The Chemistry of Hydrazyl free Radicals. I. Spectrophotometric Evidence on the Structure of α,α-Diphenyl-β-Picrylhydrazyl and α,α-Diphenyl-β-Picryl-β-Oxyhydrazyl

Poirier, R. H.; Kähler, E.; Benington, F.

doi:10.1021/jo50011a003

Cited by 71 publications

(12 citation statements)

References 7 publications

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“…DPPH-H was prepared by the reaction of picryl chloride with 1,l-diphellylhydrazine (10,11). Melting point 170-171 "C. D P P H was prepared by lead dioxide oxida~ion of DPPH-H and was recrystallized from a benzene-ether mixture.…”

Section: Experimental ;Idaterialsmentioning

confidence: 99%

SPECTROSCOPIC STUDIES OF THE REVERSIBLE REACTION BETWEEN 2,2-DIPHENYL-1-PICRYLHYDRAZYL AND 2,4,6-TRI-t-BUTYLPHENOL

Ayscough¹,

Russell²

1965

Can. J. Chem.

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A B S T R A C T T h e reaction between 2,2-diphenyl-1-picrylhydrazyl ( D P P H ) and 2,4,6-tri-t-butylphe~lol in benzene solution has been studied b y optical and electron spin resonance methods. I n f h e absence o f oxygen, equilibrium is reached with t h e products 2,2-diphenyl-1-picryll~ydrame and t h e tri-t-butylphenoxy radical. T h e equilibriuln constant for t h e reaction isT h e corresponding activatlon energies are 6.5 f 0.8 kcal/mole and 7.7 f 0.7 kcal/mole. T h e rate constant for t h e reverse reaction is approximately 2 l/(mole s ) a t 20 OC and t h e activation energy is 4.8 f 1 kcal/mole. I N T R O D U C T I O N2,2-Diphenyl-1-picrylhydrazyl (DPPH) reacts with a wide range of hydrogen donors including aliphatic thiols ( I ) , aromatic amines (2, 3), hydroaromatic co~npounds (4, 5), and phenols (6,7,8). The major product of these reactions is 2,2-diphenyl-1-picrylhydrazine (DPPH-H) and kinetic studies have shown that in reactions with phenols the rate-determining step involves hydrogen abstraction fro111 the OH group (7,8). Since DPPI-I is a free radical and the solvent e.g. benzene, is of low polarity, it is probable that the rate-determining step can be represented by eq. [I].The reactions with phenols are, however, quite sensitive to inductive effects of inetasubstituents, and changes in para-substituents can alter the rate constants a t 30 O C by factors as great as 20 000. IliIcGowan, Powell, and Raw (6) have compared the effect of substituents on the rate of hydrogen abstraction by DPPI-I from phenols with their effect on the rates of solvolysis of dimethylbenzyl chlorides and have suggested that DPPH inay abstract hydride ions rather than hydrogen atoms from phenols.The reactions of DPPH with aromatic amines (3), phenols (7), and acetic acid and ethanol (9) are retarded by the product DPPI-I-H. The retardation of the reactions with anlines and phenols has been explained in terms of the reversibility of the rate-determining step [:I.]. Pro11 and Sutcliffe (9) argue that the hydrogen abstraction process is not reversible when acetic acid and ethanol act as donors, and state that retardation is due solely to complex formation between DPPH and DPPI-I-H. If their explanation is correct it should also apply to the reactions of D P P H with anlines and phenols. The radical nature of the reaction between DPPI-I and phenols a d the reversibility of the primary step can be most simply studied if a stable free radical X -is produced in

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Section: Experimental ;Idaterialsmentioning

confidence: 99%

SPECTROSCOPIC STUDIES OF THE REVERSIBLE REACTION BETWEEN 2,2-DIPHENYL-1-PICRYLHYDRAZYL AND 2,4,6-TRI-t-BUTYLPHENOL

Ayscough¹,

Russell²

1965

Can. J. Chem.

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“…(6). The purple solid xvas dried in vaczbo for several hours a t 80' to remove the complexed chloroform (3).…”

Section: Methodsmentioning

confidence: 99%

Hydrogen Abstraction Reactions of Diphenylpicrylhydrazyl

Brook¹,

Anderson²,

Patot³

1958

Can. J. Chem.

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The stable free radical diphenylpicrylhybrazyl ( D P P . ) has been found t o react quantitatively with ammonia and hydrazine forming nitrogen and diphenylpicrylhydrazine, and less cleanly with hydrosylamine forming diphenylpicrylhydrazine and nitrous oside. The reactions of D P P with a variety of arnines are not clean, in part owing to the formation of co~nplexes of the amines with the reaction product diphenylpicrylhydrazine. Preliminary investigations of the reactions of D P P with ~uercaptans have shown that these otherwise clean reactions have a variable stoichiometry, dependent on the concentration and other reaction conditions.

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“…In the case of nitric oxide (NO), it was reported that NO does not react with DPPH. 16) Nevertheless, the possibility of the reaction between other radical species and DPPH is still remained. Therefore, in case, other assay(s) in combination with the DPPH method might be required or the effects of other radical species should be eliminated when reactive radical species and peroxyradicals are simultaneously determined.…”

Section: Non-reductive Dpph-scavenging By Peroxyradicalmentioning

confidence: 99%

Non-reductive Scavenging of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) by Peroxyradical: A Useful Method for Quantitative Analysis of Peroxyradical

Nishizawa

Kohno

Nishimura³

et al. 2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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For quantitative investigations of hydrogen-radical donation, stable radicals have the advantage that their concentrations are readily and directly measurable. Among them a stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) 1) was investigated as a reactive hydrogen acceptor 2) and further found to be useful for the antioxidant determination.3) Since then DPPH has been mainly used to examine radical scavenging activity of antioxidative vitamins and polyhydroxy aromatic compounds 4,5) based on the reactions in Fig. 1. Besides DPPH-scavenging by reductive hydrogen transfer between various donors and DPPH, non-reductive DPPH-decomposing and -scavenging were found to be induced by reacting with tertiary hydroperoxides 6) and by radical-binding at the para position in the phenyl rings of DPPH, 7) respectively.However, nowadays non-reductive DPPH-scavenging has hardly applied for biochemical and physicochemical purposes. It has been reported that peroxyradicals are unique among reactive oxygen species implicated in the production of DNA damage because they possess an extremely long half-life (order of seconds) and are predicted to have a relatively greater chemical selectivity in its reactions as compared with other radical intermediates. A stable radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) has long been used as a convenient method for the antioxidant assay of biological materials such as cysteine, glutathione, ascorbic acid, tocopherol and polyhydroxy aromatic compounds (hydroquinone, pyrogallol, etc). In this study, non-reductive scavenging of DPPH was investigated by electron spin resonance (ESR) analyses for the purpose of developing a useful method for quantitative determination of peroxyradical. Since DPPH was degraded in the presence of peroxyradical derived from UV-irradiated benzoylperoxide and the peroxyradical-induced degradation of DPPH was inhibited by the addition of a spin trapping agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), it is concluded that DPPH is non-reductively scavenged by peroxyradical. Therefore, it is suggested that DPPH could be a useful agent for the quantitative measurement of peroxyradical.Key words 1,1-diphenyl-2-picrylhydrazyl (DPPH); non-reductive scavenging; peroxyradical; electron spin resonance (ESR) Fig. 1. The Reaction Scheme between DPPH and the Conjugated Group of Ascorbic Acid (a) or Hydroquinone (b)

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The Chemistry of Hydrazyl free Radicals. I. Spectrophotometric Evidence on the Structure of α,α-Diphenyl-β-Picrylhydrazyl and α,α-Diphenyl-β-Picryl-β-Oxyhydrazyl

Cited by 71 publications

References 7 publications

SPECTROSCOPIC STUDIES OF THE REVERSIBLE REACTION BETWEEN 2,2-DIPHENYL-1-PICRYLHYDRAZYL AND 2,4,6-TRI-t-BUTYLPHENOL

SPECTROSCOPIC STUDIES OF THE REVERSIBLE REACTION BETWEEN 2,2-DIPHENYL-1-PICRYLHYDRAZYL AND 2,4,6-TRI-t-BUTYLPHENOL

Hydrogen Abstraction Reactions of Diphenylpicrylhydrazyl

Non-reductive Scavenging of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) by Peroxyradical: A Useful Method for Quantitative Analysis of Peroxyradical

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