Kinetic Study on the Oxidation Reaction of Substituted Benzyl Alcohols by Cr(VI)-Heterocyclic Complex (2,2'-Bipyridinium Dichromate)

크롬(VI)-헤테로고리 착물(2,2'-Bipyridinium Dichromate)에 의한 치환 벤질 알코올류의 산화반응에 대한 속도론적 연구

  • Kim, Young Sik (Department of Chemical Engineering, Kangwon National University) ;
  • Park, Young Cho (Department of Chemical Engineering, Kangwon National University)
  • 김영식 (강원대학교 화학공학과) ;
  • 박영조 (강원대학교 화학공학과)
  • Published : 2012.04.10

Abstract

Cr(VI)-heterocyclic complex (2,2'-bipyridinium dichromate) was synthesized by the reaction between of 2,2'-bipyridine and chromium trioxide in $H_2O$, and characterized by IR and ICP. The oxidation of benzyl alcohol using 2,2'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant, in the order: cyclohexene < chloroform < acetone < N,N-dimethylformamide. In the presence of DMF solvent with acidic catalyst such as $H_2SO_4$ solution, 2,2'-bipyridinium dichromate oxidized the benzyl alcohol and its derivatives (p-$p-OCH_3$, $m-CH_3$, H, $m-OCH_3$, m-Cl, $m-NO_2$). Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant was -0.66 (303 K). The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

크롬(VI)-헤테로고리 착물(2,2'-bipyridinium dichromate)를 합성하여, 적외선분광광도법(IR), 유도결합 플라즈마(ICP) 등으로 구조를 확인하였다. 여러 가지 용매 하에서 2,2'-bipyridinium dichromate를 이용하여 벤질 알코올의 산화반응을 측정한 결과 유전상수(${\epsilon}$) 값이 큰 용매 순서인 시클로헥센 < 클로로포름 < 아세톤 < N,N-디메틸포름아미드 용매 하에서 높은 산화반응성을 보였다. 산 촉매($H_2SO_4$)를 이용한 DMF 용매 하에서 2,2'-bipyridinium dichromate는 벤질 알코올과 그의 유도체들($p-OCH_3$, $m-CH_3$, H, $m-OCH_3$, m-Cl, $m-NO_2$)을 효과적으로 산화시켰다. 그리고 전자받개 그룹들은 반응 속도가 감소한 반면에 전자주개 치환체들은 반응속도를 증가시켰다. 또한 Hammett 반응상수$({\rho})$ 값은 -0.66 (303 K)이였다. 그러므로 본 실험에서 알코올의 산화반응 과정은 속도결정단계에서 수소화 전이가 일어나는 메카니즘임을 알 수 있었다.

Keywords

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