Chemists tend to think about the ways in which molecules behave — the shapes they are most likely to adopt, the molecular partners with which they are most likely to bind, or the rates and outcomes of their reactions — in terms of energies. But in the light of reports that applied forces can direct new chemical transformations1, 2, 3, 4, or induce unusual stress responses in materials5, 6, it is becoming increasingly profitable to consider molecular behaviour in terms of forces. Writing in the Journal of the American Chemical Society, Akbulatov et al.7 provide a crucial benchmark for force-induced reactivity (chemomechanics) by uniting internally and externally stress-induced chemical behaviour across time- and length-scales of several orders of magnitude.
The authors' study centres on the reactivity of gem-dibromocyclopropane, a chemical group that contains a ring of three carbon atoms (Fig. 1). This ring can be pulled open mechanically to give a product (known as an alkene) that is both longer and more stable than its precursor