Bond Dissociation Energies of the N−H Bond and Rate Constants for the Reaction with Alkyl, Alkoxyl, and Peroxyl Radicals of Phenothiazines and Related Compounds

1999 ◽  
Vol 121 (49) ◽  
pp. 11546-11553 ◽  
Author(s):  
Marco Lucarini ◽  
Pamela Pedrielli ◽  
Gian Franco Pedulli ◽  
Luca Valgimigli ◽  
Didier Gigmes ◽  
...  
Keyword(s):  
Rate Constants ◽  
Peroxyl Radicals ◽  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Related Compounds

scholarly journals Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations

2020 ◽  
Author(s):  
Abdul Malik ◽  
Riccardo Spezia ◽  
William L. Hase
Keyword(s):  
Internal Energy ◽  
Rate Constants ◽  
Activation Energies ◽  
Bond Dissociation Energies ◽  
Excitation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions ◽  
Dynamics Simulations ◽  
Threshold Energies

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Commonly used ions are benzylpyridinium ions with different substituents. More recently benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems; para-methyl-benzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). The theoretical bond dissociation energies match closely with the experiment. Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations.

scholarly journals Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations

2020 ◽  
Author(s):  
Abdul Malik ◽  
Riccardo Spezia ◽  
William L. Hase
Keyword(s):  
Internal Energy ◽  
Rate Constants ◽  
Activation Energies ◽  
Bond Dissociation Energies ◽  
Excitation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions ◽  
Dynamics Simulations ◽  
Threshold Energies

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Commonly used ions are benzylpyridinium ions with different substituents. More recently benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems; para-methyl-benzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). The theoretical bond dissociation energies match closely with the experiment. Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations.

scholarly journals Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations

2020 ◽  
Author(s):  
Abdul Malik ◽  
Riccardo Spezia ◽  
William L. Hase
Keyword(s):  
Internal Energy ◽  
Rate Constants ◽  
Activation Energies ◽  
Bond Dissociation Energies ◽  
Excitation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions ◽  
Dynamics Simulations ◽  
Threshold Energies

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Commonly used ions are benzylpyridinium ions with different substituents. More recently benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems; para-methyl-benzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). The theoretical bond dissociation energies match closely with the experiment. Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations.

Equilibrium Acidities and Homolytic Bond Dissociation Energies of Acidic C−H Bonds in α-Arylacetophenones and Related Compounds

2002 ◽  
Vol 67 (25) ◽  
pp. 9016-9022 ◽  
Author(s):  
Mikhail S. Alnajjar ◽  
Xian-Man Zhang ◽  
Gerald J. Gleicher ◽  
Scott V. Truksa ◽  
James A. Franz
Keyword(s):  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Related Compounds
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