Gas-phase reactions of cyclopropenylidene with protonated alkyl amines

Abstract

Vinylidene carbenes (C₃H₂) are of high interest to interstellar, combustion, and organic chemistry. Due to their high instability, the direct experimental investigation of their chemical reactivity has rarely been achieved. Herein, we report a first study on the reactions of cyclopropenylidene (c-C₃H₂) with protonated alkyl amines in the gas phase using a home-built ion trap mass spectrometer. The high gas-phase basicity (GB) of (¹A₁) c-C₃H₂ (calculated as 920 kJ mol⁻¹) facilitates the formation of a proton-bound dimer with protonated amines as the first step in the reaction. The dimer can stay as it is or rearrange to a covalent product. The formation of the covalent complex is highly exothermic and its yield is affected by the GB of alkyl amines. The highest yield (82%) was achieved when the GB of the amine was slightly lower but comparable to that of c-C₃H₂. Our results demonstrate a new reaction pathway of c-C₃H₂, which has long been considered as a “dead end” in interstellar carbon chemistry.