Chlorination Chemistry. 3. Ab Initio Study of the Reaction of Chlorine Atom with Allene

Published

February 2, 2002

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 of the Cl + allene reaction in the gas phase. Seven transition state structures governing the mechanism of the title reaction were computed at seven different levels of theory. The results show that UMP2 calculations are adversely affected by contamination from higher spin states. QCISD(T) calculations illustrate the importance of correlation including triple electron excitations in the quadratic configuration wavefunction for obtaining an accurate description of the potential energy surface. Results computed at the QCISD(T)/6-31+G(d,p)//QCISD/6-31+G(d,p) level indicate that chlorine atom addition at the center and end carbons of allene are barrierless processes and that the chemically activated C₃H₄Cl complex may isomerize through chlorine atom transfer but not through hydrogen atom transfer. The metathesis transition state corresponding to hydrogen abstraction by chlorine lies 15 kJ mol_-1 above reactants. The isomerization reaction path between the 3-chloro-1-propene-2-yl and 2-chloroallyl radical adducts lies below the initial reactants, permitting the incipient C₃H₄Cl ensembles to establish equilibrium. Thus, the dominant addition product of Cl + allene is the 2-chloroallyl radical.

Citation

Journal of Physical Chemistry A

Volume

106

Issue

No. 9

Pub Type

Journals

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Keywords

ab initio calculation, addition reaction, allene, branching ratio, chlorination reaction, chlorine, metathesis, molecular orbital, reaction mechanism

Citation

Hudgens, J. and Gonzalez, C. (2002), Chlorination Chemistry. 3. Ab Initio Study of the Reaction of Chlorine Atom with Allene, Journal of Physical Chemistry A, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=831765 (Accessed April 26, 2024)