Imaging the dynamics of ion–molecule reactions

Abstract

A range of ion-molecule reactions have been studied in the last years using the crossed-beam ion imaging technique, from charge transfer and proton transfer to nucleophilic substitution and elimination. This review presents the detailed insights that have been gained with respect to the dynamics of both cation-molecule and anion-molecule reactions studied with this method. In particular, we show the recent progress that has been achieved to understand the atomistic energetics and dynamics of ion-molecule reactions, such as the effects of vibrational quantum states, the formation of carbon-carbon bonds, and the competition between nucleophilic substitution and elimination.

Charge transfer dynamics in Ar+ + CO

“…This process could also be identified by both measuring differential cross sections and calculating quasi-classical trajectories in the proton transfer reaction ArH + +CO [43]. Since the two states CO + (X 2 + , ν = 6 i ,7 ii ) are the closest accessible ones to the reactant Ar + in its two spin-orbital states, this suggests a resonant charge transfer as the dominant mechanism [44]. This is similar to the reaction of Ar + with H 2 [9], however no indirect part is observed there.…”

A benchmark ab initio study of the complex potential energy surfaces of the OH− + CH3CH2Y [Y = F, Cl, Br, I] reactions

“…In organic chemistry the bimolecular nucleophilic substitution (SN2) and the base-induced bimolecular elimination (E2) are elemental reactions and the competitions of these processes have been widely studied both experimentally and theoretically over the past 40 years. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The traditional Walden-inversion and front-side attack mechanisms of SN2 reactions were described by Ingold and co-workers in the center of the 20th century. 19,20 In a simple SN2 reaction, X − + CH3Y → CH3X + Y − , the Walden-inversion mechanism goes through X − •••CH3Y and XCH3•••Y − minima connected by a central [X•••CH3•••Y] − transition state.…”

Ab Initio Molecular Dynamics Simulation Study on the Stereo Reactions between Atomic Oxygen Anion and Methane

“…On the other hand, as a highly reactive free radical anion, atomic oxygen anion (O − at 2 P state) can effectively activate the C-H bond, which is involved in the ion–molecule reaction. Here, ion–molecule reaction between O − and molecules has a profound significance in aspects of atmospheric chemistry, combustion, and environmental pollution control [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. As a prototype reaction for ion–molecule reaction in hydrocarbon flames, the reaction between O − and methane (CH 4 ) is an important example.…”