• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.461-466
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• 2004

Kinetics for the nucleophiles have been studied under high vacuum and high pressures in various temperatures. Pseudo-first order rate constants, second order rate constants, thermodynamic parameters and Hammett ${\rho}$-values are determined. The values of ${\Delta}V^{\neq},\;{\Delta}{\beta}^{\neq}\;and\;{\Delta}S^{\neq}$are all negative. The Hammett r-values are negative for the nucleophile (${\rho}$x) over the pressure range studied. The results of kinetic studies for pressure and nucleophilet show that these reactions proceed in typical $S_N2$ reaction mechanism and change of mechanism.

• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.517-522
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• 1992

The reaction of ${\beta}$-picoline with substituted benzoyl chlorides has been studied by means of conductometry under various pressures in acetonitrile. From the values of pseudo-first order and second order rate constants, the activation parameters (${\Delta}V{\neq}$, ${\Delta}{\beta}{\neq}$, ${\Delta}H{\neq}$, ${\Delta}S{\neq}$ and ${\Delta}G{\neq}$) and the pressure dependence of Hammett ${\rho}$ value were studied. The activation volume, the activation compressibility coefficient and the activation entropy were all negative. By increasing pressure the rate constant and Hammett ${\rho}$ value were increased, and the reaction mechanism was proceed in bond formation favored.

• Analytical Science and Technology
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• v.17 no.5
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• pp.375-380
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• 2004

Kinetics have been studied by high vacuum and high pressure apparatus under various temperatures and pressures for the nucleophilic substitution reaction. Rate constants, activated parameters and Hammett ${\rho}$-values are determined. The values of ${\Delta}V^{\ddag}$, ${\Delta}{\beta}^{\ddag}$ and ${\Delta}S^{\ddag}$ are all negative. The Hammett ${\rho}$-values are negative for the nucleophile (${\rho}x$) over the pressure range studied. Consequently the rate constant increases as the pressure increases, and some decrease in vacuum. So these reactions proceed in typical $S_N2$ reaction mechanism.

• Journal of the Korean Chemical Society
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• v.48 no.3
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• pp.254-260
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• 2004

The reaction rates of para-substituted benzoyl chlorides ($p-CH_3$, p-H, $p-NO_2$) with pyridine have been measured employing the conductometry method in acetonitrile. The pseudo first-order and second-order rate constants were determined at various pressures and temperatures. The activation parameters (${\Delta}V{\ddagger},\;{\Delta}{\beta}{\ddagger},\;{\Delta}H{\ddagger},\;{\Delta}S{\ddagger},\;{\Delta}G{\ddagger}$) and the Hammett ${\rho}$-values are determined from the values of rate constant. The values of ${\Delta}V{\ddagger},\;{\Delta}{\beta}{\ddagger}\;and\;{\Delta}S{\ddagger}$ are all negative. The Hammett ${\rho}$-values are positive for the substrate (${\rho}_Y$) over the given pressure range. The results of kinetic studies, for the pressure and substituent changes, show that these reactions are proceeded by a typical $SN_2$reaction mechanism and its bond formation is favored with elevating pressure.

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.31-36
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• 1989

The second-order rate constants for the nucleophilic substitution reactions of para-substituted benzyl nitrates with para-substituted anilines in acetonitrile were conductometrically determined. Hammett ${\rho}$x and ${\rho}$y values and Bronsted ${\beta}$ values were obtained from these kinetic data. The reactions of Benzyl nitrates with the series of anilines showed linear Hammett plots with negative slopes. For the change of substituents in the benzyl nitrates, nonlinear Hammett plots with a concave upwards curve were obtained. We applied the potential energy surface and the quantum mechanical models in order to examine the transition state variations caused by changes in substituents on the nucleophile and the substrate. The results showed that the reaction was proceeded via the $S_{N}2$-type reaction mechanism in which the extent of bond-formation was greatly changed depending on the property of the substituents in substrate.

• Journal of the Korean Chemical Society
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• v.22 no.5
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• pp.281-288
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• 1978

Pseudo-first order rate constants $k_{obs}$ were determined for the reactions of naphthalenesulfonyl chlorides (1-NSC and 2-NSC) and anilines. The second order rate constant $k_2$ and third order catalytic $k_3$ were then determined from $k_{obs}$. For 1-NSC peri-hydrogen effect was observed. The large Brønsted ${\beta}$ and large negative slopes ${\rho}$ for the Hammett plots were obtained. These results with the unsually low values of activation parameters were consistent with the $S_AN$-elimination mechanism, but these can be equally well interpreted with the associative $S_N2$mechanism.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.456-460
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• 1999

Rates of 1-adamantyl fluoroformate with substituted pyridines ($3-CH_3,\;4-CH_3,\;H,\;3-Cl,\;3,4-(CH_3)_2,\;3,5-(CH_3)_2$) in methanol have been measured by conductometric method at various temperatures and concentrations. The activation parameters (${\Delta}H^{\neq},\;{\Delta}S^{\neq}$) and Hammett reaction constant (${\rho}$) or Bronsted coefficient (${\beta}$) were evaluated from rate constants. The activation entropies are large and negative, and the activation enthalpies are small and positive. The Hammett reaction constant (${\rho}$) and Bronsted coefficient (${\beta}$) values were -4.15 and 0.63, respectively. From the above results, it may be concluded that this reaction proceeds to a concerted displacement mechanism in methanol.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.718-722
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• 2011

2,4'-Bipyridinium dichromate [$(C_{10}H_8N_2H)_2Cr_2O_7$] was synthesized by the reaction of 2,4'-bipyridinie with chromium trioxide in $H_2O$. The structure was characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase in the order of the dielectric constant (${\varepsilon}$), in the order : cyclohexene < chloroform < acetone < N,N'-dimethylformamide. In the presence of hydrochloric acid, 2,4'-bipyridinium dichromate effectively oxidized benzyl alcohol and its derivatives ($p-CH_3$, H, m-Br, $m-NO_2$) in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant (${\rho}$) was -0.65 at 303 K. The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.372-376
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• 2015

6-MQCC (Cr(VI)-6-methylquinoline) complex was synthesized by the reaction of 6-methylquinoline with chromium(VI) trioxide in 6 M HCl. The structure was characterized using IR (Infrared Spectroscopy) and ICP (Inductively Coupled Plasma) analysis. The oxidation of benzyl alcohol using 6-MQCC in various solvents showed that the reactivity increased with the increase of the dielectric constant, in descending order of DMF > acetone > chloroform > cyclohexene. In the presence of DMF solvent with acidic catalyst such as sulfuric acid ($H_2SO_4$), 6-MQCC oxidized benzyl alcohol (H) and its derivatives ($p-OCH_3$, $m-CH_3$, $m-OCH_3$, m-Cl, $m-NO_2$) were effectively oxidized. Electron-donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. The Hammett reaction constant (${\rho}$) was -0.69 (308 K). The observed experimental data was used to rationalize the fact that the hydride ion transfer occurred at the rate-determining step.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.110-114
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• 2016

Cr(VI)-pyrazine complex (PZCC) was synthesized by the reaction of pyrazine with chromium (VI) trioxide in 6 M HCl. The structure was characterized using IR spectroscopy and inductively coupled plasma (ICP). The oxidation of benzyl alcohol using PZCC in various solvents showed that the reactivity increased with the increase of the dielectric constant, in the order: N,N'-dimethylform-amide > acetone > chloroform > cyclohexene. In the presence of N,N'-dimethylformamide solvent with an acidic catalyst such as sulfuric acid ($H_2SO_4$ solution), PZCC oxidized benzyl alcohol (H) and its derivatives ($p-OCH_3$, $m-CH_3$, $m-OCH_3$, m-Cl, $m-NO_2$). Electron-donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. Hammett reaction constant (${\rho}$) was -0.70 (308 K). The observed experimental data were used to rationalize the hydride ion transfer in the rate-determining step.