title: Reversible addition of the OH radical to p-cymene in the gas phase: kinetic analysis assuming formation of a single adduct. Part 1.
abstract: A flash photolysis-resonance fluorescence (FP-RF) technique was employed to study the kinetics and mechanism of the reaction of OH radicals with p-cymene at temperatures between 297 and 413 K in helium buffer gas. FP-RF experiments involved time-resolved detection of OH radicals by RF following vacuum-UV flash photolysis of H2O-p-cymene-He and H2O-He mixtures. Biexponential functions were fitted to decays of OH radicals according to reversible addition of OH radicals to p-cymene to form a single adduct. A rate constant of (15.7 ± 1.1) × 10(-12) is obtained (in units of cm(3) s(-1)) at room temperature (298 K) for the sum of the addition and abstraction channels (k1a + k1b) according to this simplified model. The Arrhenius plot reveals the step function typical of other aromatics and can be described using the expressions: 2 × 10(-13) exp(+1300 K/T) at temperatures between 297 K and 324 K and 10(-11) exp(-250 K/T) at temperatures between 345 K and 413 K. After consideration of the abstraction channel an equilibrium constant of k1a/k-1a = 6 × 10(-26) exp(+9700 K/T) cm(3) is obtained at temperatures between 297 and 325 K and 2 × 10(-36) exp(+17,000 K/T) cm(3) at temperatures between 325 and 380 K.
authors.affiliation: Atmospheric Chemistry Research Laboratory, University of Bayreuth, 95448, Bayreuth, Germany. cornelius.zetzsch@uni-bayreuth.de.
authors.forename: Paulo
authors.initials: P
authors.lastname: Alarcón
authors.forename: Rafal
authors.initials: R
authors.lastname: Strekowski
authors.forename: Cornelius
authors.initials: C
authors.lastname: Zetzsch
mesh_terms: D000081007:Cymenes; D005740:Gases / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D039821:Monoterpenes / Q000737:chemistry*; D010782:Photolysis; D013696:Temperature; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D000081007:Cymenes; D005740:Gases; D039821:Monoterpenes; D014867:Water; C007210:4-cymene; D017665:Hydroxyl Radical