Energy disposal in gas‐phase nucleophilic displacement reactions

Abstract

The partitioning of reaction exothermicity into relative translational energy of the products of gas-phase S, 2 (F-+ CH,CI) and nucleophilic aromatic substitution (F-+ C,H,CI) reactions has been investigated using kinetic energy release Fourier transform ion cyclotron resonance spectroscopy. The chloride product ion is observed to be highly translationally excited for the SN2 reaction, indicating a cold internal energy distribution for the products. For the chlorobenzene reaction the products are not generated with large translational energies The results are compared with a statistical model. Ion-intensity profiles for the CH,CI reaction deviate significantly from the statistical model whereas the chlorobenzene results are consistent with this model. The kinetic energy release for the CH,CI reaction is compared with energy-disposal results for the photodissociation and dissociative electron-attachment processes of halomethanes. In all three cases a node in the molecular orbital between the carbon atom and the departing halogen results in a repulsive energy release. Ion-retention curves for the nucleophilic aromatic substitution reaction are consistent with the existence of a long-lived ion-dipole complex on the exit channel for this reaction.

Protonated nitro group as a gas-phase electrophile: Experimental and theoretical study of the cyclization of o-nitrodiphenyl ethers, amines, and sulfides

“…Thus, any P 10 formed would be uncompetitive in generating a second OH radical loss. 12 , from M 5 requires less energy than passing over the previous transition state, TS 4 ; hence there would be sufficient available energy to drive the first loss of OH radical (Tables 4a, 4b, Scheme 3). In addition, we performed CASSCF type calculations on M 5 and transition states for OH radical loss from even-electron M 5 : TS(M 5 -P 12 ) and TS(M 5 -P 13 ) yielding P 12 and P 13 , respectively (Table 4c).…”

“…Cycloaddition reactions involving ion-molecule reactions in the gas phase and comparison to reactions in solution are the subjects of a recent review [10]. These and other examples show the utility of a mass spectrometer as a "reaction vessel" for investigating gas-phase reactions of potential synthetic utility [11][12][13][14]. The gas-phase cyclizations of the radical cations of several disubstituted aromatic compounds led to the discovery of new methods [15,16] for the synthesis of heterocyclic compounds.…”

Molecular Complexes of Simple Anions with Electron‐Deficient Arenes: Spectroscopic Evidence for Two Types of Structural Motifs for Anion–Arene Interactions

“…[30][31][32][33] Also on mechanistic grounds, the ion-molecule reactions of anions with substituted benzenes bearing electron-withdrawing groups display a varied and rich chemistry in the gas phase. [34][35][36][37] The strong drive towards formation of anionic complexes displayed by polynitroaromatics used widely as explosives, such as trinitrotoluene, has been developed into a selective probe for their mass spectrometric detection. [38,39] Insights into the structural features of the anion interaction with an aromatic ring in an isolated state have been obtained in recent theoretical work.…”

Direct ab initio molecular dynamics study on a microsolvated SN2 reaction of OH−(H2O) with CH3Cl

“…These features are in good agreement with previous dynamics studies by Hase and co-workers. 13 From an experimental point of view, VanOrden et al 15 measured the energy distribution of the products in the gasphase S N 2 reaction ͑F − +CH 3 Cl͒ using Fourier transform ion cyclotron resonance ͑FT-ICR͒ spectroscopy, and found that the reaction proceeds with a large fraction of the exothermicity partitioned into the relative translational energy of the products.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Nevertheless, fewer studies have addressed the role of solvation in these reactions. 16,17 From an experimental point of view, O'Hair et al investigated solvent effects on the S N 2 reaction of fluoride ion with methyl chloride and measured the product ions formed by the reaction F − ͑H 2 O͒ +CH 3 Cl.…”