Kinetic Energy Release and Position of the Transition State for С6Н7+ Ions Produced from Isomeric C7H8O Precursors

1991 ◽  
Vol 46 (12) ◽  
pp. 1021-1025 ◽  
Author(s):  
Ezzat T. M. Selim ◽  
M. A. Rabbih ◽  
M. A. Fahmey
Keyword(s):  
Kinetic Energy ◽  
Transition State ◽  
Energy Release ◽  
Benzyl Alcohol ◽  
Kinetic Energy Release ◽  
Heat Of Formation ◽  
Molecular Ions ◽  
Energy Partitioning ◽  
Endothermic Reaction ◽  
Late Transition

Abstract The energetic requirement and mechanisms for CHO' loss from the molecular ions of isomeric C7H8O precursors have been reported. The heat of formation of [C6H7]+ (protonated benzene) was determined and ε* evaluated. Measurement of the kinetic energy release TB gives the energy-partitioning quotients q= TB/εr* which range from 0.38 to 0.99. The energy available and TB are small for the strongly endothermic reaction of benzyl alcohol but increase sharply in the case of the weakly endothermic reaction of anisole. All reactions have "late" transition states, the position X0*of the transition state on the reaction coordinate varying from 0.64 to 0.93

scholarly journals Ringöffnung CO+- und COOCH3+·-substituierter Cyclopropane und CO-Eliminierung aus isomeren C3H5CO+-Ionen / Ring Opening of CO+ and COOCH3+· Substituted Cyclopropanes and CO Loss from Isomeric C3H5CO+ Ions

1979 ◽  
Vol 34 (3) ◽  
pp. 488-494 ◽  
Author(s):  
Helmut Schwarz ◽  
Chrysostomos Wesdemiotis
Keyword(s):  
Kinetic Energy ◽  
Energy Release ◽  
Ring Opening ◽  
Collisional Activation ◽  
Kinetic Energy Release ◽  
Ester Group ◽  
Molecular Ions ◽  
Peak Shape ◽  
Metastable Peak ◽  
Substituted Cyclopropanes

Abstract The non-decomposing molecular ions of methyl cyclopropanecarboxylate (14) are found to rearrange to ionised methyl but-3-enoate (15). For ions with sufficient internal energy to decompose, this isomerization is in competition with · OCH3 loss, via direct cleavage of the ester group. Collisional activation spectroscopy may be used to distinguish between the C3H5CO+ ions formed by · OCH3 loss from the molecular ions of 14, 15 and other isomeric precursors. Four distinct C3H5CO+ species (18-21) can be identified in this way; these C3H5CO+ ions may themselves decompose, via CO elimination. Consideration of the metastable peak shape for CO loss, in conjunction with collisional activation spectroscopy on the resulting C3H5+ -ions, leads to two main conclusions, (i) Two C3H5+ ions (22 and 27) exist in potential energy wells. The very narrow metastable peaks for CO loss from 19 and 21 (leading to 22 and 27, respectively) show that these processes are continuously endothermic. In contrast, CO loss from either 18 or 20 gives rise to much broader metastable peaks. This suggests that rate-determining rearrangement of the incipient C3H5+ cations, to a more stable isomer, occurs prior to decomposition, (ii) Elimination of CO from the [M- · OCH3]+ fragment of 14 gives rise to a composite metastable peak, thus indicating the occurrence of two competing channels for dissociation. These channels are assigned to CO loss from 18 (larger kinetic energy release) and CO loss from 19 (smaller kinetic energy release).

Kinetic Energy Release and Energy Partitioning During the Ionic Fragmentation in Metastable Ions

1983 ◽  
Vol 38 (5) ◽  
pp. 524-527
Author(s):  
F. H. Abd El-Kader ◽  
M. S. Abd El-Fattah
Keyword(s):  
Kinetic Energy ◽  
Temperature Dependence ◽  
Kinetic Energy Release ◽  
Molecular Ions ◽  
Energy Partitioning ◽  
Unimolecular Decomposition ◽  
Centrifugal Barrier ◽  
Metastable Ions ◽  
Significant Temperature ◽  
Ionic Fragmentation

The kinetic energy released in the unimolecular decomposition of some metastable transitions has been investigated. It was found to have a significant temperature dependence in cases of H‘ loss from molecular ions. This is attributed to the tunelling of H• atom through the centrifugal barrier.The activation energies of the reverse reactions “εr≠” and the kinetic energy released “TB” have been determined for the loss of H• from acetonitrile and elimination of HCN from benzonitrile. The partitioning energy quotients q=TB/εr≠ are found = 0.91 and 0.58 for acetonitrile and benzonitrile respectively.

scholarly journals Low kinetic energy release upon dissociation of benchmark molecular ions

2012 ◽  
Vol 388 (3) ◽  
pp. 032016
Author(s):  
B Gaire ◽  
M Zohrabi ◽  
J McKenna ◽  
A M Sayler ◽  
Nora G Johnson ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Energy Release ◽  
Kinetic Energy Release ◽  
Molecular Ions
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