Rearrangements that change the connectivity of a carbon skeleton are often useful in synthesis, but it can be difficult to follow their mechanisms. Scanning probe microscopy can be used to manipulate a skeletal rearrangement at the single-molecule level, while monitoring the geometry of reactants, intermediates and final products with atomic resolution. We studied the reductive rearrangement of 1,1-dibromo alkenes to polyynes on a NaCl surface at 5 K, a reaction that resembles the Fritsch–Buttenberg–Wiechell rearrangement. Voltage pulses were used to cleave one C–Br bond, forming a radical, then to cleave the remaining C^•–Br bond, triggering the rearrangement. These experiments provide structural insight into the bromo-vinyl radical intermediates, showing that the C=C^•–Br unit is nonlinear. Long polyynes, up to the octayne Ph–(C≡C)₈–Ph, have been prepared in this way. The control of skeletal rearrangements opens a new window on carbon-rich materials and extends the toolbox for molecular synthesis by atom manipulation.

改变碳骨架连通性的重排通常在合成中很有用，但很难遵循它们的机制。扫描探针显微镜可用于在单分子水平上操纵骨架重排，同时以原子分辨率监测反应物、中间体和最终产物的几何形状。我们研究了 1,1-二溴烯烃在 5 K 的 NaCl 表面上还原重排为多炔，该反应类似于 Fritsch-Buttenberg-Wiechell 重排。电压脉冲用于裂解一个 C-Br 键，形成自由基，然后裂解剩余的 C ^• -Br 键，触发重排。这些实验提供了对溴-乙烯基自由基中间体的结构洞察，表明 C=C ^•–Br 单位是非线性的。以这种方式制备了长多炔，直至辛炔 Ph-(C≡C) _{8 -Ph。}骨架重排的控制打开了富碳材料的新窗口，并扩展了通过原子操作进行分子合成的工具箱。