18851-76-8Relevant articles and documents
Reaction of Atmospheric Ions with Selected Hydrofluorocarbons
Morris, Robert A.,Viggiano, A. A.,Arnold, Susan T.,Paulson, J. F.,Liebman, Joel F.
, p. 5992 - 5999 (1995)
Selected atmospheric ions have been studied for reactivity with the hydrofluorocarbons (HFC's) CF3CH2F, CF3CHFCF3, and CF3CHFCHF2 and with CHBrF2; the reactant ions chosen for study are O+, O2+, O-, O2-, H3O+, H3O+*H2O, H3O+*(H2O)2, NO3-, and NO3-*HNO3.Rate constants and product branching fractions for these ion-molecule reactions were measured using a selected ion flow tube (SIFT) instrument operated at 300 K.The ions O+ and O- reacted at the collisional rates, forming a number of ionic products in most cases.Most of the other reactions studied were found to be inefficient.The ions H3O+ and NO3- reacted inefficiently by association in all cases.The solvated ions H3O+*H2O, H3O+*(H2O)2, and NO3-*HNO3, which are representative of the abundant ionic species in the lower atmosphere, were unreactive with the compounds investigated; we conclude from this that atmospheric ion chemistry is not a significant sink for these HFC's.The observation of proton transfer from CF3CHFCF3 and CF3CHFCHF2 to O- allows a lower bound to the gas-phase acidities of these HFC's to be assigned: ΔHacid(CF3CHFCF3) and ΔHacid(CF3CHFCHF2) -1.
Chemistry of CFn(1+) (n = 1-3) Ions with Halocarbons
Morris, Robert A.,Viggiano, A. A.,Doren, Jane M. Van,Paulson, John F.
, p. 2597 - 2603 (1992)
The gas-phase reactions of CF(1+), CF2(1+), and CF3(1+) with the halocarbons CF3Cl, CF3Br, CF3I, CF4, and C2F6 have been studied using a variable-temperature-selected ion flow tube (VT-SIFT) instrument at 300 and 496 K.The ion CF(1+) reacts rapidly with CF3X (X = Cl, Br, I) producing the ions CF2X(1+).In the reaction of CF(1+) with CF3Cl, CF3(1+) is also produced as a minor product.Curvature was observed in the pseudo-first-order kinetics plots for the reactions of CF(1+) with CF4 and C2F6.In both cases the curvature is attributed to the presence of two or more CF(1+) states (probably vibrational) of differing reactivities toward the perfluorocarbon of interest.This conclusion is supported by our observation of charge transfer from CF(1+) to NO, a reaction which is endothermic by 15 kJ/mol for the ground state of CF(1+).CF(1+) is unreactive with O2, N2, and Xe.The reactions of CF2(1+) with CF3X yield CF3(1+) and CF2X(1+) for X = Cl and Br; for X = I, CF2I(1+) and CF3I(1+) are produced.The overall reactions proceed at approximately the collision rate at 300 and 496 K, and the branching ratios are not strongly dependent on temperature.The reactions of CF2(1+) with CF4 and C2F6 produce CF3(1+) and C2F5(1+), respectively.The rate constants decrease significantly with increasing temperature.CF2(1+) reacts rapidly by charge transfer with NO.The reaction of CF2(1+) with O2, producing CF2O(1+), is inefficient.CF2(1+) is unreactive with N2.CF3(1+) reacts with CF3X (X = Cl, Br, I) at rates below the collision values, producing a single ionic product, CF2X(1+).While the rate constants for the reactions of CF3(1+) with CF3X increase in the series with increasing CF3X mass, the rate constants for reaction with each CF3X decrease sharply with increasing temperature.A mechanism is proposed in which the reaction proceeds on a double-well potential energy surface.No reaction was observed for the CF3(1+)/CF4 system.CF3(1+) appeared to react very slowly with C2F6 and NO, producing C2F5(1+) and NO(1+), respectively, but reactions with impurities in the neutral reagents cannot be ruled out as the source of these ions.CF3(1+) is unreactive with O2 and N2.
Study of the gas phase reactions of several perfluorocarbons with positive ions of atmospheric interest
Jarvis, Gary K.,Mayhew, Chris A.,Tuckett, Richard P.
, p. 17166 - 17174 (2007/10/03)
The bimolecular rate coefficients and ion products for the reactions of H3O+, NO+, O2+, H2O+, N2O+, O+, CO2+, CO+, N+, and N2+ with three fluoroalkenes (C2F4, C3F6, and 2-C4F8) and three fully saturated perfluorocarbons (C2F6, C3F8, and n-C4F10) at 300 K are reported. All six perfluorocarbons are found to be unreactive with NO+. C2F6 is also unreactive with O2+, H2O+, and N2O+, and C3F8 and n-C4F10 are also unreactive with O2+. C3F6 is the only perfluorocarbon studied that reacts with H3O+ at a measurable rate. All the other reactions take place at or close to the collisional rate, the exceptions being the reactions of N2O+ with C2F4 and C3F8, and CO2+ with C2F4 and C2F6, for which the experimental rate coefficients show marked departures from the collisional values. It is proposed that most of the reactions proceed through a complex intermediate resulting in electrophilic attack by the ion on the perfluorocarbon. This mechanism generally takes precedent over "long-range" (formal) charge transfer. This work is of possible relevance to atmospheric ion-chemistry and plasma processes and may also be pertinent to the use of chemical ionization mass spectrometers for the trace detection of perflurocarbons in the environment.
Reactions of Ar+ with halocarbons and of I+ with CF3I
Morris, Robert A.,Doren, Jane M. Van,Viggiano, A. A.,Paulson, John F.
, p. 173 - 179 (2007/10/02)
The gas phase reactions of Ar+ with the halocarbons CF3Cl, CF3Br, CF3I, CF4, C2F6, and C2F4 have been studied using a variable temperature-selected ion flow tube (VT-SIFT) instrument operated at 298 and 500 K.Rate constants and product branching percentages were measured at both temperatures.Ar+ reacts at the collisional rate with all of the above neutrals at both 298 and 500 K.The reactions with CF3X yield CF3+ and CF2X+ for all X (the reaction with CF4 produces only CF3+).For X = I, there is an additional channel leading to the ionic product I+.The reaction of Ar+ with C2F6 produces both CF3+ and C2F5+.The reaction of Ar+ with C2F4 forms a rich product spectrum consisting of the ions CF+, CF2+, CF3+, C2F3+, and C2F4+.The reaction product distributions are compared with results from ionization experiments such as photoion-photoelectron coincidence (PIPECO) and electron impact mass spectrometry, and in some cases excellent agreement is found.The reaction of I+ with CF3I, which is a secondary reaction in the Ar+/CF3I system, was investigated at 298 K in separate experiments.This reaction is rapid and forms four product ions: CF3+, CF2I+, CF3I+, and I2+.The results are compared with previously published information.
