The Inhibited Autoxidation of Styrene: Part Ii. The Relative Inhibiting Efficiencies of Meta- And Para-Substituted Phenols

Howard, J. A.; Ingold, K. U.

doi:10.1139/v63-251

Cited by 134 publications

(63 citation statements)

References 25 publications

(27 reference statements)

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“…The excellent agreement between the 4-t-alkyl-2,6-di-t-butyl phenols and the other phenols in this series indicates that there is little or no hindrance by the 4-substituent towards the attack of a styrylperoxy radical a t the 4-position of the initially formed phenoxy radical (1,12).…”

Section: Discussionmentioning

confidence: 62%

“…1 The results can be represented by, where (k6)0 = 46X lo3 l./mole sec and a: = -0.5 mole/kcal. This value of a: is significantly smaller than the value obtained with the t-butoxy radicals (i.e., -1.23 mole/kcal) presumably because the secondary styrylperoxy radicals are much less subject to steric factors than are the t-butoxy radicals.…”

Section: Discussionmentioning

confidence: 99%

“…The experimental techniques and the kinetic treatment of the results have been described previously in Parts I (5) and I1 (1). Many of the phenols used in this work were carefully purified commercial products.…”

Section: E X P E R I M E N T a Lmentioning

confidence: 99%

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The Inhibited Autoxidation of Styrene: Part Iii. The Relative Inhibiting Efficiencies of Ortho-Alkyl Phenols

Howard¹,

Ingold²

1963

Can. J. Chem.

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The relative rates of reaction of a large number of ortho-allryl phenols with styrylperoxy radicals have been measured a t 65' C. These groups have both a n accelerating effect owing to their electron-donating character and a retarding effect which arises from steric factors. With two ortho-alkyl groups both the reaction rate and the overall polar contribution to the transition state decrease as the size of the alkyl groups is increased. A single o-t-butyl group produces a small enhancement of the reaction rate over and above its polar effect but this is not observed with any other alkyl groups.

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Section: Discussionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 99%

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The Inhibited Autoxidation of Styrene: Part Iii. The Relative Inhibiting Efficiencies of Ortho-Alkyl Phenols

Howard¹,

Ingold²

1963

Can. J. Chem.

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“…The reaction of t-butoxy radicals \\-it11 substituted toluenes in CCI4 is therefore similar to the majority of hydrogen atom abstraction reactions which involve radicals of moderate to high electron affinity (1,5). If the transition state is represented by the following extreme resonance forms (4) then the correlation with a+ constants implies that structure I1 makes a very i~nportant contribution to the transition state (1, 4, 5 ) .…”

Section: Discussionmentioning

confidence: 92%

“…Data for a \vide variety of such relations were sulnnlarized in a recent paper from this laboratory (1). I t was shown that with few exceptions, notably hydrogen abstraction by t-butoxy radicals fro111 substituted toluenes (2,3), a better correlation was usually obtained with (I+ constants rather than with u constant^.^ Further support for this generalization has been provided by Russell and Willianlson (5) who specifically pointed out that for the t-butoxy radical the proper substituents had not been exanlined to distinguish clearly betxveen a U-and a u+-correlation.…”

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Reactions of Alkoxy Radicals: I. Hydrogen Atom Abstraction From Substituted Toluenes

Kennedy¹,

Ingold²

1966

Can. J. Chem.

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The relative rates of hydrogen atom abstractio~l from ten substituted toluenes by t-butoxy radicals in carbon tetrachloride a t 40 OC have been measured and the data fitted to the Hammett equation. A much better correlation is obtained with the a+ constants than with the u constants of the substituents. In this respect, therefore, the reaction is similar to the majority of hydrogen atom abstraction reactions by radicals of moderate and high electron affinity. That is, the polar properties of the substituents are much more important than their stabilizing effect on the benzyl radical formed in the reaction.The cumyloxy radical has a similar reactivity to the t-butoxy radical. The p-nitrocumyloxy radical appears to be slightly more reactive and also slightly more susceptible to the polar elfects of substituents than are t-butoxy or cu~nyloxy radicals.The relative rates of hydrogen atom abstraction from compounds of the type XC6H4YH by free radicals can frequently be correlated by means of the Hamlnett p u relationship. Data for a \vide variety of such relations were sulnnlarized in a recent paper from this laboratory (1). I t was shown that with few exceptions, notably hydrogen abstraction by t-butoxy radicals fro111 substituted toluenes (2,3), a better correlation was usually obtained with (I+ constants rather than with u constant^.^ Further support for this generalization has been provided by Russell and Willianlson (5) who specifically pointed out that for the t-butoxy radical the proper substituents had not been exanlined to distinguish clearly betxveen a U-and a u+-correlation. With this point in mind we decided to reinvestigate this reaction with particular attention to those substituents having significantly different (I and 6 constants. While this \vork was in progress a similar study by Gilliom and Ward appeared (6). However, we feel that our results and conclusions differ sufficiently from theirs to warrant the present communication. EXPERIMENTAL ReagentsToluene, 112-xylene, p-sylene, ethylbenzene, and cumene were Phillips Research Grade materials. m-Chlorotoluene, p-chlorotoluene, vz-nitrotoluene, p-nitrotoluene, and p-methoxytoluene were obtained from Eastman. These compou~lds were used a s supplied, their purity being checked by gas-liquid chromatography (g.1.c.). Toluene-0-ds was obtained fro111 Merck, Sharp & Dohme; it contained over 95% trideuterotoluene. We are grateful to the Benzol Products Company for a generous sample of p-methoxybenzyl chloride.p-Phenoxytoluene was prepared by the method of Russell and Williamson (5). p-Cyanotoluene was prepared by the dehydration of p-tolualdehyde oxime with acetic anhydride (cf. ref. 7). t-Butyl hypochlorite was prepared as described by Teeter and Bell (8). Cumyl hypochlorite and p-nitrocumyl hypochlorite were prepared from the corresponding alcohols by the method of Zavitsas and Seltzer (9). The p-nitrocu~nyl alcohol was prepared from cumene by nitration (10) followed by oxidation of the purified p-nitrocuinene by the method of Icwart and Francis (...

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Influence of added menadione (vitamin K3) on dissolution and dimerization of tocopherols and autoxidation of triacylglycerols during storage of plant oils

Kupczyk¹,

Gogolewski²

2001

Nahrung

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The effect of added menadione (vit. K3) to stored rapeseed and soybean oil on the dissolution and dimerization of natural tocopherols and autoxidation of triacylglycerols was studied. Commercial rapeseed and soybean oils with added menadione and pure oil were stored at +20 degrees C in brown and transparent glass bottles. During storage their peroxide value, changes of the content of fatty acids and dissolution of tocopherols were measured. Destruction of individual tocopherols in tested oils with added menadione stored in both dark and transparent glass bottles were greater than in the oil samples without menadione. However, the degradation of individual tocopherols was different in each oil. Addition of menadione to the rapeseed and soybean oils resulted in the accelerated process of autoxidation of these oils. The oxidative state of the oils was lower in the oils stored in transparent bottles than in the oils stored in brown bottles. The prooxidant activity of menadione was additionally activated by light. Menadione added to the vegetable oils influenced the dissolution of natural tocopherols as well as their dimerization. It is conduced that addition of menadione to vegetable oils decreases their nutritive value.

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The Inhibited Autoxidation of Styrene: Part Ii. The Relative Inhibiting Efficiencies of Meta- And Para-Substituted Phenols

Cited by 134 publications

References 25 publications

The Inhibited Autoxidation of Styrene: Part Iii. The Relative Inhibiting Efficiencies of Ortho-Alkyl Phenols

The Inhibited Autoxidation of Styrene: Part Iii. The Relative Inhibiting Efficiencies of Ortho-Alkyl Phenols

Reactions of Alkoxy Radicals: I. Hydrogen Atom Abstraction From Substituted Toluenes

Influence of added menadione (vitamin K3) on dissolution and dimerization of tocopherols and autoxidation of triacylglycerols during storage of plant oils

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