Experimental and theoretical study of the reaction system of 2NO_2?N_2O_4 and some fluorinated derivatives of tert-butanol in the gas phase

摘要

The reversible reaction between NO_2/N_2O_4 and CF_3C(CH_3)_2OH has been studied using UV–Vis spectrophotometry. The final product -CF_3C(CH_3)_2ONO- of this reaction was identified by its UV spectrum in the wavelength range of 340–420 nm. The absorption spectrum of CF_3C(CH_3)_2ONO was recorded and the values of the absorption cross sections for prominent bands at 354.0; 367.5; 390.0 nm were derived. The kinetics of the reaction has been investigated in the temperature range of 298–358 K to follow the NO_2 decay in a real time of the reaction. The rate constant for the forward k_5 as well as for the reverse k_6 reaction has been obtained and their values at 298 K are: 10(-19) k_5/cm~3 molecule~(-1) s~(-1) 1.4 ± 0.3 and 10(-19) k_6/cm~3 molecule~(-1) s~(-1) 15.0 ± 4.0. From the temperature dependence of the rate constants the activation energy for the forward E5 and for the reverse E6 reaction has been calculated. It was proposed that the reaction mechanism is complex and N_2O_4 is the reactive species. The UV–Vis spectra have for all studied compounds been calculated. The possible reason of absence of the reaction between (CF_3)_3COH, CH_3C(CF_3)_2OH and N_2O_4 has been proposed. All possible stable conformers of studied moieties have been obtained. Molecular Electrostatic Potential Surfaces (MEPS) of all structures have been derived.