TY - JOUR
T1 - Electron-Withdrawing β-Substituent, Ring-Strain, and Ortho Effects on Reactivity, Selectivity, and Stability of o-Alkoxybenzyl Carbocations
AU - Tseng, Meng Yun
AU - Hung, Hsin Yi
AU - Sung, Kuangsen
PY - 2015/4/30
Y1 - 2015/4/30
N2 - 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. (Chemical Equation Presented).
AB - 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. (Chemical Equation Presented).
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U2 - 10.1021/acs.jpca.5b02234
DO - 10.1021/acs.jpca.5b02234
M3 - Article
C2 - 25853459
AN - SCOPUS:84929485454
SN - 1089-5639
VL - 119
SP - 3905
EP - 3912
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 17
ER -