Solvent Effects in the Reactions of Free Radicals and Atoms. IX. Effect of Solvent Polarity on the Reactions of Peroxy Radicals

Hendry, Dale G.; Russell, Glen A.

doi:10.1021/ja01066a014

Cited by 59 publications

(31 citation statements)

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“…GTlzis i s sitzaller t h a n the ~a l r l e of 0.8 used previously ,itz ckloroben-ene which partly c~ccollnts for the lover (!a111es of hp/(2kt)liZ for styrc?ze a?zd a-rrtethylstyrelze co?rzpared witlt tlze previoz~sly gizre?t r!alaes of' kP/kt1" (9) T h e roizcrining di'erence is probably dzre to the higlzer slcbstrnte col~centrntions en~ployed ,i?z t 1 1~ preserrt mork. IIncludes concurrent first orcler chain terniiilation and tl~erefore Bj,,l, ca11110t be calc~llated from lrt at 30 "C. "Calculated from the k t values at 30 O C given in Table 11.…”

Section: B V I O~~s L Y This ~Izetl~od Will Not Give Kt For Styrenementioning

confidence: 97%

Absolute Rate Constants for Hydrocarbon Autoxidation: Iv. Tetralin, Cyclohexene, Diphenylmethane, Ethylbenzene, and Allylbenzene

Howard¹,

Ingold²

1966

Can. J. Chem.

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.ibsolute rate constants have been measured for the autoxidation of five hydrocarbons under a variety of conditions. 'The propagation (k,) and termination ( k t ) rate constants a t 30 "C (in I mole-Is-') are: tetralin in chlorobenzene 6.3 and 3.S X lO"espectively, cyclohexene in chlorobenzene 6.1 and 2.5 X 10" diphenyllnethane 4.6 and 8.0 X lo7, ethylbenzene 0.11 and 2.0 X lo7, and allylbenzene 10 and 2.2 X 108. Measurements on tetralin, a-methylstyrene, and allylbcnzcne in different solvents indicate that the effect of solvents on oxidation rates is mainly connected with changes in the rate of termination rather than propagation. Experimcnts with a,a-d?-diphenyl~iiethane gave isotope effects k n / k o -5.1 for k, and -1.4 for kt. 'I'he rate constant for hydrogen atom abstraction from 2,6-di-t-butyl-4-methylphenol by peroxy radicals decreases in the order expected if steric effects are important, i.e., prinlary peroxy > secottdary peroxy > tertiary peroxy radical.The co-oxidation method of estilnating chain termination constants is criticized on the grounds that it can only be used t o distinguish the fairly large changes in k t commonly encountered between hydrocarbons giving tertiary peroxy radicals and those giving secondary --or primary radicals.The effect of hydrocarbon structure on bimolecular chain termination rate constants is reviewed. There is a gradation in k t from -2 X l o 8 1 mole-Is-' for primary peroxy radicals, through the ranee S X lo7 to 1 X loG for secondarv radicals, to the range from 3 X lo5 to 3 X for tertiary peroxy radicals.

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Section: B V I O~~s L Y This ~Izetl~od Will Not Give Kt For Styrenementioning

confidence: 97%

Absolute Rate Constants for Hydrocarbon Autoxidation: Iv. Tetralin, Cyclohexene, Diphenylmethane, Ethylbenzene, and Allylbenzene

Howard¹,

Ingold²

1966

Can. J. Chem.

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“…In particular, the effect of solvent dielectric constant and polarity on the propagation and termination rate constants (k p /2k t ratio) of substrates were studied 195 -197 . Hendry and Russell attempted to determine if an increase in solvent polarity would increase the value of k p , which could have been attributed to increased solvation of the polar peroxyl radical structure and polar transition state for hydrogen atom abstraction; however, there was insufficient evidence to state this absolutely 197 . Instead, they concluded that the increased solvent polarity had a more significant effect on the 2k t value, since the polar character of the peroxyl is lost upon termination, a theory which has been supported by other groups 198 .…”

Section: β-Scissionmentioning

confidence: 99%

Phenols as Antioxidants

Ross

Barclay

Vinqvist

2009

Patai's Chemistry of Functional Groups

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“…Hendry and Russell,8) and Howard and Ingold9) studied the oxidation of several hydrocarbons in a number of solvents and found that the rates of oxidation increased with the increase in the dielectric constants of the solvents. They suggested that the dipolar transition state was involved in the propagation step and the contribution of the solvation at this stage enhanced the rates of propagation and oxidation.…”

mentioning

confidence: 99%

Solvent Effects in the Oxidation of Hydrocarbons. II. Oxidations of Tetralin in Various Solvents

Niki¹,

Kamiya²,

Ohta³

1969

Bulletin of the Chemical Society of Japan

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solution as well as the kinds of solvents. It was found that the solvents affected the initiation step approximately as much as they affected the propagation and/or temination step. The rate of initiation by AIBN was mainly dependent on the viscosity of the medium, while that of propagation and termination was mainly determined by the dielectric constant of the medium. The correlation between log (kp/(2kt)1/2) and (D-1)/(2D+1) was discussed, where kp and kt are the rate constants for propagation and termination steps, respectively, and D is the dielectric constant of the medium, under conditions where the complication caused by the selective solvation could be excluded.

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Solvent Effects in the Reactions of Free Radicals and Atoms. IX. Effect of Solvent Polarity on the Reactions of Peroxy Radicals

Cited by 59 publications

References 1 publication

Absolute Rate Constants for Hydrocarbon Autoxidation: Iv. Tetralin, Cyclohexene, Diphenylmethane, Ethylbenzene, and Allylbenzene

Absolute Rate Constants for Hydrocarbon Autoxidation: Iv. Tetralin, Cyclohexene, Diphenylmethane, Ethylbenzene, and Allylbenzene

Phenols as Antioxidants

Solvent Effects in the Oxidation of Hydrocarbons. II. Oxidations of Tetralin in Various Solvents

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