Acid Is Key to the Radical-Trapping Antioxidant Activity of Nitroxides

Haidasz, Evan A.; Meng, Derek; Amorati, Riccardo; Baschieri, Andrea; Ingold, K. U.; Valgimigli, Luca; Pratt, Derek A.

doi:10.1021/jacs.6b00677

Cited by 61 publications

(61 citation statements)

References 52 publications

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“…With some exceptions, [17] most antioxidants used today to stabilizem an-made and naturalm aterials act on as toichiometric basis. Thus, each molecule of ap henol or aromatic amine additive can quench, at most, two peroxyl radicals before it is consumed.…”

Section: Discussionmentioning

confidence: 99%

Substituent Effects in Chain‐Breaking Aryltellurophenol Antioxidants

Poon

Yan

Jorner

et al. 2018

Chemistry A European J

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2-Aryltellurophenols substituted in the aryltelluro or phenolic parts of the molecule were prepared by lithiation of the corresponding tetrahydropyran-protected 2-bromophenol, followed by reaction with a suitable diaryl ditelluride then deprotection. In a two-phase system containing N-acetylcysteine as a co-antioxidant in the aqueous phase, all of the compounds quenched lipid peroxyl radicals more efficiently than α-tocopherol, with three to five-fold longer inhibition times. Thus, these compounds offer better and longer-lasting antioxidant protection than recently prepared alkyltellurophenols. Compounds with electron-donating para substituents in the aryltelluro or phenolic part of the molecule showed the best results. The mechanism for quenching peroxyl radicals was considered and discussed with respect to the calculated O-H bond-dissociation energies, deuterium-labelling experiments and studies of thiol consumption in the aqueous phase.

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Section: Discussionmentioning

confidence: 99%

Substituent Effects in Chain‐Breaking Aryltellurophenol Antioxidants

Poon

Yan

Jorner

et al. 2018

Chemistry A European J

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“…The overall B(C 6 F 5 ) 3 ‐induced reaction of two TEMPO . equivalents with dihydrogen to give two TEMPOH product molecules is overall calculated to be exergonic by about −11 kcal mol −1 …”

Section: Methodsmentioning

confidence: 99%

Rapid Dihydrogen Cleavage by Persistent Nitroxide Radicals under Frustrated Lewis Pair Conditions

Tao

Kehr

Wang

et al. 2016

Chemistry A European J

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Persistent radicals undergo hydrogen atom abstraction reactions with a great variety of substrates, but not with dihydrogen. It has now been found that the TEMPO radical splits dihydrogen under mild conditions in the presence of the strong bulky B(C6 F5 )3 boron Lewis acid. The reaction is thought to proceed by a typical frustrated Lewis pair mechanism with the TEMPO radical acting as the active Lewis base. The reaction was analyzed by DFT, which indicates that no significant spin density on the hydrogen atoms is accumulated along the H2 splitting reaction path.

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“…There is an asymmetric dual peak of SL-Temp near g ¼ 2.00253, which has the characteristic of typical double radicals. 22 In addition, SL-Temp 3 has a stronger signal intensity, which means that more stable Tempo is produced by SL-Temp. This is benecial to promote the cycle process of scavenging alkyl free radicals.…”

Section: Characterizations Of Sl-tempmentioning

confidence: 99%