Step-Scan FT-IR Monitoring of Transient HCO Radicals in a Room Temperature Zeolite

Formyl radical has been detected in zeolite NaY at room temperature by step-scan FT-infrared spectroscopy upon photodissociation of glycolaldehyde or acetaldehyde precursor. Identification was made by the CO stretch absorption at 1847 cm-1 and a 13C isotope shift of 40 cm-1. The decay shows biphasi...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2003-07, Vol.107 (26), p.6286-6291
Main Authors: Yeom, Y. H, Frei, H
Format: Article
Language:English
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Summary:Formyl radical has been detected in zeolite NaY at room temperature by step-scan FT-infrared spectroscopy upon photodissociation of glycolaldehyde or acetaldehyde precursor. Identification was made by the CO stretch absorption at 1847 cm-1 and a 13C isotope shift of 40 cm-1. The decay shows biphasic kinetics independent of the precursor used. In the case of glycolaldehyde, the final products recorded by static FT-IR spectroscopy can be explained by the exclusive reaction of HCO and CH2OH radicals. This allowed us to assign the initial decay with a lifetime of 24 ± 3 μs to geminate reactive encounters of HCO and CH2OH radicals. The subsequent long tail extending to 500 μs is well described by a second-order rate law consistent with nongeminate reaction of the radicals. This is the first direct kinetic observation of geminate and nongeminate radical reactions in a zeolite.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp022394h