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Aminolysis of 2,4-Dinitrophenyl and 3,4-Dinitrophenyl Benzoates: Effect of ortho-Nitro Group on Reactivity and Mechanism
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  • Aminolysis of 2,4-Dinitrophenyl and 3,4-Dinitrophenyl Benzoates: Effect of ortho-Nitro Group on Reactivity and Mechanism
  • Aminolysis of 2,4-Dinitrophenyl and 3,4-Dinitrophenyl Benzoates: Effect of ortho-Nitro Group on Reactivity and Mechanism
저자명
Seo. Jin-A,Lee. Hye-Min,Um. Ik-Hwan
간행물명
Bulletin of the Korean Chemical Society
권/호정보
2008년|29권 10호|pp.1915-1919 (5 pages)
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대한화학회
파일정보
정기간행물|ENG|
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이 논문은 한국과학기술정보연구원과 논문 연계를 통해 무료로 제공되는 원문입니다.
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Second-order rate constants ($k_N$) have been measured spectrophotometrically for reactions of 3,4-dinitrophenyl benzoates (5b) with a series of alicyclic secondary amines in 80 mol % $H_2O$/20 mol % DMSO at 25.0 ${pm}$ 0.1 ${^{circ}C}$. The kinetic data have been compared with the data reported previously for the corresponding reactions of 2,4- dinitrophenyl benzoates (5a) to investigate the effect of changing the nucleofuge from 2,4-dinitrophenoxide to 3,4-dinitrophenoxide on reactivity and mechanism. The kinetic results show that aminolyses of 5a and 5b proceed through the same mechanism, i.e., a zwitterionic tetrahedral intermediate ($T^{pm}$) with a change in the rate-determining step (RDS). Substrate 5a is more reactive than 5b when breakdown of $T^{pm}$ is the RDS but less reactive when formation of $T^{pm}$ is the RDS. Dissection of kN values into the microscopic rate constants (e.g., $k_1$ and $k_2/k_{-1 }$ ratio) has revealed that 5a results in larger $k_2/k_{-1}$ ratios but smaller k1 values than 5b for all the amines studied. Since 2,4-dinitrophenoxide is less basic and a better nucleofuge than 3,4-dinitrophenoxide, the larger $k_2/k_{-1}$ ratios determined for the reactions of 5a than for those of 5b are as expected. The steric hindrance exerted by the ortho-nitro group on 5a contributes to the smaller k1 values found for the reactions of 5a than for those of 5b.