• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.273-276
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• 1991

The rate constants of hydrolysis of ${\alpha}$, N-diphenylnitrone and its derivatives have been determined by UV spectrophotometry from pH 2.0 to 13.5, and a rate equation which can be applied over a wide pH range was obtained. On the basis of rate equation, hydrolysis product, and general base and substituent effects, a plausible mechanism of hydrolysis has been proposed: Below pH 5, the hydrolysis was initiated by the protonation and followed by the addition of water to ${\alpha}$-carbon. However, above pH 11, the hydrolysis was proceeded by the addition of hydroxide ion to ${\alpha}$-carbon. In the range of pH 5-11, the addition of water to nitrone is rate controlling step.

• Journal of the Korean Chemical Society
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• v.19 no.2
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• pp.123-129
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• 1975

The rate constants of the hydrolysis of phenylvinylsulfone were determined by ultraviolet spectrophotometry at various pH and a rate equation which can be applied over wide pH range was obtained. The reaction mechanism of hydrolysis of phenylvinylsulfone and especially the catalytic contribution of hydroxide ion which did not study carefully before in acidic media, can be fully explained by the rate equation obtained. The rate equation reveals that: below pH 7, the reaction is initiated by the addition of water molecule to phenylvinylsulfone. At above pH 9, the overall rate constant is only dependent upon the concentration of hydroxide ion.

• Bulletin of the Korean Chemical Society
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• v.9 no.3
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• pp.157-160
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• 1988

The rates of hydrolysis of N-(benzenesulfonyl) benzimidoyl chlorides (p-H, $p-CH_3,\;p-CH_3,\;p-NO_2\;and m-NO_2$) have been measured by UV spectrometry in 60% methanol-water at $25^{\circ}C$ and a rate equation which can be applied over wide pH range was obtained. Below pH 7.00, the substituent effect on the hydrolysis rate of N-(benzenesulfonyl) benzimidoyl chloride was found to conform to the Hammett ${\sigma}$ constant with ${\rho}$ = -0.91, whereas above pH 9.00, with ${\rho}$ = 0.94. On the basis of the rate equation obtained and the effect of solvent, substituents and salt, the following reaction mechanism were proposed; below pH 7.00, the hydrolysis of N-(benzenesulfonyl) benzimidoyl chloride proceeds by $S_N1$ mechanism, however, above pH 9.00, the hydrolysis is initiated by the attack of the hydroxide ion and in the range of pH 7.00-9.00, these two reactions occur competitively.

• Journal of the Korean Applied Science and Technology
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• v.6 no.2
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• pp.59-65
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• 1989

The rate constants of the hydrolysis of cinnamanilide derivatives were determined UV spectrometry in $H_2SO_4\;(5{\sim}20N)$, NaOH($5{\sim}11N)\;at\;50{\sim}110^{\circ}C$ and rate equation could be applied over a strong acid and strong base were obtained. Final product of the hydrolysis was a cinnamic acid. The ${\rho}$ values obtained from the slope of linear plots of log $k_{abs}$ vs. Hammet $t{\sigma}$ constants were slightly negatives, Substituents on cinnamanilide showed a relatively small effect, with hydrolysis facilitated be electron donating group. Activation energy(Ea)was also calculated for the hydrolysis of the cinnamanilide. From this reaction rate equation, substituent effect and experimental of rate constants, that the hydrolysis of cinnamanillde was Initiated by the netural molecule of $H_2O$ which do not dissociate at strong acid, and proceeded by hydroxide ion at strong base.

• Journal of the Korean Applied Science and Technology
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• v.15 no.2
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• pp.1-9
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• 1998

The rate constants of hydrolysis of N-tert-butyl-${\alpha}$-phenylnitrone and its derivatives have been determined by UV spectrophotometry at $25^{\circ}C$ and a rate equation which can be applied over a wide pH range was obtained. On the basis of rate equations derived and judging from the hydrolysis products obtained and general base and substituent effects, plausible mechanism of hydrolysis in various pH range have been proposed. Below pH 4.5, the hydrolysis was initiated by the protonation and followed by the addition of water to ${\alpha}-carbon$. Above pH 10.0, the hydrolysis was proceeded by the addition of hydroxides ion to ${\alpha}-carbon$. In the range of 4.5${\sim}$10.0 the addition of water to nitrone was rate controlling step.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.130-135
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• 1973

The rate-constants of hydrolysis of 3, 4-methylenedioxyphenylmethylenemalononitrile are determined by ultraviolet spectrophotometry at various pH and a rate equation which can be applied over wide pH range is obtained. The rate equation reveals that below pH 5.0 and above pH 9.0, the hydrolysis is initiated by the addition of water and hydroxide ion respectively. However, at pH 6.0-8.0 the competitive addition of water and hydroxide ion occurs. The catalytic contribution of hydroxide ion and water can be fully explained by the rate equation obtained.

• Journal of the Korean Chemical Society
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• v.18 no.6
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• pp.430-436
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• 1974

The rate constants of hydrolysis of 1,1-dicyano-2-p-dimethylaminophenyl-2-chloroethylene(DPC) were determined at various pH and the rate equation which can be applied over wide pH range is obtained. From the rate equation the mechanism of the hydrolysis of a DPC over wide pH range is fully explained; below pH 3 and above pH 7.5, the rate constant is proportional to the concentration of hydronium ion and hydroxide ion, respectively. However, in the range of pH 3 to 7.5, water, hydronium ion and hydroxide ion catalyze the hydrolysis of DPC.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1213-1217
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• 1999

Hydrolysis reactions of 2-phenyl-4H,5H,6H-3-methyl-3-thiazinium perchlorate (PTP) and its derivatives at various pH have been investigated kinetically. The hydrolysis is quantitative, producing N-3-mercaptopropyl-N-methylbenzamide as the only product in the all pH ranges. The observed rate of hydrolysis of PTP was always of the first-order. For hydrolysis from PTP, Hammett ρvalues were 0.53, 0.84 and 1.13 for pH 5.0, 8.0, and 10.0, respectively. Bronsted βvalue was 0.53 for general base catalysis. This reaction is catalyzed by general w acetate concentration. However, as the amount of base becomes larger, the rate of hydrolysis reaction approaches the limiting values. The plot of log k vs. pH shows that the rate constants (kt) are two different regions in the profile; one part is directly proportional to hydroxide ion concentration and the other is not. On the bases of these result, the plausible hydrolysis mechanism and a reaction equation were proposed: Below pH 4.5, the hydrolysis was initiated by the addition of water to α-carbon. Above pH 9.0, the hydrolysis was proceeded by the addition of hydroxide ion to α-carbon. However, in the range of pH 4.5-8.0, these two reactions occured competitively.

• Journal of the Korean Applied Science and Technology
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• v.8 no.1
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• pp.1-7
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• 1991

The kinetic of hydrolysis for cinnamylidene aniline derivatives has been investigated by ultraviolet spectrophotometry in 20% (v/v) dioxane - $H_2O$ at $25^{\circ}C$. A rate equation which can be applied over wide pH range was obtained. The substituent effects on cinnamylidene aniline derivatives were studied and the hydrolysis was facilitated by electron attracting group. Final products of the hydrolysis were cinnamaldehyde and aniline. From the rate equation, substituent effect and final products, the hydrolysis of cinnamylidene aniline derivatives was initiated by the neutral molecule of $H_2O$ which does not dissociate at below pH 9.0${\sim}$12.0, but proceeded by the hydrogen ion at above pH 5.0${\sim}$9.0.

• Bulletin of the Korean Chemical Society
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• v.26 no.12
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• pp.1981-1985
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• 2005

Kinetic studies have been performed for alkaline hydrolysis of a series of [(methoxy)(p-substituted styryl)carbene]pentacarbonyl chromium(0) complexes ($(CO)_5$Cr=$C(OCH_3)CH=CHC_6H_4X$, X = p-$OCH_3$, p-$CH_3$, H, p-Cl, p-$NO_2$). Second-order rate constants $(k_{{OH}^-})$ for the alkaline hydrolysis in 50% acetonitrile-water(v/v) were determined spectrophotometrically at various temperatures. At a low pH region (pH < 7.5), the observed rate constant $(k_{obs})$ remained constant with a small value, while in a high pH region (pH > 9.5), $k_{obs}$ increases linearly with increasing the pH of the medium. The second-order rate constants $(k_{{OH}^-})$ increase as the substituent X changes from a strong electron donating group to a strong electron withdrawing group. The Hammett plot obtained for the alkaline hydrolysis is consisted of two intersecting straight lines. The nonlinear Hammett plot might be interpreted as a change in the rate-determining step. However, the fact that the corresponding Yukawa-Tsuno plot is linear with $\rho$ and r values of 0.71 and 1.14, respectively indicates that the nonlinear Hammett plot is not due to a change in the rate-determing step but is due to ground-state stabilization through resonance interaction. The positive $\rho$ value suggests that nucleophilic attack by $OH^-$ to form a tetrahedral addition intermediate is the rate-determining step. The large negative ${\Delta}S^\neq$ value determined in the present system is consistent with the proposed mechanism.