Influence of irradiation on oxygen-containing compounds in the presence of olefins

Шостенко, А. Г.; Zagorets, P.A.; Tarasova, N. P.; Myshkin, V. E.

doi:10.1007/bf02520504

Cited by 12 publications

(2 citation statements)

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“…The higher reactivity of the phosphonyl radical is consistent with experimental precedent: for example, while the Ph 2 P(=O) • radical reacts with acrylonitrile with a rate constant of 2.0 × 10 7 L mol −1 s −1 (room temperature), 7 the t BuC(=O) • radical adds to the same substrate with a rate constant of 5 × 10 5 L mol −1 s −1 (300 K) 3b and the n PrC(=O) • radical adds to ethylene with a rate constant of 1.4 × 10 3 L mol −1 s −1 (453 K). 9 This journal is © The Royal Society of Chemistry 2008 Taking addition to ethylene as a reference system, one finds that both radicals experience lower barriers if either an electrondonating substituent (OMe, NH 2 ) or an electron-withdrawing substituent (CN) is attached to the double bond. That is, both radicals display ambiphilic behaviour, with the changeover point from apparently nucleophilic behaviour to apparently electrophilic behaviour occurring roughly at the parent system (within the sample of alkenes examined).…”

Section: Kinetics and Thermodynamics Of Additions To Unsaturated Substratesmentioning

confidence: 99%

A comparison of orbital interactions in the additions of phosphonyl and acyl radicals to double bonds

Krenske

Schiesser

2008

Org. Biomol. Chem.

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Calculation of the barriers for addition of the H2P(=O) and HC(=O) radicals to alkenes, at the CCSD(T)/aug-cc-pVDZ//BHandHLYP/6-311G** level, indicates that both radicals display ambiphilic behaviour. For the HC(=O) radical this behaviour occurs because a secondary orbital interaction of the type pi*(C=O)<--HOMO acts in conjunction with the primary SOMO<--HOMO interaction to balance the SOMO-->LUMO interaction. For the H2P(=O) radical, on the other hand, the much higher-lying LUMO (the sigma*P-O orbital) allows for only minimal secondary interaction, and this radical's ambiphilic behaviour is therefore reflective of a balance between SOMO-->LUMO and SOMO<--HOMO interactions.

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Section: Kinetics and Thermodynamics Of Additions To Unsaturated Substratesmentioning

confidence: 99%

A comparison of orbital interactions in the additions of phosphonyl and acyl radicals to double bonds

Krenske

Schiesser

2008

Org. Biomol. Chem.

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“…By an indirect telomerization technique, Myshkin et al [15] derived k,,, = 280 M-'s-' for the addition of .CH,CO,H to ethene which we believe to be at least two orders of magnitude too low. However, several relative rate data confirm our reactivity ratios.…”

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confidence: 96%

Absolute Rate Constants for the Addition of Cyanomethyl (·CH₂CN) and (tert‐Butoxy)carbonylmethyl (·CH₂CO₂C(CH₃)₃) radicals to alkenes in solution

Beranek

Fischer

1995

Helvetica Chimica Acta

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Absolute rate constants and their temperature dependence were determined by time-resolved electron spin resonance for the addition of the radicals 'CH,CN and .CH,CO,C(CH,), to a variety of mono-and 1,l-disubstituted and to selected 1,2-and trisubstituted alkenes in acetonitrile solution. To alkenes CH,=CXY, .CH,CN adds at the unsubstituted C-atom with rate constants ranging from 3.3.10' M-Is- ' (ethene) to 2.4.106 M-IS-'( 1 , ldiphcnylethene) at 278 K, and the frequency factors are in the narrow range of log (A/M-'s-') = 8.7 * 0.3.. CH2C02C(CH,), shows a very similar reactivity with rate constants at 296 K ranging from 1.1 lo4 M-'s-' (ethene) to lo7 M-'s-' (],I-diphenylethene) and frequency factors log (A/M-'s-') = 8.4 f 0.1. For both radicals, the rate constants and the activation energies for addition to CH,=CXY correlate well with the overall reaction enthalpy. In contrast to the expectation of an electro-or ambiphilic behavior, polar alkene-substituent effects are not clearly expressed, but some deviations from the enthalpy correlations point to a weak electrophilicity of the radicals. The rate constants for the addition to 1,2-and to trisubstituted alkenes reveal additional steric substituent effects. Self-termination rate data for the title radicals and spectral properties of their adducts to the alkenes are also given.1. Introduction. -The addition of carbon-centered radicals to C=C bonds is one of the most useful radical reactions. However, its rate constants are far from being quantitatively understood and predictable, because they reflect a complex interplay of polar, steric, and enthalpic substituent effects [l]. To provide a larger basis for their analysis, we have developed a technique of time-resolved electron spin resonance (ESR) which yields reliable rate data for large series of reactions with moderate efforts. Hitherto 121, the addition rates of the easily oxidizable radicals tert-butyl, hydroxymethyl, and 2-hydroxy-2-propyl to various alkenes CH,=CXY were found to correlate well with the alkene electron affinities. This means that these radicals are nucleophilic, and indicates a substantial stabilization of the transition state by partial electron transfer to the substrates. The variations of the reaction enthalpy had little or no effect. On the other hand, these were found to govern the rate constants for the addition of the 2-cyano-2-propyl radical [3] which exhibits no clear polar effects, and the benzyl radical shows an intermediate, weakly nucleophilic behavior [4]. In related studies, other groups demonstrated clearcut electrophilic reactivity patterns for perfluoroalkyl [5], dicyanomethyl [6], and malonyl [7] radicals.Here, we present rate data for the addition of the cyanomethyl (. CH,CN) and the

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Rate constants for the addition of the 2‐hydroxy‐2‐propyl radical to alkenes in solution

Héberger

Fischer

1993

Int J of Chemical Kinetics

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Absolute rate constants for the addition of the 2-hydroxy-2-propyl radical to 18 substituted alkenes (CH2 = C X Y ) were determined at (296 -+ 1) Kin 2-propanol by time-resolved electronspin-resonance spectroscopy. With alkene substitution the rate constants vary by more than 6 orders of magnitude. For 3,3-dimethyl-but-l-ene the temperature dependence is given by log k/M-' . s-l = 6.4 -19.1/0 where 0 = 2.303 RT in kJ/mol-l. As shown by a good correlation with the alkene electron affinities, log k296lM-l . s-l = 6.46 + 1.71 . EA/eV ( r = 0.930), 2-hydroxy-2-propyl is a very nucleophilic radical, and its addition rates are highly governed by polar effects. 0 1993 John Wiley & Sons, Inc.

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Influence of irradiation on oxygen-containing compounds in the presence of olefins

Cited by 12 publications

References 4 publications

A comparison of orbital interactions in the additions of phosphonyl and acyl radicals to double bonds

A comparison of orbital interactions in the additions of phosphonyl and acyl radicals to double bonds

Absolute Rate Constants for the Addition of Cyanomethyl (·CH₂CN) and (tert‐Butoxy)carbonylmethyl (·CH₂CO₂C(CH₃)₃) radicals to alkenes in solution

Rate constants for the addition of the 2‐hydroxy‐2‐propyl radical to alkenes in solution

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Influence of irradiation on oxygen-containing compounds in the presence of olefins

Cited by 12 publications

References 4 publications

A comparison of orbital interactions in the additions of phosphonyl and acyl radicals to double bonds

A comparison of orbital interactions in the additions of phosphonyl and acyl radicals to double bonds

Absolute Rate Constants for the Addition of Cyanomethyl (·CH2CN) and (tert‐Butoxy)carbonylmethyl (·CH2CO2C(CH3)3) radicals to alkenes in solution

Rate constants for the addition of the 2‐hydroxy‐2‐propyl radical to alkenes in solution

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Absolute Rate Constants for the Addition of Cyanomethyl (·CH₂CN) and (tert‐Butoxy)carbonylmethyl (·CH₂CO₂C(CH₃)₃) radicals to alkenes in solution