Shaking up reaction-site selectivity: It seems intuitive that putting vibrational energy into a chemical bond ought to promote selective cleavage of that bond. In fact, the relation of vibrational excitation to reactivity has generally proven subtler and more complex. Thomas et al. studied how strong coupling of specific vibrational modes to an optical cavity might influence a molecule with two competing reactive sites. The molecule had two silicon centers that could react with fluoride by respective cleavage of a Si–C or Si–O bond. Exciting the vibrations at either center slowed down the overall reaction while favoring otherwise disfavored Si–O cleavage. Science , this issue p. 615

The ground‐state deprotection of a simple alkynylsilane is studied under vibrational strong coupling to the zero‐point fluctuations, or vacuum electromagnetic field, of a resonant IR microfluidic cavity. The reaction rate decreased by a factor of up to 5.5 when the Si−C vibrational stretching modes of the reactant were strongly coupled. The relative change in the reaction rate under strong coupling depends on the Rabi splitting energy. Product analysis by GC‐MS confirmed the kinetic results. Temperature dependence shows that the activation enthalpy and entropy change significantly, suggesting that the transition state is modified from an associative to a dissociative type. These findings show that vibrational strong coupling provides a powerful approach for modifying and controlling chemical landscapes and for understanding reaction mechanisms.

Hexafluoroisopropanol (HFIP) is a solvent with unique properties that has recently gained attention for promoting a wide range of challenging chemical reactions.