19252-53-0Relevant academic research and scientific papers
12. Gas-phase reactions of aliphatic alcohols with 'bare' FeO+
Schroeder, Detlef,Wesendrup, Ralf,Schalley, Christoph A.,Zummack, Waltraud,Schwarz, Helmut
, p. 123 - 132 (2007/10/03)
Ion/molecule reactions of 'bare' FeO- with linear and branched aliphatic alcohols have been examined by Fourier -transform ion-cyclotron resonance mass spectrometry. Depending on the chain length of the alcohol, three different types of reactions can be distinguished: i) Oxidation of the alcohols in the α-positions, to yield the corresponding carbonl-Fe+ complexes, involves an initial O-H bond activation of the alcohol resulting in the formation of RO-Fe+-OH as the central intermediate. ii) The formation of Fe(OH)+2, concomitant by loss of the corresponding neutral alkenes, competes with the generation of neutral OFeOH and a carbocation R+ These couples point to the existence of an intracomplex acid-base equilibrium and are connected with each other by a proton transfer from either acid to the other, e.g. i-C3H+7 + OFeOH?C3H6 + Fe(OH)+2. The process is driven by the Lewis acidity of FeO+ and starts with the abstraction of a hydroxide anion from the alcohol. iii) For longer alcohols, e.g. pentanol, functionalization of non-activated C-H bonds which are remote from the O functionality is observed. Here, the OH group of the alcohol serves as an anchor, which directs the reactive metal-oxide cation toward a particular site of the hydrocarbon chain.
Ion-Molecule Reaction of CO2+ with Butane and Isobutane at Thermal Energy
Tsuji, Masaharu,Matsumura, Ken-ichi,Funatsu, Tsuyoshi,Nishimura, Yukio,Obase, Hiroshi,et al.
, p. 2864 - 2870 (2007/10/02)
Rate constants and product ion distributions have been determined for thermal energy reactions of CO+2 with n-C4H10 and i-C4H10 by using an ion-beam apparatus.The total rate constants are (9.8+/-2.0)*10-10 and (1.0+/-0.2)*10-9 cm3 s-1 for n-C4H10 and i-C4H10, respectively.These values amount to about 75percent of the collision rate constants estimated from the Langevin theory.C4H+9, C3H+n (n=5-7), and C2H+n (n=3-5) are produced from n-C4H10 with branching ratios of 6, 56, and 38percent, while C4H+9 and C3H+n (n=5-7) are formed from i-C4H10 with branching ratios of 7 and 93percent, respectively.The lack of C2H+n fragments from i-C4H10 is attributed to a low probability of significant rearrangement of chemical bonds for the formation of the C2H+n fragments.The product ion distribution in the CO+2/n-C4H10 reaction is in good agreement with that predicted from the fragmentation pattern of n-C4H+10 at 13.78 eV, indicating that the CO+2/n-C4H10 reaction proceeds through a near-resonant charge transfer without momentum transfer.
Ion-Molecule Reactions of Vibrationally State-Selected NO+ with Small Alkyl Halides
Wyttenbach, Thomas,Bowers, Michael T.
, p. 8920 - 8929 (2007/10/02)
The effects of vibrational excitation in NO+ (v=0-5) on its reactivity with small alkyl halides (CnH2n+1X; n=1-3; X=Cl, Br, I) have been investigated under thermal translational conditions.The method combines resonance enhanced multiphoton ionization to form state-selected NO+(v), and Fourier transform in cyclotron resonance techniques to trap, react, and detect ions.Besides vibrational quenching of NO+(v > 0), which is found to be very efficient with alkyl halides, three reaction channels are observed: charge transfer, halide transfer, and CnH2nNO+ formation.Branching ratios and rate constants have been determined for the different channels as a function of the NO+(v=0) vibrationally energy.Endoergic charge transfer is efficiently driven by vibrational excitation.Halide transfer is the major channel if it is significantly exothermic for NO+(v=0).If this is not the case, adding vibrational energy in NO+(v=0) is only marginally effective in driving this channel.The data suggest that rearrangements in NO+-alkyl halide reaction intermediates and in carbonium ions are very rapid.The CnH2nNO+ formation channel is only observed with n-propyl and isopropyl chloride where it is dominant for NO+(v=0).Increasing vibrational excitation inhibits C3H6NO+ formation.The results are discussed in terms of possible reaction mechanisms.
Hydride-Transfer Reactions. Temperature Dependence of Rate Constants for i-C3H7++HC(CH3)3=C3H8+C(CH3)3+. Clusters of i-C3H7+ and t-C4H9+ with Propane and Isobutane
Sunner, Jan A.,Hirao, Kimihiko,Kebarle, Paul
, p. 4010 - 4016 (2007/10/02)
The rate constant k1 for the hydride-tranfer reaction i-C3H7++i-C4H10=C3H8+t-C4H9+ was measured between 125 and 640 K with a pulsed electron beam high-pressure mass spectrometer.The results for k1 were in good agreement with earlier work of Meot-Ner and Field; however, the transition between the near-collision-limit near-temperature-independent rate constant at low temperature and the negative temperature dependence at high temperature was found to be more gradual.Theoretical calculations of the energy of the reaction complex with the STO-3G basis set, along the reaction coordinate obtained from the MNDO method, indicate that the potential does not have an internal barrier, i.e. is not of the double-well type.This result is consistent with the fact that no stabilised C3H7+*C4H10 complexes were found even at the lowest temperatures used.In mixtures of propane and isobutane, three other adducts were formed: C3H7+*C3H8, C4H9+*C4H10 and C4H9+*C3H8.The third-order rate constants and the ΔH0 and ΔS0 values for the formation of these complexes were determined.A semiempirical treatment of k1 based on the assumption that the back dissociation (kb) of the excited collision complex (C3H7+*C4H10)* can be approximated by that for (C3H7+*C3H8)* leads to a prediction for the temperature dependence of the rate constant for the unimolecular decomposition of (C3H7+*C4H10)* in the product channel (kp).This analysis indicates that only a gradual transition is expected for k1 and that the actual collision limit is reached only at very low temperatures.
Stabilities of Halonium Ions from a Study of Gas-Phase Equilibria R(1+)+XR'=(RXR')(1+)
Sharma, Dilip K. Sen,Hoejer, Sarah Meza de,Kebarle, Paul
, p. 3757 - 3762 (2007/10/02)
The gas-phase ion equilibria R(1+)+B=RB(1+), where R(1+)=Et(1+), i-Pr(1+), c-Pe(1+), t-Bu(1+), 2-Me-2-Bu(1+), and 2-Nb(1+) and B=CH3Cl, CH2Cl2, CHCl2, CHCl3, SO2F2, CF3H, and CF4 were determined in a pulsed electron beam high pressure mass spectrometer. van't Hoff plots provide ΔG0300, ΔH0, and ΔS0.For the chloronium ions the following trends were observed.The bond energy D(R(1+)-ClR0), where R(1+) changes and R0 is constant, decreases with increasing electronic stabilization of R(1+), i.e., in the order Me(1+), Et(1+), i-Pr(1+), c-Pe(1+), t-Bu(1+), Nb(1+).The same order was observed earlier in this laboratory for D(R(1+)-Cl(1-)), i.e., the chloride affinity of R(1+).However, the changes of D(R(1+)-ClR0) for R(1+)=2-Me-2-Bu(1+), Nb(1+), and t-Bu(1+) are very small.This means that little differential, specific nucleophilic solvation of these ions in solution is to be expected when solvents of low nucleophilicity like CH2Cl2 and SO2ClF are used.The bond energies D(Me(1+)-ClR) increase in the order R=Me, Et, i-Pr, t-Bu.The bond energies D(t-Bu(1+)-B) decrease in the order B=C2H5Cl, CH2Cl2 ca.CH3Cl, CCl3H, SO2F2, CF3H, CF4.The significance of these trends is discussed.
