Photochemistry of Phenols

Horspool, W. M.

doi:10.1002/9780470682531.pat0290

Cited by 2 publications

(2 citation statements)

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“…Azoxybenzenes are known to undergo photochemical rearrangements to hydroxy-azo compounds (photo-Wallach rearrangement), in cases where there is a free ortho position in the ring constituent more distant from the N-O function (Fig 4). In this rearrangement, the oxygen atom of the azoxy group migrates to the ortho position of the aryl group more distant from the N-O function [63, 82]. It is conceivable that azoxybenzenes arising from 4-nitroso or 4-phenylhydroxylamino derivatives of TNT could be susceptible to this rearrangement.…”

Section: Resultsmentioning

confidence: 99%

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene

Thorn

2019

PLoS ONE

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Photolysis is one of the main transformation pathways for 2,4,6-trinitrotoluene (TNT) released into the environment. Upon exposure to sunlight, TNT is known to undergo both oxidation and reduction reactions with release of nitrite, nitrate, and ammonium ions, followed by condensation reactions of the oxidation and reduction products. In this study, compound classes of transformation products from the aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene (TNT) have been identified by liquid and solid state 13C and 15N NMR. Aqueous phase experiments were performed on saturated solutions of T15NT in deionized water, natural pond water (pH = 8.3, DOC = 3.0 mg/L), pH 8.0 buffer solution, and in the presence of Suwannee River Natural Organic Matter (SRNOM; pH = 3.7), using a Pyrex-filtered medium pressure mercury lamp. Natural sunlight irradiations were performed on TNT in the solid phase and dissolved in the pond water. In deionized water, carboxylic acid, aldehyde, aromatic amine, primary amide, azoxy, nitrosophenol, and azo compounds were formed. 15N NMR spectra exhibited major peaks centered at 128 to 138 ppm, which are in the range of phenylhydroxylamine and secondary amide nitrogens. The secondary amides are proposed to represent benzanilides, which would arise from photochemical rearrangement of nitrones formed from the condensation of benzaldehyde and phenylhydroxylamine derivatives of TNT. The same compound classes were formed from sunlight irradiation of TNT in the solid phase. Whereas carboxylic acids, aldehydes, aromatic amines, phenylhydroxylamines, and amides were also formed from irradiation of TNT in pond water and in pH 8 buffer solution, azoxy and azo compound formation was inhibited. Solid state 15N NMR spectra of photolysates from the lamp irradiation of unlabeled 2,6-dinitrotoluene in deionized water also demonstrated the formation of aromatic amine, phenylhydroxylamine/ 2° amide, azoxy, and azo nitrogens.

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Section: Resultsmentioning

confidence: 99%

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene

Thorn

2019

PLoS ONE

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“…The current great interest in the photophysics, photochemistry, and catalytic activity of d 10 complexes of the coinage metals is fully supported in the literature. − Gold in particular plays an important role in scientific and technological areas ranging from catalysis, medical, and pharmacological research to optoelectronics. − It is well-known that the electronic structure and properties of gold are strongly influenced by relativity. In particular, the relativistic 6s-contraction/stabilization results in an increase of both the first ionization potential and electron affinity, which combined with the (indirect) relativistic expansion/destabilization of the 5d shell leads to a substantial decrease of the d/s gap.…”

Section: Introductionmentioning

confidence: 99%

The Chemical Bond and s–d Hybridization in Coinage Metal(I) Cyanides

et al. 2019

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We present a four-component relativistic density functional theory study of the chemical bond and s-d hybridization in the group-11 cyanides MCN (M = Cu, Ag, Au). The analysis is carried out within the charge-displacement/natural orbital for chemical valence (CD-NOCV) scheme, which allows us to single out meaningful contributions to the total charge rearrangement that arises upon bond formation and to quantify the components of the Dewar-Chatt-Duncanson bonding model (the ligand-tometal donation and metal-to-ligand back-donation). The M-CN bond is characterized by a large donation from the cyanide ion to the metal cation and by two small backdonation components from the metal towards the cyanide anion. The case of gold cyanide elucidates the peculiar role of the relativistic eects in determining the characteristics of the AuC bond with respect to the copper and silver homologues. In AuCN, the donation and back-donation components are signicantly enhanced and the spinorbit coupling, removing the degeneracy of the 5d atomic orbitals, induces a substantial split in the back-donation components. A simple spatial analysis of the NOCV-pair density, related to the ligand-to-metal donation component, allows us to quantify, with unprecedented accuracy, the charge rearrangement due to the s-d hybridization occurring at the metal site. The s-d hybridization plays a key role in determining the shape and size of the metal: it removes electron density from the bond axis and induces a signicant attening at the metal site in trans position to the ligand. The s-d hybridization is present in all noble metal complexes, inuencing the bond distances, and its eect is enhanced for Au, which is consistent with the preference of gold to form linear complexes. A comparative investigation of simple complexes [AuL] +/0 of Au + with dierent ligands (L=F − , N-Heterocyclic Carbene, CO, PH 3) shows that the s-d hybridization mechanism is also inuenced by the nature of the ligand.

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Photochemistry of Phenols

Abstract: Introduction General Observations Hydrogen Transfer Reactions Chalcones Quinonemethides from Phenol Derivatives Cyclizations within o ‐Allylphenols Rearrangements Carbene Formation … Show more

Cited by 2 publications

References 325 publications

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene

The Chemical Bond and s–d Hybridization in Coinage Metal(I) Cyanides

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