The effect of substituents on the reactivity of aniline with phosphate radical
TL;DR: In this paper, the reaction between aromatic amines and phosphate radical has been investigated and the reaction is accelerated by electron releasing substituents and retarded by electron-withdrawing substitusents pointing to an electrophilic attack by the PO 4 2xxx radical.
About: This article is published in Tetrahedron.The article was published on 1988-01-01. It has received 2 citations till now. The article focuses on the topics: Radical-nucleophilic aromatic substitution & Reactivity (chemistry).
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TL;DR: A training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose to specific for the likely rate-limiting step of one-electron oxidation potentials (Eox).
Abstract: New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate and effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines, and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide (MnO2) is a common environmental oxidant and model system for kinetic studies of aromatic amine oxidation. In this study, a training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose [Hammett σ constants (σ–), pKas of the amines, and energies of the highest occupied molecular orbital (EHOMO)] to specific for the likely rate-limiting step [one-electron oxidation potentials (Eox)]. The selection of calculated descriptors (pKa, EHOMO, and Eox) was based on validation with experimental d...
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01 Apr 2016
TL;DR: This work used a hybrid, partially in silico approach to QSAR development, where some of the calibration data (both the target variable and the descriptor variables) were calculated from molecular structure theory.
Abstract: : Predicting the environmental fate of novel munitions compounds requires data for the key properties that control contaminant fate, and the most common way to predict these properties is with empirical quantitative structure-activity relationships (QSARs). However, the traditional approach to QSAR development (calibration with experimental data) is challenging for new explosives compounds because of limitations to the availability of these materials. Some of the necessary environmental fate properties can be calculated directly from molecular structure theory, but reliable calculations of this type require considerable theoretical expertise and computational effort. To overcome this combination of challenges, we used a hybrid, partially in silico approach to QSAR development, where some of the calibration data (both the target variable and the descriptor variables) were calculated from molecular structure theory.
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TL;DR: In this article, the rate constants for the reactions of the acid-base forms of the phosphate radical, as well as those of the sulfate radical, with several inorganic compounds were determined.
Abstract: The phosphate radicals were produced by the reaction of e/sub eq//sup -/ with peroxodiphosphate ions and their spectra and acid-base equilibria were determined. The reaction of OH with phosphate ions was also examined and discrepancies in the literature are discussed. The rate constants for the reactions of the acid-base forms of the phosphate radical, as well as those of the sulfate radical, with several inorganic compounds were determined. These reactions involve either hydrogen abstraction or one-electron oxidation. The radicals formed by H abstraction from H/sub 2/O/sub 2/, HOP/sub 3//sup 2 -/, and H/sub 2/PO/sub 2//sup -/ can reduce peroxodisulfate and peroxodiphosphate efficiently and thus propagate a chain reaction. The rate constants for the abstraction reactions are similar for SO/sub 4//sup -/ and H/sub 2/PO/sub 4/ but slower for HPO/sub 4//sup -/ and PO/sub 4//sup 2 -/. The rate constants for oxidation differ considerably for the different radicals and substrates. From these rates it is concluded that the oxidation capabilities decrease in the order SO/sub 4//sup -/ greater than H/sub 2/PO/sub 4/ greater than HPO/sub 4/ greater than PO/sub 4//sup 2 -/.
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118 citations
TL;DR: In this article, the rate constant for reaction of OH radicals with peroxomonophosphate at pH 7 was found to be 4.6 and 4.3 x 10/sup 7/M/sup -1/ s/sup 1.6.
Abstract: Radiolytic studies of peroxomonophosphoric acid, H/sub 3/PO/sub 5/, and peroxomonosulfuric acid, H/sub 2/SO/sub 5/, have been carried out over a wide pH range. Unlike the corresponding peroxodiacids, H/sub 4/P/sub 2/O/sub 8/ and H/sub 2/S/sub 2/O/sub 8/, the peroxomono acids undergo radiolytic chain decomposition, with G values increasing from about 6 to 60 in going from pH 1 to 12.6. Sharp rises in G values appear at pH values near the pK/sub a/ of the hydroperoxy proton (highest pK/sub a/). The mechanism suggested for these chain reactions involves successive oxidation and reduction of the parent compounds by radicals produced in the preceding step. Pulse radiolysis experiments showed that the reaction of e/sub eq//sup -/ with peroxomonophosphate (k = 4.4 x 10 M/sup -1/ s/sup -1/ at pH 7) produces OH radicals twice as frequently as HPO/sub 4//sup -/ radicals. Previous results with peroxomonosulfate showed a factor of 4 for similar reactions. The rate constant for reaction of OH radicals with peroxomonophosphate at pH 7 was found to be 4.3 x 10/sup 7/ M/sup -1/ s/sup -1/, and with peroxomonosulfate 1.7 x 10/sup 7/ M/sup -1/ s/sup -1/ at pH 7 and 2.1 x 10/sup 9/ M/sup -1/ s/sup -1/ at pHmore » 11. The reactions of OH are suggested to be the chain initiation step and possibly responsible for the main chain propagation as well.« less
117 citations