Electron affinities of substituted nitrobenzenes

1989 ◽  
Vol 67 (4) ◽  
pp. 603-610 ◽  
Author(s):  
S. Chowdhury ◽  
H. Kishi ◽  
G. W. Dillow ◽  
P. Kebarle
Keyword(s):  
High Pressure ◽  
Electron Transfer ◽  
Gas Phase ◽  
Substituent Effects ◽  
Negative Ions ◽  
Radical Anions ◽  
Electron Affinities ◽  
Frontier Orbital ◽  
Data Set ◽  
Qualitative Discussion

The electron affinities of 14 substituted nitrobenzenes including nitrobiphenyls were determined by measurement of electron transfer equilibria [1] in the gas phase with a pulsed high pressure mass spectrometer: A− + B = A + B− [1]. These data, when combined with previous determinations from this laboratory, lead to electron affinities for 35 substituted nitrobenzenes and provide a comprehensive data set for the examination of substituent effects. The data are used to derive Taft gas-phase substituent parameters. A qualitative discussion based on frontier orbital molecular theory examines the substituent effect on the benzene and nitrobenzene LUMOs. The lifetimes for electron autodetachment from excited nitrobenzene negative ions, (A−)*, studied earlier by Christophorou, are examined in light of the present electron affinity data. Keywords: electron affinities, substituent effects, frontier orbital treatment, electron autodetachment from nitrobenzene radical anions.

Electron affinities of aza-substituted polycyclic aromatic hydrocarbons

1989 ◽  
Vol 67 (10) ◽  
pp. 1628-1631 ◽  
Author(s):  
Glen W. Dillow ◽  
P. Kebarle
Keyword(s):  
Electron Transfer ◽  
Gas Phase ◽  
Aromatic Hydrocarbons ◽  
Radical Anions ◽  
Electron Affinities ◽  
Reduction Potentials ◽  
Dilute Gas ◽  
Solvation Energies ◽  
Polycyclic Aromatic ◽  
Electron Reduction

Electron affinities for aza-substituted polycyclic aromatics were determined from measurements of electron transfer equilibria in the dilute gas phase with a pulsed electron high pressure mass spectrometer (PHPMS). These are (in kcal/mol): quinazoline (12.7), quinoxaline (15.8), cinnoline (16.0), acridine (20.3), benzo[c]cinnoline (20.6), pyrido[2,3-b]pyrazine (22.5), phenazine (29.5). Solvation energies of the corresponding radical anions in acetonitrile and dimethylformamide are derived from the gas phase data and literature on electron reduction potentials in solution. An observed linear relationship between the electron affinities and the reduction potentials allows estimates of electron affinities to be made for 12 aza compounds whose EA's are too low to be measured with the present method. Keywords: aza-substituted aromatic hydrocarbons, electron affinities, electron transfer, radical anions, reduction potentials, solvation energies of radical anions, stabilities of radical anions.

Electron affinities of benzaldehydes. Substituent effects on stabilities of aromatic radical anions

1993 ◽  
Vol 34 (26) ◽  
pp. 4223-4226 ◽  
Author(s):  
Masaaki Mishima ◽  
Chul Huh ◽  
Hirotaka Nakamura ◽  
Mizue Fujio ◽  
Yuho Tsuno
Keyword(s):  
Substituent Effects ◽  
Radical Anions ◽  
Electron Affinities ◽  
Aromatic Radical

Theoretical insight into the substituent effects on the antioxidant properties of 8-hydroxyquinoline derivatives in gas phase and in polar solvents

2018 ◽  
Vol 96 (5) ◽  
pp. 453-458
Author(s):  
Anes El-Hadj Saïd ◽  
Sidi Mohamed Mekelleche ◽  
Taki-Eddine Ahmed Ardjani
Keyword(s):  
Electron Transfer ◽  
Gas Phase ◽  
Antioxidant Properties ◽  
Substituent Effects ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Antioxidant Power ◽  
Theoretical Insight ◽  
Insight Into

The objective of this work is to perform a theoretical analysis of the antioxidant properties of a series of 8-hydroxyquinolines (8-HQs) to rationalize the available experimental results and to design new potent 8-HQ derivatives. The study was carried out in gas phase and in methanol at the DFT/B3LYP/ 6-311++G(d,p) computational level. The formation of stable ArO• radicals is discussed on the basis of different mechanisms, namely, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and single proton loss electron transfer (SPLET). The obtained results show that the HAT mechanism is, thermodynamically, more favoured in gas phase, whereas the SPLET pathway is more favoured in polar solvents. The calculated thermochemical descriptors allow classification of the antioxidant power of the studied compounds.

Chemistry of radical ions: the absolute rate constant of dimerization of radical anions of 1 ,1-diphenyl ethylene

1965 ◽  
Vol 288 (1413) ◽  
pp. 212-223 ◽  
Keyword(s):  
Electron Transfer ◽  
Rate Constant ◽  
Transfer Process ◽  
Aromatic Hydrocarbons ◽  
Radical Anions ◽  
Electron Affinities ◽  
Absolute Rate ◽  
Radical Ions ◽  
Electron Transfer Process ◽  
Absolute Rate Constant

The combination of the labile radical ions, (Ph 2 C:CH 2 )7~, Na+, into dimeric dianions Na + , C - (Ph) 2 .CH 2 .CH 2 .C(Ph) - 2, Na+ was investigated by a flow and a stopflow technique. The bimolecular rate constant of combination was found to be 2 to 3 x 106 1. mole-1 s-1. The reaction was initiated by an electron transfer naphthalene^ + (P/*,2C:CH2) naphthalene+ (P/*,2C:CH^) or terphenylener + (P7fc2C:CH2) ⇔ terphenylene + (Pfe2C:CH^). The equilibrium constant of the first electron transfer process was found to be 20 and of the second about 16. These results are consistent with recent determinations of electron affinities of aromatic hydrocarbons.

Hydration of CN−, NO2−, NO3−, and OH− in the Gas Phase

1971 ◽  
Vol 49 (20) ◽  
pp. 3308-3314 ◽  
Author(s):  
J. D. Payzant ◽  
R. Yamdagni ◽  
P. Kebarle
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Linear Correlation ◽  
Equilibrium Constants ◽  
Negative Ions ◽  
Thermochemical Data ◽  
Electron Affinities ◽  
Hydration Energies

By measuring the A−(H2O)n−1 + H2O = A−(H2O)n equilibria in the gas phase and their temperature dependence, the equilibrium constants and ΔHn, n–1 and ΔSn, n–1 for some of the hydrates of NO2−, NO3−, CN−, and OH− were determined. Available thermochemical data are used for the evaluation of the total heats of hydration of the above ions. The total heats of hydration were then compared with the ΔH1,0. Relative to the total hydration energies the ΔH1,0 of the above ions were found larger than the ΔH1,0 of the halide ions.An approximate linear correlation was found to exist between ΔH1,0 of negative ions and the heterolytic bond dissociation energy D(A−–H+). With this relationship independent estimates for the electron affinities of NO2 and NO3 could be obtained.The ΔHn, n–1 of OH− were found in essential agreement with earlier measurements from this laboratory and in disagreements with recent measurements (Friedman) which gave much higher values.

The acidity of polyhalogenated silanes and silyl radicals

1992 ◽  
Vol 70 (8) ◽  
pp. 2234-2240 ◽  
Author(s):  
C. F. Rodriquez ◽  
A. C. Hopkinson
Keyword(s):  
Gas Phase ◽  
Molecular Orbital ◽  
Electron Affinity ◽  
Substituent Effects ◽  
Linear Interpolation ◽  
Molecular Orbital Calculations ◽  
Electron Affinities ◽  
Silyl Radicals ◽  
Experimental Values ◽  
Cl Atom

The results of abinitio molecular orbital calculations at the MP4SDTQ/6-31++G(d,p)//HF/6-31++G(d,p) level have been used to calculate acidities of fluoro- and chloro-substituted silanes and silyl radicals. The radicals are more acidic than the silanes and substituent effects are also slightly larger in the radicals. For the gas phase deprotonation of fluorosilanes at 298 K, ΔHr (kcal/mol) values are SiH4, 378.5; SiH3F, 374.5; SiH2F, 366.7, and SiHF3, 351.0, i.e., interaction between fluorine atoms leads to increased enhancement of acidity. For chlorosilanes substituent effects are larger but strictly additive (13 kcal/mol for each Cl atom) with ΔHr values SiH3Cl, 365.4; SiH2Cl2 352.5, and SiHCl3 339.4. The electron affinities of silyl radicals calculated using isogyric reactions at the MP4SDTQ/6-31++G(d,p) level are too low by ~0.3 eV, but at the MP4SDTQ/6-311++G(2df,p) level the calculated electron affinity of SiH3 is 1.39 eV, compared with an experimental value of 1.44 ± 0.03 eV. This higher level of theory gives calculated electron affinities of 1.53 eV for SiH2F and 1.92 eV for SiH2Cl. Heats of formation obtained by using isogyric reactions to calculate atomization energies at the MP4SDTQ/6-311++G(2df,p) level are within 3 kcal/mol of experimental values except for SiH2F (where the "experimental" value was obtained from linear interpolation between SiH3 and SiF3). [Formula: see text] (kcal/mol) calculated for the anions are SiH3−, 14.4; SiH2F−, −78.0; and SiH2Cl−, −37.6.

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