Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom.
J Am Chem Soc. 2021 Mar 3;143(8):3033-3036. doi: 10.1021/jacs.0c11259. Epub 2020 Dec 31.
In mechanochemistry, molecules under tension can react in unexpected ways. The reactivity of mechanophores (mechanosensitive molecules) can be controlled using various geometric or electronic factors. Often these factors affect the rate of mechanical activation but sometimes give rise to alternative reaction pathways. Here we show that a simple isotope substitution (H to D) leads to a reversal of selectivity in the activation of a mechanophore. Remarkably this isotope effect is not kinetic in nature but emerges from dynamic effects in which deuteration reduces the ability of the reactant to follow a post-transition-state concerted trajectory on the bifurcated force-modified potential energy surface. These results give a new insight into the reactivity of molecules under tension.
在机械化学中，处于张力下的分子可以以意想不到的方式发生反应。机械基团（机械敏感分子）的反应性可以通过各种几何或电子因素来控制。通常这些因素会影响机械活化的速率，但有时会产生替代反应途径。在这里，我们表明，简单的同位素取代（H 到 D）会导致机械基团活化的选择性发生逆转。值得注意的是，这种同位素效应不是动力学性质的，而是源于动态效应，其中氘化会降低反应物在分叉力修正势能表面上遵循过渡后协同轨迹的能力。这些结果为张力下分子的反应性提供了新的见解。
