17030-74-9Relevant academic research and scientific papers
Oxidation of alkyl ions, CnH2n+1+ (n = 1-5), in reactions with O2 and O3 in the gas phase
Williams, Skip,Knighton,Midey, Anthony J.,Viggiano,Irle, Stephan,Wang, Qingfang,Morokuma, Keiji
, p. 1980 - 1989 (2007/10/03)
Rate constants and product ion branching fractions are reported for the reactions of CH3+, C2H5+, s-C3H7+, s-C4H9+, t-C4H9+, and t-C5H11+ with O2 and O3 at 300 K in a variable-temperature selected-ion flow tube (VT-SIFT). The reaction rate constant for CH3+ with O3 is large and approximately equal to the thermal energy capture rate constant given by the Su-Chesnavich equation. The C2H5+, s-C3H7+, and s-C4H9+ ions are somewhat less reactive, reacting at approximately 7-46% of the thermal capture rate. The HCO+ and C2H3O+ ions are the major products in these reactions. The t-C4H9+ and t-C5H11+ ions are found to be unreactive, with rate constants -12 cm3 s-1, which is the present detection limit of our apparatus using this ozone source. Ozone is a singlet in its ground state, and ab initio calculations at the B3LYP/6-31G(d) level of theory indicate that reactant complexes can be formed, decreasing in stability with the size of alkyl chains attached to the cationic carbon atom. The decreasing reactivity of the alkyl ions with increasing order of the carbocation is attributed to a greatly reduced O3 binding energy. The ions listed above do not undergo two-body reactions with O2, k -13 cm3 s-1, despite the availability of reaction channels with exothermicities of several hudnred kilojoules per mole. Ab initio calculations at the B3LYP/6-31G(d) level of theory indicate that the O2 reaction systems form weak complexes with large C-O bond distances (repulsive at smaller distances) on the lowest energy triplet potential energy surface. Access to the singlet surface is required for bond formation; however, this surface is not accessible at thermal energies.
Ion - Molecule Reaction Studies of Hydroxyl Cation and Ionized Water with Ethylene
Fishman, Vyacheslav N.,Grabowski, Joseph J.
, p. 4879 - 4884 (2007/10/03)
Rate coefficients and product branching ratios for the ion - molecule reactions of the hydroxyl cation, ionized water, and their deuterated analogues with ethylene have been determined using a selected ion flow tube (SIFT) at room temperature and in 0.5 Torr of helium buffer gas. In all cases, reactions proceed at or near the collision rate. The major product is always charge transfer: 79% for L2O?+and 66% for LO+ and does not depend on the isotopic form of hydrogen present (L = H or D). For the L2O?+ reactions, the remaining 21% of products are from proton or deuteron transfer, with no evidence of an isotope effect on this step even in the HOD?+ reaction. The greater exothermicity of the initial charge transfer in the LO+ reaction is revealed by the observation of additional product channels, forming the vinyl cation and protonated carbon monoxide. Multistep mechanisms that proceed through rate-determining charge-transfer, followed by a product-determining step, are postulated to explain these observations.
Mass-Spectrometric Study on Ion-Molecule Reactions of CF3+ with Monosubstituted Benzenes Carrying a Carbonyl Group at Near-Thermal Energies
Tsuji, Masaharu,Aizawa, Masato,Nishimura, Yukio
, p. 1055 - 1063 (2007/10/03)
The gas-phase ion-molecule reactions of CF3+ with five monosubstituted benzenes carrying a carbonyl group (PhCOX: X=H, CH3, C2H5, OCH3, OC2H5) have been studied at near-thermal energies using an ion-beam apparatus. The major product channel for PhCHO, PhCOCH3, and PhCOOCH3 is electrophilic addition to the O-atom leading to initial adduct ions, which are 80.3 - 95.0% of the total product ions. Although no initial adduct ions are observed for PhCOC2H5 and PhCOOC2H5, major product ions are formed by electrophilic addition to the O-atom followed by dissociation and molecular eliminations. The reaction mechanism is discussed based on product ion distributions and semi-empirical calculations of the energies of intermediates and products. The results obtained are compared with reported-ion-cyclotron-resonance data for aliphatic carbonyl compounds.
Proton affinity and absolute heat of formation of trifluoromethanol
Chyall,Squires
, p. 16435 - 16440 (2007/10/03)
The proton affinity and absolute heat of formation of trifluoromethanol have been derived from translational energy threshold measurements for reactions involving oxygen-protonated trifluoromethanol. The reaction of ionized iodotrifluoromethane with water was used to prepare CF3OH2+ in the flow tube of a flowing afterglow triple-quadrupole instrument. The isomeric cluster ion, (HF)CF2OH+, was shown to be more stable than CF3OH2+ by the base-catalyzed conversion of CF3 OH2+ to (HF)CF2OH+ using either SO2 or OCS as the catalyst. The proton affinity of CF3OH at oxygen was determined from the enthalpy change for the endothermic proton transfer reaction CF3OH2+ + CO → CF3OH + HCO+. The measured enthalpy change, was combined with the known value for the proton affinity of CO (141.9 kcal mol-1) to yield a value for the oxygen proton affinity of CF3OH. The dissociation energy for the loss of water from CF3OH2+ was measured by energy-resolved collision-induced dissociation. This value was used in a thermochemical cycle along with the measured proton affinity of CF3OH to derive the gas-phase heat of formation of CF3OH. This experimental value is slightly lower than, but in good agreement with, the 298 K heat of formation of CF3OH that is predicted by high-level molecular orbital calculations.
