title: Detection and characterization of products from photodissociation of XCH2CH2ONO (X = F, Cl, Br, OH).
abstract: Alkyl nitrites have been used previously to produce alkoxy radicals, which are important intermediates in the oxidation of alkanes in atmospheric and combustion processes. Substituted alkoxy radicals, particulary hydroxyalkoxy radicals, are also important intermediates in the atmospheric oxidation of alkenes and combustion of alcohols. In order to produce substituted alkoxy radicals we have photolyzed at 351 nm substituted alkyl nitrites, XCH(2)CH(2)ONO (X = F, Cl, Br, OH). Using laser-induced fluorescence only in the case of X = F do we observe the spectrum of substituted alkoxy radical, XCH(2)CH(2)O; but we always observe the electronic transitions of formaldehyde, HCHO, and vinoxy radical, CH(2)CHO. HCHO can be formed by the dissociation of XCH(2)CH(2)O in its ground state as the barrier to C-C bond dissociation is less than the photon energy remaining after O-NO bond breakage. However, the barrier along the reaction path directly leading from XCH(2)CH(2)O to CH(2)CHO + HX is much higher than the available energy remaining after O-NO bond breakage. A roaming mechanism, involving a frustrated dissociation of X followed by HX extraction, might explain the apparent paradox. Under the conditions of our observations vinoxy retains considerable vibrational excitation but the observed rotational temperatures of both HCHO and CH(2)CHO are ≲7 K.
authors.affiliation: Department of Chemistry, The Ohio State University, 120 West 18th Avenue, Columbus Ohio 43210, USA.
authors.forename: Rabi
authors.initials: R
authors.lastname: Chhantyal-Pun
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Chen
authors.forename: Dianping
authors.initials: D
authors.lastname: Sun
authors.forename: Terry A
authors.initials: TA
authors.lastname: Miller