19252-53-0Relevant articles and documents
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 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.
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.
