An \b[<alternant hydrocarbon>] has a pi-site graph that can be divided into two sets so that every retained neighbouring resonance interaction joins different sets. Equivalently, the graph is bipartite. A chain and an even ring satisfy this condition; an odd ring does not. The classification refers to the model's coupling graph, rather than simply to which bonds are drawn double in one <Lewis structure>.

Solution

Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge / 2022 / Paper 2A / Section A / 20 / a / Solution

 Solution (source code)