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Chlorination Chemistry I: Rate Coefficients, Reaction Mechanisms, and Spectra of the Chlorine and Bromine Adducts of Propargyl Halides

Published

Author(s)

D B. Atkinson, Jeffrey W. Hudgens

Abstract

Cavity ring-down spectroscopy (CRDS), end-product analysis, and ab initio calculations have determined the reaction rate coefficients, mechanisms and thermochemistry relevant to the addition of halogen atoms to propargyl chloride and propargyl bromide. Halogen atoms were produced by laser photolysis and halogen addition reaction products were probed at a variable delay by CRDS using a second laser pulse. We report the continuum spectra of C3H3Cl2, C3H3ClBr, and C3H3Br2 between 238 and 252 nm and the absorption cross-sections, ς 240(C3H3Cl2) = 4.20 + 1.05 x 10-17 cm2-molec-1 and ς242(C3H3Br2) = 1.04 + 0.31 x 10-17 cm2-molec-1. When a chlorine atom adds to the acetylenic carbon of propargyl chloride, the incipient radical regenerates a chlorine atom and produces chloroallene. Chlorine atom addition at the center carbon of propargyl chloride forms the 2,3-dichloro-1-propene-2-yl radical, which we monitor with CRDS. By fitting the observed data to complex reaction schemes, the 295K rate coefficients for formation of 2,3-dihalo-1-propene-2-yl radicals were found to be k(Cl+C3H3Cl, 665 Pa)= 1.2+0.2x10-10 cm3molec-1s-1 and k(Br+C3H3Br, 625 Pa)= 2+1 x 10-12 cm3molec-1s-1. Self-reaction rate coefficients of the adducts at 295K were found to be k(C3H3Cl2+C3H3Cl2)= 3.4+0.9x10-11 cm3molec-1s-1 and k(C3H3Br2+C3H3Br2)= 1.7 + 1.1 x 10-11 cm3molec-1s-1. The listed uncertainties are twice the standard deviation of individual determinations and the rate coefficients include the uncertainty of the appropriate absorption cross-section.
Citation
Journal of Physical Chemistry A
Volume
103

Keywords

ab initio calculation, bromine reaction, C<sub>3</sub>H<sub>3</sub> + C<sub>3</sub>H<sub>3</sub>Cl<sub>2</sub> reaction, cavity ring-down spectra, chlorine reaction, Cl + C<sub>3</sub>H<sub>3</sub>Cl<sub>1</sub> reaction, electronic spectrum, reaction mechanism, reaction rate coefficient

Citation

Atkinson, D. and Hudgens, J. (1999), Chlorination Chemistry I: Rate Coefficients, Reaction Mechanisms, and Spectra of the Chlorine and Bromine Adducts of Propargyl Halides, Journal of Physical Chemistry A, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=831544 (Accessed April 15, 2024)
Created September 15, 1999, Updated October 12, 2021