Solvent-equilibrated ion pairs from carbene fragmentation reactions |
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Authors: | Moss Robert A Zheng Fengmei Fedé Jean-Marie Johnson Lauren A Sauers Ronald R |
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Institution: | Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, USA. moss@rutchem.rutgers.edu |
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Abstract: | R(+) OC Cl(-)] ion pairs were generated in methanol/dichloroethane solutions, with R(+) as the 1-bicyclo2.2.2]octyl, 1-adamantyl, or 3-homoadamantyl cation. Ion pairs were produced either by the direct fragmentation of alkoxychlorocarbenes (ROCCl), with R = 1-bicyclo2.2.2]octyl, 1-adamantyl, or 3-homoadamantyl, or by the ring expansion-fragmentation of R'CH(2)OCCl, with R' = 1-norbornyl, 3-noradamantyl, or 1-adamantyl. Correlations of the ROMe]/RCl] product ratios as a function of the mole fraction of MeOH in dichloroethane showed that the homoadamantyl chloride ion pairs, produced by either the direct or ring expansion-fragmentations, were identical, solvent- and anion-equilibrated, and precursor independent. Laser flash photolysis experiments gave 20-30 ps as the time required for solvent equilibration and precursor independence. Methanol/chloride selectivities of the (less-stable) 1-adamantyl chloride and 1-bicyclo2.2.2]octyl chloride ion pairs were not independent of their ROCCl or R'CH(2)OCCl precursors. Computational studies provided transition states for the fragmentations and for the structures of the ion pairs. |
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