Electron transfer from aromatic hydrocarbons and their .pi.-complexes with metals. Comparison of the standard oxidation potentials and vertical ionization potentials

Abstract

The energetics of electron transfer from an extensive series of alkyl-substituted benzenes are measured both in solution and in the gas phase. The standard oxidation potentials stem from the reversible cyclic voltammograms (CV) in trifluoroacetic acid using the recently developed microvoltammetric electrodes. These values show an excellent correlation with the vertical ionization potentials 7p of the same aromatic hydrocarbons in the gas phase. Thermochemical analysis indicates that the slope of less than unity for the correlation arises mainly from solvation differences, particularly in the highly substituted polyalkylbenzenes. The values of £Ar°a lso correlate extremely well with the anodic peak potentials £p of the irreversible cyclic voltammograms, which can be readily measured in acetonitrile at a standard sweep rate. A slope of unity for the linear correlation is discussed in terms of the maximum error in the CV peak shift (£_ -£°) resulting from the electrochemical kinetics of the EC mechanism for arene oxidation. The correlation of E^0 and £p affords a prediction of the standard oxidation potential of benzene, which otherwise could not be measured directly. The same series of alkylbenzenes form stable x-complexes with chromium tricarbonyl that show reversible electrochemical behavior. The standard oxidation potentials £ArCr°o f the complexes also correlate very well with E^f of the free arene. The diminished slope of the correlation arises from the nonbonding character of the HOMO.The predicted value of E^0 for benzene from this relationship is in reasonable agreement with that obtained from the irreversible peak potentials.

Partial Ionization Cross Sections of Organic Molecules

“…The PES values used here, along with the ab initio values that they replace, are listed below for all affected molecules. o-Xylene and m-xylene: For the highest-lying molecular orbital, B = 8.56 eV [29] replaced the theoretical CCSD(T) value of 8.70 eV.…”

“…p-Xylene: For the HOMO, B = 8.44 eV [29] replaced the theoretical CCSD(T) value of 8.58 eV. Styrene: For three highest orbitals, values of B/eV = 8.49, 9.27, and 10.55 [30] replaced the corresponding theoretical values of 8.56 [CCSD(T)], 9.22 (P3), and 10.71 (P3).…”

Products of Thymine Oxygenation by a Non-heme Oxygenation Model, Fe^II(MeCN)₆²⁺–Ac₂O–H₂O₂, and the Transition State Model between Oxoiron and Thymine

“…In the case of the active species 13b, a stronger oxygenation force than that of 12a is expected because the redox potential (E 0 ) is given approximately by relation E 0 ϰe homo . 27) Indeed, it was found that the oxoiron of 9 is extracted by oxidizing a proton from the Me-group of the AcO ligand and transferring to 11, as illustrated in Fig. 4.…”

Physical chemical properties and kinetics of redox processes in water/soybean oil microemulsions

“…Even in this case, an UME has the advantage of a reduced charge time, 22,23 which allows the study of very fast reactions, of the order of microseconds. 24 In this sense, linear voltammetry measurements 25 in resistive media 26 like the w/o MEs employed in this study, can be performed by an UME.…”

“…Even in this case, an UME has the advantage of a reduced charge time, 22,23 which allows the study of very fast reactions, of the order of microseconds. 24 In this sense, linear voltammetry measurements 25 in resistive media 26 like the w/o MEs employed in this study, can be performed by an UME.The aim of this work was to evaluate the influence of the surfactant/co-surfactant ratio on the physical-chemical characteristics of water/soybean oil w/o MEs using measurements of the hydrodynamic radius (R H ), refractive index, viscosity and electrical conductivity, as well as to study the kinetic of redox processes by using cyclic voltammetry with an UME in the presence of ferrocene as a probe. Vegetable oil analysis is usually performed by a number of analytical techniques.…”