Abstract
The partitioning of reaction exothermicity into relative translational energy of the products of gas‐phase S~N~2 (F^−^ + CH~3~Cl) and nucleophilic aromatic substitution (F^−^ + C~6~H~5~Cl) 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 S~N~2 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~3~Cl reaction deviate significantly from the statistical model whereas the chlorobenzene results are consistent with this model. The kinetic energy release for the CH~3~C1 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.