The Role of the Solvent in Radical Decomposition Reactions: Phenylazotriphenylmethane

Alder, Marilyn G.; Leffler, John E.

doi:10.1021/ja01634a086

Cited by 51 publications

(14 citation statements)

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“…Similar solvent effects on product distribution are observed in the alkylation of sodium j8-naphthoxide with methyl or normal propyl bromide or and in the reactions of alkali phenoxides with allyl chloride or bromide or with benzyl chloride [402]. presented [405] for the case where â = 320. These data indicate that a phenoxide strongly paired with a small cation or strongly solvated reacts at carbon preferentially, thus indicating shielding of the oxygen atom of the phenoxide ion by cation pairing or solvation.…”

Section: Further Cation Solvator Considerationssupporting

confidence: 60%

Solvent Influence on Rates and Mechanisms

Amis

Hinton

1973

Solvent Effects on Chemical Phenomena

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Section: Further Cation Solvator Considerationssupporting

confidence: 60%

Solvent Influence on Rates and Mechanisms

Amis

Hinton

1973

Solvent Effects on Chemical Phenomena

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“…The rate data are analyzed using the linear free energy relationship. It is generally known that the linear free energy relationships apply to a reaction series in which either the entropy of activation for the series is constant or the variation in the entropy of activation is linearly related to changes in enthalpy of activation . The isokinetic relationship is verified by Equation :

Δ H^{#} = Δ {H_{0}}^{#} + β \cdot Δ S^{#}

where Δ H 0 # is the enthalpy of activation when Δ S # = 0 and usually has no physical significance and β is the isokinetic temperature.…”

Section: Resultsmentioning

confidence: 99%

Cr(VI) oxidation using cetylpicolinium dichromate: Kinetics of oxidation of benzaldehydes with a green protocol

Priyadarshini

Dash

2018

Int J of Chemical Kinetics

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Oxidation kinetics of benzaldehyde and some of its ortho‐ and para‐monosubstituted derivatives have been studied using cetylpicolinium dichromates, a class of novel phase transfer oxidants, in dichloromethane medium. The rate of reaction is first order with respect to oxidant and fractional order with respect to the substrates. The Michaelis–Menten type oxidation was observed with respect to the substrates. Benzaldehydes are found to be oxidized to their corresponding acids. The mechanism of oxidation reaction has been suggested based on the solvent isotope effect, Hammett plot, and thermodynamic study. The solvent isotope effect (kCHCl3/kCDCl3 = 1.57) indicates the involvement of hydrogen exchange with the medium during oxidation reactions. A strong influence of specific solute–solvent interactions on the rate of the reaction is observed. Both the electron‐withdrawing and electron‐releasing substituents on the substrates accelerate the rate of reaction.

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“…Unlike in the case of AIBN, which is an aliphatic azo compound, the solvent effects dominate the decomposition kinetics of aromatic azo compounds such as phenylazotriphenyl methane (Alder and Leffler, 1954). Although the variations are partly nullified by the compensation effect, significant differences are observed.…”

Section: Decomposition Of Natmentioning

confidence: 98%

Diffusion effects in initiator decomposition in highly viscous and macromolecular solutions

Kulkarni¹,

Mashelkar²

1981

AIChE Journal

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Diffusional limitations in single bond and multibond initiators were experimentally investigated. The concept of "microviscosity" was proposed to account for diffusional resistance in different media. This was then used to obtain a unified correlation of the diffusional phenomena regardless of the nature of viscogen.Parameters related to the kinetic and diffusive processes were evaluated and interpreted giving clear fundamental and pragmatic implications of the findings. There is no prior study which provides a framework for analysis of diffusional limitations in initiator decomposition reactions arising in pragmatically important high viscosity systems, especially in polymer solutions. The present paper bridges this important gap by providing extensive experimental data on decomposition of typical single bond and multibond initiators in a variety of media. It also provides a theoretical framework within which such processes could be analyzed. CONCLUSIONS AND SIGNIFICANCEAn experimental investigation of the decomposition of a typical two bond initiator [AIBN] and a one bond initiator [NAT] was undertaken in three media; viz., polyethylene glycols, polyacrylonitrile solutions in D M F and glycerol solutions in DMF. A kinetic model was proposed for the analysis of the decomposition, recombination and diffusive separation processes. The rate constant for diffusional separation of initiator fragments was proposed to be calculated by Smoluchowski relation.In order to account for the diffusional resistance in different environments created by different types of viscogens, a unifying concept of microviscosity ( v*) was proposed. A method to calculate ( v*) from easily available physico-chemical data wasproposed.The governing kinetic parameters for decomposition reaction and recombination reaction as well as for diffusive separation were evaluated. It was found that for a multibond initiator such as AIBN, the rate constant is independent of the viscosity of the medium. In the case of one bond initiator such as NAT, a number of interesting conclusions emerged. The results in polyethylene glycol media show that increasing chain length above a threshold value has no influence on the diffusion of fragments from the cage, indicating that segmental motion controlled the diffusional process. Comparison of kinetic data for glycerol and polymer solutions in D M F indicated that in the former case the reduction in rate constant was very significant. Use of ( q * ) evaluated by the method proposed in this paper provided unique plots which were helpful in correlating the diffusional effects in decomposition processes irrespective of the nature of viscogen used. The conclusions arrived at are of interest from a fundamental view point since they reveal interesting observations concerning the manner in which diffusional phenomena take place in environments created by different viscogens. These are also of considerable pragmatic interest since in the modelling of polymerization reactors, a simple approach to account for the initiator ...

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The Role of the Solvent in Radical Decomposition Reactions: Phenylazotriphenylmethane

Cited by 51 publications

References 0 publications

Solvent Influence on Rates and Mechanisms

Solvent Influence on Rates and Mechanisms

Cr(VI) oxidation using cetylpicolinium dichromate: Kinetics of oxidation of benzaldehydes with a green protocol

Diffusion effects in initiator decomposition in highly viscous and macromolecular solutions

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