One-Electron Reduction Potentials from Chemical Structure Theory Calculations

Abstract

Many redox reactions of importance in aquatic chemistry involve elementary steps that occur by single-electron transfer (SET). This step is often the first and rate limiting step in redox reactions of environmental contaminants, so there has been a great deal of interest in the corresponding one-electron reduction potentials (E 1 ). Although E 1 can be obtained by experimental methods, calculation from first-principles chemical structure theory is becoming an increasingly attractive alternative. Sufficient data are now available to perform a critical assessment of these methods-and their results-for two types of contaminant degradation reactions: dehalogenation of chlorinated aliphatic compounds (CACs) and reduction of nitro aromatic compounds (NACs). Early datasets containing E 1 's for dehalogenation of CACs by dissociative SET contained a variety of errors and inconsistencies, but the preferred datasets show good agreement between values calculated from thermodynamic data and quantum mechanical models. All of the datasets with E 1 's for reduction of NACs by SET are relatively new, were calculated with similar methods, and yet yield a variety of systematic differences. Further analysis of these differences is likely to yield computational methods for E 1 's of NAC nitro reduction that are similar in reliability to those for CAC dechlorination. However, comparison of the E 1 data compiled here with those calculated with a more universal predictive model (like SPARC) highlight a number

Predicting Reduction Rates of Energetic Nitroaromatic Compounds Using Calculated One-Electron Reduction Potentials

“…23- 28 We compiled and compared the results of many of these studies previously, in addition to presenting preliminary results from our own calculations of E 1 NAC . 26 In this paper, we have expanded on our previous results and applied these computational methods to a larger set of compounds. We also present kinetic data for the nitro reduction of three energetic NACs-2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (DNAN)-and use these to test the range of applicability of the correlation calibrated with non-energetic model compounds.…”

Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

“…Adsorption is needed for a dissolved species to remain in contact with a solid surface and occurs before electrons are transferred between the electrode surface and the chemical species. Interaction between a mineral surface and a chemical species can be an important parameter in quantifying the thermodynamics of electron transfer mediated by a mineral surface in that it can cause deviation from theoretical equilibrium redox potentials within a few hundred mV [46,[54][55][56]. Here, energetic contributions of adsorption to Se redox thermodynamics were calculated using the computational code, Gaussian 09.…”

In silico environmental chemical science: properties and processes from statistical and computational modelling

“…79,80 In addition, the overall accuracy of DFT calculations can be improved by using methods that make use of empirical additivity rules for molecular properties, where various properties of larger molecules can be thought of as being made up of additive contributions of atoms, bonds, or collections of atoms and bonds (i.e., functional groups) of the molecule. 81,82 These approaches have proven to be effective for small organic molecules, [83][84][85][86][87][88][89][90] and recently they have been used in advanced computational algorithms that can be used to simulate extremely large molecules, even including complex proteins and DNA chains. 91,92 Compared with DFT, the higher level theory used in wave function and quantum Monte-Carlo methods 93 can give significantly more accurate results, if the underlying electronic structure is well understood.…”