Stereochemistry has an essential role in organic synthesis, biological catalysis and physical processes. In situ chirality identification and asymmetric synthesis are non-trivial tasks, especially for single-molecule systems. However, going beyond the chiral characterization of a large number of molecules (which inevitably leads to ensemble averaging) is crucial for elucidating the different properties induced by the chiral nature of the molecules. Here we report direct monitoring of chirality variations during a Michael addition followed by proton transfer and keto–enol tautomerism in a single molecule. Taking advantage of the chirality-induced spin selectivity effect, continuous current measurements through a single-molecule junction revealed in situ chirality variations during the reaction. Chirality identification at a high sensitivity level provides a promising tool for the study of symmetry-breaking reactions and sheds light on the origin of the chirality-induced spin selectivity effect itself.

立体化学在有机合成、生物催化和物理过程中发挥着重要作用。原位手性识别和不对称合成是一项艰巨的任务，特别是对于单分子系统。然而，超越大量分子的手性表征（这不可避免地导致整体平均）对于阐明分子手性性质引起的不同性质至关重要。在这里，我们报告了在迈克尔加成过程中直接监测手性变化，然后在单个分子中进行质子转移和酮-烯醇互变异构。利用手性诱导的自旋选择性效应，通过单分子结的连续电流测量揭示了反应过程中原位手性变化。