An experimental and computational study on the rate constant of electrochemically generated n-acetyl-p- quinoneimine with dimethylamine

Shafiei, H. (Hadi) ; Sharif University of Technology

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  1. Type of Document: Article
  2. Abstract:
  3. Electrochemical oxidation of acetaminophen (N–acetyl–p–aminophenol) (1) has been studied in the presence of dimethylamine (2) as a nucleophile in aqueous solution, by means of cyclic voltammetry and controlled-potential coulometry. The results indicate the participation of electrochemically generated N-acetyl-p-quinoneimine (1a) in Michael reaction with dimethylamine (2). Based on ECE mechanism, the observed homogeneous rate constant (kobs) of the above mentioned reaction is estimated by comparing the experimental cyclic voltammograms with the digital simulated results. Further more; kinetics and mechanism of the reaction were studied with ab initio calculation, Monte Carlo and QM/MM simulations in gas phase and aqueous phase. Geometrical parameters and charge calculations show that these reactions proceed through the 1,4-Michael addition mechanism and first step of mentioned reaction is rate determining. Solvent effects on these reactions were studied by inserting water molecules in reaction media, Onsager model, Monte Carlo and QM/MM simulations. Activation parameters indicate the expected variation in activation energy and reaction coordinate in aqueous phase in comparison to the gas phase. The free energy perturbation calculation from Monte Carlo simulation yielded the profiles along a reaction coordinate. Free energies of activation have been computed to be in close agreement with experimental values
  4. Keywords:
  5. Cyclic voltammetry ; Acetaminophen ; Dimethylamine ; Ab initio ; Monte Carlo ; Onsager model
  6. Source: International Journal of Electrochemical Science ; Vol.3, Issue 10 , September , 2008 , PP. 1092-1107 ; 14523981
  7. URL: http://www.electrochemsci.org/papers/vol3/3101092.pdf