Thermal Decomposition of CF2ClO2NO2

Article abstract of DOI:10.1021/j100090a015

The temperature and pressure dependence of the thermal decomposition kinetics of CF2ClO2NO2 in the presence of N2 diluent have been investigated over the temperature range 272-289 K and over the total pressure range 3-40 Torr by time-resolved mass spectrometry.The measurements were performed by directly monitoring the molecular ion CF2O2NO2⁺ (m/z=128), a fragment of Cf2ClO2NO2.The CF2ClO2NO2 decay rates are first order, with rate coefficients that are pressure dependent and well into the unimolecular falloff.The rate coefficients at 29 and 10 Torr can be expressed in Arrhenius form as k_d(29 Torr) = (1.1+/-0.8)E16exp<-(98042+/-3465) J mol^-1/RT>s^-1; k_d(10 Torr)=(2.6+/-1.6)E4exp<-(90871+/-2772) J mol^-1/RT> s^-1.The equilibrium constant has been determined to be K(T)=1.36E-28(T/298)^-0.35exp<(100495+/-100) j mol^-1/RT>cm^-3 by combining decomposition rate coefficients with those for the reverse reaction (Int.J.Chem.Kinet. 1991, 23, 701-715).The value of the critical energy, 100 495 J mol^-1, obtained from the equilibrium constant, has permitted a calculation of the limiting high-pressure unimolecular rate coefficient by means of a microcanonical method based on inversion of the interpolated partition function.It may be expressed in Arrhenius form as k_dinfinite=6.7E16exp<-98700 J mol^-1/RT> s^-1.The pressure dependence of the unimolecular rate coefficients was fit by a variational RRKM calculation and by the F_CENT method.The rate coefficients for the reverse reaction were also fit by these two procedures, yielding a unified model of the CF2ClO2NO2 <--> CF2ClO2 + NO2 reaction over a range of temperature and pressure characteristic of the atmosphere.