title: Shock tube measurements of the tert-butanol + OH reaction rate and the tert-C4H8OH radical β-scission branching ratio using isotopic labeling.
abstract: The overall rate constant for the reaction tert-butanol + OH → products was determined experimentally behind reflected shock waves by using (18)O-substituted tert-butanol (tert-butan(18)ol) and tert-butyl hydroperoxide (TBHP) as a fast source of (16)OH. The data were acquired from 900 to 1200 K near 1.1 atm and are best fit by the Arrhenius expression 1.24 × 10(-10) exp(-2501/T [K]) cm(3) molecule(-1) s(-1). The products of the title reaction include the tert-C4H8OH radical that is known to have two major β-scission decomposition channels, one of which produces OH radicals. Experiments with the isotopically labeled tert-butan(18)ol also lead to an experimental determination of the branching ratio for the β-scission pathways of the tert-C4H8OH radical by comparing the measured pseudo-first-order decay rate of (16)OH in the presence of excess tert-butan(16)ol with the respective decay rate of (16)OH in the presence of excess tert-butan(18)ol. The two decay rates of (16)OH as a result of reactions with the two forms of tert-butanol differ by approximately a factor of 5 due to the absence of (16)OH-producing pathways in experiments with tert-butan(18)ol. This indicates that 80% of the (16)OH molecules that react with tert-butan(16)ol will reproduce another (16)OH molecule through β-scission of the resulting tert-C4H8(16)OH radical. (16)OH mole fraction time histories were measured using narrow-line-width laser absorption near 307 nm. Measurements were performed at the line center of the R22(5.5) transition in the A-X(0,0) band of (16)OH, a transition that does not overlap with any absorption features of (18)OH, hence yielding a measurement of (16)OH mole fraction that is insensitive to any production of (18)OH.
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States. istranic@stanford.edu
authors.forename: Ivo
authors.initials: I
authors.lastname: Stranic
authors.forename: Genny A
authors.initials: GA
authors.lastname: Pang
authors.forename: Ronald K
authors.initials: RK
authors.lastname: Hanson
authors.forename: David M
authors.initials: DM
authors.lastname: Golden
authors.forename: Craig T
authors.initials: CT
authors.lastname: Bowman
mesh_terms: D006878:Hydroxides / Q000737:chemistry*; D007553:Isotope Labeling; D007700:Kinetics; D015394:Molecular Structure; D011789:Quantum Theory; D020002:tert-Butyl Alcohol / Q000737:chemistry*
chemical_list: D006878:Hydroxides; C031356:hydroxide ion; D020002:tert-Butyl Alcohol