title: Ion chemistry of 1H-1,2,3-triazole.
abstract: A combination of experimental methods, photoelectron-imaging spectroscopy, flowing afterglow-photoelectron spectroscopy and the flowing afterglow-selected ion flow tube technique, and electronic structure calculations at the B3LYP/6-311++G(d,p) level of density functional theory (DFT) have been employed to study the mechanism of the reaction of the hydroxide ion (HO-) with 1H-1,2,3-triazole. Four different product ion species have been identified experimentally, and the DFT calculations suggest that deprotonation by HO- at all sites of the triazole takes place to yield these products. Deprotonation of 1H-1,2,3-triazole at the N1-H site gives the major product ion, the 1,2,3-triazolide ion. The 335 nm photoelectron-imaging spectrum of the ion has been measured. The electron affinity (EA) of the 1,2,3-triazolyl radical has been determined to be 3.447 +/- 0.004 eV. This EA and the gas-phase acidity of 2H-1,2,3-triazole are combined in a negative ion thermochemical cycle to determine the N-H bond dissociation energy of 2H-1,2,3-triazole to be 112.2 +/- 0.6 kcal mol-1. The 363.8 nm photoelectron spectroscopic measurements have identified the other three product ions. Deprotonation of 1H-1,2,3-triazole at the C5 position initiates fragmentation of the ring structure to yield a minor product, the ketenimine anion. Another minor product, the iminodiazomethyl anion, is generated by deprotonation of 1H-1,2,3-triazole at the C4 position, followed by N1-N2 bond fission. Formation of the other minor product, the 2H-1,2,3-triazol-4-ide ion, can be rationalized by initial deprotonation of 1H-1,2,3-triazole at the N1-H site and subsequent proton exchanges within the ion-molecule complex. The EA of the 2H-1,2,3-triazol-4-yl radical is 1.865 +/- 0.004 eV.
authors.affiliation: JILA, University of Colorado and National Institute of Standards and Technology, Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0440, USA.
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Ichino
authors.forename: Django H
authors.initials: DH
authors.lastname: Andrews
authors.forename: G Jeffery
authors.initials: GJ
authors.lastname: Rathbone
authors.forename: Fuminori
authors.initials: F
authors.lastname: Misaizu
authors.forename: Ryan M D
authors.initials: RM
authors.lastname: Calvi
authors.forename: Scott W
authors.initials: SW
authors.lastname: Wren
authors.forename: Shuji
authors.initials: S
authors.lastname: Kato
authors.forename: Veronica M
authors.initials: VM
authors.lastname: Bierbaum
authors.forename: W Carl
authors.initials: WC
authors.lastname: Lineberger