Готові списки джерел за темами / O-nitrobenzyl esters

Добірка наукової літератури з теми "O-nitrobenzyl esters"

Автор: Grafiati

Опубліковано: 14 березня 2023

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Статті в журналах з теми "O-nitrobenzyl esters"

Schupp, H., W. K. Wong, and W. Schnabel. "Mechanistic studies of the photorearrangement of o-nitrobenzyl esters." Journal of Photochemistry 36, no. 1 (January 1987): 85–97. http://dx.doi.org/10.1016/0047-2670(87)87064-8.

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Humeres, Eduardo, Luiz Fernando Sequinel, Mauricéa Nunes, Célia MS Oliveira, and Patrick J. Barrie. "Kinetic effects induced by cellulose on water-catalyzed reactions. Hydrolysis of 2,4-dinitrophenyl cellulose xanthate and some sugar xanthate ester analogues." Canadian Journal of Chemistry 76, no. 6 (June 1, 1998): 960–65. http://dx.doi.org/10.1139/v98-046.

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The hydrolysis of 2,4-dinitrophenyl cellulose xanthate (CelXDNP) was studied in 10% v/v aqueous ethanol at 25°C and μ = 0.1 (KCl). The water-catalyzed hydrolysis showed that, as for p-nitrobenzyl cellulose xanthate, it occurs through two parallel reactions with rate constants k'H2O = 4.40 x 10-3 s-1 for the fast hydrolysis, and k''H2O = 6.90 x 10-5 s-1 for the slow hydrolysis. The entropy of activation of the fast hydrolysis was 0.7 ± 1.8 cal K-1 mol-1. External nucleophiles such as hydroxide and simple amines show simple first-order kinetics. The spontaneous hydrolysis of CelXDNP in acetone-water mixtures indicates that the fast reaction does not occur through water polymers and that for water molarity higher than 30 M there are no acetone molecules (or very few) in the highly ordered cybotactic region of cellulose. The spontaneous hydrolysis of methyl 4,6-O-benzylidene- α -D-glucopyranoside 3-(S-p-nitrobenzyl-xanthate) although is faster than the 6-isomer, it is slower than the fast hydrolysis of p-nitrobenzyl cellulose xanthate (CelXNB). Also Δ Sdouble dagger is highly negative (-41.0 cal K-1 mol-1), as it is for alkyl and sugar analogues. Only for the fast hydrolyses of CelXDNP and CelXNB is the entropy of activation almost zero. It is concluded that there is no neighbouring OH effect on the fast hydrolysis of cellulose xanthate esters. Key words: hydrolysis, water catalysis, cellulose xanthate esters, methyl glucose, xanthate esters, neighbouring OH effect.

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Zhu, Q. Q., W. Schnabel, and H. Schupp. "Formation and decay of nitronic acid in the photorearrangement of o-nitrobenzyl esters." Journal of Photochemistry 39, no. 2 (August 1987): 317–32. http://dx.doi.org/10.1016/0047-2670(87)80041-2.

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Huczyński, Adam, Tomasz Pospieszny, Rafał Wawrzyn, Małgorzata Ratajczak-Sitarz, Andrzej Katrusiak, Bogumil Brzezinski, and Franz Bartl. "Structural and spectroscopic studies of new o-, m- and p-nitrobenzyl esters of lasalocid acid." Journal of Molecular Structure 877, no. 1-3 (April 2008): 105–14. http://dx.doi.org/10.1016/j.molstruc.2007.07.020.

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Romano, Angelo, Ignazio Roppolo, Elisabeth Rossegger, Sandra Schlögl, and Marco Sangermano. "Recent Trends in Applying Ortho-Nitrobenzyl Esters for the Design of Photo-Responsive Polymer Networks." Materials 13, no. 12 (June 19, 2020): 2777. http://dx.doi.org/10.3390/ma13122777.

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Polymers with light-responsive groups have gained increased attention in the design of functional materials, as they allow changes in polymers properties, on demand, and simply by light exposure. For the synthesis of polymers and polymer networks with photolabile properties, the introduction o-nitrobenzyl alcohol (o-NB) derivatives as light-responsive chromophores has become a convenient and powerful route. Although o-NB groups were successfully exploited in numerous applications, this review pays particular attention to the studies in which they were included as photo-responsive moieties in thin polymer films and functional polymer coatings. The review is divided into four different sections according to the chemical structure of the polymer networks: (i) acrylate and methacrylate; (ii) thiol-click; (iii) epoxy; and (iv) polydimethylsiloxane. We conclude with an outlook of the present challenges and future perspectives of the versatile and unique features of o-NB chemistry.

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Chen, Jian, and Glenn D. Prestwich. "Regioselective synthesis of photolabile P(1,2)- and P(4,5)-(o-nitrobenzyl) esters of myo-inositol 1,2,3,4,5,6-hexakisphosphate." Tetrahedron Letters 38, no. 6 (February 1997): 969–72. http://dx.doi.org/10.1016/s0040-4039(96)02501-4.

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Humeres, Eduardo, Valdir Soldi, Marilene Klug, Mauricéa Nunes, Célia MS Oliveira, and Patrick J. Barrie. "Hydrolysis and aminolysis of alkyl xanthate esters and cellulose analogues." Canadian Journal of Chemistry 77, no. 5-6 (June 1, 1999): 1050–56. http://dx.doi.org/10.1139/v99-107.

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The hydrolysis and aminolysis of a series of S-substituted O-alkylxanthate esters was studied in 20% v/v aqueous methanol at 35°C. The pH-rate profiles of the hydrolyses showed water and hydroxide-ion-catalyzed reactions. The reaction of 2,4-dinitrophenyl cellulose xanthate (CelXDNP) and p-nitrobenzyl cellulose xanthate (CelXNB) with polyalanine and lysozyme produced a covalent bond between the polypeptide and the cellulose matrix, as shown by solid-state 13C NMR. However, the nature of the bonding could not be identified. The reaction of nucleophiles (H2O, OH-, RNH2) and xanthic esters was consistent with an addition-elimination mechanism through a tetrahedral intermediate. Brønsted plots against the pKa of the nucleophile (βnu) or the nucleofuge of the substrate (βlg) were used to characterize the rate-determining step. The pKa values of the nucleophiles ranged between -1.74 and 15.74, and for the nucleofuges, they were in the range of 10.50-0.92. For nucleophiles with pKa values up to about 10, βlg was 0.10-0.15, and βnu changed from 0.48 to 0.35 for the strongest electron-withdrawing nucleofuge. It was concluded that the water-catalyzed hydrolyses, and also aminolyses with moderately basic amines, occur with rate-determining formation of the tetrahedral intermediate. For strong bases such as hydroxide ion, the disappearance of the intermediate becomes the slowest step. The reaction of cellulose xanthic esters with external nucleophiles as hydroxide ion and amines shows simple first-order kinetics and is slower than alkyl or sugar xanthates, probably due to the diffusion effect through the tight cybotactic region of cellulose. Key words: hydrolysis, aminolysis, alkyl xanthic esters, cellulose xanthic esters, sugar xanthic esters.

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CHEN, J., and G. D. PRESTWICH. "ChemInform Abstract: Regioselective Synthesis of Photolabile P(1,2)- and P(4,5)-(o- Nitrobenzyl) Esters of myo-Inositol 1,2,3,4,5,6-Hexakisphosphate." ChemInform 28, no. 24 (August 3, 2010): no. http://dx.doi.org/10.1002/chin.199724210.

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McIntosh, J. Trevor, Ali Nazemi, Colin V. Bonduelle, Sebastien Lecommandoux, and Elizabeth R. Gillies. "Synthesis, self-assembly, and degradation of amphiphilic triblock copolymers with fully photodegradable hydrophobic blocks." Canadian Journal of Chemistry 93, no. 1 (January 2015): 126–33. http://dx.doi.org/10.1139/cjc-2014-0263.

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Анотація:

The development of stimuli-responsive materials is of significant interest for many applications including drug delivery, medical imaging, sensors, and microfluidic devices. Among the available stimuli, light is particularly attractive as it can be applied with high spatial and temporal resolution. We describe here the synthesis of amphiphilic triblock copolymers composed of poly(ethylene glycol) and a hydrophobic block containing o-nitrobenzyl esters throughout the backbone using copper-catalyzed azide–alkyne cycloaddition chemistry. These materials were designed to have a high weight fraction of the hydrophobic block to favour nonmicellar aggregates. The self-assembly in water was studied using nanoprecipitation and the resulting assemblies were characterized by dynamic light scattering and transmission electron microscopy. Under optimized conditions, it was possible to prepare polymer vesicles, commonly referred to as polymersomes, with diameters of approximately 100 nm. The degradation of these materials in response to UV light was studied by spectroscopy, light scattering, and electron microscopy, demonstrating that the vesicles were broken down. These results suggest the potential of these materials for applications such as encapsulation and release.

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Hou, Wanting, Ruiqi Liu, Siwei Bi, Qian He, Haibo Wang, and Jun Gu. "Photo-Responsive Polymersomes as Drug Delivery System for Potential Medical Applications." Molecules 25, no. 21 (November 5, 2020): 5147. http://dx.doi.org/10.3390/molecules25215147.

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Due to a strong retardation effect of o-nitrobenzyl ester on polymerization, it is still a great challenge to prepare amphiphilic block copolymers for polymersomes with a o-nitrobenzyl ester-based hydrophobic block. Herein, we present one such solution to prepare amphiphilic block copolymers with pure poly (o-nitrobenzyl acrylate) (PNBA) as the hydrophobic block and poly (N,N’-dimethylacrylamide) (PDMA) as the hydrophilic block using bulk reversible addition-fragmentation chain transfer (RAFT) polymerization of o-nitrobenzyl acrylate using a PDMA macro-RAFT agent. The developed amphiphilic block copolymers have a suitable hydrophobic/hydrophilic ratio and can self-assemble into photoresponsive polymersomes for co-loading hydrophobic and hydrophilic cargos into hydrophobic membranes and aqueous compartments of the polymersomes. The polymersomes demonstrate a clear photo-responsive characteristic. Exposure to light irradiation at 365 nm can trigger a photocleavage reaction of o-nitrobenzyl groups, which results in dissociation of the polymersomes with simultaneous co-release of hydrophilic and hydrophobic cargoes on demand. Therefore, these polymersomes have great potential as a smart drug delivery nanocarrier for controllable loading and releasing of hydrophilic and hydrophobic drug molecules. Moreover, taking advantage of the conditional releasing of hydrophilic and hydrophobic drugs, the drug delivery system has potential use in medical applications such as cancer therapy.

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Більше джерел

Дисертації з теми "O-nitrobenzyl esters"

ROMANO, ANGELO. "Photo-responsive polymer networks for the design of polymer coatings with light-tunable properties." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2903512.

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