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A quantitative study of alkyl radical reactions by kinetic spectroscopy III. Absorption spectrum and rate constants of mutual interaction for the ethyl radical
Author(s) -
Adachi Hiroyuki,
Basco N.,
James D. G. L.
Publication year - 1979
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550110906
Subject(s) - chemistry , absorbance , reaction rate constant , analytical chemistry (journal) , absorption spectroscopy , alkyl , kinetic energy , yield (engineering) , spectroscopy , molar absorptivity , photodissociation , photochemistry , kinetics , thermodynamics , organic chemistry , chromatography , physics , quantum mechanics , optics
Intrinsic spectral and kinetic parameters have been measured for the ethyl radical, which was formed in the gas phase by the flash photolysis of azoethane. Absolute values of the extinction coefficient ϵ(λ) were derived from complementary measurements of the yield of nitrogen and the absorbance of an equivalent concentration of the ethyl radical. The absorption spectrum is broad, structureless, and comparatively weak; ϵ(247) = 4.8 × 10 2 l/mol·cm at the maximum, and the oscillator strength is (9.1 ± 0.5) × 10 −3 . This is in good qualitative agreement with a spectrum obtained independently using the technique of molecular modulation spectrometry. The biomolecular reactions of mutual interaction were the only significant reactions of the ethyl radical in this system; kinetic analysis of the second‐order decline of the absorbance during the dark period yielded a value of k /ϵ(λ) for each experiment. The rate constant for mutual interaction was evaluated from the product of corresponding measurements of k /ϵ(λ) and ϵ(λ) individual values are independent of the wavelength of measurement, and the mean value is k = (1.40 ± 0.27) × 10 10 l/mol·sec. The rate constant for mutual combination was derived with the aid of product analysis as k 2 = (1.24 ± 0.23) × 10 10 l/mol·sec; it stands in close agreement with the set of “high” values obtained by direct measurement using a variety of methods.