Reaction mechanisms
Direct SN2 rebound survives bulky alkyl iodides
Open access · cc by · source: Europe PMC
Even with extra methyl groups on the alkyl iodide, Cl− and CN− still show a direct backward SN2 rebound channel at high collision energy rather than fully statistical dynamics.
Key findings
Direct backward SN2 opens at higher energy as methylation increases, yet at 1.9 eV more than half of Cl−/CN− + CH3CH2I events are direct rebound; energy into product internals stays below 60%. Direct SN2 outcompetes E2 above 1 eV.
Methodology
The authors crossed mass-selected Cl− or CN− with CH3I, CH3CH2I or (CH3)2CHI beams and recorded I− product velocity-map images at relative collision energies of 0.4, 1.1 and 1.9 eV, comparing angular/energy partitioning with computed SN2 and E2 barriers.
Limitations
These are isolated gas-phase ion–molecule collisions, not condensed-phase SN2 rates or stereochemical inversion yields in solution.
How this study connects
Role on claims
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Evidence for the claim as stated.
Even with extra methyl groups on the alkyl iodide, Cl− and CN− still show a direct backward SN2 rebound channel at high collision energy rather than fully statistical dynamics.
Evidence for the claim as stated.
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