32792-60-2Relevant articles and documents
Alkaline Hydrolysis of 4-Nitrophenyl X-Substituted-Benzoates Revisited: New Insights from Yukawa–Tsuno Equation
Shin, Young-Hee,Kang, Ji-Sun,Um, Ik-Hwan
, p. 2062 - 2065 (2016/12/16)
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Aminolysis of Y-substituted-phenyl 2-methoxybenzoates in acetonitrile: Effect of the o-methoxy group on reactivity and reaction mechanism
Um, Ik-Hwan,Bae, Ae Ri
experimental part, p. 7510 - 7515 (2011/11/13)
Second-order rate constants (kN) were measured for aminolyses of Y-substituted-phenyl 2-methoxybenzoates 2a-i and 4-nitrophenyl X-substituted-benzoates 3a-j in MeCN at 25.0 °C. The Bronsted-type plot for the reactions of 2a-i with piperidine curves downward, indicating that a change in rate-determining step (RDS) occurs. The Hammett plot for the reactions of 3a-j with piperidine consists of two intersecting straight lines, which might be taken as evidence for a change in RDS. However, the nonlinear Hammett plot has been suggested not to be due to a change in RDS but rather to the stabilization of the ground state of substrates possessing an electron-donating group (EDG) (e.g., 3a-c) through a resonance interaction, since the corresponding Yukawa-Tsuno plot exhibits an excellent linear correlation with ρ = 0.54 and r = 1.54. The ρ value found for the reactions of 3a-j in MeCN is much smaller than that reported previously for the corresponding reactions in H2O (i.e., ρ = 0.75). It is proposed that the reactions of 3a-j in MeCN proceed through a forced concerted mechanism due to instability of T± in the aprotic solvent, while the reactions of 2a-i proceed through a stepwise pathway with a stabilized T ± through an intramolecular H-bonding interaction.
Structure-reactivity correlations in nucleophilic substitution reactions of Y-substituted phenyl X-substituted benzoates with anionic and neutral nucleophiles
Um, Ik-Hwan,Lee, Ji-Youn,Fujio, Mizue,Tsuno, Yuho
, p. 2979 - 2985 (2008/02/11)
A kinetic study is reported for the reactions of 4-nitrophenyl X-substituted benzoates (1a-l) and Y-substituted phenyl benzoates (2a-l) with two anionic nucleophiles (OH- and CN-) and three amines (piperidine, hydrazine, and glycylglycine) in 80 mol% H2O-20 mol% dimethyl sulfoxide (DMSO) at 25.0 ± 0.1 °C. Each Hammett plot exhibits two intersecting straight lines for the reactions of 1a-l with the anionic nucleophiles and piperidine, while the Yukawa-Tsuno plots for the same reactions are linear. The Hammett plots for the reactions of 2a-l with hydrazine and glycylglycine demonstrate much better linear correlations with σ- constants than with σ° or σ constants, indicating that the leaving group departure occurs at the rate determining step (RDS). On the contrary, σ- constants result in poorer Hammett correlation than σ° constants for the corresponding reactions with OH- and CN-, indicating that the leaving group departure occurs after the RDS for the reactions with the anionic nucleophiles. The large ρX value (1.7 ± 0.1) obtained for the reactions of 1a-l with the anionic nucleophiles supports the proposal that the reactions proceed through an addition intermediate with its formation being the RDS. The Royal Society of Chemistry 2006.