title: Electron-Withdrawing β-Substituent, Ring-Strain, and Ortho Effects on Reactivity, Selectivity, and Stability of o-Alkoxybenzyl Carbocations.
abstract: o-Alkoxybenzyl carbocations 1 and 2 were generated by laser flash photolysis of the corresponding o-alkoxybenzyl alcohols 3 and 4 to understand how the electron-withdrawing β-substituent, the ring-strain, and the ortho effects affect the reactivity (electrophilicity), selectivity, and stability of 1 and 2, and to fit the electrophilicity of 1 and 2 into the current carbocation electrophilicity scale (E). Our finding is that both the electron-withdrawing β-substituent and the ring-strain effects make 1 less stable than 2 by 3.0 kcal/mol. These effects plus the ortho effect of 2 make 1 more reactive than 2, but the selectivity of 1 and 2 toward amine nucleophiles is almost the same within experimental errors. The electrophilicity of 1 and 2 has been fit into the current carbocation electrophilicity scale (E) quite well.
authors: Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
authors: Meng-Yun
authors: MY
authors: Tseng
authors: Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
authors: Hsin-Yi
authors: HY
authors: Hung
authors: Department of Chemistry, National Cheng Kung University, Tainan, Taiwan.
authors: Kuangsen
authors: K
authors: Sung
mesh_terms: D001593:Benzyl Compounds / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D004583:Electrons; D007700:Kinetics; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D001593:Benzyl Compounds; D002412:Cations