Carbonyl ylides photogenerated from isomeric stilbene oxides. Temperature dependence of decay kinetics
Upon 266-nm laser excitation in fluid solutions, trans- and cis-stilbene oxides form isomeric carbonyl ylides (lambda/sub max/'s = 470 and 490 nm) that are spectrally and kinetically distinct from one another. Red shifted in absorption and considerably shorter-lived, the ylide photogenerated from the cis oxirane is assigned the cis-exo,exo structure on the basis of symmetry rules for electrocyclic ring opening; its counterpart from the trans oxirane is given the trans-exo,endo structure. The short lifetimes of the ylides arise in part from moderately small activation enthalpies (6-7 kcal mol/sup -1/) and in part from small and negative activation entropies (-5 to -7 eu). Laser flash photolysis in acetonitrile gives rise to a second, longer-lived transient species (lambda/sub max/ = 335 nm) assignable as the nitrile ylide derived from phenylcarbene and an acetonitrile molecule. Bimolecular rate constants in the range 10/sup 6/-10/sup 9/ M/sup -1/ s/sup -1/ are presented for the reactions of carbonyl and nitrile ylides with several dipolarophiles. 22 references, 5 figures, 3 tables.
- Research Organization:
- Univ. of Notre Dame, IN
- OSTI ID:
- 6009446
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 88:8; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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400600* -- Radiation Chemistry
ABSORPTION SPECTROSCOPY
ACETONITRILE
ACRYLIC ACID ESTERS
ALCOHOLS
ALKANES
CARBOXYLIC ACID ESTERS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
CORRELATIONS
CYCLOALKANES
DATA
DATA ANALYSIS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENERGY-LEVEL TRANSITIONS
ENTHALPY
ENTROPY
EPOXIDES
ESTERS
EXCITATION
EXPERIMENTAL DATA
FLUORINATED ALIPHATIC HYDROCARBONS
FURANS
GLYCOLS
HALOGENATED ALIPHATIC HYDROCARBONS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
HYDROXY COMPOUNDS
INFORMATION
IONIZATION
ISOMERS
KINETICS
LASER RADIATION
LEAST SQUARE FIT
MATHEMATICAL MODELS
MAXIMUM-LIKELIHOOD FIT
METHANOL
MONITORING
NITRILES
NUMERICAL DATA
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANIC SOLVENTS
PHOTOCHEMICAL REACTIONS
PHOTOIONIZATION
PHOTOLYSIS
PHYSICAL PROPERTIES
RADIATIONS
REACTION INTERMEDIATES
REACTION KINETICS
SOLVENTS
SPECTROSCOPY
TETRAHYDROFURAN
THERMODYNAMIC PROPERTIES