Chemical reactions usually proceed through a radical, concerted or ionic mechanism; transformations in which all three mechanisms occur are rare. In polymer mechanochemistry, a mechanical force, transduced along polymer chains, is used to activate covalent bonds in mechanosensitive molecules (mechanophores). Cleavage of a C–C bond often follows a homolytic pathway, but some mechanophores have also been designed that react in a concerted or, more rarely, a heterolytic manner. Here, using ¹H- and ¹⁹F-nuclear magnetic resonance spectroscopy in combination with deuterium labelling, we show that the dissociation of a mechanophore built around an N-heterocyclic carbene precursor proceeds with the rupture of a C–C bond through concomitant heterolytic, concerted and homolytic pathways. The distribution of products probably arises from a post-transition-state bifurcation in the reaction pathway, and their relative proportion is dictated by the polarization of the scissile C–C bond.

化学反应通常通过自由基，协同或离子机理进行。发生所有三种机制的转化很少。在聚合物机械化学中，沿聚合物链传递的机械力用于激活机械敏感分子（机械载体）中的共价键。C–C键的裂解通常遵循均溶途径，但是还设计了一些机械分子，它们以协同的或更稀疏的方式反应。在这里，使用¹ H-和¹⁹F核磁共振波谱结合氘标记，我们显示，围绕N杂环卡宾前体建立的机械团的解离通过伴随杂合，协同和均质途径的C–C键断裂而进行。产物的分布可能来自反应路径中的过渡后状态分叉，它们的相对比例由易断裂的C–C键的极化决定。