- Kinetic study on aminolysis of 4-chloro-2-nitrophenyl X-substituted-benzoates in Acetonitrile and in 80 mol % H2O/20 mol % DMSO: Effect of medium on reactivity and reaction mechanism
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A kinetic study on aminolysis of 4-chloro-2-nitrophenyl X-substituted-benzoates (6a-i) in MeCN is reported. The Hammett plot for the reactions of 6a-i with piperidine consists of two intersecting straight lines, while the Yukawa-Tsuno plot exhibits an exc
- Kim, Ha-Ram,Um, Tae-Il,Kim, Min-Young,Um, Ik-Hwan
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p. 1128 - 1132
(2014/05/06)
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- The α-effect in hydrazinolysis of 4-chloro-2-nitrophenyl x-substituted-benzoates: Effect of substituent x on reaction mechanism and the α-effect
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Second-order rate constants (kN) have been measured spectrophotometrically for the reaction of 4-chloro-2- nitrophenyl X-substituted-benzoates (6a-6h) with a series of primary amines including hydrazine in 80 mol % H2O/20 mol % DMSO at 25.0°C. The Bronsted-type plot for the reaction of 4-chloro-2-nitrophenyl benzoate (6d) is linear with βnuc = 0.74 when hydrazine is excluded from the correlation. Such a linear Bronsted-type plot is typical for reactions reported previously to proceed through a stepwise mechanism in which expulsion of the leaving group occurs in the rate-determining step (RDS). The Hammett plots for the reactions of 6a-6h with hydrazine and glycylglycine are nonlinear. In contrast, the Yukawa-Tsuno plots exhibit excellent linear correlations with ?X = 1.29-1.45 and r = 0.53-0.56, indicating that the nonlinear Hammett plots are not due to a change in RDS but are caused by resonance stabilization of the substrates possessing an electron-donating group (EDG). Hydrazine is ca. 47-93 times more reactive than similarly basic glycylglycine toward 6a-6h (e.g., the α-effect). The α-effect increases as the substituent X in the benzoyl moiety becomes a stronger electronwithdrawing group (EWG), indicating that destabilization of the ground state (GS) of hydrazine through the repulsion between the nonbonding electron pairs on the two N atoms is not solely responsible for the substituent-dependent α-effect. Stabilization of transition state (TS) through five-membered cyclic TSs, which would increase the electrophilicity of the reaction center or the nucleofugality of the leaving group, contributes to the α-effect observed in this study.
- Kim, Min-Young,Kim, Tae-Eun,Lee, Jieun,Um, Ik-Hwan
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p. 2271 - 2276
(2014/09/29)
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- N-(2-hydroxyaryl)benzamide synthesis from 2-nitroaryl benzoates via an Indium-mediated reduction-migration reaction
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A one-pot reduction-triggered N-(2-hydroxyaryl)benzamide synthesis from 2-nitroaryl benzoate substrates was investigated. In the presence of indium/AcOH in THF/H2O, 2-nitroaryl benzoates produced reasonable yields of the benzo group migrated N-
- Lee, Hyejeong,Kim, Minki,Jun, Young Moo,Kim, Byeong Hyo,Lee, Byung Min
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scheme or table
p. 158 - 167
(2011/10/08)
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- Kinetics and mechanism of nucleophilic displacement reactions of Y-substituted phenyl benzoates with cyanide Ion
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Second-order rate constants (kCN-) have been measured for nucleophilic substitution reactions of Y-substituted phenyl benzoates (1a-r) with CN- ion in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 °C. The Bronsted-type plot is linear with βlg = -0.49, a typical βlg value for reactions reported to proceed through a concerted mechanism. Hammett plots correlated with σo and σ-constants exhibit many scattered points. In contrast, the Yukawa-Tsuno plot for the same reaction exhibits excellent linearity with pY = 1.37 and r = 0.34, indicating that a negative charge develops partially on the oxygen atom of the leaving aryloxide in the rate-determining step (RDS). Although two different mechanisms are plausible (i.e., a concerted mechanism and a stepwise pathway in which expulsion of the leaving group occurs at the RDS), the reaction has been concluded to proceed through a concerted mechanism on the basis of the magnitude of βlg and pY values.
- Kim, Song-I,Kim, Eun-Hee,Um, Ik-Hwan
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experimental part
p. 689 - 693
(2010/08/19)
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- Photolysis of 2-Nitrophenyl Benzyl Ethers in Neutral and Acidic Media
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2-Nitrophenyl benzyl ethers (1a-d) on irradiation afford N-benzoyl-2-aminophenols (4) as the major products.The other minor products are 2-nitrophenol (2), 4-benzyl-2-nitrophenol (3), 2-phenylbenzoxazoles (5) and 2-nitrophenyl benzoate (6).A plausible mechanism to account for the formation of various products is discussed.
- Jacob E. Dominic,Joshua, C. P.
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p. 808 - 810
(2007/10/02)
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