Time-resolved study of the solvent and temperature dependence of singlet oxygen (1Δg) reactivity toward enol ethers: Reactivity parameters typical of rapid reversible exciplex formation

A. A. Gorman, Ian Gould, I. Hamblett

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Abstract

Pulsed nitrogen laser excitation has been used to examine and compare the reactivities of four enol ethers toward singlet oxygen (1Δg) in five solvents. The experimental values of ΔH (0 ± 1.0 kcal mol-1), ΔS (-23 to -34 eu), and the overall reaction rate constants (104-108 L mol-1 s-1) are characteristic of excited-state processes involving rapid reversible exciplex formation. Solvent effects are small but in some cases significant. It is concluded that such effects are the result of solvation entropy requirements at the transition state leading from exciplex to product, particularly in the case of dioxetane formation. The possibility is raised that the reversible exciplex mechanism operates generally for O2 (1Δg) reactions.

Original languageEnglish (US)
Pages (from-to)7098-7104
Number of pages7
JournalJournal of the American Chemical Society
Volume104
Issue number25
StatePublished - 1982
Externally publishedYes

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Singlet Oxygen
Time and motion study
Ethers
Temperature
Laser excitation
Oxygen
Gas Lasers
Solvation
Entropy
Excited states
Reaction rates
Rate constants
Lasers
Nitrogen

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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abstract = "Pulsed nitrogen laser excitation has been used to examine and compare the reactivities of four enol ethers toward singlet oxygen (1Δg) in five solvents. The experimental values of ΔH‡ (0 ± 1.0 kcal mol-1), ΔS‡ (-23 to -34 eu), and the overall reaction rate constants (104-108 L mol-1 s-1) are characteristic of excited-state processes involving rapid reversible exciplex formation. Solvent effects are small but in some cases significant. It is concluded that such effects are the result of solvation entropy requirements at the transition state leading from exciplex to product, particularly in the case of dioxetane formation. The possibility is raised that the reversible exciplex mechanism operates generally for O2 (1Δg) reactions.",
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T1 - Time-resolved study of the solvent and temperature dependence of singlet oxygen (1Δg) reactivity toward enol ethers

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AU - Gorman, A. A.

AU - Gould, Ian

AU - Hamblett, I.

PY - 1982

Y1 - 1982

N2 - Pulsed nitrogen laser excitation has been used to examine and compare the reactivities of four enol ethers toward singlet oxygen (1Δg) in five solvents. The experimental values of ΔH‡ (0 ± 1.0 kcal mol-1), ΔS‡ (-23 to -34 eu), and the overall reaction rate constants (104-108 L mol-1 s-1) are characteristic of excited-state processes involving rapid reversible exciplex formation. Solvent effects are small but in some cases significant. It is concluded that such effects are the result of solvation entropy requirements at the transition state leading from exciplex to product, particularly in the case of dioxetane formation. The possibility is raised that the reversible exciplex mechanism operates generally for O2 (1Δg) reactions.

AB - Pulsed nitrogen laser excitation has been used to examine and compare the reactivities of four enol ethers toward singlet oxygen (1Δg) in five solvents. The experimental values of ΔH‡ (0 ± 1.0 kcal mol-1), ΔS‡ (-23 to -34 eu), and the overall reaction rate constants (104-108 L mol-1 s-1) are characteristic of excited-state processes involving rapid reversible exciplex formation. Solvent effects are small but in some cases significant. It is concluded that such effects are the result of solvation entropy requirements at the transition state leading from exciplex to product, particularly in the case of dioxetane formation. The possibility is raised that the reversible exciplex mechanism operates generally for O2 (1Δg) reactions.

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