Kinetics of the reactions of halogenated methyl radicals (CF₃, CF₂Cl, CFCl₂, and CCl₃) with molecular chlorine

Abstract

The kinetics of four gas-phase reactions involving halogenated methyl radicals (R,==CF,, CF2C1, CFCI,, and eel,) with molecular chlorine have been studied using a tuhular reactor coupled to a photoionization mass spectrometer. The radicals were homogeneously generated by the pulsed photolysis of precursor molecules at 193 nm. The subsequent decays of the radical concentrations were monitored in real-time experiments as a function of Clz concentration to obtain the rate constants of these R + C1, reactions.Where possible, the rate constants were measured as a function of temperature to determine Arrhenius parameters. Apparent discrepancies between these measiired rate constants for CF, and CCl, with Clz and ones obtained in prior indirect studies are explained.The higher activation energies for these R + Clz reactions compared to that of the CH, + Clz reaction are attributed in part to the different polarities of the transition states formed.

An Experimental Study of the Kinetics of the Reactions of Isopropyl,sec-Butyl, andtert-Butyl Radicals with Molecular Chlorine at Low Pressures (0.5-7.0 Torr) in the Temperature Range 190-480 K

“…sum of the Hammett σ p constants of the three substituents (see Table S1 in the Supporting Information). We combined our current measurements with previous data [4,8,[24][25][26][27][28][29] and plotted k 300 K against ࢣ 3 i = 1 σ p,i . As can be seen from Fig.…”

“…Poutsma observed a good linear correlation between the log 10 ( k 300 K ) value of a reaction and the ∑ 3 i = 1 σ p, i value of the reacting radical, where ∑ 3 i = 1 σ p, i is the sum of the Hammett σ p constants of the three substituents (see Table S1 in the Supporting Information). We combined our current measurements with previous data and plotted k 300 K against ∑ 3 i = 1 σ p, i . As can be seen from Fig.…”

Kinetics of the R+Cl2 (R=CH2Cl, CHBrCl, CCl3 and CH3CCl2) reactions. An ab initio study of the transition states

“…The initial radical concentrations were typically \1 ] 1011 cm~3. Under these conditions, only the following two radical reactions were signiÐcant for the observed 2), ( 3) or ( 4) R ] Heterogeneous loss on the wall (5) Low initial radical concentrations ensured that any reaction between open-shell molecules had negligible rates compared to reactions (1)È( 5). This was veriÐed by measuring wall-loss decays, of the radical under di †erent conditions where the k 5 , radical precursor concentration was held steady but the radical concentration was changed by a factor of two.…”

Boundary continuity and analytical potentials in continuum solvent models. Implications for the Born model

“…Based on this and other considerations, no single function bulk dielectric modification of the type presented, including those with fractional n, appears capable of matching the surprisingly good correlations of solvation free energies reported in ref 13 / )( / )2 and /, and u¡ are the lower and upper radial bounds, relative to cavity size, of this region of solvent within which the dielectric function / ) holds. For dual (solvent) region models, there are two finite boundaries of importance, i.e., /,, at the cavity interface with nearest-neighbor solvent, and u¡ = l2, where the two solvent regions meet, and one u2, at infinity.…”