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Chlorination Chemistry 4. Ab Initio Study of the Addition, Metathesis, and Isomerization Channels Governing the Reaction of Chlorine Atom with Propargyl Chloride

Published

Author(s)

Jeffrey W. Hudgens, Carlos A. Gonzalez

Abstract

Highly correlated ab initio molecular orbital calculations have been used to map out the potential energy surface corresponding to the reaction of Cl + propargyl chloride (C3H3Cl) in the gas phase. Nine transition state structures governing the mechanism of the title reaction were computed at seven different levels of theory up to the QCISD(T)/6-311+G(d,p)// QCISD(T)/6-31+G(d,p) level. Chlorine atom additions at the center and end unsaturated carbons are barrierless processes forming incipient 2,3-dichloro-1-propene-1-yl and 1,3-chloro-1-propene-2-yl radicals, respectively. High energy transition state structures inhibit isomerization of the incipient radicals through hydrogen atom transfer. The presence of a chlorine atom transfer transition state below the energy of the initial reactants establishes equilibrium between the incipient radicals. A second accessible chlorine transfer transition state enables the 1,3-dichloro-1-propene-2-yl radical to isomerize into the more stable 1,2-dicloroallyl radical. The chemically activated 1,3-dichloro-1-propene-2-yl radical also undergoes bond scission of the chlorine atom in the chloromethyl group forming chloroallene and Cl atom. Chlorine atom attack on the chloromethyl group encounters metathesis transition states for HCl and Cl2 formation at 5 kJ mol-1 and 124 kJ mol-1 above the initial reactants, respectively. Thus, at ambient temperature the ab initio results predict that the dominant products of chlorine atom addition to propagryl chloride are the Cl atom, chloroallene, and the 1,2-dichloroallyl radical.
Citation
Journal of Physical Chemistry A
Volume
106
Issue
No. 25

Keywords

ab initio calculation, addition reaction, chlorination reaction, chlorine, isomerization, metathesis, propargyl chloride, propargyl radical, reaction mechanism

Citation

Hudgens, J. and Gonzalez, C. (2002), Chlorination Chemistry 4. Ab Initio Study of the Addition, Metathesis, and Isomerization Channels Governing the Reaction of Chlorine Atom with Propargyl Chloride, Journal of Physical Chemistry A, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=831764 (Accessed April 14, 2024)
Created June 1, 2002, Updated February 17, 2017