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

摘要

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-1,5,7triazabicyclo[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: k_H = 1.32 × 107 – 2.00 × 107 and 2.82 × 107 – 4.84 × 107 dm3 mol– 1 s– 1 for MTBD and TBD respectively. The enthalpies of activation H_MTBD = 13.5 and H_TBD = 18.1 kJmol–1. The entropies of activation are negative: S&ne:_MTBD = -62.3 and S_TBD = -40.3 Jmol–1 K–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.