ozonolysis is one of the simplest of all organic reactions to perform, yet the ozonolysis mechanism often leads to confusion when presented in undergraduate Organic Chemistry. If the reaction is so simple, then why is the ozonolysis mechanism so challenging? Well, there’s the 1,3-dipolar cycloaddition followed by a retro 1,3-cycloaddition and recombination via a second 1,3-cycloaddition leading to an intermediate with an electrophilic oxygen that gets attacked by a sulfur nucleophile. Sounds kinda like listening to someone’s story of getting from point A to point Z via a tour through La La Land, huh?
Part of running an unbiased and feature driven Organic Chemistry education service is recommending students to outside websites for alternative stimulating content. The Chemistry Cascade is a WordPress blog site that highlights interesting recent developments in synthetic and mechanistic Organic Chemistry. The brief articles encapsulating novel chemical research are abstracted from major American Chemical Society journals, and are well presented.
The first really interesting reaction seen by Organic Chemistry students is the Diels-Alder [4+2] cycloaddition, an example of a concerted process where all the bond making and breaking take place concomitantly. The SN2 is also a concerted process, however the Diels-Alder reaction is a gem because of the high density of relative stereochemistry that can be established in a single synthetic step. The most interesting and unique of all organic reactions learned fall within the narrow category of sigmatropic rearrangements, intramolecular pericyclic processes wherein one σ-bond is exchanged for another σ-bond. Example reactions are the Cope and Claisen rearrangements.
Few reactions have the capacity to introduce densely packed relative stereochemistry to a molecule in one single step as does the Diels-Alder reaction, a concerted [4+2] cycloaddition. This highly synthetically useful reaction permits facile entry into complex fused ring systems endemic to some natural products exhibiting medicinal properties. This article focuses on the rudimentary elements of the Diels-Alder reaction. Students interested in a more detailed understanding of the dynamics of the reaction are encouraged to engage in the suggested readings.