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Dual-parameter correlations on rate of an aromatic nucleophilic substitution reaction in aqueous solutions of methanol, ethanol, and propan-2-ol

Gholami, M. R ; Sharif University of Technology | 2001

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  1. Type of Document: Article
  2. DOI: 10.1002/1097-4601(200102)33:2<118::AID-KIN1003>3.0.CO;2-U
  3. Publisher: John Wiley & Sons Inc , 2001
  4. Abstract:
  5. Reaction kinetics of 1-chloro-2,4-dinitrobenzene with piperidine was studied spectrophotometrically in aqueous solutions of methanol, ethanol, and propan-2-ol at 25 °C. The reaction in these solutions is not catalyzed by piperidine. The plots of second-order rate constants of the reaction vs. mole fraction of water show maxima in the all-aqueous solutions. Single-parameter correlations of log k2 vs. π* (dipolarity/polarizability), α (hydrogen-bond donor acidity), and ETN (normalized polarity parameter) are very poor in the all solutions (for example, in aqueous solutions of ethanol, regression coefficients are 0.814, 0.113, and 0.486, respectively). Dual-parameter correlations of log k2 vs. π* and α in all cases represent significant improvement with regard to the single-parameter models (in aqueous solutions of ethanol: n = 11, r = 0.980, and s = 0.034). Dipolarity/polarizability and hydrogen-bond donor acidity (HBD) of media have opposite effects on the reaction rate. The activated complex leading to the zwitterionic intermediate is expected to be favored by increasing the solvent dipolarity/polarizability parameter. Increasing the hydrogen-bond donor acidity of solvent stabilizes piperidine and hence the reaction rate decreases. A dual-parameter equation of log k2 vs. π* and α was obtained in the all-aqueous solutions (n = 31, r = 0.956, s = 0.055) in which π* and α have approximately equal and opposite effects on the reaction rate
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  8. Source: International Journal of Chemical Kinetics, New York, NY, United States ; Volume 33, Issue 2 , 2001 , Pages 118-123 ; 05388066 (ISSN)
  9. URL: https://onlinelibrary.wiley.com/doi/10.1002/1097-4601%28200102%2933%3A2%3C118%3A%3AAID-KIN1003%3E3.0.CO%3B2-U