J. Sehested

Stability and infrared spectra of mono-, di-, and trichloromethanol

Abstract CH 2 ClOH, CHCl 2 OH, and CCl 3 OH were prepared by UV irradiation of CH 3 OH/Cl 2 /N 2 gas mixtures. Absorption cross-sections (base e) of σ (CH 2 ClOH) at 1093 cm −1 =6.16×10 −19 , σ (CHCl 2 OH) at 1109 cm −1 =1.22×10 −18 , and σ (CCl 3 OH) at 1119 cm −1 =8.96×10 −19 cm 2 molecule −1 were determined. The chlorinated methanols decayed with first-order kinetics to HCl and the corresponding carbonyl compound. The decay rates increased with increased contact of the chloromethanols with the reactor walls, indicating that decomposition is heterogeneous. An upper limit of 1.05×10 −2 s −1 was established confirm this slow rate of homogeneous decomposition.

UV–visible spectrum of the phenyl radical and kinetics of its reaction with NO in the gas phase

Abstract Pulse radiolysis transient UV–visible absorption spectroscopy was used to study the UV–visible absorption spectrum (225–575 nm) of the phenyl radical, C 6 H 5 (⋅), and kinetics of its reaction with NO. Phenyl radicals have a strong broad featureless absorption in the region of 225–340 nm. In the presence of NO phenyl radicals are converted into nitrosobenzene. The phenyl radical spectrum was measured relative to that of nitrosobenzene. Based upon σ (C 6 H 5 NO) 270xa0nm =3.82×10 −17 cm 2 molecule −1 we derive an absorption cross-section for phenyl radicals at 250 nm, σ (C 6 H 5 (⋅)) 250xa0nm =(2.75±0.58)×10 −17 cm 2 molecule −1 . At 295 K in 200–1000 mbar of Ar diluent k (C 6 H 5 (⋅)+NO)=(2.09±0.15)×10 −11 cm 3 molecule −1 s −1 .

Atmospheric chemistry of 1,4-dioxane

A pulse radiolysis technique was used to measure the UV absorption spectra of c-C n 4 nH n 7 nO n 2 n and (c-C n 4 nH n 7 nO n 2 n)O n 2 n radicals over the range 220–320 nm, σ(c-C n 4 nH n 7 nO n 2 n) n 250nm n = (5.9 ± 0.6) × 10 n −18 n and σ[(c-C n 4 nH n 7 nO n 2 n)O n 2 n] n 240nm n = (4.8 ± 0.8) × 10 n −18 cm n 2 n molecule n −1 n. The observed self-reaction rate constants for the c-C n 4 nH n 7 nO n 2 n and (c-C n 4 nH n 7 nO n 2 n)O n 2 n radicals, defined as −d[c-C n 4 nH n 7 nO n 2 n]/dt = 2k n 4 n[c- C n 4 nH n 7 nO n 2 n] n 2 n and −d[(c-C n 4 nH n 7 nO n 2 n)O n 2 n]/dt = 2k n 5obs n[(c-C n 4 nH n 7 nO n 2 n)O n 2 n] n 2 n were k n 4 n = (3.3 ± 0.4) × 10 n −11 and k n 5obs n = (7.3 ± 1.2) × 10 n −1 2 n cm n 3 n molecule n −1 n s n −1 n. The rate constants for reactions of (c-C n 4 nH n 7 nO n 2 n)O n 2 n radicals with NO and NO n 2 n were k n 6 n (1.2 ± 0.3) × 10 n −11 n and k n 7 n = (1.3 ± 0.3) × 10 n −11 cm n 3 n molecule n −1 n s n −1 n, respectively. The rate constants for the reaction of F atoms with 1,4-dioxane and the reaction of c-C n 4 nH n 7 nO n 2 n radicals with O n 2 n, were k n 3 n = (2.4 ± 0.7) × 10 n −10 and k n 2 n = (8.8 ± 0.9) × 10 n −12 cm n 3 n molecule n −1 n s n −1 n, respectively. A relative rate technique was used to measure the rate constant for the reaction of Cl atoms with 1,4-dioxane, k n 17 n = (2.0 ± 0.3) × 10 n −10 cm n 3 n molecule n −1 n s n −1 n. A long-pathlength FTIR spectrometer coupled to a smog chamber system was used to show that the sole atmospheric fate of the alkoxy radical (c-C n 4 nH n 7 nO n 2 n)O is decomposition via C–C bond scission leading to the formation of H(O)COCH n 2 nCH n 2 nOC(O)H (ethylene glycol diformate).

Atmospheric chemistry of CFC replacement compounds : synthesis of bis(trifluoromethyl) trioxide and anomalies in its mass spectral analysis

Abstract The photolysis of CF 3 H/F 2 /O 2 mixtures is shown to be a rapid and simple method for the production of pure samples of CF 3 O 3 CF 3 . Complications associated with the mass spectrometric analysis of CF 3 O 3 CF 3 are highlighted.