Reactivity and intersystem crossing of singlet methylene in solution
Evidence is reported which demonstrates that singlet methylene, produced from the photolysis of diazomethane or diazirine, undergoes intersystem crossing to form triplet methylene in perfluorohexane solvent. The results of triplet sensitized photolysis and of direct photolysis experiments with dilute concentrations of substrate (cis- and trans-2-pentene and chloroform) appear to be essentially identical. Stern-Volmer analyses of the competition kinetics between acetonitrile and 2-pentenes or chloroform for singlet methylene are consistent with the near diffusion controlled reactivity of singlet methylene. With the assumption of diffusion-controlled reactions for singlet methylene, plots of the quantum yield for singlet vs. triplet reaction for methylene allow the first estimate (less than or equal to 8 x 10/sup 8/ s/sup -1/) of the rate of intersystem crossing of singlet methylene in the condensed phase. This value is considerably smaller than the value that is extrapolated to the solution phase from results in the gas phase. The possible reasons for this difference are discussed.
- Research Organization:
- Columbia Univ., New York, NY
- OSTI ID:
- 6508735
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:7; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201 -- Chemical & Physicochemical Properties
400500* -- Photochemistry
ALKENES
CARBENES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
CHLOROFORM
DATA
DECOMPOSITION
DIAZO COMPOUNDS
DIFFUSION
DISPERSIONS
EFFICIENCY
EXPERIMENTAL DATA
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROCARBONS
INFORMATION
KINETICS
MIXTURES
MULTIPLETS
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PENTENES
PHASE STUDIES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
QUANTUM EFFICIENCY
RADICALS
REACTION KINETICS
SOLUTIONS
TRIPLETS