Reactions of 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) with Two Syringylic Phenols or One Aroxide Derivative

Hristea, Elena; Covaci-Cîmpeanu, Irina C.; Ioniţaǎ, Gabriela; Ioniță, Petre; Drăghici, Constantin; Caǎproiu, Miron T.; Hillebrand, Mihaela; Constantinescu, Titus; Balaban, Alexandrù T.

doi:10.1002/ejoc.200800735

Cited by 16 publications

(12 citation statements)

References 55 publications

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“…The diffusion-edited spectrum gives a value of ∼0.03 but is known to overestimate species that have slower T 2 relaxation rates, such as rapidly rotating methyl groups. By analyzing the expanded aromatic region (Figure 4d), there is a peak at 7.11 ppm, which is consistent with a literature assignment (methyl syringate, 7.32 ppm, CDCl 3 ) 31 for the aromatic C–H of the syringyl ester attached to the polymer. However, the intensity of the peak is rather low, indicating up to ∼0.005 (0.5%) molar equivalents vs C1.…”

Section: Resultssupporting

confidence: 88%

Plasticized Cellulosic Films by Partial Esterification and Welding in Low-Concentration Ionic Liquid Electrolyte

et al. 2019

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Alternatives to petroleum-based plastics are of great significance not only from the point of view of their scientific and practical impact but to reduce the environmental footprint. Inspired by the composition and structure of wood’s cell walls, we used phenolic acids to endow cellulosic fibers with new properties. The fiber dissolution and homogeneous modification were performed with a recyclable ionic liquid (IL) (tetrabutylammonium acetate ([N4444][OAc]):dimethyl sulfoxide) to attain different levels of reaction activity for three phenolic acids (p-hydroxybenzoic acid, vanillic acid, and syringic acid). The successful autocatalytic Fischer esterification reaction was thoroughly investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, and nuclear magnetic resonance spectroscopy (13C CP-MAS, diffusion-edited 1H NMR and multiplicity-edited heteronuclear single quantum coherence). Control of the properties of cellulose in the dispersed state, welding, and IL plasticization were achieved during casting and recrystallization to the cellulose II crystalline allomorph. Films of cellulose carrying grafted acids were characterized with respect to properties relevant to packaging materials. Most notably, despite the low degree of esterification (DS < 0.25), the films displayed a remarkable strength (3.5 GPa), flexibility (strains up to 35%), optical transparency (>90%), and water resistance (WCA ∼ 90°). Moreover, the measured water vapor barrier was found to be similar to that of poly(lactic acid) composite films. Overall, the results contribute to the development of the next-generation green, renewable, and biodegradable films for packaging applications.

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Section: Resultssupporting

confidence: 88%

Plasticized Cellulosic Films by Partial Esterification and Welding in Low-Concentration Ionic Liquid Electrolyte

et al. 2019

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“…To the best of our knowledge this is the first time, when DPPH is involved into Csp 2 Csp 3 bond formation. The literature examples describe products, in which DPPH is attached to antioxidant molecule via ether linkage . Another known example is capture of nitrophenyl radical by DPPH leading to new Csp 2 Csp 2 bond .…”

Section: Resultsmentioning

confidence: 99%

Novel type of carbon‐centered antioxidants arylmethyl Meldrum's acids − inhibit free radicals

Mieriņa

Jure

Zēberga

et al. 2017

Euro J Lipid Sci & Tech

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Monosubstituted Meldrum's acids are found out as a new class of powerful antioxidants. These compounds act as carbon radical scavengers due to the presence of acidic hydrogen in the moiety of cyclic 1,3‐dicarbonyl compound. The presence of phenol and benzylic moiety is favored, but these structural elements are not crucial for the antiradical activity in polar media. The antiradical and antioxidant activity of the substituted Meldrum's acids is not significantly affected by the substituents in the aromatic ring. The 5‐substituted 1,3‐dioxan‐4,6‐diones demonstrate high scavenging capacity of free radicals. The inhibition of DPPH and GO achieved even ∼100 and 80%, respectively. All substituted Meldrum's acids are better antioxidants than BHT, and activity of some of them even exceed vitamin C. It is found out that in polar media the compounds act via SPLET mechanism. Substituted Meldrum's acids turned out as powerful antioxidants for inhibition of oxidation processes of fatty acid alkyl esters, too. The oxidative stability of the last with the title compound additive was significantly higher than with BHT additive. It seems, that the antioxidant activity of the substituted Meldrum's acids in fatty acid esters is both due to benzylic position and 1,3‐dicarbonyl moiety. Practical applications: Arylmethyl Meldrum's acids should be highlighted as potential antioxidants for increasing oxidative stability of various products containing, for example, esters of poly‐unsaturated fatty acids. It should be admitted that the structure of the title compounds can be widely modified by substituents in the aromatic ring without remarkable loss of antioxidant and antiradical activity, but other properties (like solubility) may be improved. In order to apply the title antioxidants into products like cosmetics additional tests regarding toxicity are required. However, these antioxidants can be recommended for increasing oxidative stability for products used in technique. Monosubstituted Meldrum's acids act as carbon radical scavengers due to the presence of acidic hydrogen in the moiety of cyclic 1,3‐dicarbonyl compound. The substituted Meldrum's acids demonstrate high scavenging capacity of free radicals DPPH and GO. These compounds turned out as powerful antioxidants for inhibition of oxidation processes of fatty acid alkyl esters. The antioxidant activity of the substituted Meldrum's acids in fatty acid esters is both due to benzylic position and 1,3‐dicarbonyl moiety. Few of the monosubstituted Meldrum's acids were better antioxidants than BHT, TBHQ, α‐tocopherol, or vitamin C.

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“…11,20,21 The aryloxyl radicals of syringaldehyde and methyl syringate (two phenolic compounds) react in dichloromethane with excess DPPH • to yield para-substitution products at the picryl ring (see Figure 3). 11 Interestingly, the supramolecular complex of the anion of syringaldehyde with crown ethers yields instead a para-substitution product at the phenyl rings (see Figure 3). 11 22 and thiols 23 are of interest, too.…”

Section: ■ Introductionmentioning

confidence: 99%

Use and Abuse of the DPPH^• Radical

Foti

2015

J. Agric. Food Chem.

297

193

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The 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) radical is approaching 100 years from its discovery in 1922 by Goldschmidt and Renn. This radical is colored and remarkably stable, two properties that have made it one of the most popular radicals in a wide range of studies. First, there is the evaluation of the antioxidant abilities of phenols and other natural compounds (A-H) through a "test" that-at a closer look-is utterly inappropriate. In fact, the test-derived EC50, that is, the concentration of A-H able to scavenge 50% of the initial DPPH(•), is not a kinetic parameter and hence its purported correlation with the antioxidant properties of chemicals is not justified. Kinetic measurements, such as the second-order rate constants for H-atom abstraction from A-H by DPPH(•), in apolar media, are the only useful parameters to predict the antioxidant ability of A-H. Other applications of DPPH(•) include kinetic and mechanistic studies, kinetic solvent effects, EPR spectroscopy, polymer chemistry, and many more. In this review these applications are evaluated in detail by showing the usefulness of some and the uselessness of others. The chemistry of DPPH(•) is also briefly reviewed.

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Reactions of 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) with Two Syringylic Phenols or One Aroxide Derivative

Cited by 16 publications

References 55 publications

Plasticized Cellulosic Films by Partial Esterification and Welding in Low-Concentration Ionic Liquid Electrolyte

Plasticized Cellulosic Films by Partial Esterification and Welding in Low-Concentration Ionic Liquid Electrolyte

Novel type of carbon‐centered antioxidants arylmethyl Meldrum's acids − inhibit free radicals

Use and Abuse of the DPPH^• Radical

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Reactions of 2,2‐Diphenyl‐1‐picrylhydrazyl (DPPH) with Two Syringylic Phenols or One Aroxide Derivative

Cited by 16 publications

References 55 publications

Plasticized Cellulosic Films by Partial Esterification and Welding in Low-Concentration Ionic Liquid Electrolyte

Plasticized Cellulosic Films by Partial Esterification and Welding in Low-Concentration Ionic Liquid Electrolyte

Novel type of carbon‐centered antioxidants arylmethyl Meldrum's acids − inhibit free radicals

Use and Abuse of the DPPH• Radical

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Use and Abuse of the DPPH^• Radical