Kyriakos G. Kambanis

Absolute reaction rate of chlorine atoms with iodomethane

Abstract The reaction of atomic chlotine with iodomethane was studied in the gas phase with the very low pressure reactor technique over the temperature range 273–363 K. The absolute rate constant was given by the expression k = (1.33 ± 0.49) × 10−11 exp [ −(573 ± 1.00 kJ mol −1 RT ] cm 3 molecule −1 s −1 . The reaction proceeds through an intermediate weakly bound adduct CH3ICl and results in the formation of HCl and iodomethyl radical CH2I. The kinetic isotope effect k H k D of the reaction was independent of temperature and found to be 1.09 ± 0.4.

Ab initio computational study of the interaction of Cl atoms with HI, CH3I and CH3OCH2I

Abstract Ab initio calculations at the MP2/3–21 + + G(2d,2p) level of theory suggest that the interaction of chlorine atoms with RI (R = H, CH 3 and CH 3 OCH 2 ) molecules leads to weakly bound adducts with potential energy wells of −31.839, −57.749 and −59.760 kJ mol −1 , respectively. The corresponding standard enthalpies of the adduct formation reactions at 298 K were calculated to be −31.056, −52.409 and −51.337 kJ mol −1 . The structure of the parent RI molecules were only slightly perturbed during the chlorine atom attachment to the iodine atom. The ICl bond length was always found to be ca. 2.8 A and the RICl angle was close to 80°.

Kinetic studies of the reaction of Cl atoms with SiH4

The reaction kinetics of chlorine atoms with silane has been studied over the temperature range 273–363 K using the very low pressure reactor technique. The reaction proceeds via a hydrogen-atom abstraction and leads to SiH3 and HCl products. The absolute rate constant was found to be independent of temperature with a value k1=(3.25 ± 0.40)× 10–10 cm3 molecule–1 s–1. Ab initio calculations at the MP2/6–311G(d,p) level of theory did not show any evidence for the formation of an intermediate SiH4–Cl adduct. The thermochemical version of conventional transition-state theory indicated that the transition-state geometry is almost linear, with a Si—H—Cl angle of ca. 170°.

Gas phase reaction kinetics of Cl atoms with ICH2OCH3

Abstract The reaction of chlorine atoms with iodomethyl-methyl ether ICH 2 OCH 3 was studied over the temperature range 273–363 K using the very low pressure reactor technique. The absolute rate constant was measured at various temperatures, and was given by the expression k = (1.53 ± 0.82) × 10 −11 exp[(1.49 ± 0.60 kcal mol −1 )/ RT ] cm 3 molecule −1 s −1 . The negative temperature dependence of the rate constant suggests that the reaction proceeds via an intermediate adduct, ClICH 2 OCH 3 , which further decomposes unimolecularly and yields HCl. Moreover, HCl may be produced via a direct hydrogen abstraction pathway.

Kinetic studies of the reaction of Cl atoms with CH3SSCH3

The reaction of Cl atoms with dimethyl disulfide, CH3SSCH3, was studied in the gas phase and over the temperature range 273–363 K with the very low pressure reactor (VLPR) technique. The reaction proceeds via two competing pathways: (a) hydrogen atom abstraction that produces CH3SSCH2 radicals, with a rate given by the expression k1a=(1.83 ± 0.08)× 10–10 exp [–(2.43 ± 0.21)/RT] cm3 molecule–1 s–1, (R in kJ mol–1 K–1, 2σ uncertainty); and (b) an intermediate adduct CH3S(Cl)SCH3 formation channel, which further leads to CH3SCl and CH3S products, its rate is given by the expression k1b=(5.17 ± 0.32)× 10–11 exp [(3.39 ± 0.29)/RT] cm3 molecule–1 s–1. The branching ratio k1a/k1b was found to be 0.35 at room temperature and low pressure conditions.