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Current advances on the photocatalytic degradation of fluoroquinolones: photoreaction mechanism and environmental application
No full textHeterogeneous photocatalysis is one of the most studied and promising techniques for degradation of contaminants of emerging concern, especially pharmaceuticals, and it represents a potential application in wastewater treatment of recalcitrant pollutants, such as fluoroquinolones, which are almost not abated by standard WWTPs. Although photodegradation partially contributes to alleviate their accumulation into the aquatic systems, heterogeneous photocatalysis assures complete sequestration and mineralization of FQs and their photoproducts and offers many advantages with respect to the other advanced oxidation processes (AOPs). The present brief review summarizes the most recent studies regarding the development and application of novel photocatalytic materials to the removal of FQs from contaminated waters. The collected data are arranged relating the mechanistic aspects to specific catalysts' properties, such as adsorption capacity, easy recovery, and reusability, especially under actual conditions.[GRAPHICS]
Photoarylation/Alkylation of Bromo-Naphthols
No full textThe photochemistry of 6-bromo-2-naphthols has been studied in acetonitrile, aqueous acetonitrile, and isopropyl alcohol in the absence and in the presence of triethylamine by product distribution analysis, laser flash photolysis (LFP), fluorescence, phosphorescence, electrochemical measurements, and DFT calculations. Hydrobromic acid loss in the presence of Et3N occurs from the triplet state of 6-bromo-2-naphthol, generating an electrophilic carbene intermediate, which has been successfully trapped by oxygen, allyltrimethylsilane, 2,3-dimethylbut-2-ene, pyrrole, acrylonitrile, 1,4-dimethoxybenzene, and also pyridine.
The generation and the reactivity of a triplet carbene intermediate has been supported by LFP, with the
detection of 2,6-naphthoquinone-O-oxide (530-650 nm) in the presence of O2. The electrophilic diradical character of the carbene has been supported by DFT calculations, using the B3LYP, PBE0, and MPWB1K functionals, with the 6-31+G(d,p) basis set and PCM solvation model
Photochemistry of some non zwitterionic fluoroquinolones
No full textTwo non zwitterionic analogues of fluoroquinolone drugs, viz. 1-ethyl-7-piperidino-8-fluoroquinol-4-
one-3-carboxylic acid and 1-ethyl-7-piperidino-6,8-difluoroquinol-4-one-3-carboxylic acids have been
synthesized and their photochemistry has been investigated. Both compound undergo photoheterolysis
of the C8 F bond generating a triplet cation that either inserts into the 1-alkyl chain or is trapped or
reduced by external nucleophiles. The reaction is analogous to that observed with the corresponding
(zwitterionic) 7-piperazino derivatives, but the quantum yield is ca five times lower. This supports the
rationalization that in the latter case assistance to defluorination by the N+ H bond has a determining
role
Photoarylation of Alkenes and Heteroaromatics by Dibromo-BINOLs in Aqueous Solution
No full textThe photochemistry of 6,6’-dibromo-BINOLs (BINOL=2,2’-dihydroxy-1,1’-binaphthyl) under mild conditions has been investigated in neat and aqueous acetonitrile through product distribution analysis and laser flash photolysis. Arylation and alkylation have been successfully achieved in the presence of allyltrimethylsilane, ethyl vinyl ether, pyrrole, pyridine, thiophene, benzene, and indole. Such a photoreactivity offers a metal and protecting group free synthetic protocol toward mono- and disubstituted 6-aryl/alkyl BINOLs, since the BINOL chirality is preserved in the photoactivation process
Botanical and biological pesticides elicit a similar Induced Systemic Response in tomato (Solanum lycopersicum) secondary metabolism
No full textNatural pesticides have attracted substantial interest due to the increase in organic agriculture and enhanced attention to environmental pollution. Plant Growth Promoting Bacteria (PGPB) are applied for both disease control and growth enhancement; PGPBs are known to elicit Induced Systemic Response (ISR) in plants. However, less is known about the effect of botanical pesticides, such as the azadirachtincontaining neem extracts, on plant metabolism. This study aimed to investigate the effects of foliar application of the above-mentioned natural pesticides on the metabolic profiling of tomato. Leaf application of Bacillus subtilis fostered Induced Systemic Resistance (ISR) in treated plants via the Jasmonic acid pathway, and enhanced production of secondary metabolites such as flavonoids, phytoalexins and auxins. Changes in sterols and terpenes, as well as an increase in glucosinolates were also observed. Interestingly, azadirachtin-treated tomatoes also showed an increase in ISR and our results revealed that most of the enriched metabolites are shared with a B. subtilis treatment, suggesting conserved biochemical responses. These (un)expected findings indicate that plants are not insensitive to application of natural pesticide and while Azadirachtin is applied as a direct pesticide, it also stimulates a defense response in tomatoes very similar to B. subtilis induced ISR
g-C3N4-promoted degradation of ofloxacin antibiotic in natural waters under simulated sunlight
No full textThis is the first report on the photodegradation of ofloxacin under simulated solar light and in actual environmental matrices in the presence of a g-C3N4 suspension. The catalyst, prepared from the polymerization of dicyandiamide (650 degrees C, reaction yield 60%), was characterized by means of powder X-ray diffraction (PXRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and BET surface area measurements. The experiments were carried out in a lab-scale batch reactor at concentrations in the range of micrograms/milligrams per liter. The course of the reaction was monitored by high-pressure liquid chromatography with UV-vis and fluorescence detectors. The g-C3N4-promoted photodegradation occurred at a rate 10 times faster than the direct photolysis and obeyed a first-order kinetics; in addition, the photodegradation kinetics of sonicated g-C3N4 resulted to be of the same order of that caused by P25 TiO2. Finally, the photochemical paths and the photoproducts have been identified and compared to those obtained by using P25 TiO2. Fromthe results of this study, it can be concluded that g-C3N4 is a very attractive photocatalyst compared to P25 TiO2 in view of its ease of preparation, low cost, excellent oxidizing properties, large fraction of solar radiation absorbed, and intrinsically layered structure
Environmental photochemistry of fluoroquinolones in soil and in aqueous soil suspensions under solar light
No full textThe photodegradation fate of widely used fluoroquinolone
(FQ) drugs has been studied both at the water–soil
interface and in soil at actual concentrations (500 ng g−1) under
natural solar light. Both human and veterinary drugs have been
examined, namely ciprofloxacin, danofloxacin, enrofloxacin,
levofloxacin, marbofloxacin and moxifloxacin. After spiking
and irradiation, samples were submitted to microwave-assisted
extraction and analyzed by high-performance liquid chromatography
coupled to fluorescence detection (HPLC–FD). FQs
degradation was faster in aqueous soil suspension than in neat
soil (but lower than in “clean” water). A number of byproducts
were identified by HPLC electrospray ionization tandem mass
spectrometry after a post-extraction cleanup based on a molecularly
imprinted polymer phase, for a more accurate detection.
The distribution in the suspension was intermediate between
those observed in soils and in aqueous solutions
Inter- and Intramolecular Photochemical Reactions of Fleroxacin.
Full text linkIn the cation formed by photoinduced C−F bond cleavage in fleroxacin, intramolecular reaction with the N−ethyl chain is prevented by the electron-withdrawing effect of fluorine and intermolecular attack by nucleophiles is facilitated
A Fluorine 1,2-Migration via Aryl Cation/Radical/Radical Anion/Radical Sequence
No full textIrradiation of a 7-piperazino-8-fluoroquinolone causes formal 1,2-fluorine migration, piperazine loss and reduction, or nucleophile addition in 8. Product study, laser flash photolysis, and computational modeling support F- detachment to yield a triplet 8-quinolyl cation that either inserts intramolecularly or is trapped by Cl-, Br-. However, iodide and pyrrole reduce it to the radical that continues the ‘redox tour’ (aryl cation -
radical - radical anion - radical and then again radical or radical anion) leading to the rearranged products
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