Stability of phenol and thiophenol radical cations – interpretation by comparative quantum chemical approaches

Hermann, Ralf; Naumov, Sergej; Mahalaxmi, Ganapati R.; Brede, O.

doi:10.1016/s0009-2614(00)00601-1

Cited by 28 publications

(18 citation statements)

References 8 publications

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“…Antioxidant radicals, which are stabilized by delocalization, may retard the propagation rates of autoxidation 28. Hermann et al 29 reported that methylendioxy group of sesamol makes more stable state of sesamol radical. Thus, strong antioxidant capacity of sesamol may be due to its high resonance stability of sesamol radical during thermal oxidation and its relatively high activation energy.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of antioxidant capacity of sesamol and free radical scavengers at different heating temperatures

Yeo

Park

Lee

2011

Euro J Lipid Sci & Tech

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Sesamol is a natural antioxidant found in sesame oil from roasted sesame seeds. Activation energy and antioxidant capacity of sesamol were determined and compared with other free radical scavengers (FRSs) including tert-butylated-hydroxyquinone (TBHQ), butylated-hydroxyanisol (BHA), or a-tocopherol in a lard model system treated with different heating temperature. Each FRS was added in lard and heated at 90, 120, 150, and 1808C for 48, 24, 8, or 2 h, respectively and antioxidant capacity was evaluated by conjugated dienoic acid (CDA) value, conjugated diene hydroperoxides, p-anisidine value ( p-AV), and a modified 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Apparent activation energy of sesamol was determined as 12.98 kcal/mol in a lard model system. Antioxidant capacity of sesamol was as good as that of TBHQ and was higher than those of BHA and a-tocopherol at 90, 120, and 1508C based on CDA, conjugated diene hydroperoxides, and p-AV assays. The results of a modified DPPH method showed that each FRS showed different distribution of radical scavenging compounds from oxidized lipids (RSOLs) during oxidation. Sesamol may replace synthetic FRSs like TBHQ and BHA in processed foods treated with high temperature.Practical application: Processed foods are frequently treated with high temperature during ovendrying, roasting, baking, and deep-fat frying. This study showed that sesamol, one of natural antioxidants, had stronger antioxidant capacities than other synthetic FRSs at the temperature ranges from 90 to 1808C. The results of this study can be applied in food industries producing deep-fat fried foods including snacks, chips, and French fries to extend the shelf-life of final foods with high temperature treatment.

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Section: Discussionmentioning

confidence: 99%

Evaluation of antioxidant capacity of sesamol and free radical scavengers at different heating temperatures

Yeo

Park

Lee

2011

Euro J Lipid Sci & Tech

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“…Reactivity of radicals in general, and phenoxyl radicals in particular, is known to be dependent on spin density at the reactive site [62,63].…”

Section: Gas-phase Reactivity Of Model Compoundsmentioning

confidence: 99%

The effects of intramolecular hydrogen bonding on the reactivity of phenoxyl radicals in model systems

Lesslie

Piatkivskyi

Lawler

et al. 2015

International Journal of Mass Spectrometry

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a b s t r a c tThe effects of hydrogen bonding and spin density at the oxygen atom on the gas-phase reactivity of phenoxyl radicals were investigated experimentally and theoretically in model systems and the dipeptide LysTyr. Gas-phase ion-molecule reactions were carried out between radical cations of several aromatic nitrogen bases with the neutrals nitric oxide and n-propyl thiol. Reactivity of radical cations 4-6 correlated with the spin density. The possibility of hydrogen bonding was explored in compounds which allowed four-, five-, and six-membered ring to be formed between the protonated nitrogen and the phenoxyl oxygen, while possessing similar spin density at the oxygen atom. The N + -H· · ·O • bond length was calculated to decrease in the series (1-3), consistent with the theoretical calculations finding weak hydrogen bonding in 2 and strong hydrogen bonding in 3. This coincided with the decrease in reaction rates of 1-3 with both nitric oxide and n-propyl thiol. DFT calculations found that the lowest energy structure of the distonic radical cation of the dipeptide [LysTyr(O • )] + has a short hydrogen bond between the protonated Lys side chain and the phenoxyl oxygen, 1.70Å, which is consistent with its low reactivity.

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“…Adding EUV sensitizers (phenol types) did not show effects as that were as obvious as the addition of PAGs. We explored different types of phenolic sensitizers, including but not limited to 2,5-dimethyl phenol, 4-nitro-phenol, 4-methoxy-phenol, 2,6-dinitro-4-bromo-phenol, and various bisphenol 15 and polymer bounded phenols. Some of the phenols, such as 2,5-demehtyl phenol, have shown great effect in enhancing photospeed when added directly into photoresist.…”

Section: The Photospeed Enhancement Of Euv Resist By Adding Pags And/mentioning

confidence: 99%

Underlayer designs to enhance the performance of EUV resists

Blackwell

Younkin

et al. 2009

Advances in Resist Materials and Processing Technology XXVI

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Extreme ultraviolet (EUV) lithography has gained momentum as the method of choice for <32-nm half-pitch device fabrication. In this paper, we describe our initial attempts to increase an EUV resist's sensitivity without compromising resolution and line roughness via introduction of a thermally crosslinkable underlayer. The main purpose is to test the possibility of using a combination of photoacid generators (PAGs) and EUV sensitizers (phenol type) in the underlayer designs to enhance the overall performance of EUV resists. We have demonstrated the possible benefits of adding an EUV underlayer into the regular EUV litho stack and investigated the effect of PAG types and loadings on the photospeed and litho performance of three different EUV resists.

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Stability of phenol and thiophenol radical cations – interpretation by comparative quantum chemical approaches

Cited by 28 publications

References 8 publications

Evaluation of antioxidant capacity of sesamol and free radical scavengers at different heating temperatures

Evaluation of antioxidant capacity of sesamol and free radical scavengers at different heating temperatures

The effects of intramolecular hydrogen bonding on the reactivity of phenoxyl radicals in model systems

Underlayer designs to enhance the performance of EUV resists

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