Kinetic and equilibrium study of the deprotonation of 4-nitrophenyl[bis(ethylsulphonyl)]methane by organic bases in acetonitrile in the presence of common cation BH+ and tetrabutylammonium perchlorate

Abstract

The results of kinetic and equilibrium experiments with the set of reaction of proton abstraction from 4-nitrophenyl[bis(ethylsulphonyl)]methane in acetonitrile are reported. Two strong organic bases are used: 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). The rates of proton transfer reaction have been measured by T-jump method in the presence of perchlorate of the appropriate base as a common cation BH+ and supporting electrolyte - tetrabutylammonium perchlorate (TBAP) in the temperature range between 20-40 °C are: kH = 1.32×107 - 2.00×107 and 2.82×107 - 4.84×107 dm3mol-1s-1 for MTBD and TBD respectively. The enthalpies of activation ΔHMTBD≠ = 13.5 and ΔHTBD≠= 18.1 kJmol-1. The entropies of activation are negative: ΔSMTBD≠ = -62.3 and ΔSTBD≠ = -40.3 Jmol-1K-1. The change of the absorbance of the anion of 4-nitrophenyl[bis(ethylsulphonyl)]methane at the temperature 25 °C in the presence of common cation BH+ gives the equilibrium constants K = 705 and 906 M-1 for MTBD and TBD respectively. Kinetic and equilibrium results are discussed. The possible mechanism of proton transfer reaction between 4-nitrophenyl[bis(ethylsulphonyl)]methane and cyclic organic bases: MTBD and TBD in acetonitrile is proposed. © Central European Science Journals. All rights reserved.