Deprotonation yields, pKa, and aci-nitro decay rates in some substituted o-nitrobenzaldehydes

Abbruzzetti, Stefania; Carcelli, Mauro; Rogolino, Dominga; Viappiani, Cristiano

doi:10.1039/b301818k

Cited by 36 publications

(32 citation statements)

References 35 publications

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“…Photoinitiated proton-releasing reactions are important not only for investigating the dynamics of pH-dependent phenomena such as protein folding kinetics, but also for rapidly changing the proton concentration in solutions [38]. In particular, it would be useful to change the solution pH inside intact materials such as hydrogels.…”

Section: Photoinduced Ph-jump Reaction Of Pagsmentioning

confidence: 99%

A smart hydrogel-based time bomb triggers drug release mediated by pH-jump reaction

Techawanitchai

Idota

Uto

et al. 2012

Science and Technology of Advanced Materials

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We demonstrate a timed explosive drug release from smart pH-responsive hydrogels by utilizing a phototriggered spatial pH-jump reaction. A photoinitiated proton-releasing reaction of o-nitrobenzaldehyde (o-NBA) was integrated into poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) (P(NIPAAm-co-CIPAAm)) hydrogels. o-NBA-hydrogels demonstrated the rapid release of protons upon UV irradiation, allowing the pH inside the gel to decrease to below the pK a value of P(NIPAAm-co-CIPAAm). The generated protons diffused gradually toward the non-illuminated area, and the diffusion kinetics could be controlled by adjusting the UV irradiation time and intensity. After irradiation, we observed the enhanced release of entrapped L-3,4-dihydroxyphenylalanine (DOPA) from the gels, which was driven by the dissociation of DOPA from CIPAAm. Local UV irradiation also triggered the release of DOPA from the non-illuminated area in the gel via the diffusion of protons. Conventional systems can activate only the illuminated region, and their response is discontinuous when the light is turned off. The ability of the proposed pH-jump system to permit gradual activation via proton diffusion may be beneficial for the design of predictive and programmable devices for drug delivery.

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Section: Photoinduced Ph-jump Reaction Of Pagsmentioning

confidence: 99%

A smart hydrogel-based time bomb triggers drug release mediated by pH-jump reaction

Techawanitchai

Idota

Uto

et al. 2012

Science and Technology of Advanced Materials

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“…This UV exposure will allow regeneration of chitosan from its imino derivative while assisting in the sterilization of the scaffold system. The mechanism of 2‐nitrobenzaldehyde photolysis has been well established and been explored for other photoactivatable‐caged compounds used in imaging applications . The tentative photolysis mechanism of iminochitosan is presented in the Fig.…”

Section: Resultsmentioning

confidence: 99%

A smart methodology to fabricate electrospun chitosan nanofiber matrices for regenerative engineering applications

Nada

James

Shelke

et al. 2014

Polymers for Advanced Techs

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The electrospinning of chitosan remains challenging due to its rigid crystalline structure, insufficient viscosity, and limited solubility in common organic solvents. This work presents a “smart” chitosan modification that allows electrospinning irrespective of molecular weight or deacetylation value and without blending with synthetic polymers. A novel derivative, namely 2‐nitrobenzyl‐chitosan (NB), at various molar compositions of chitosan:2‐nitrobenzaldehyde (1:1 (NB‐1), 1:0.5 (NB‐2), 1:0.25 (NB‐3)) was synthesized by the reaction between amino groups of chitosan and aldehyde groups of 2‐nitrobenzaldehyde. In this Schiff base, 2‐nitrobenzaldehyde protects the amine functionalities of chitosan and improves its solubility in trifluoroacetic acid. 2‐nitrobenzaldehyde is a photoactivatable‐caged compound that cleaves off from iminochitosan on ultraviolet exposure yielding neat chitosan. Derivatives showed improved solubility in trifluoroacetic acid and dynamic viscosities in the range of 1.34 ± 0.7 to 12 ± 0.5 Pa·s based on the degree of substitution and concentration. Electrospinning conditions were optimized to produce bead free nanofibers in the range of 100–600 nm, and concentrations beyond 12% (wt/v) for NB‐1 and NB‐2, and 15% (wt/v) for NB‐3 were suitable. Photolysis did not alter fiber morphology; however, regenerated chitosan matrices were soluble in culture media presumably due to the presence of 2‐nitrosobenzoic acid in trace amounts. Human skin fibroblasts exhibited excellent (>90%) cytocompatibility on treatment with polymer extractions from cross‐linked regenerated chitosan matrices prepared to the ISO standard. Newly synthesized iminochitosan derivatives were very effective against microorganisms including bacteria (Gram‐positive and Gram‐negative), fungi, and yeast. These fiber matrices may serve as scaffolds for a variety of tissue healing and factor delivery applications. Copyright © 2014 John Wiley & Sons, Ltd.

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“…The shift might be attributed to the presence of a tautomeric form of 2,4DC6NP, characterised by a conjugated structure involving the C-N bond of the nitro group. The protonation of nitro groups in substituted aromatic compounds has been demonstrated [34,35], together with the formation of stable quinone- like structures when the protonated group is in para or ortho position relative to the phenolic one [36,37]. For these reasons we hypothesise that 2,4DC6NP behaves like a diprotic acid in solution, able to generate three species (a, b and c), as described in Figure 4.…”

Section: Acute Toxicity Test With Artemia Salinamentioning

confidence: 88%

Chemical characterisation of a new estuarine pollutant (2,4-Dichloro-6-Nitrophenol) and assessment of the acute toxicity of its quinoid form forArtemia salina

Tognazzi

Dattilo

Bracchini

et al. 2012

International Journal of Environmental Analytical Chemistry

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It is known that the compound 2,4-dichloro-6-nitrophenol (2,4DC6NP) is formed upon nitration of 2,4-dichlorophenol, which in turn is a transformation intermediate of the herbicide dichlorprop. However, the chemical and spectroscopic characteristics of 2,4DC6NP, as well as its toxicity, are poorly known. This work shows that 2,4DC6NP behaves as a diprotic acid in aqueous solutions, with pK a values of 3.0 AE 0.9 and 4.9 AE 0.5. At pH < 3, 2,4DC6NP would undergo protonation. The absorption spectra suggest that anionic 2,4DC6NP, which prevails at pH > 5 would have an ortho-quinoid structure that is responsible for the absorption peak centred at 428 nm. Considering that 2,4DC6NP has been detected in the brackish lagoons of the Rhoˆne delta (southern France), where its levels are comparable to those of the parent herbicide, it is necessary to examine the possible effects of 2,4DC6NP on the species living in that environment. For this reason, the acute toxicity of the anionic form of 2,4DC6NP was assessed for the brine shrimp Artemia salina, a zooplankton species that lives both in brackish and in saline aquatic environments. The toxicity test yielded a LC 20 value of 8 AE 2 mg L À1 and a LC 50 value of 18.7 AE 0.8 mg L À1 . Such values are safely higher than the maximum detected concentration of 2,4DC6NP in the Rhoˆne delta lagoons. Further studies should be concentrated on the long-term effects of 2,4DC6NP, and in particular on its potential genotoxicity.

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Deprotonation yields, pKa, and aci-nitro decay rates in some substituted o-nitrobenzaldehydes

Cited by 36 publications

References 35 publications

A smart hydrogel-based time bomb triggers drug release mediated by pH-jump reaction

A smart hydrogel-based time bomb triggers drug release mediated by pH-jump reaction

A smart methodology to fabricate electrospun chitosan nanofiber matrices for regenerative engineering applications

Chemical characterisation of a new estuarine pollutant (2,4-Dichloro-6-Nitrophenol) and assessment of the acute toxicity of its quinoid form forArtemia salina

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