Flyby reaction trajectories: Chemical dynamics under extrinsic force

Shear selectivity Chemical reactions typically proceed by distributing energy statistically among all accessible molecular vibrations. Liu et al. report that external shear forces can sometimes pry open strained carbon rings without dissipating energy into adjacent bond rotations. Through careful design and synthesis of polymer-embedded cyclobutyl rings, the authors showed that certain relative substituent geometries are preserved when sonication induces ring opening. Accompanying simulations support the instigation of “flyby” trajectories that channel energy narrowly to cleave the cyclic sigma bonds and then rapidly form acyclic pi bonds. Science , abi7609, this issue p. 208