title: Low-energy reaction rate constants for the Ni+-assisted decomposition of acetaldehyde: observation of C-H and C-C activation.
abstract: Rate constants for the low-energy Ni(+)-assisted dissociative reaction of acetaldehyde have been measured under jet-cooled conditions in the gas phase. The rate constants are acquired through monitoring the time dependence of fragment Ni(+)CO formation. The decomposition of the precursor Ni(+)-acetaldehyde cluster ion proceeds via consecutive, parallel reaction coordinates that originate with the Ni(+)-assisted cleavage of either a C-C or an aldehyde C-H bond. The energies used to initiate these reactions are well below that required to cleave sigma-bonds in the isolated acetaldehyde molecule. Direct measurement of the reaction kinetics over a range of energies indicates that the rate-limiting step in the dissociative mechanism changes at cluster ion internal energies = 17,200 +/- 400 cm(-1). Arguments are presented that this energy marks the closure of the dissociative coordinate that initiates with C-H sigma-bond activation and thus provides a measure of the activation energy of this dissociative pathway.
authors.affiliation: Department of Chemistry and Biochemistry, Baylor University, One Bear Place 97348, Waco, Texas 76798-7348, USA.
authors.forename: S Jason
authors.initials: SJ
authors.lastname: Dee
authors.forename: Vanessa A
authors.initials: VA
authors.lastname: Castleberry
authors.forename: Otsmar J
authors.initials: OJ
authors.lastname: Villarroel
authors.forename: Ivanna E
authors.initials: IE
authors.lastname: Laboren
authors.forename: Darrin J
authors.initials: DJ
authors.lastname: Bellert