Addition of Methyl Radical to Substituted Alkenes: A Theoretical Study of the Reaction Mechanism

Wong, Ming Wah; Pross, Addy; Radom, Leo

doi:10.1002/ijch.199300048

Cited by 40 publications

(44 citation statements)

References 40 publications

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“…[ 52 ] π‐electron‐accepting substituents (e.g., to alkenes) enhance reactivity via Δ G PF for PF. For CH 3 • , polar contributions to the TSs are of minor consequence to Δ G ‡ , [ 53 ] but PF can include polar effects [ 54 ] ; PF can explain ~90% of its reactivity (Figure 3). Figures 3 and 7/8 illustrate the difference between CH 3 • and CO 3 • − / 3 O 2 .…”

Section: Discussionmentioning

confidence: 99%

A universal free energy relationship for both hard and soft radical addition in water

Nolte

Hendriks

Novák

et al. 2022

J of Physical Organic Chem

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Prioritization of (eco)toxicological risks and technological endpoints among 100,000+ potential substances, conditions and mechanisms requires computationally ‘inexpensive’ and accurate tools to ‘screen’ reactivity and identify reaction products. Such prediction tools are very scarce. Left unresolved, charge‐transfer and hydration complicate predictions. Based on experimental reaction of radicals (3O2, CH3•, CO3•− etc.) with organic substrates, we hypothesized that a universal linear free energy relationship (LFER) can rationalize these reactions to accurately predict addition rates. We calculated free energies of forming charge‐separated intermediates from explicit descriptions of addition reaction products. We combined these energies, via a thermodynamic cycle, with electron transfer energies to calculate product formation energies. All energies include consideration of hydration effects by water. We ascribe feasibilities of ‘hard’ (ionic) and ‘soft’ (covalent) mechanisms to the relevance of the charge‐separated intermediate. Analysis shows that activation energies effectively relate to a combination of product formation energies and charge‐separation energies. The relative importance of these is determined by a mixing parameter, which is mostly constant for a given radical (substrate). Via the Eyring equation, our universal LFER explains up to 94% of the variance in data for rate constants. Prediction error is a factor 5 (2 SD), only slightly larger than variation in experimentation, particularly sensitive to varying reaction conditions. Minimal parametrization ensures that our new framework for calculating reactivity of radical addition is accurate, robust and with satisfactory rational. Calculation time for 100 reactions is <1 h on a standard desktop PC. In anticipation of underpinning with an even wider range of reagents, this ‘inexpensive’ calculus can more easily assess a greater domain of structures and extrapolate to new structures. This helps to better assess and select favourable non‐toxic, environmentally friendly and technologically superior chemical (sub)structures.

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Section: Discussionmentioning

confidence: 99%

A universal free energy relationship for both hard and soft radical addition in water

Nolte

Hendriks

Novák

et al. 2022

J of Physical Organic Chem

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“…In addition to experimental studies, much theoretical work has been devoted to the methyl radical. − Ab initio studies have been done to examine activation energies, transition states, and heats of reaction. − , Results have been used to obtain rate constants for certain reactions, which agree fairly well with experiment. Additionally, methods to estimate reactivity ratios, most notably Alfrey-Price Q-e parameters, − have been developed. , But, such methods require some experimental work for each substrate.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to experimental studies, much theoretical work has been devoted to the methyl radical. [6][7][8][9][10][11] Ab initio studies have been done to examine activation energies, transition states, and heats of reaction. [7][8][9]11 Results have been used to obtain rate constants for certain reactions, which agree fairly well with experiment.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Methyl Radical Addition Rate Constants from Molecular Structure

Bakken

Jurs

1999

J. Chem. Inf. Comput. Sci.

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Multiple linear regression and computational neural networks (CNNs) are used to develop quantitative structure-property relationships for methyl radical addition rate constants. Structure based descriptors are used to numerically encode substrate information for 191 compounds. Descriptors can be classified as topological, geometric, electronic, or combination. A six-descriptor CNN was developed that produced training set rms error ) 0.381 log units and rms error ) 0.496 log units for an external prediction set. A sevendescriptor CNN was used to build a model for a subset of 172 of the compounds. Training set rms error was 0.424 log units and prediction set rms error reduced to 0.409 log units. Model predictions were on the order of experimental error.

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“…However, the question of whether CH 3 • was significantly nucleophilic in addition reactions led to active debate. − The “philicity” issue was summarized by Fischer and Radom in a joint survey of solution-phase experimental data and gas-phase computations for a wide variety of radical addition reactions. In addition to the role of Δ r H , they explicitly considered the role of charge-transfer states (R + Ol – and R – Ol + , each stabilized by favorable distance-dependent Coulombic interaction) in VB-inspired state correlation diagrams.…”

Section: Introductionmentioning

confidence: 99%

Extension of Structure–Reactivity Correlations for the Hydrogen Abstraction Reaction to the Methyl Radical and Comparison to the Chlorine Atom, Bromine Atom, and Hydroxyl Radical

Poutsma

2016

J. Phys. Chem. A

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Recently, we presented structure-reactivity correlations for the gas-phase rate constants for hydrogen abstraction from sp(3)-hybridized carbon by three electrophilic radicals (X(•) + HCR3 → XH + (•)CR3; X = Cl(•), HO(•), and Br(•)); the reaction enthalpy effect was represented by the independent variable ΔrH and the "polar effect" by the independent variables F and R, the Hammett-Taft constants for field/inductive and resonance effects. Here we present a parallel treatment for the less electronegative CH3(•). In spite of a limited and scattered database, the resulting least-squares fit [log k437(CH3(•)) = -0.0251(ΔrH) + 0.96(ΣF) - 0.56(ΣR) - 19.15] was modestly successful and useful for initial predictions. As expected, the polar effect appears to be minor and its directionality, i.e., the "philicity" of CH3(•), may depend on the nature of the substituents.

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Addition of Methyl Radical to Substituted Alkenes: A Theoretical Study of the Reaction Mechanism

Cited by 40 publications

References 40 publications

A universal free energy relationship for both hard and soft radical addition in water

A universal free energy relationship for both hard and soft radical addition in water

Prediction of Methyl Radical Addition Rate Constants from Molecular Structure

Extension of Structure–Reactivity Correlations for the Hydrogen Abstraction Reaction to the Methyl Radical and Comparison to the Chlorine Atom, Bromine Atom, and Hydroxyl Radical

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