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ChemPlusChem Nov 2022Rate constants for the reaction of nitrate radical (NO ⋅) with several carboxylic acids (RCO H) were measured in acetonitrile using laser flash photolysis, and found...
Rate constants for the reaction of nitrate radical (NO ⋅) with several carboxylic acids (RCO H) were measured in acetonitrile using laser flash photolysis, and found to be on the order of 10 -10 M s . No observable H/D kinetic isotope effect was observed at the carboxyl O-H group, α-C-H bond and (possibly) in the case of formic acid, the formylic C-H bond. This suggests that NO ⋅ does not abstract hydrogen from any of these positions despite the fact that all these processes are thermodynamically favorable. Reactivity increases with increased length and/or branching of the alkyl side chain (R), and approaches, but does not quite reach, that of an alkane towards NO ⋅. The relative inertness of carboxylic acids towards NO ⋅ can be explained by the polar effect.
Topics: Nitrates; Photolysis; Carboxylic Acids; Kinetics; Hydrogen
PubMed: 36005275
DOI: 10.1002/cplu.202200213 -
The Science of the Total Environment Jan 2022Antidepressants have become ubiquitous emerging organic pollutants. Therefore, it is essential to investigate photodegradation of the antidepressants in environment...
Antidepressants have become ubiquitous emerging organic pollutants. Therefore, it is essential to investigate photodegradation of the antidepressants in environment waters for their ecological risk assessment. However, photodegradation behavior of antidepressants varied from different structures and photodegradation mechanism was rarely known for most antidepressants. Herein, citalopram (CIT), paroxetine (PAR) and fluvoxamine (FLUVO) were employed to study the photodegradation behavior of antidepressants in lake water. Results show that direct photolysis of CIT decreased when pH increased from 6 to 9 while the pH effect was not obvious on direct photolysis of FLUVO and PAR. Photodegradation of CIT occurred from its triplet-state and can undergo self-photosensitization through reaction with the generated hydroxyl radical (·OH). In lake water, PAR and FLUVO are degraded mainly via direct photolysis, while CIT is transformed mainly via indirect photolysis. Dissolved organic matter (DOM) and NO was proved to be the main factors affecting antidepressants photodegradation in lake water. DOM and NO showed inhibition effect on photodegradation of FLUVO and PAR, while promoted CIT degradation. The promotion effect of CIT was mainly through reaction with ·OH and excited triplet-state of DOM while singlet oxygen played a minor role. Based on the photodegradation products identified by MS/MS, the photodegradation pathways were proposed for CIT and PAR, respectively. For FLUVO, one (Z)-isomer degradation product was also found. Understanding the photodegradation behavior of antidepressants is vital for providing data to do ecological risk assessment.
Topics: Antidepressive Agents; Nitrates; Photolysis; Tandem Mass Spectrometry; Water Pollutants, Chemical
PubMed: 34450438
DOI: 10.1016/j.scitotenv.2021.149825 -
Journal of Agricultural and Food... Jan 2020Folic acid, a synthetic form of folate, is a water-soluble vitamin that is essential during periods of rapid cell division and growth. However, it decomposes upon... (Comparative Study)
Comparative Study
Folic acid, a synthetic form of folate, is a water-soluble vitamin that is essential during periods of rapid cell division and growth. However, it decomposes upon ultraviolet irradiation to form inactive photoproducts. In this study, the protective effect and mechanisms of antioxidants, including cinnamic acids, flavonoids, catechol and its derivatives, stilbenes, -benzoquinone and its derivatives, isoprenoids, curcumin, oleic acid, and linoleic acid, against folic acid photodecomposition were investigated by using fluorescence and absorbance spectroscopy, high-performance liquid chromatography, and antioxidant assay. It was found that antioxidants could inhibit or delay the folic acid decomposition in varying degrees, among which caffeic acid was the most effective. The increase in its remarkable antioxidant efficiency and absorbance in the UVA region during irradiation contributed to its effective protection. This finding could be useful for the protection of photolabile components in food and other uses.
Topics: Antioxidants; Benzoquinones; Catechols; Cinnamates; Flavonoids; Folic Acid; Photolysis; Stilbenes; Ultraviolet Rays
PubMed: 31874034
DOI: 10.1021/acs.jafc.9b06263 -
Molecules (Basel, Switzerland) Dec 2018Chloro- and dichloro-methylsulfonyl nitrenes, CH₂ClS(O)₂N and CHCl₂S(O)₂N, have been generated from UV laser photolysis (193 and 266 nm) of the corresponding...
Chloro- and dichloro-methylsulfonyl nitrenes, CH₂ClS(O)₂N and CHCl₂S(O)₂N, have been generated from UV laser photolysis (193 and 266 nm) of the corresponding sulfonyl azides CH₂ClS(O)₂N₃ and CHCl₂S(O)₂N₃, respectively. Both nitrenes have been characterized with matrix-isolation IR and EPR spectroscopy in solid N₂ (10 K) and glassy toluene (5 K) matrices. Triplet ground-state multiplicity of CH₂ClS(O)₂N (|/| = 1.57 cm and |/| = 0.0026 cm) and CHCl₂S(O)₂N (|/| = 1.56 cm and |/| = 0.0042 cm) has been confirmed. In addition, dichloromethylnitrene CHCl₂N (|/| = 1.57 cm and |/| = 0 cm), formed from SO₂-elimination in CHCl₂S(O)₂N, has also been identified for the first time. Upon UV light irradiation (365 nm), the two sulfonyl nitrenes R⁻S(O)₂N (R = CH₂Cl and CHCl₂) undergo concomitant 1,2-R shift to -sulfonlyamines R⁻NSO₂ and 1,2-oxygen shift to -nitroso compounds R⁻S(O)NO, respectively. The identification of these new species with IR spectroscopy is supported by N labeling experiments and quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) level. In contrast, the thermally-generated sulfonyl nitrenes CH₂ClS(O)₂N (600 K) and CHCl₂S(O)₂N (700 K) dissociate completely in the gas phase, and in both cases, HCN, SO₂, HCl, HNSO, and CO form. Additionally, ClCN, OCCl₂, HNSO₂, •NSO₂, and the atmospherically relevant radical •CHCl₂ are also identified among the fragmentation products of CHCl₂S(O)₂N. The underlying mechanisms for the rearrangement and decomposition of CH₂ClS(O)₂N and CHCl₂S(O)₂N are discussed based on the experimentally-observed products and the calculated potential energy profile.
Topics: Electron Spin Resonance Spectroscopy; Isomerism; Light; Nitroso Compounds; Photolysis; Quantum Theory; Spectrophotometry, Infrared; Spectrum Analysis; Temperature
PubMed: 30551679
DOI: 10.3390/molecules23123312 -
The Journal of Organic Chemistry Mar 2022Photoremovable protecting groups (photocages) based on 1-amino-2-hydroxymethylnaphthalene were developed, and their applicability to release alcohols and carboxylic...
Photoremovable protecting groups (photocages) based on 1-amino-2-hydroxymethylnaphthalene were developed, and their applicability to release alcohols and carboxylic acids in photohydrolysis was investigated. Compound cannot release alcohol since -demethylation takes place instead. However, the photorelease of carboxylic acids from - was demonstrated on caged substrates, including some nonsteroidal drugs and a neurotransmitter. A simultaneous use of aniline and aminonaphthalene cages allows for the chromatic orthogonality and selective deprotection by UV-B or near-visible and UV-A light, respectively. The photochemical reaction mechanism of decaging was investigated by fluorescence measurements and laser flash photolysis, indicating that the heterolysis and elimination of carboxylic acids take place in the singlet excited state, delivering carbocation as an intermediate. The photoheterolysis in the singlet excited state, which directly releases caged substrates, is highly applicable for the photocages and has advantages compared to hitherto used nitrobenzyl derivatives.
Topics: Alcohols; Carboxylic Acids; Fluorescence; Light; Photolysis
PubMed: 35084183
DOI: 10.1021/acs.joc.1c02407 -
Bioorganic & Medicinal Chemistry Letters Aug 2023Previously we have demonstrated that light can be used to control the release of insulin in diabetic animals, followed by a reduction in blood glucose. This is...
Previously we have demonstrated that light can be used to control the release of insulin in diabetic animals, followed by a reduction in blood glucose. This is accomplished using a photoactivated depot (PAD) of insulin injected into the skin, and irradiated by a small external LED light source. In this work for the first time we demonstrate dose-response, showing that we can vary insulin release and commensurate blood glucose reduction by varying the amount of light administered. In addition to demonstrating dose-response, we have shown multi-day depot response, with insulin being released on two different days from the same depot. The material used in these studies was CD-insulin, a form of insulin that has a highly non-polar cyclododecyl group attached, markedly reducing the solubility of the modified material, and allowing it to form a depot upon injection. Upon photolysis, the cyclododecyl group is removed, releasing fully native, soluble insulin. Variable response and multi-day response as demonstrated strongly support the potential utility of the PAD approach for the variable and extended release of therapeutic peptides.
Topics: Animals; Insulin; Blood Glucose; Skin; Solubility; Photolysis
PubMed: 37369330
DOI: 10.1016/j.bmcl.2023.129388 -
The Journal of Physical Chemistry. A Feb 2022Criegee intermediates are important atmospheric oxidants, formed via the reaction of ozone with volatile alkenes emitted into the troposphere. Small Criegee...
Criegee intermediates are important atmospheric oxidants, formed via the reaction of ozone with volatile alkenes emitted into the troposphere. Small Criegee intermediates (e.g., CHOO and CHCHOO) are highly reactive, and their removal via unimolecular decay or bimolecular chemistry dominates their atmospheric lifetimes. As the molecular complexity of Criegee intermediates increases, their electronic absorption spectra show a bathochromic shift within the solar spectrum relevant to the troposphere. In these cases, solar photolysis may become a competitive contributor to their atmospheric removal. In this article, we report the conformer-dependent simulated electronic absorption spectra of two four-carbon-centered Criegee intermediates, methyl vinyl ketone oxide (MVK-oxide) and methacrolein oxide (MACR-oxide). Both MVK-oxide and MACR-oxide contain four low-energy conformers, which are convoluted in the experimentally measured spectra. Here, we deconvolute each conformer and estimate contributions from each of the four conformers to the experimentally measured spectra. We also estimate the photolysis rates and predict that solar photolysis should be a more competitive removal process for MVK-oxide and MACR-oxide (cf. CHOO and CHCHOO).
Topics: Acrolein; Butanones; Electronics; Oxides; Photolysis
PubMed: 35049299
DOI: 10.1021/acs.jpca.1c08381 -
Journal of Colloid and Interface Science May 2022The design and development of efficient and durable catalysts with visible-light response for photocatalytic hydrogen production and pollutants degradation is considered...
The design and development of efficient and durable catalysts with visible-light response for photocatalytic hydrogen production and pollutants degradation is considered as one of the most challenging tasks. In present work, a novel CuWS/NiTiO (abbreviated as × CWS/NTO; x = 0.25, 0.50, 0.75 and 1.00) composite was prepared via a facile electrospinning/calcination technique along with a convenient hydrothermal method. The as-prepared CWS/NTOcomposite was composed of 2D CWS nanosheets and 1D NTO nanofibers manifested by SEM and TEM images. The results of XPS verified the interfacial interaction between CWS and NTO, confirming the heterojunction formation in CWS/NTOcomposite. Photocatalytic tests demonstrated as-prepared CWS/NTO catalysts exhibited outstanding and stable photocatalytic performances for H production and pollutants degradation under visible light (λ > 420 nm) irradiation. Specially, 0.50 CWS/NTO sample displayed the highest H-evolution activity of 810 μmol·g·h with the apparent quantum efficiency (AQE) value of 1.65 % at 420 nm. Additionally, it also exhibited the optimal photodegradation properties with the rate constants of 0.030, 0.413 and 0.028 min for TC, RhB and Cr(VI), respectively. The excellent catalytic activities could be attributed to the enhanced visible-light adsorption, high specific surface area and efficient separation of photogenerated charge carriers. The ESR tests and free radicals capturing experiments confirmed that ·O and h were primary active species for TC/RhB degradation. Eventually, the probable catalytic mechanism was put forward and detailly analysed. The present work provides perspectives of rational design on NiTiO-based catalysts with superior photocatalytic performance for energy regeneration and environmental remediation.
Topics: Adsorption; Catalysis; Environmental Pollutants; Light; Photolysis
PubMed: 35033765
DOI: 10.1016/j.jcis.2021.10.179 -
Environmental Science and Pollution... Jul 2022Attaining a sustainable environment has become a prime area of research interest, as it is an utmost necessity for a healthy life. Hence, ample studies have been carried... (Review)
Review
Attaining a sustainable environment has become a prime area of research interest, as it is an utmost necessity for a healthy life. Hence, ample studies have been carried out in adopting different processes and utilizing various materials to attain the goal. Herein, we present an exclusive discussion on one such material, i.e., polyaniline (PANI) and its derivatives. Being an intrinsic conducting type, it has grabbed more attention due to its durability in different doped/un-doped states, promptness in structural alteration, and solution processability. This review presents an exhaustive discussion on published reports showing utilization of PANI and its derivative in various forms like pure and composites, for cleaning the environment through adsorption, photodegradation, etc., and the various methods adopted in order to achieve an optimum operating condition to obtain the maximum outcome. In addition to these merits and demerits, various technical challenges faced with materials have been also presented. Therefore, it is expected that this piece of work, presenting the exhaustive discussion on PANI and; its derivatives would help to develop a better understanding of this excellent conducting polymer PANI and provide a state of art on the role of this material for attaining sustainable surroundings for the living beings.
Topics: Adsorption; Aniline Compounds; Environmental Pollutants; Photolysis
PubMed: 35596869
DOI: 10.1007/s11356-022-20916-5 -
Environmental Technology Nov 2021In the present study, the HS photolysis using the self-made high-frequency discharge electrodeless lamp (light distribution was 90% at 254 nm and 10% at 185 nm) was...
In the present study, the HS photolysis using the self-made high-frequency discharge electrodeless lamp (light distribution was 90% at 254 nm and 10% at 185 nm) was studied and simulated by MATLAB software. Firstly, the effects of the initial HS concentration, irradiation time, oxygen content and relative humidity on HS photolysis efficiency were experimentally investigated. The results indicated that the photolysis efficiency decreased from 100% to 90.13% with the increase in the initial concentration from 3 to 30 mg/m, and the main product was HSO. With the relative humidity increased from 0% to 99%, HS photolysis efficiency was obviously improved under different atmospheres (O> air > Ar), indicating the significant effect of relative humidity and oxygen concentration. The simulation results were consistent with the experimental results, indicating the feasibility of the simulation model. Moreover, based on the photoreactions, model simulation and equilibrium analysis of sulphur species, the photodegradation pathway of HS was further inferred. HS was oxidized to HSO by O and other strong oxidizing radicals excited by 185 nm UV light.
Topics: Oxidation-Reduction; Photolysis; Ultraviolet Rays
PubMed: 32290784
DOI: 10.1080/09593330.2020.1756421