Solvent effect on the sensitized photooxygenation of 2,3-dihydropyrazine derivatives

Else Lemp, Antonio L. Zanocco, German Günther, Nancy Pizarro

Resultado de la investigación: Article

5 Citas (Scopus)

Resumen

Detection of O2(1Δg) phosphorescence emission, λmax = 1270 nm, following laser excitation and steady-state methods was employed to determine the total rate constant, kT, and the chemical reaction rate constant, kR, for reaction between 5,6-disubstituted-2,3-dihydropyrazines and singlet oxygen in several solvents. Values of kT ranged from 0.26 × 105 M-1 s-1 in hexafluoro-2-propanol to 58.9 × 105 M-1 s-1 in N,N-dimethylacetamide for 5,6-dimethyl-2,3-dihydropyrazine (DMD) and from 5.74 × 105 M-1 s-1 in trifluoroethanol to 159.0 × 105 M-1 s-1 in tributyl phosphate for 5-methyl-6-phenyl-2,3-dihydropyrazine (MPD). Chemical reaction rate constants, kR, for DMD are similar to kT in polar solvents such as propylencarbonate, whereas for MPD in this solvent, the contribution of the chemical channel to the total reaction is about of 4%. Dependence of the total rate constant on solvent microscopic parameters, α and π*, for DMD can be explained in terms of a reaction mechanism that involves formation of a perepoxide exciplex. Replacement of the methyl by a phenyl substituent enhances dihydropyrazine ring reactivity toward singlet oxygen and modifies the dependence of kT on solvent parameters, specially on the Hildebrand parameter. These results are explained in terms of an additional reaction path, involving a perepoxide-like exciplex stabilized by the interaction of the negative charge on the terminal oxygen of the perepoxide with the aromatic π system.

Idioma originalEnglish
Páginas (desde-hasta)3009-3016
Número de páginas8
PublicaciónJournal of Organic Chemistry
Volumen68
N.º8
DOI
EstadoPublished - 18 abr 2003

Huella dactilar

Rate constants
Derivatives
Singlet Oxygen
Reaction rates
Chemical reactions
Trifluoroethanol
Phosphorescence
Laser excitation
Oxygen

ASJC Scopus subject areas

  • Organic Chemistry

Citar esto

Lemp, Else ; Zanocco, Antonio L. ; Günther, German ; Pizarro, Nancy. / Solvent effect on the sensitized photooxygenation of 2,3-dihydropyrazine derivatives. En: Journal of Organic Chemistry. 2003 ; Vol. 68, N.º 8. pp. 3009-3016.
@article{d98efaabb82f46b2b56f6a6f301513d6,
title = "Solvent effect on the sensitized photooxygenation of 2,3-dihydropyrazine derivatives",
abstract = "Detection of O2(1Δg) phosphorescence emission, λmax = 1270 nm, following laser excitation and steady-state methods was employed to determine the total rate constant, kT, and the chemical reaction rate constant, kR, for reaction between 5,6-disubstituted-2,3-dihydropyrazines and singlet oxygen in several solvents. Values of kT ranged from 0.26 × 105 M-1 s-1 in hexafluoro-2-propanol to 58.9 × 105 M-1 s-1 in N,N-dimethylacetamide for 5,6-dimethyl-2,3-dihydropyrazine (DMD) and from 5.74 × 105 M-1 s-1 in trifluoroethanol to 159.0 × 105 M-1 s-1 in tributyl phosphate for 5-methyl-6-phenyl-2,3-dihydropyrazine (MPD). Chemical reaction rate constants, kR, for DMD are similar to kT in polar solvents such as propylencarbonate, whereas for MPD in this solvent, the contribution of the chemical channel to the total reaction is about of 4{\%}. Dependence of the total rate constant on solvent microscopic parameters, α and π*, for DMD can be explained in terms of a reaction mechanism that involves formation of a perepoxide exciplex. Replacement of the methyl by a phenyl substituent enhances dihydropyrazine ring reactivity toward singlet oxygen and modifies the dependence of kT on solvent parameters, specially on the Hildebrand parameter. These results are explained in terms of an additional reaction path, involving a perepoxide-like exciplex stabilized by the interaction of the negative charge on the terminal oxygen of the perepoxide with the aromatic π system.",
author = "Else Lemp and Zanocco, {Antonio L.} and German G{\"u}nther and Nancy Pizarro",
year = "2003",
month = "4",
day = "18",
doi = "10.1021/jo026303o",
language = "English",
volume = "68",
pages = "3009--3016",
journal = "Journal of Organic Chemistry",
issn = "0022-3263",
publisher = "American Chemical Society",
number = "8",

}

Solvent effect on the sensitized photooxygenation of 2,3-dihydropyrazine derivatives. / Lemp, Else; Zanocco, Antonio L.; Günther, German; Pizarro, Nancy.

En: Journal of Organic Chemistry, Vol. 68, N.º 8, 18.04.2003, p. 3009-3016.

Resultado de la investigación: Article

TY - JOUR

T1 - Solvent effect on the sensitized photooxygenation of 2,3-dihydropyrazine derivatives

AU - Lemp, Else

AU - Zanocco, Antonio L.

AU - Günther, German

AU - Pizarro, Nancy

PY - 2003/4/18

Y1 - 2003/4/18

N2 - Detection of O2(1Δg) phosphorescence emission, λmax = 1270 nm, following laser excitation and steady-state methods was employed to determine the total rate constant, kT, and the chemical reaction rate constant, kR, for reaction between 5,6-disubstituted-2,3-dihydropyrazines and singlet oxygen in several solvents. Values of kT ranged from 0.26 × 105 M-1 s-1 in hexafluoro-2-propanol to 58.9 × 105 M-1 s-1 in N,N-dimethylacetamide for 5,6-dimethyl-2,3-dihydropyrazine (DMD) and from 5.74 × 105 M-1 s-1 in trifluoroethanol to 159.0 × 105 M-1 s-1 in tributyl phosphate for 5-methyl-6-phenyl-2,3-dihydropyrazine (MPD). Chemical reaction rate constants, kR, for DMD are similar to kT in polar solvents such as propylencarbonate, whereas for MPD in this solvent, the contribution of the chemical channel to the total reaction is about of 4%. Dependence of the total rate constant on solvent microscopic parameters, α and π*, for DMD can be explained in terms of a reaction mechanism that involves formation of a perepoxide exciplex. Replacement of the methyl by a phenyl substituent enhances dihydropyrazine ring reactivity toward singlet oxygen and modifies the dependence of kT on solvent parameters, specially on the Hildebrand parameter. These results are explained in terms of an additional reaction path, involving a perepoxide-like exciplex stabilized by the interaction of the negative charge on the terminal oxygen of the perepoxide with the aromatic π system.

AB - Detection of O2(1Δg) phosphorescence emission, λmax = 1270 nm, following laser excitation and steady-state methods was employed to determine the total rate constant, kT, and the chemical reaction rate constant, kR, for reaction between 5,6-disubstituted-2,3-dihydropyrazines and singlet oxygen in several solvents. Values of kT ranged from 0.26 × 105 M-1 s-1 in hexafluoro-2-propanol to 58.9 × 105 M-1 s-1 in N,N-dimethylacetamide for 5,6-dimethyl-2,3-dihydropyrazine (DMD) and from 5.74 × 105 M-1 s-1 in trifluoroethanol to 159.0 × 105 M-1 s-1 in tributyl phosphate for 5-methyl-6-phenyl-2,3-dihydropyrazine (MPD). Chemical reaction rate constants, kR, for DMD are similar to kT in polar solvents such as propylencarbonate, whereas for MPD in this solvent, the contribution of the chemical channel to the total reaction is about of 4%. Dependence of the total rate constant on solvent microscopic parameters, α and π*, for DMD can be explained in terms of a reaction mechanism that involves formation of a perepoxide exciplex. Replacement of the methyl by a phenyl substituent enhances dihydropyrazine ring reactivity toward singlet oxygen and modifies the dependence of kT on solvent parameters, specially on the Hildebrand parameter. These results are explained in terms of an additional reaction path, involving a perepoxide-like exciplex stabilized by the interaction of the negative charge on the terminal oxygen of the perepoxide with the aromatic π system.

UR - http://www.scopus.com/inward/record.url?scp=0037453556&partnerID=8YFLogxK

U2 - 10.1021/jo026303o

DO - 10.1021/jo026303o

M3 - Article

C2 - 12688767

AN - SCOPUS:0037453556

VL - 68

SP - 3009

EP - 3016

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

IS - 8

ER -