Generation of neutral and cationic hydrogen shift isomers of pyridine: a combined experimental and computational investigation11Dedicated to Professor Fulvio Cacace in recognition of his pioneering and stimulating work on gas-phase ion chemistry and physics.

Azacyclohexatriene-3-ylidene (3), an isomer of pyridine (2) and its previously generated Hammick intermediate (1), is accessible in the gas phase by one-electron reduction of the corresponding radical cation in neutralization-reionization mass spectrometric experiments. The experimental finding that this carbene is stable on the microsecond time scale is in agreement with results of quantum chemical calculations, which indicate that all these …