Theoretical Study of X−H Bond Energetics (X = C, N, O, S):  Application to Substituent Effects, Gas Phase Acidities, and Redox Potentials

1999 ◽  
Vol 103 (11) ◽  
pp. 1653-1661 ◽  
Author(s):  
G. A. DiLabio ◽  
D. A. Pratt ◽  
A. D. LoFaro ◽  
J. S. Wright
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects ◽  
Redox Potentials ◽  
S Application

Theoretical study of substituent effects on the gas-phase stabilities of phenoxide anions

2012 ◽  
Vol 26 (2) ◽  
pp. 115-123 ◽  
Author(s):  
Kazuhide Nakata ◽  
Mizue Fujio ◽  
Kichisuke Nishimoto ◽  
Yuho Tsuno
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects

Theoretical Study of Substituent Effects on the Gas-Phase Acidities of Benzoic and Phenylacetic Acids

ChemPlusChem ◽  
2013 ◽  
Vol 78 (9) ◽  
pp. 1099-1108 ◽  
Author(s):  
Kazuhide Nakata ◽  
Mizue Fujio ◽  
Kichisuke Nishimoto ◽  
Yuho Tsuno
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects

THEORETICAL STUDY OF THE SUBSTITUENT EFFECTS ON THE REACTION ENTHALPIES OF THE ANTIOXIDANT MECHANISMS OF STOBADINE DERIVATIVES IN THE GAS-PHASE AND WATER

2013 ◽  
Vol 12 (02) ◽  
pp. 1250116 ◽  
Author(s):  
MEYSAM NAJAFI ◽  
MOHAMMAD NAJAFI ◽  
HOUSHANG NAJAFI
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects ◽  
Partial Charge ◽  
Action Mechanisms ◽  
Dissociation Enthalpy ◽  
Proton Dissociation ◽  
Highest Occupied Molecular Orbital ◽  
Phase Water ◽  
Antioxidant Mechanisms

In this paper the reaction enthalpies of three antioxidant action mechanisms, HAT, SET–PT, and SPLET, for mono-substituted Stobadines were calculated in gas-phase and water. Results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. Results show that IP and BDE values can be successfully correlated with the indolic N–H bond length after electron abstraction, R(N–H+•), and the partial charge on the indolyl radical nitrogen atom, q( N ). Furthermore, calculated IP and PA values for mono-substituted Stobadines show linear dependence on the energy of the highest occupied molecular orbital (E HOMO ) of studied molecules in the two environments. SPLET represents the thermodynamically preferred mechanism in water.

Theoretical study of substituent effects on the geometry and strain enthalpy in [2,2]paracyclophanes

2016 ◽  
Vol 9 (1) ◽  
pp. 6-13 ◽  
Author(s):  
Martin Michalík ◽  
Peter Poliak ◽  
Vladimír Lukeš
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Theoretical Study ◽  
Substituent Effects ◽  
Functional Theory ◽  
Out Of Plane ◽  
Phenyl Rings ◽  
Strain Enthalpy ◽  
Substituent Constants ◽  
Repulsive Forces

Abstract The substituent effect on the geometry and strain enthalpy of [2,2]paracyclophane is theoretically investigated by density functional theory. Gas-phase calculations were performed for twenty distinct electron donating and electron withdrawing substituents. The largest out-of-plane distortion of phenyl rings is exhibited by —SCN and —CF3 groups. On the other hand, —OH, —CH3 and —F groups show the minimal deformation. The strain enthalpy for unsubstituted [2,2]paracyclophane associated with repulsive forces between phenyl units reached up to 118.5 kJ mol−1. Any substitution causes increase of the strain enthalpy value proportionally to the absolute values of Hammett para-substituent constants. Two separate linear dependences with similar slopes were obtained for monosubstituted as well as double symmetrically substituted derivatives.

Correlation of the photoelectron and electronic spectra of thiochromones and thiochromanones with their electrochemical data

1979 ◽  
Vol 57 (6) ◽  
pp. 638-644 ◽  
Author(s):  
Rafik O. Loutfy ◽  
Ian W. J. Still ◽  
Michael Thompson ◽  
Toong S. Leong
Keyword(s):  
Gas Phase ◽  
Substituent Effects ◽  
Spectroscopic Properties ◽  
Oxidation Potential ◽  
Molecular Orbitals ◽  
Absolute Difference ◽  
Linear Free Energy Relationship ◽  
Redox Potentials ◽  
Reduction Potentials ◽  
Oxidation Potentials

The gas phase ionization potentials, electrochemical redox potentials and spectroscopic properties of a series of thiochroman-4-one and thiochromone derivatives have been studied. A dramatic shift in the energies of the lowest vacant and highest occupied molecular orbitals of the parent thiochromanone as a function of the addition of a double bond and/or oxidation of the sulphur atom was observed. This shift in energy of the molecular orbitals was reflected in their spectroscopic characteristics. The lowest singlet (and triplet) state of compounds 1–3 in solution is π,π* in nature, while that of compounds 4–6 is n,π*. These results are best explained in terms of substituent effects on the energetics of the acetophenone moiety. The change in the nature of the lowest excited state from π,π* (1–3) to n,π* (4–6) should result in quite different types of photochemistry for the two series.A linear free-energy relationship between the singlet and triplet energies and the absolute difference between the oxidation and reduction potentials of the two series was found. These correlations have been utilized to estimate the half-wave oxidation potentials of compounds 3–6. A correlation was found to exist between the gas phase ionization potential and the solution electrochemical oxidation potential.

Theoretical study of substituent effects on gas-phase stabilities of benzylic anions

2010 ◽  
Vol 23 (11) ◽  
pp. 1057-1065 ◽  
Author(s):  
Kazuhide Nakata ◽  
Mizue Fujio ◽  
Kichisuke Nishimoto ◽  
Yuho Tsuno
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects
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