Methyl Substituent Effects in [HnX∴XHn]+Three-Electron-Bonded Radical Cations (X = F, O, N, Cl, S, P;n= 1−3). An ab Initio Theoretical Study

2002 ◽  
Vol 124 (10) ◽  
pp. 2371-2378 ◽  
Author(s):  
Benoît Braïda ◽  
Sandrine Hazebroucq ◽  
Philippe C. Hiberty
Keyword(s):  
Ab Initio ◽  
Theoretical Study ◽  
Substituent Effects ◽  
Radical Cations ◽  
Methyl Substituent

Magnesium porphyrin radical cations: a theoretical study of substituent effects on the ground state

1992 ◽  
Vol 114 (24) ◽  
pp. 9538-9544 ◽  
Author(s):  
A. Geoffrey Skillman ◽  
Jack R. Collins ◽  
Gilda H. Loew
Keyword(s):  
Ground State ◽  
Theoretical Study ◽  
Substituent Effects ◽  
Radical Cations

Excited states in polyene radical cations. An ab initio theoretical study

1995 ◽  
Vol 236 (1-2) ◽  
pp. 167-176 ◽  
Author(s):  
M.P. Fülscher ◽  
S. Matzinger ◽  
T. Bally
Keyword(s):  
Ab Initio ◽  
Excited States ◽  
Theoretical Study ◽  
Radical Cations

Methyl substituent effects in protonated aliphatic amines and their radical cations

1972 ◽  
Vol 94 (13) ◽  
pp. 4728-4729 ◽  
Author(s):  
W. G. Henderson ◽  
M. Taagepera ◽  
D. Holtz ◽  
R. T. McIver ◽  
J. L. Beauchamp ◽  
...  
Keyword(s):  
Substituent Effects ◽  
Radical Cations ◽  
Aliphatic Amines ◽  
Methyl Substituent

Electrostatic effects on ionization equilibria: An MNDO study of proton and hydrogen transfer reactions of 4-fluorobutylamine

1990 ◽  
Vol 55 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Zdeněk Friedl ◽  
Stanislav Böhm
Keyword(s):  
Hydrogen Transfer ◽  
Substituent Effects ◽  
Radical Cations ◽  
Transfer Reactions ◽  
Protonated Forms ◽  
Minor Part ◽  
Bond Strengths ◽  
Ionization Equilibria ◽  
A Minor ◽  
Gas Phase Basicities

The relative enthalpies of proton transfer δ ΔH0and homolytic bond strengths δDH0(B-H+) were calculated by the MNDO method for the sp and ap conformers of 4-flurobutylamine. The data obtained, along with the experimental gas phase basicities, are compared with the values predicted by the electrostatic theory. It is shown that the substituent polar effects FD on the basicities of amines are predominantly due to interactions in their protonated forms (X-B-H+) and/or radical-cations (X-B+.), those in the neutral species (X-B) playing a minor part. A contribution, which is considerably more significant in the sp conformer than in the ap conformer, arises probably also from substituent effects on the homolytic bond strength DH0(B-H+.

A Combined ab initio and Density Functional Study of the Electronic Structure of Thymine and 2-Thiothymine Radicals

2003 ◽  
Vol 68 (12) ◽  
pp. 2322-2334 ◽  
Author(s):  
Robert Vianello ◽  
Zvonimir B. Maksić
Keyword(s):  
Ab Initio ◽  
Spin Density ◽  
Density Functional ◽  
Radical Cations ◽  
Functional Study ◽  
Theory Approach ◽  
Functional Theory ◽  
Adiabatic Ionization Potential ◽  
Highest Occupied Molecular Orbital ◽  
Positively Charged

The electronic and energetic properties of thymine (1) and 2-thiothymine (2) and their neutral and positively charged radicals are considered by a combined ab initio and density functional theory approach. It is conclusively shown that ionization of 1 and 2 greatly facilitates deprotonation of the formed radical cations thus making the proton transfer between charged and neutral precursor species thermodynamically favourable. The adiabatic ionization potential of 1 and 2 are analysed. It appears that ADIP(1) is larger than ADIP(2) by 10 kcal/mol, because of greater stability of the highest occupied molecular orbital (HOMO) of the former. It is also shown beyond any doubt that the spin density in neutral and cationic radical of 2 is almost exclusively placed on the σ-3p AO of sulfur implying that these two systems represent rather rare sigma-radicals. In contrast, the spin density of radicals of 1 is distributed over their π-network.

scholarly journals Substituent Effects on EI-MS Fragmentation Patterns of 5-Allyloxy-1-aryl-tetrazoles and 4-Allyl-1-aryl-tetrazole-5-ones; Correlation with UV-Induced Fragmentation Channels

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3282
Author(s):  
Alina Secrieru ◽  
Rabah Oumeddour ◽  
Maria L. S. Cristiano
Keyword(s):  
Theoretical Calculations ◽  
Substituent Effects ◽  
Radical Cations ◽  
Electronic Effects ◽  
Diverse Range ◽  
The Matrix ◽  
Electron Impact Mass ◽  
Fragmentation Patterns ◽  
Tetrazole Derivatives ◽  
Impact Mass

1,4- and 1,5-disubstituted tetrazoles possess enriched structures and versatile chemistry, representing a challenge for chemists. In the present work, we unravel the fragmentation patterns of a chemically diverse range of 5-allyloxy-1-aryl-tetrazoles and 4-allyl-1-aryl-tetrazolole-5-ones when subjected to electron impact mass spectrometry (EI-MS) and investigate the correlation with the UV-induced fragmentation channels of the matrix-isolated tetrazole derivatives. Our results indicate that the fragmentation pathways of the selected tetrazoles in EI-MS are highly influenced by the electronic effects induced by substitution. Multiple pathways can be envisaged to explain the mechanisms of fragmentation, frequently awarding common final species, namely arylisocyanate, arylazide, arylnitrene, isocyanic acid and hydrogen azide radical cations, as well as allyl/aryl cations. The identified fragments are consistent with those found in previous investigations concerning the photochemical stability of the same class of molecules. This parallelism showcases a similarity in the behaviour of tetrazoles under EI-MS and UV-irradiation in the inert environment of cryogenic matrices of noble gases, providing efficient tools for reactivity predictions, whether for analytical ends or more in-depth studies. Theoretical calculations provide complementary information to articulate predictions of resulting products.

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