Entropy changes and electron affinities from gas-phase electron-transfer equilibria: A- + B = A + B-

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.

Download Full-text

Electron affinities of di- and tetracyanoethylene and cyanobenzenes based on measurements of gas-phase electron-transfer equilibria

Journal of the American Chemical Society ◽

10.1021/ja00278a014 ◽

1986 ◽

Vol 108 (18) ◽

pp. 5453-5459 ◽

Cited By ~ 56

Author(s):

Swapan. Chowdhury ◽

Paul. Kebarle

Keyword(s):

Electron Transfer ◽

Gas Phase ◽

Electron Affinities

Download Full-text

Summary of gas phase acidity measurements involving acids AH. Entropy changes in proton transfer reactions involving negative ions. Bond dissociation energies D(A—H) and electron affinities EA(A)

Canadian Journal of Chemistry ◽

10.1139/v78-001 ◽

1978 ◽

Vol 56 (1) ◽

pp. 1-9 ◽

Cited By ~ 156

Author(s):

J. B. Cumming ◽

P. Kebarle

Keyword(s):

Proton Transfer ◽

Gas Phase ◽

Negative Ions ◽

Bond Dissociation Energies ◽

Electron Affinities ◽

Bond Dissociation ◽

Dissociation Energies ◽

Entropy Changes ◽

Gas Phase Acidity ◽

Proton Transfer Reactions

The complete ladder of ΔG10 determinations obtained from measurements of some 110 gas phase proton transfer equilibria A1− + A2H = A1H + A2− involving some 60 acids AH and connecting to the standard acid HCl is given. Evaluation of the entropy changes leads to values for the deprotonation energies ΔHD0 and ΔGD0 (at room temperature) corresponding to the gas phase process AH = A− + H+; ΔHD0 = D(A—H) − EA(A) + 313.6 kcal/mol. Comparison of the present data with literature determinations of the bond dissociation energies and electron affinities shows agreement within 2 kcal/mol. Some experimentally determined entropy changes ΔS10 are compared with the theoretically calculated values.

Download Full-text

Electron affinities of aza-substituted polycyclic aromatic hydrocarbons

Canadian Journal of Chemistry ◽

10.1139/v89-249 ◽

1989 ◽

Vol 67 (10) ◽

pp. 1628-1631 ◽

Cited By ~ 21

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.

Download Full-text