Gas-Phase Acid-Induced Nucleophilic Displacement Reactions. 5. Quantitative Evaluation of Neighboring-Group Participation in Bifunctional Compounds

Article abstract of DOI:10.1021/ja00403a030

A previous radiolytic study on the stereochemistry of gas-phase nuclephilic displacement on several classes of positively charged intermediates, formed from the attack of gaseous acids (CH5⁺, C2H5⁺, CH3FCH3⁺, etc.) on suitable substrates, is now completed with the assessment of the detailed mechanism and the relative extent of the other major reaction pathways accompanying them.The analysis of the stereoisomeric distribution of the neutral end products allows a quantitative evaluation of the gas-phase neighboring-group participation in such systems.A participating-group ability trend of OH >> Br >/= Cl is found, which is appreciably dependent on the nature of the leaving group and the configuration of the starting substrate.The evaluation of the adjacent-group "effective concentration" in these gaseous systems provides the first direct evidence for a gas-phase anchimerically assisted ionic reaction, involving a three-membered ring formation.The results obtained in the gas phase differ significantly from those concerning related solvolytic processes.