Unimolecular Rearrangements and Fragmentations in the Gas Phase: [1,3] Sigmatropic Isomerizations and [2 + 2] Cycloreversions

2003 ◽  
Vol 56 (5) ◽  
pp. 453 ◽  
Author(s):  
Mohammad R. Ahmad ◽  
Steven R. Kass
Keyword(s):  
Gas Phase ◽  
Wide Temperature Range ◽  
Variable Temperature ◽  
Collision Induced Dissociation ◽  
Triple Quadrupole ◽  
Flowing Afterglow ◽  
Temperature Range ◽  
Sigmatropic Rearrangements ◽  
Ion Molecule Reactions ◽  
Trimethylsilyl Ethers

Trimethylsilyl ethers of 3-buten-2-ol, 1-vinylcyclopropanol, 1-vinylcyclobutanol, and cyclobutanol were treated with fluoride over a wide temperature range (–40 to 300°C) in a variable-temperature flowing afterglow–triple quadrupole device. The structures of the resulting alkoxides and enolates were probed by ion–molecule reactions and their collision-induced dissociation (CID) spectra. Activation energies were obtained for several anion-accelerated [1,3] sigmatropic rearrangements and [2 + 2] cycloreversions. The mechanisms for these isomerizations and fragmentations (stepwise versus concerted) and their synthetic potential are discussed.

The bond dissociation energies of SO3—X– (X = F, Cl, Br, and I)

2005 ◽  
Vol 83 (11) ◽  
pp. 2013-2019 ◽  
Author(s):  
Changtong Hao ◽  
Thomas M Gilbert ◽  
Lee S Sunderlin
Keyword(s):  
Gas Phase ◽  
Lewis Acids ◽  
Basis Sets ◽  
Collision Induced Dissociation ◽  
Bond Dissociation Energies ◽  
Flowing Afterglow ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Upper Limit ◽  
Bond Strengths

The gas-phase strengths of the SO3—X- bonds (X = Cl, Br, and I) have been determined to be 222 ± 13, 179 ± 11, and 161 ± 9 kJ/mol, respectively, by measuring thresholds for collision-induced dissociation in a flowing afterglow-tandem mass spectrometer. An upper limit of D(SO3—F–) ≤ 488 ± 19 kJ/mol was also determined. The periodic trends in the halide affinities of SO3 closely parallel those for SO2 and other Lewis acids. Bond strengths computed using the B3LYP, MP2, QCISD(T), and other models with several basis sets are generally lower than experiment.Key words: bond dissociation energies, computational chemistry, Lewis acids, superacids, halide affinities.

scholarly journals Gas-phase structure and reactivity of the keto tautomer of the deoxyguanosine radical cation

2015 ◽  
Vol 17 (39) ◽  
pp. 25837-25844 ◽  
Author(s):  
Linda Feketeová ◽  
Bun Chan ◽  
George N. Khairallah ◽  
Vincent Steinmetz ◽  
Philippe Maître ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Computational Chemistry ◽  
Gas Phase ◽  
Radical Cation ◽  
Phase Structure ◽  
Collision Induced Dissociation ◽  
Ion Molecule Reactions ◽  
Gas Phase Structure

Gas-phase IR spectroscopy, ion–molecule reactions, collision-induced dissociation and computational chemistry in combination form a powerful tool to gain insights into the structure of one-electron oxidised guanine in DNA and its resultant chemistry.

Kinetics of isobaric ion/molecule reactions determined by the flowing afterglow-triple quadrupole technique

1993 ◽  
Vol 7 (5) ◽  
pp. 383-391 ◽  
Author(s):  
Mark D. Brickhouse ◽  
Leonard J. Chyall ◽  
Lee S. Sunderlin ◽  
Robert R. Squires
Keyword(s):  
Triple Quadrupole ◽  
Flowing Afterglow ◽  
Ion Molecule Reactions ◽  
Kinetics Of

Some ion-molecule reactions of hydrogen cyanide

1978 ◽  
Vol 31 (5) ◽  
pp. 963 ◽  
Author(s):  
CG Freeman ◽  
PW Harland ◽  
JP Liddy ◽  
MJ McEwan
Keyword(s):  
Gas Phase ◽  
Hydrogen Cyanide ◽  
Rate Coefficient ◽  
Rate Coefficients ◽  
Flowing Afterglow ◽  
Ion Molecule Reactions ◽  
Positive Ions

Rate coefficients for the reactions of several positive ions with HCN in the gas phase have been measured by the flowing afterglow technique. The reactions are all of the form ������������������������ X++HCN → products . where X+ and the corresponding rate coefficient, in units of cm3 molecule-1 s-1, are: X+ = HCN+ (k 9.8×10-10); C2N+ (k 3.1×10-10); CN+ (k 2.8×10-9 CH+ (k 3.2×10-9); H3O+ (k 4.5×10-9 and HCO+ (k 3.9×10-9).

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