Trapping a Diradical Transition State by Mechanochemical Polymer Extension

Abstract

Forced Open Traditionally, the study of reaction chemistry has relied on random encounters between molecules to initiate the proceedings. Heating and stirring increase the power and frequency of such encounters but provide little finer control. Very recently, chemists have learned how to initiate reactions more directly by embedding precursors in the backbone of a polymer large enough to manipulate with shear forces. Lenhardt et al. (p. 1057 ) applied this technique to a cyclopropyl ring-opening reaction. When the strained triangular carbon rings were embedded within a polymer, shear force applied by sonication ruptured their bonds as the polymer backbone stretched. The taut polymer then redirected the ring-opened intermediates toward a product differently arranged from that generated by simple heating.