Über ein stabiles Sauerstoffradikal, das 2.4.6‐Tri‐<i>tert</i>.‐butyl‐phenoxyl‐(1), I. Mitteil.

Müller, Eugen; Ley, Kurt

doi:10.1002/cber.19540870622

Cited by 111 publications

(15 citation statements)

References 15 publications

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“…Melting point 131-132 OC. Tri-t-butylphenoxyl was prepared by oxidation of tri-t-butylphenol using an alkaline ferricyanide solution (13). It was stored in an atmosphere of nitrogen.…”

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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“…Melting point 131-132 OC. Tri-t-butylphenoxyl was prepared by oxidation of tri-t-butylphenol using an alkaline ferricyanide solution (13). It was stored in an atmosphere of nitrogen.…”

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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“…In fact, after gas-phase reaction10 over alumina of an equimolar mixture of 211 and tert-butyl hypochlorite (added dropwise, from the top, to a heated (125 °C) column charged with alumina pellets, using nitrogen as carrier gas and collecting the product at the bottom of the column in a liquid air cooled trap), VPC analysis of the reaction mixture revealed formation of a product (37% yield) with the same retention time as 3. The same analysis revealed also formation of a product (37% yield) with retention time as for (E)-2-methylcrotonaldehyde (8) A key intermediate in the Pommer industrial synthesis of vitamin A acetate from ß-ionone is (£)-4-acetoxy-2methylcrotonaldehyde (4).1 However, the known syntheses of the latter derivative are multistep and/or low-yield procedures.1™4…”

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confidence: 91%

A two-step synthesis of (E)-4-chloro-2-methylcrotonaldehyde from isoprene. An unprecedented oxidative chlorination of a 1,3-diene monoepoxide by cupric chloride

Eletti‐Bianchi¹,

Centini²,

Re³

1976

J. Org. Chem.

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“…Heptane was employed for the reaction of 1 at 90°C. The reaction of VOCI, with the tritertbutylpheno::yl radical was effected by adding the VOCI, to a hexane solution of the radical prepared by standard procedures (15).…”

Section: Oxidcitions Using Vocimentioning

confidence: 99%

Reactions of some substituted phenols with chromyl and vanadyl chlorides

Harrod¹,

Pathak²

1980

Can. J. Chem.

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. Can. J. Chem. 58,686 (1980). The oxidation of 2,4,6-tritertbutylphenol and several other alkyl and halophenois by CrO,Cl, and VOC1, was studied. The products of CrO,Cl, oxidation are mostly quinones and diphenoquinones, whilst those of VOCL, oxidation also include major amounts of dealkylated phenols and C-C coupled dimers. The product distributions are interpreted in terms of a mechanism involving phenoxyl radicals, ligand transfer from metal to radical, and either phenoxonium ions or metallate esters where there is sufficient electron withdrawal from the organic group for it to exhibit carbenium ion properties. The differences in behaviour between CrO,CI,, VOCI,, and CuCl, are attributed to different balances between the oxidation potential and Lewis acidity of the metal complexes. It is concluded that CrO,Cl, is not a good model for proposed ferry1 intermediate in heme oxidase systems since it induces 1 + 3 rather than 1 + 2 halogen shifts and an NIH shift that is best explained by carbenium ion-like intermediates. JOHN F. HARROD et ASHA PATHAK. Can. J. Chem. 58,686 (1980). On aetudie l'oxydation du tritert-butyl-2,4,6phenol et de plusieurs autres phenols alkyles et halogenes par CrO,Cl, et VOC1,. Les produits de l'oxydation par CrO,CI, sont principalement des quinones et des diphenoquinones alors que ceux resultant de I'oxydation par VOCI, comprennent egalement des quantitez appreciables de phenols desalkyles et des dimeres lies par une liaison C-C. On interprkte la repartition des produits en fonction d'un mecanisme qui fait intervenir des radicaux phenoxyles, des transferts de ligands du metal au radical et soit des ions phenoxonium ou des esters de type metallique dans lequel le groupe organique est suffisamment polarise pour exhiber les proprietes d'un ion carbenium. On attribue les differences de comportement entre le CrO,Cl,, le VOCI, et le CuCI, aux differents equilibres entre les potentiels d'oxydation et I'aciditC de Lewis des complexes metalliques. On a conclu que le CrO,Cl, n'est pas un bon modele pour I'intermediaire ferryle propose dans les systemes heme oxydase puisqu'il indui.t un glissement 1+3 d'halogtne plutBt que 1 4 2 et un glissement NIH qui s'explique mieux par un intermediaire de type carbenium.[Traduit par le journal]

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Über ein stabiles Sauerstoffradikal, das 2.4.6‐Tri‐tert.‐butyl‐phenoxyl‐(1), I. Mitteil.

Cited by 111 publications

References 15 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

A two-step synthesis of (E)-4-chloro-2-methylcrotonaldehyde from isoprene. An unprecedented oxidative chlorination of a 1,3-diene monoepoxide by cupric chloride

Reactions of some substituted phenols with chromyl and vanadyl chlorides

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