Activation of Methane by the Pyridine Radical Cation and its Substituted Forms in the Gas Phase

Abstract

Abstract. We present an experimental study of methane activation by pyridine cation and its substituents in the gas phase. Mass spectrometric experiments in an ion trap demonstrate that pyridine cation and some of its substituent cations are able to react with methane. The deuterated methane experiment has confirmed that the hydrogen atom in the ionic product of reaction does come from methane. The collected information about kinetic isotope effects has been used to distinguish the nature of the bond activation as a hydrogen abstraction. Furthermore, experimental results demonstrated that the substituent groups on the pyridine ring can crucially influence their reactivity in methane bond activation processes. Density functional calculation (DFT) was employed to study the electronic structures of the complex and reaction mechanism of CH 4 +C 5 H 5 N + . The calculations confirmed the hypothesis from the experimental observation, namely, the reaction is rapid with no energy barrier.

Vacuum Ultraviolet Photoionization Induced Proton Migration and Formation of a New C–N Bond in Pyridine Clusters Revealed by Infrared Spectroscopy and Mass Spectrometry

“…The nitrogen atom in pyridine is nucleophilic so that pyridine is employed as a catalyst in acylation reactions. , Pyridine has a high proton affinity (936.5 kJ/mol); protonated pyridine (H + (Pyd), pyridinium) reacts as an acid, and its salts are produced in many acid–base reactions. The gas phase reactivities of the pyridine radical cation Pyd + and pyridinium H + (Pyd) have been extensively studied by mass spectrometry using collision-induced dissociation, − ion mobility, − ion-trap, flow-tube mass, and Fourier transform (FT)-mass techniques . In addition, the structure of H + (Pyd) was investigated by low-temperature Fourier transform infrared (FTIR) spectroscopy .…”