ORCID Profile
0000-0003-3541-6770
Current Organisations
Birla Institute of Technology and Science - Goa Campus
,
Hochschulen Fresenius gemeinnützige Trägergesellschaft mbH
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Organic Chemistry | Physical Organic Chemistry | Technology not elsewhere classified | Natural Products Chemistry | Organic Green Chemistry | Organic Chemical Synthesis | F-Block Chemistry
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in Technology |
Publisher: American Chemical Society (ACS)
Date: 17-12-2011
DOI: 10.1021/JP108832X
Abstract: The photoinduced oxidation of 1-naphthol to 1,4-naphthoquinone and of 5-hydroxy-1-naphthol to 5-hydroxy-1,4-naphthoquinone was studied by steady-state and time-resolved techniques. The direct photooxidation of naphthols in methanol or water takes place by reaction of the naphoxyl radical ((•)ONaph) with the superoxide ion radical (O(2)(•-)), the latter of which results from the reaction of the solvated electron with oxygen after photoionization. The sensitized oxidation takes place by energy transfer from the xanthene triplet state to oxygen. From the two oxygen atoms, which are consumed, one is incorporated into the naphthol molecule giving naphthoquinone and the second gives rise to water. The effects of eosin, erythrosin, and rose bengal in aqueous solution, pH, and the oxygen and naphthol concentrations were studied. The quantum yield of the photosensitized transformation was determined, which increases with the naphthol concentration and is largest at pH > 10. The quantum yield of oxygen uptake is similar. The pathway involving singlet molecular oxygen is suggested to operate for the three sensitizers. The alternative pathway via electron transfer from the naphthol to the xanthene triplet state and subsequent reaction of (•)ONaph with O(2)(•-), the latter of which is formed by scavenging of the xanthene radical anion by oxygen, does also contribute.
Publisher: Informa UK Limited
Date: 15-11-2011
Publisher: Springer Science and Business Media LLC
Date: 30-03-2017
DOI: 10.1038/SREP45599
Abstract: Optically transparent, smooth, defect-free, chemically inert and with good adhesion to a variety of substrates, plasma polymers from plant-derived secondary metabolites have been identified as promising encapsulating materials for organic electronics and photovoltaics. Here, we demonstrate that an encapsulating layer of plasma polymerized γ-terpinene reduces degradation-related loss in conversion efficiency in PCPDTBT:PC 70 BM solar cells under ambient operating conditions. The stability of γ-terpinene films was then investigated under extreme UV irradiation conditions as a function of deposition power. When exposed to ambient air, prolonged exposure to UV–A and UV–B light led to notable ageing of the polymer. Photooxidation was identified as the main mechanism of degradation, confirmed by significantly slower ageing when oxygen was restricted through the use of a quartz cover. Under unnatural high-energy UV–C irradiation, significant photochemical degradation and oxidation occurred even in an oxygen-poor environment.
Publisher: Elsevier BV
Date: 09-2016
DOI: 10.1016/J.TALANTA.2016.05.043
Abstract: The discovery of in-vitro systematic evolution of ligands by exponential enrichment (SELEX) process has considerably broaden the utility of aptamer as bio-recognition element, providing the high binding affinity and specificity against the target analytes. Recent research has focused on the development of structure switching signaling aptamer assay, transducing the aptamer- target recognition event into an easily detectable signal. In this paper, we demonstrate the development of structure switching aptamer assay for determination of aflatoxin M1 (AFM1) employing the quenching-dequenching mechanism. Hybridization of fluorescein labelled anti-AFM1 aptamer (F-aptamer) with TAMRA labelled complementary sequences (Q-aptamer) brings the fluorophore and the quencher into close proximity, which results in maximum fluorescence quenching. On addition of AFM1, the target induced conformational formation of antiparallel G-quadruplex aptamer-AFM1 complex results in fluorescence recovery. Under optimized experimental conditions, the developed method showed the good linearity with limit of detection (LOD) at 5.0ngkg(-1) for AFM1. The specificity of the sensing platform was carefully investigated against aflatoxin B1 (AFB1) and ochratoxin A (OTA). The developed assay platform showed the high specificity towards AFM1. The practical application of the developed aptamer assay was verified for detection of AFM1 in spiked milk s les. Good recoveries were obtained in the range from 94.40% to 95.28% (n=3) from AFM1 spiked milk s le.
Publisher: Springer Science and Business Media LLC
Date: 31-08-2014
DOI: 10.1007/S11356-014-3411-9
Abstract: Nanostructured titania supported on activated carbon (AC), termed as integrated photocatalytic adsorbents (IPCAs), were prepared by ultrasonication and investigated for the photocatalytic degradation of acetaminophen (AMP), a common analgesic and antipyretic drug. The IPCAs showed high affinity towards AMP (in dark adsorption studies), with the amount adsorbed proportional to the TiO2 content the highest adsorption was at 10 wt% TiO2. Equilibrium isotherm studies showed that the adsorption followed the Langmuir model, indicating the dependence of the reaction on an initial adsorption step, with maximum adsorption capacity of 28.4 mg/g for 10 % TiO2 IPCA. The effects of initial pH, catalyst amount and initial AMP concentration on the photocatalytic degradation rates were studied. Generally, the AMP photodegradation activity of the IPCAs was better than that of bare TiO2. Kinetic studies on the photocatalytic degradation of AMP under UV suggest that the degradation followed Langmuir-Hinshelwood (L-H) kinetics, with an adsorption rate constant (K) that was considerably higher than the photocatalytic rate constant (k r), indicating that the photocatalysis of AMP is the rate-determining step during the adsorption hotocatalysis process.
Publisher: Walter de Gruyter GmbH
Date: 04-1998
Publisher: Royal Society of Chemistry (RSC)
Date: 2006
DOI: 10.1039/B605906F
Publisher: Elsevier BV
Date: 11-2009
Publisher: Wiley
Date: 05-04-2004
Publisher: Elsevier BV
Date: 04-2018
Publisher: Wiley
Date: 25-04-2000
Publisher: Wiley
Date: 03-04-2009
Publisher: Elsevier BV
Date: 02-2006
Publisher: Springer Science and Business Media LLC
Date: 14-09-2012
Publisher: American Chemical Society (ACS)
Date: 20-08-2012
DOI: 10.1021/OL301773R
Abstract: A novel, multimicrocapillary flow reactor (MμCFR) was constructed and applied to a series of sensitized photoadditions involving 2(5H)-furanones. The reactor allowed for rapid and energy-, time-, and space-efficient sensitizer screening, process optimization, validation, scale-up, and library synthesis.
Publisher: Elsevier BV
Date: 02-2006
Publisher: Wiley
Date: 12-03-2012
Publisher: Wiley
Date: 26-03-2007
DOI: 10.1002/CHIR.20391
Abstract: Ultraviolet absorption (UV) and electronic circular dichroism (ECD) spectra of enantiopure (Z)-8-methoxy-4-cyclooctenone (MCO) were measured in hexane to give a normal single UV absorption band at 298 nm, which is assigned to the carbonyl's pi*<--n transition. Unexpectedly, the ECD spectrum exhibited an apparent couplet pattern with vibrational fine structures. Obviously, the conventional CD exciton coupling mechanism cannot be applied to this bisignate CD signal observed for single-chromophoric MCO. Variable temperature-ECD and vibrational circular dichroism (VCD) spectral measurements, simultaneous UV and ECD spectral band resolution, and density functional theory (DFT) calculations of energy and structure revealed that this apparent CD couplet originates from a rather complicated spectral overlap of more than three conformers of MCO, two of which exhibit mirror-imaged ECD spectra at appreciably deviated wavelengths. In the simultaneous band-resolution analysis, the observed UV and ECD spectra were best fitted to four overlapping bands. Two major conformers were identified by comparing the experimental IR and VCD spectra with the simulated ones, and the other two by comparing the observed UV and ECD spectra with the theoretical ones obtained by time-dependent DFT calculations. It was shown that the combined use of experimental ECD and VCD spectra and theoretical DFT calculations can give a reasonable interpretation for the Cotton effects of the conformationally flexible molecule MCO.
Publisher: Informa UK Limited
Date: 19-05-2015
Publisher: American Chemical Society (ACS)
Date: 11-05-2016
DOI: 10.1021/ACS.CHEMREV.5B00720
Abstract: Natural sunlight offers a cost-efficient and sustainable energy source for photochemical reactions. In contrast to the lengthy and small-scale "flask in the sun" procedures of the past, modern solar concentrator systems nowadays significantly shorten reaction times and enable technical-scale operations. After a brief historical introduction, this review presents the most important solar reactor types and their successful application in preparative solar syntheses. The ex les demonstrate that solar manufacturing of fine chemicals is technically feasible and environmentally sustainable. After over 100 years, Ciamician's prophetic vision of "the photochemistry of the future" as a clean and green manufacturing methodology has yet to be realized. At the same time, his warning "for nature is not in a hurry but mankind is" is still valid today. It is hoped that this review will lead to a renewed interest in this truly enlightening technology, that it will stimulate photochemists and photochemical engineers to "go back to the roots onto the roofs" and that it will ultimately result in industrial applications in the foreseeable future.
Publisher: Springer Science and Business Media LLC
Date: 06-06-2014
Publisher: MDPI AG
Date: 09-03-2022
DOI: 10.3390/MOLECULES27061781
Abstract: Flavonoids are polyphenols with broad known pharmacological properties. A series of 2,3-dihydroflavanone derivatives were thus synthesized and investigated for their anti-inflammatory activities. The target flavanones were prepared through cyclization of 2′-hydroxychalcone derivatives, the later obtained by Claisen–Schmidt condensation. Since nitric oxide (NO) represents an important inflammatory mediator, the effects of various flavanones on the NO production in the LPS-induced RAW 264.7 macrophage were assessed in vitro using the Griess test. The most active compounds were flavanone (4G), 2′-carboxy-5,7-dimethoxy-flavanone (4F), 4′-bromo-5,7-dimethoxy-flavanone (4D), and 2′-carboxyflavanone (4J), with IC50 values of 0.603, 0.906, 1.030, and 1.830 µg/mL, respectively. In comparison, pinocembrin achieved an IC50 value of 203.60 µg/mL. Thus, the derivatives synthesized in this work had a higher NO inhibition capacity compared to pinocembrin, demonstrating the importance of pharmacomodulation to improve the biological potential of natural molecules. SARs suggested that the use of a carboxyl-group in the meta-position of the B-ring increases biological activity, whereas compounds carrying halogen substituents in the para-position were less active. The addition of methoxy-groups in the meta-position of the A-ring somewhat decreased the activity. This study successfully identified new bioactive flavanones as promising candidates for the development of new anti-inflammatory agents.
Publisher: Wiley
Date: 09-10-2001
Publisher: American Chemical Society (ACS)
Date: 24-10-2018
Publisher: Elsevier BV
Date: 05-2005
Publisher: Elsevier BV
Date: 05-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1TA10608B
Abstract: Radio frequency (RF) plasma polymerization of plant extracts offers an effective large scale encapsulation method for organic photovoltaics (OPVs).
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 10-2002
Publisher: American Chemical Society (ACS)
Date: 17-11-2010
DOI: 10.1021/IE101304A
Publisher: Elsevier BV
Date: 06-2018
Publisher: Wiley
Date: 19-11-2002
Publisher: Elsevier BV
Date: 11-2009
Publisher: MDPI AG
Date: 26-12-2016
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/EN13098
Abstract: Environmental context Diclofenac, a common non-steroidal anti-inflammatory drug, is not completely removed from surface and drinking water by conventional treatment methods. Consequently, this drug is present in the aquatic environment and has been subsequently linked to toxic effects on organisms. We show that photolysis and TiO2-catalysed degradation in circulating batch reactors efficiently results in diclofenac removal under a variety of conditions. These photochemical methods thus may lead to more effective water treatment processes. Abstract The occurrence of diclofenac (DCF) as an emerging pollutant in surface waters and drinking water has been attributed to elevated global consumption and the inability of sewage treatment plants to remove DCF. In this study, DCF spiked drinking water and river water was subjected to photolysis and TiO2 photocatalytic treatments in a circulating laboratory-scale (immersion-well) and a demonstration-scale loop reactor (Laboclean). The operational parameters for the immersion-well reactor were optimised as follows: TiO2 P25 loading, 0.1gL–1 natural pH, 6.2 initial concentration, 30mgL–1 water type, distilled water. Complete DCF removal was realised within 15min under the optimised conditions using the immersion-well reactor. Sunlight-mediated photochemical degradation required a prolonged exposure period of up to 360min for complete DCF removal. DCF in distilled and drinking water was efficiently degraded in the larger Laboclean reactor. Differences were, however, observed based on their pseudo-first-order rate constants, which implies that the water matrix has an effect on the degradation rate. Six major photoproducts, 2-(8-chloro-9H-carbazol-1-yl)acetic acid, 2-(8-hydroxy-9H-carbazol-1-yl)acetic acid, 2,6-dichloro-N-o-tolylbenzenamine, 2-(phenylamino)benzaldehyde, 1-chloromethyl-9H-carbazole and 1-methyl-9H-carbazole, generated from TiO2 photocatalysis of DCF were identified by liquid chromatography–mass spectrometry (LCMS) and Fourier transform–ion cyclotron resonance–mass spectrometry (FT-ICR-MS). This work has shown that photocatalytic degradation kinetics of DCF are dependent on both the geometry of the photoreactor and the nature of the water matrices.
Publisher: Wiley
Date: 04-2001
DOI: 10.1002/1521-3765(20010401)7:7<1530::AID-CHEM1530>3.0.CO;2-L
Abstract: The photophysical and photochemical properties of N-phthaloyl-methionine (1), S-methyl-N-phthaloyl-cysteine methyl ester (2) and N-phthaloyltranexamic acid (3) were studied by time-resolved UV/Vis spectroscopy, using laser pulses at 248 or 308 nm. The quantum yield of fluorescence is low (phi(f)< 10(-2)) for 1-3 in fluid and glassy media, whereas that of phosphorescence is large (0.3-0.5) in ethanol at - 196 degrees C. The triplet properties were examined in several solvents, at room temperature and below. The spectra and decay kinetics are similar, but the population of the pi(pi*) triplet state, as measured by T-T absorption, is much lower for 1 and 2 than for 3 or N-methyltrimellitimide (5') at ambient temperatures. The quantum yield (phi(delta)) of singlet molecular oxygen O2(1deltag) formation is substantial for 3 and 5' in several air- or oxygen-saturated solvents at room temperature, but small for 2 and 1. The quantum yield of decomposition is substantial (0.2-0.5) for 3 and small (<0.05) for 2 and 1. It is postulated that photoinduced charge separation in the spectroscopically undetectable 3n,pi* state may account for the cyclization products of 1 and 2. In aqueous solution, this also applies for 3, whereas in organic solvents cyclization involves mainly the lower lying 3pi,(pi*) state. Triplet acetone, acetophenone and xanthone are quenched by 1-3 in acetonitrile the rate constant is close to the diffusion-controlled limit, but smaller for benzophenone. While the energy transfer from the triplet ketone occurs for 3, a major contribution of electron transfer to the N-phthalimide derivative is suggested for 1 and 2, where the radical anion of benzophenone or 4-carboxybenzophenone is observed in alkaline aqueous solution.
Publisher: American Chemical Society (ACS)
Date: 23-08-2002
DOI: 10.1021/JA025804O
Abstract: An elaborated protocol is described which allows the efficient transformation of di-, tri-, and tetrapeptides into cyclopeptides with a minimum of protection and activation chemistry using the photoinduced electron transfer initiated decarboxylation of N-phthaloyl peptides resulting in C-C coupling between the initially formed carbon radicals.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2GC16439F
Publisher: Springer Science and Business Media LLC
Date: 26-05-2016
Publisher: Walter de Gruyter GmbH
Date: 2007
Abstract: Three photochemical reactions were investigated under solar irradiation conditions with moderately concentrated sunlight: the photoacylation of naphthoquinone with butyraldehyde and the dye-sensitized photooxygenations of citronellol and 1,5-dihydroxynaphthalene, respectively. All reactions were easily performed on multigram-to-kilogram scales using cheap and commercially available starting materials, and yielded important key intermediates for industrial applications.
Publisher: Springer Science and Business Media LLC
Date: 09-2011
DOI: 10.1039/C1PP05024A
Abstract: Three types of micro-photoreactor setups were investigated using DMBP-sensitized additions of isopropanol to furanones as model reactions. The results were compared to experiments using a conventional batch reactor. Based on conversion rates, reactor geometries and energy efficiency calculations the microsystems showed superior performances over the batch process. Of the three micro setups examined, the LED-driven microchip gave the best overall results.
Publisher: American Chemical Society (ACS)
Date: 23-01-2002
DOI: 10.1021/JP011090C
Publisher: Springer Science and Business Media LLC
Date: 04-2003
DOI: 10.1039/B212357F
Publisher: MDPI AG
Date: 05-09-2011
Publisher: Walter de Gruyter GmbH
Date: 04-2001
Publisher: Springer Science and Business Media LLC
Date: 11-2008
DOI: 10.1039/B808778D
Abstract: The use of a confined space in which to carry out reactions has proven popular in recent years, as demonstrated by the large volume of work published on 'molecular microreactors' such as zeolites, micelles and nanoparticles. This article looks at reactions in microstructured reactors, also known as microchannelled reactors or microreactors. In general, these consist of a 'chip' with narrow channels etched into it. Microstructured reactors have been the subject of several review articles to date, focusing on preparation, types of reactions that may be carried out and on the potential for 'green' applications. However, the use of microstructured reactor technology in photochemistry has, until now, not been subject to review. This perspective aims to outline the work done to date in this area and in particular to demonstrate the advantages and future prospectives of this technology in photochemical processes. Photochemistry in microstructured reactors is an emerging area of interest and to date has demonstrated significant potential as a viable alternative to traditional photochemical synthesis.
Publisher: Wiley
Date: 28-09-1999
Publisher: Walter de Gruyter GmbH
Date: 06-01-2015
Abstract: Radicals are easily generated via hydrogen transfer form secondary alcohols or tertiary amines using photochemical sensitization with ketones. They can subsequently add to the electron deficient double bond of furanones. The addition of the alcohols is particularly efficient. Therefore, this reaction was used to characterize and to compare the efficiency of different photochemical continuous flow microreactors. A range of micro-structured reactors were tested and their performances evaluated. The enclosed microchip enabled high space-time-yields but its microscopic dimensions limited its productivity. In contrast, the open microcapillary model showed a greater potential for scale-up and reactor optimization. A 10-microcapillary reactor was therefore constructed and utilized for typical R& D applications. Compared to the corresponding batch processes, the microreactor systems gave faster conversions, improved product qualities and higher yields. Similar reactions have also been carried out with electronically excited furanones and other α,β-unsaturated ketones. In this case, hydrogen is transferred directly to the excited olefin. This reaction part may occur either in one step, i.e., electron and proton are transferred simultaneously, or it may occur in two steps, i.e., the electron is transferred first and the proton follows. In the first case, a C–C bond is formed in the α position of the α,β-unsaturated carbonyl compound and in the second case this bond is formed in the β position. For the first reaction, the influence of stereochemical elements of the substrate on the regioselectivity of the hydrogen abstraction on the side chain has been studied.
Publisher: Springer Science and Business Media LLC
Date: 07-06-2014
DOI: 10.1007/S12010-014-0985-0
Abstract: There is a need for analytical methods capable of monitoring urea levels in urine for patients under clinical monitoring to appraise renal function. Herein, we present a practical method to quantify levels of urea in human urine s les using flow injection analysis-enzyme thermistor (FIA-ET) biosensor. The biosensor comprises a covalently immobilized enzyme urease (Jack bean) on aminated silica support, which selectively hydrolyzes the urea present in the s le. Under optimized conditions, the developed biosensor showed a linear response in the range of 10-1,000 mM, R (2) = 0.99, and response time of 90 s in 100 mM phosphate buffer (PB) (flow rate of 0.5 mL/min, s le volume of 0.1 mL, and pH 7.2). The urea-spiked human urine s les showed minimal matrix interference in the range of 10-1,000 mM. Recoveries were obtained (92.26-99.80 %) in the spiked urine s les. The reliability and reproducibility of the developed biosensor were found satisfactory with percent relative standard deviation (% RSD) = 0.741. The developed biosensor showed excellent operational stability up to 30 weeks with 20 % loss in original response when used continuously at room temperature. These results indicate that the developed biosensor could be very effective to detect low and high levels of urea in urine s les.
Publisher: Springer Science and Business Media LLC
Date: 03-2004
DOI: 10.1039/B312263H
Abstract: The photodecarboxylation reactions of omega-phthalimidoalkynoates have been studied and the influence of the geometrically restricted acetylene linker on the photocyclization efficiency investigated. Less flexible starting materials give solely CO(2)H/H-exchange products in good yields. In contrast, derivatives with appropriate chain lengths give the corresponding macrocycles in fair to moderate isolated yields. Furthermore, photodecarboxylative addition of alkynoates to N-methylphthalimide gives hydroxyphthalimidines in acceptable yields.
Publisher: American Chemical Society (ACS)
Date: 14-10-2010
DOI: 10.1021/OL102184U
Abstract: A series of acetone-sensitized photodecarboxylation reactions involving phthalimides have been investigated using conventional and microphotochemistry. Both, intra- and intermolecular transformations were compared. In all cases examined, the reactions performed in microreactors were superior in terms of conversions or isolated yields. These findings unambiguously prove the advantage of microphotochemistry over conventional photochemical techniques.
Publisher: Elsevier BV
Date: 09-2010
Publisher: Elsevier BV
Date: 09-2022
Publisher: Elsevier BV
Date: 08-2018
Publisher: Springer Science and Business Media LLC
Date: 24-08-2013
Publisher: Walter de Gruyter GmbH
Date: 12-2002
Publisher: University of Western Ontario, Western Libraries
Date: 04-08-2017
Abstract: This study explored the Walhallow Aboriginal community’s experiences with drinking water to gain a shared understanding about community concerns and to develop ways to address these concerns together. There is a strong connection between people and water, as well as a need to appreciate the social factors associated with the unique cultural and socioeconomic factors that the provision of drinking water has for Aboriginal communities. We used a mixed method design within a community-based participatory action Research (PAR) framework. Water hardness and parental influence were the key factors associated with participants’ decisions to drink rainwater. This study provides important insights for water supply authorities when assessing health risks and when choosing appropriate mitigation measures for water quality improvement programs in Aboriginal communities.
Publisher: Elsevier BV
Date: 2011
Publisher: Elsevier BV
Date: 07-2010
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C004869K
Publisher: Springer Science and Business Media LLC
Date: 06-2012
Publisher: Wiley
Date: 22-12-2015
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/CH15623
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/CH20138
Abstract: A series of photochemical transformations has been successfully conducted under continuous-flow conditions in a concentrating solar trough reactor. Photoacylations and [2+2]-photocycloadditions involving 1,4-naphthoquinones gave the corresponding photoproducts in moderate to high yields with residence times of 70min. Likewise, acetone-sensitized photodecarboxylations involving phthalimides furnished the corresponding benzylated hydroxy phthalimidines in good to excellent yields and purity with residence times of 40min. Compared with corresponding exposures to direct sunlight conducted in a solar float, flow operation generally gave superior conversions and subsequent yields.
Publisher: Wiley
Date: 10-03-2023
Abstract: Biodiesel is produced on a large scale as an eco‐friendly substitute and additive to fossil fuels. Catalytic homogeneous processes using strong acids, alkalis, and natural oils have been realized in industry. However, these traditional methods have several disadvantages, such as the generation of large volumes of waste, high water and reagent needs, use of hazardous reagents, high operation costs, and utilization of valuable feedstocks and catalysis, respectively. Different solutions have subsequently been investigated, such as cheap alternative feedstocks, co‐solvents and catalysts, sustainable operational conditions, advanced reactor designs and scales, and advantageous pre‐ and post‐reaction treatments. This review explores and analyzes the main aspects of current biodiesel technologies and opportunities. It also describes some advanced improvement strategies.
Publisher: Elsevier BV
Date: 06-2017
Publisher: Walter de Gruyter GmbH
Date: 12-2002
Publisher: Walter de Gruyter GmbH
Date: 2000
Publisher: MDPI AG
Date: 22-09-2015
Publisher: Elsevier BV
Date: 11-2015
Publisher: Wiley
Date: 03-08-1999
Publisher: Springer Science and Business Media LLC
Date: 06-2011
DOI: 10.1039/C0PP00368A
Abstract: Activated carbon-supported TiO(2) nanoparticles, termed integrated photocatalytic adsorbents (IPCAs), were prepared using an ultrasonic impregnation technique and investigated for the photocatalytic degradation of amoxicillin (AMO), a β-lactam antibiotic. The IPCAs had high adsorption affinity for AMO with the amount adsorbed proportional to the TiO(2) loading and the highest adsorption was at 10 wt% TiO(2) loading. A pseudo-second-order model was found to fit the experimental data and consistently predicted the amount of AMO adsorbed over the adsorption period. Equilibrium isotherm studies showed that the adsorption followed the Redlich-Peterson model with maximum adsorption capacity of 441.3 mg g(-1) for 10% IPCA, 23% higher than the pure activated carbon (AC). Kinetic studies on the photocatalytic degradation of AMO using non-linear regression analysis suggest that the degradation followed Langmuir-Hinshelwood (L-H) kinetics. The adsorption rate constant (K(ad)) was considerably higher than the photocatalytic rate constant (k(L-H)), indicating that the photocatalysis of AMO is the rate-determining step during the adsorption hotocatalysis process. The 10% IPCA exhibited excellent stability and reusability over four photodegradation cycles.
Publisher: Wiley
Date: 02-11-2005
Publisher: Springer Science and Business Media LLC
Date: 12-2010
DOI: 10.1039/C0PP00223B
Abstract: The DMBP-sensitized addition of isopropanol to furanones was studied in a novel LED-driven microchip reactor. Complete conversions were achieved after just 2.5 to 5 min of irradiation with 6 × 365 nm high-power LEDs. The results were compared to analogous experiments using a conventional batch reactor.
Publisher: Wiley
Date: 12-2002
Publisher: Elsevier BV
Date: 12-2010
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/CH18220
Abstract: Owing to their favourable photophysical and electrochemical properties, phthalimides undergo a variety of highly efficient photodecarboxylation reactions. These transformations have been applied to the synthesis of macrocyclic compounds as well as bioactive addition adducts. N-Acetoxyphthalimides are versatile precursors to imidyl and alkyl radicals through photodecarboxylation and have subsequently been used for a variety of coupling reactions. The generally mild reaction conditions make these reactions attractive for green chemical applications. The process protocols were successfully transferred to novel photoreactor devices, among these falling film or continuous flow reactors.
Publisher: Georg Thieme Verlag KG
Date: 12-08-2010
Publisher: Walter de Gruyter GmbH
Date: 03-1999
Publisher: Beilstein Institut
Date: 02-08-2011
DOI: 10.3762/BJOC.7.121
Abstract: A series of 4,4'-dimethoxybenzophenone mediated intra- and intermolecular photodecarboxylation reactions involving phthalimides have been examined under microflow conditions. Conversion rates, isolated yields and chemoselectivities were compared to analogous reactions in a batch photoreactor. In all cases investigated, the microreactions gave superior results thus proving the superiority of microphotochemistry over conventional technologies.
Publisher: Beilstein Institut
Date: 20-12-2017
DOI: 10.3762/BJOC.13.275
Abstract: The synthesis of various 3-arylmethylene-2,3-dihydro-1 H -isoindolin-1-ones was realized following a simple three-step process. The protocol utilized the photodecarboxylative addition of readily available carboxylates to N -(bromoalkyl)phthalimides as a versatile and efficient key step. The initially obtained hydroxyphthalimidines were readily converted to the desired N -diaminoalkylated 3-arylmethylene-2,3-dihydro-1 H -isoindolin-1-ones via acid-catalyzed dehydration and subsequent nucleophilic substitution with the corresponding secondary amines. The procedure was successfully applied to the synthesis of known local anesthetics (AL-12, AL-12B and AL-5) in their neutral forms.
Publisher: Wiley
Date: 06-01-2017
Publisher: Elsevier BV
Date: 08-2009
Publisher: Springer Science and Business Media LLC
Date: 17-11-2010
Publisher: Wiley
Date: 28-04-2022
Abstract: Methyl oleate, an ex le of a FAME (fatty acid methyl ester), was produced by oleic acid (OA) photoesterification with TiO 2 and UVA light. Different parameters were evaluated and optimised: catalyst pretreatment, temperature (25–65 °C), catalyst loading (1–30 % w/w OA ) and oleic acid : alcohol molar ratio (1 : 3–1 : 55). Response surface quadratic methodology obtained by central composite rotational design (RSM‐CCRD) was used to evaluate the main operational conditions of the photoesterification process. A high conversion of 98 % (±0.8) at 55 °C, 20 % TiO 2 (w/w OA ), and 1(OA) : 55(methanol) molar ratio was achieved. The photoesterification mechanism is furthermore proposed. The Langmuir‐Hinshelwood kinetic model considered the forward and backward reaction as first‐order fits with the best accuracy (R 2 of 0.997). The thermodynamic results (ΔG 338.15K =−20.75 kJ/mol, ΔH=13.75 kJ/mol, and ΔS=0.47 kJ/mol.K) indicate that the operating conditions are important, both to supply the energy requirement of the reaction, but also to increase the miscibility of the reactants.
Publisher: MDPI AG
Date: 11-12-2019
DOI: 10.3390/MOLECULES24244527
Abstract: An effective multi-step continuous flow approach towards N-diaminoalkylated 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones, including the local anesthetic compound AL-12, has been realized. Compared to the traditional decoupled batch processes, the combined photochemical–thermal–thermal flow setup rapidly provides the desired target compounds in superior yields and significantly shorter reaction times.
Publisher: Wiley
Date: 07-04-2004
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6OB00842A
Abstract: Organic photochemistry when applied to synthesis strongly interacts in a very fruitful way with physical chemistry. A profound understanding of the photochemical reaction mechanisms is indispensable for optimization and application of these reactions.
Publisher: Wiley
Date: 19-03-2002
Publisher: Wiley
Date: 15-12-2011
Publisher: Elsevier BV
Date: 03-2012
Publisher: Elsevier BV
Date: 06-2016
Publisher: Georg Thieme Verlag KG
Date: 26-11-2008
Publisher: MDPI AG
Date: 29-01-2014
DOI: 10.3390/PR2010158
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B816676E
Publisher: Wiley
Date: 08-09-2011
Publisher: Wiley
Date: 23-04-2014
Publisher: Elsevier BV
Date: 08-2018
DOI: 10.1016/J.JENVMAN.2018.04.103
Abstract: Pharmaceuticals, which are frequently detected in natural and wastewater bodies as well as drinking water have attracted considerable attention, because they do not readily biodegrade and may persist and remain toxic. As a result, pharmaceutical residues pose on-going and potential health and environmental risks. To tackle these emerging contaminants, advanced oxidation processes (AOPs) such as photo-Fenton, sonolysis, electrochemical oxidation, radiation and ozonation etc. have been applied to remove pharmaceuticals. These processes utilize the high reactivity of hydroxyl radicals to progressively oxidize organic compounds to innocuous products. This review provides an overview of the findings from recent studies, which have applied AOPs to degrade pharmaceutical compounds. Included is a discussion that links various factors of TiO
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B414230F
Publisher: Elsevier
Date: 2013
Publisher: MDPI AG
Date: 17-03-2021
DOI: 10.3390/MOLECULES26061685
Abstract: Photooxygenation reactions involving singlet oxygen (1O2) are utilized industrially as a mild and sustainable access to oxygenated products. Due to the usage of organic dyes as photosensitizers, these transformations can be successfully conducted using natural sunlight. Modern solar chemical reactors enable outdoor operations on the demonstration (multigram) to technical (multikilogram) scales and have subsequently been employed for the manufacturing of fine chemicals such as fragrances or biologically active compounds. This review will highlight ex les of solar photooxygenations for the manufacturing of industrially relevant target compounds and will discuss current challenges and opportunities of this sustainable methodology.
Publisher: American Chemical Society (ACS)
Date: 22-09-2000
DOI: 10.1021/JO001070R
Abstract: The regioselectivity of photoinduced electron-transfer (PET) reactions of unsymmetrical phthalimides is controlled by the spin density distribution of the intermediate radical anions. ROHF ab initio calculations were found to be most suitable for atomic spin density analysis. Intramolecular PET reactions of quinolinic acid imides were studied with the potassium butyrate and hexanoate 1a,b and a cysteine derivative 3. The photocyclizations products 2a,b and 4 were formed with moderate regioselectivities (68:32, 57:43, and 81:19) showing preferential ortho cyclization. The intermolecular reaction of potassium propionate and potassium isobutyrate with N-methylquinolinic acid imide (5) yielded as addition products the dihydropyrrolo[3,4-b]pyridines 6a,b with slight ortho regioselectivity (55:45). In contrast to these low regioselectivities, the PET reaction of potassium propionate with the methyl ester of N-methyltrimellitic acid imide (9) yielded solely the para addition product 10. Likewise, the intramolecular photoreaction of the cysteine derivative 7 gave a 75:25 (para/meta) mixture of regioisomeric cyclization products 8. The regioselectivity originates from donor-acceptor interactions prior to electron transfer and differences in spin densities in the corresponding imide radical anions. The results of DFT and ab initio calculations for the radical anions of the quinolinic acid imide (11(*)(-)) and the methyl ester of trimellitic acid imide (12(*)(-))( )()were in agreement with the latter assumption: spin densities in 11(*)(-) were higher for the imido ortho carbon atoms (indicating preferential ortho coupling) for 12(*)(-) the spin densities were higher for the imido para carbon atoms (indicating preferential para coupling). These correlations became more significant when the additional spin densities at the carbonyl oxygen and the adjacent carbon atoms were taken into account. The cyclization selectivities for 2, 4, and 8 deviate from the intermolecular ex les probably because of ground-state and solvent effects.
Publisher: Walter de Gruyter GmbH
Date: 12-2002
Publisher: Beilstein Institut
Date: 04-10-2013
DOI: 10.3762/BJOC.9.237
Abstract: [2 + 2]-Cycloadditions of cyclopentene and 2,3-dimethylbut-2-ene to furanone were investigated under continuous-flow conditions. Irradiations were conducted in a FEP-microcapillary module which was placed in a Rayonet chamber photoreactor equipped with low wattage UVC-l s. Conversion rates and isolated yields were compared to analogue batch reactions in a quartz test tube. In all cases examined, the microcapillary reactor furnished faster conversions and improved product qualities.
Publisher: Hindawi Limited
Date: 13-07-2017
DOI: 10.1111/ARE.13128
Publisher: Elsevier BV
Date: 10-2012
Publisher: Elsevier BV
Date: 10-2012
Publisher: Walter de Gruyter GmbH
Date: 04-2014
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/CH13591
Abstract: Continuous-flow microreactors offer major advantages for photochemical applications. This mini-review summarizes the technological development of microflow devices in the Applied and Green Photochemistry Group at James Cook University, and its associates, from fixed microchips for microscale synthesis to flexible multicapillary systems for parallel photochemistry. Whereas the enclosed microchip offered high space–time-yields, the open capillary-type reactor showed a greater potential for further modifications. Consequently, a 10-microcapillary reactor was constructed and used successfully for process optimization, reproducibility studies, scale-up, and library synthesis. To demonstrate the superiority of microflow photochemistry over conventional batch processes, the reactors were systematically evaluated using alcohol additions to furanones as model reactions. In all cases, the microreactor systems furnished faster conversions, improved product qualities, and higher yields. UVC-induced [2+2] cycloadditions of furanone with alkenes were exemplarily examined in a capillary reactor, thus proving the broad applicability of this reactor type.
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 09-2011
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/CH15356
Abstract: A series of photodecarboxylative benzylations of N-methoxyphthalimide were successfully realised using easily accessible starting materials. The reactions proceeded smoothly and the corresponding benzylated hydroxyphthalimidines were obtained in moderate to good yields of 52–73 %. No competing photoinduced dealkoxylation of the N-methoxy group was observed. The reaction with potassium phenylacetate was subsequently investigated in an advanced continuous-flow photoreactor. The reactor allowed rapid optimization of the reaction conditions and gave the desired benzylated product in higher yield and shorter irradiation time compared with the batch process.
Publisher: Elsevier BV
Date: 04-2017
Publisher: Wiley
Date: 29-09-2015
Publisher: Springer Science and Business Media LLC
Date: 05-11-2014
Publisher: Wiley
Date: 02-12-2010
Publisher: American Chemical Society (ACS)
Date: 30-11-2000
DOI: 10.1021/JO001089U
Abstract: The photochemistry of five linear methylthiomethyl (MTM)-esters of omega-phthalimido carboxylic acids Pht=N-(CH(2))(n)()COOCH(2)SCH(3) 1a-e (n = 1, 2, 3, 5, and 10), of the two methylthioethyl (MTE)-esters Pht=N-(CH(2))(n)()COOCH(2)CH(2)SCH(3) 2a,b (n = 1, 2), and of the two methyl-substituted MTM/MTE esters 3a and 3b was investigated. Two reaction channels were observed: (i) photocyclization to give medium-sized and macrocyclic rings, (ii) photochemical deprotection to give the free carboxylic acids. Photocyclization of 1b and 1c (n = 2, 3) resulted in 4b,c in excellent yields whereas the substrates 1a and 1d,e with shorter as well as longer spacer groups (n = 1, 5, 10) gave preferentially the deprotected products 5a,d,e. Subsequent photolysis afforded N-methylphthalimide (6) from 5a. The MTE-esters 2a and 2b gave the macrocyclic lactones 7 and E-8. Thus, the competition between cyclization and deprotection strongly depended on the chain length of the hydrocarbon linker between phthalimido chromophore and ester group. To examine the influence of the position of the ester group in the linker chain the model substrates 3a and 3b with identical number of atoms separating electron donor and acceptor group were investigated. The more flexible MTE-derivative 3b cyclized to give a 4:1 diastereoisomeric mixture of cis/trans-9b, whereas photolysis of the more reluctant MTM-ester 3a resulted in cis-9a only after prolonged irradiation. These results show that MTM can function as a photolabile protecting group whereas MTE cannot be removed photochemically. The distance dependence of the secondary reaction steps indicates that the primary electron transfer is not necessarily induced starting from close contact geometries.
Publisher: MDPI AG
Date: 11-05-2018
Publisher: Elsevier BV
Date: 05-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B913252J
Publisher: The Japan Institute of Heterocyclic Chemistry
Date: 2005
DOI: 10.3987/REV-05-601
Publisher: American Chemical Society (ACS)
Date: 05-2001
DOI: 10.1021/OL0155900
Abstract: Hydrogen bond and potassium cation mediated preorientation were detected for phthalimido acetic acid and the corresponding acetate. Evidence for these phenomena came from X-ray structure analysis as well as cyclic voltammetric and IR spectroscopic measurements. These interactions rationalize the photoinduced electron transfer (PET) reactivity of the substrates in photodecarboxylation reactions.
Publisher: Royal Society of Chemistry (RSC)
Date: 02-10-2001
DOI: 10.1039/B106425H
Location: India
Location: Japan
Location: Germany
Start Date: 08-2013
End Date: 12-2017
Amount: $240,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 02-2015
End Date: 12-2015
Amount: $270,000.00
Funder: Australian Research Council
View Funded Activity