• Title/Summary/Keyword: Hammett reaction constant (${\rho}$)

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A Study for the Reaction of ${\beta}$-Picoline with p-Substituted Benzoyl Chlorides by Pressure (압력변화에 따른 ${\beta}$-피콜린과 염화벤조일류의 반응에 대한 연구)

  • Yeong Cheul Kim;Se Kyong Kim
    • 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.

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Kinetic Analysis by High Pressure and High Vacuum Apparatus for the Nucleophilic Substitution Reaction (고압 및 고진공장치를 이용한 친핵성치환반응에 대한 속도론적 분석)

  • Kim, Se-Kyong
    • 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.

A Study for Kinetics and Oxidation Reaction of Substituted Benzyl Alcohols Using Cr(VI)-6-Methylquinoline (Cr(VI)-6-Methylquinoline을 이용한 치환 벤질 알코올류의 산화반응과 속도론에 관한 연구)

  • Park, Young Cho;Kim, Young Sik
    • 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.

Mechanism for the Oxidation Reaction of Alcohols Using Cr(VI)-Pyrazine Complex (크롬(VI)-피라진 착물을 이용한 알코올류의 산화반응과 메카니즘)

  • Park, Young Cho;Kim, Young Sik
    • 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.

A Study for Mechanism and Oxidation Reaction of Substituted Benzyl Alcohols using Cr(VI)-Heterocyclic Complex[Cr(VI)-2-methylpyrazine] (Cr(VI)-헤테로고리 착물[Cr(VI)-2-methylpyrazine]를 이용한 치환 벤질 알코올류의 산화반응과 메카니즘에 관한 연구)

  • Kim, Young-Sik;Park, Young-Cho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.11
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    • pp.6039-6046
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    • 2013
  • Cr(VI)-heterocyclic complex[Cr(VI)-2-methylpyrazine] was synthesized by the reaction between of heterocyclic compound(2-methylpyrazine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using Cr(VI)-2-methylpyrazine in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order : cyclohexene${\rho}$) was Cr(VI)-2-methylpyrazine= -0.65(308K). The observed experimental data have been ratiolized. The hydride ion transfer causes the prior formation of a chromate ester in the rate-determining step.

A Study for Kinetics and Oxidation Reaction of Substituted Benzyl Alcohols Using 2,4'-Bipyridinium Dichromate (2,4'-Bipyridinium Dichromate를 이용한 치환 벤질 알코올류의 산화반응과 반응속도에 관한 연구)

  • Kim, Young Sik;Park, Young Cho
    • 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.

Kinetics of the Oxidation of Substituted Benzyl Alcohols with 4-(Dimethylamino)pyridinium Dichromate (4-(Dimethylamino)pyridinium Dichromate를 이용한 치환 벤질 알코올류의 산화반응 속도)

  • Choi, Sun do;Park, Young Cho
    • Applied Chemistry for Engineering
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    • v.16 no.1
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    • pp.153-157
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    • 2005
  • 4-(Dimethylamino)pyridinium dichromate was synthesized by the reaction of 4-(dimethylamino)pyridine with chromium(VI)trioxide in $H_2O$, and characterized by IR, EA and ICP. The oxidation of benzyl alcohol using 4-(dimethylamino)pyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant, in the order: cyclohexen < chloroform < acetone < N,N-dimethylformamide. In the presence of hydrochloric acid(HCl), 4-(dimethylamino)pyridinium dichromate oxidized benzyl alcohol and its derivatives ($p-CH_3$, H, m-Br, $m-NO_2$) smoothly in N,N-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron-withdrawing groups retarded the reaction. The Hammett reaction constant($\rho$) was -0.70 at 303K. The observed experimental data have been rationalized as follows: the proton transfer occurs after the prior formation of a chromate ester in the rate-determining step.

Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohols by Cr(VI)-4,4'-Bipyridine Complex (크롬(VI)-4,4'-Bipyridine 착물에 의한 치환 벤질 알코올류의 산화반응 속도론과 메카니즘)

  • Kim, Young-Sik;Park, Young-Cho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.1
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    • pp.462-469
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    • 2012
  • Cr(VI)-4,4'-bipyridine complex(4,4'-bipyridinium dichromate) was synthesized by the reaction of 4,4'-bipyridine with chromium trioxide in H2O, and characterized by IR, ICP. The oxidation of benzyl alcohol using 4,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene$CH_3$, H, m-Br, m-$NO_2$) smoothly in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.63(303K). The observed experimental data have been rationalized as follows; the proton transfer occurs after the prior formation of a chromate ester in the rate determining step.

Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohols by Cr(VI)-Heterocyclic Complex (2,4'-Bipyridinium Chlorochromate) (크롬(VI)-헤테로고리 착물(2,4'-비피리디늄 클로로크로메이트)에 의한 치환 벤질 알코올류의 산화반응에서 속도론과 메카니즘)

  • Park, Young Cho;Kim, Young Sik
    • Applied Chemistry for Engineering
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    • v.25 no.6
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    • pp.648-653
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    • 2014
  • Cr(VI)-heterocyclic complex (2,4'-bipyridinium chlorochromate) was synthesized by the reaction between heterocyclic compound(2,4'-bipyridine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium chlorochromate in various solvents showed that the reactivity increased with the increase of the dielectric constant (${\varepsilon}$), in the order : N,N-dimet-hylformamide (DMF) > acetone > chloroform > cyclohexene. In the presence of DMF solvent with acidic catalyst such as hydrochloric acid (HCl solution), 2,4'-bipyridinium chlorochromate oxidized benzyl alcohol (H) and its derivatives (p-$CH_3$, m-Br, m-$NO_2$). Electron-donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. The Hammett reaction constant (${\rho}$) was -0.67 (303 K). The observed experimental data have been rationalize the proton transfer occurred followed the formation of a chromate ester in the rate-determining step.

Kinetics of the Oxidation of Substituted Benzyl Alcohols using 6-Methylquinolinium Dichromate (6-Methylquinolinium Dichromate를 이용한 치환 벤질 알코올류의 산화반응 속도)

  • Kim, Young-Sik;Park, Young-Cho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.12
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    • pp.5990-5996
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    • 2011
  • 6-Methylquinolinium dichromate[$(C_{10}H_9NH)_2Cr_2O_7$] was synthesized by the reaction of 6-methylquinoline with chromium trioxide in $H_2O$, and characterized by IR, ICP. The oxidation of benzyl alcohol using 6-methylquinolinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene < chloroform < acetone < N,N- dimethylformamide. In the presence of hydrochloric acid($H_2SO_4$ solution), 6-methylquinolinium dichromate oxidized benzyl alcohol and its derivatives(p-$OCH_3$, m-$CH_3$, H, m-$OCH_3$, m-Cl, m-$NO_2$) smoothly in DMF. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.67(303K). The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.