Theoretical Studies on the CH<sub>3</sub>CO + Cl Reaction: Hydrogen Abstraction versus CO
Displacement
Raman Sumathi
Minh Tho Nguyen
10.1021/jp981312f.s001
https://acs.figshare.com/articles/journal_contribution/Theoretical_Studies_on_the_CH_sub_3_sub_CO_Cl_Reaction_Hydrogen_Abstraction_versus_CO_Displacement/3726906
The geometries, energies, and vibrational frequencies of the reactants, transition structures, intermediates,
and products of the reaction of the acetyl radical with atomic chlorine have been determined by ab initio
molecular orbital theory at the second-order Møller Plesset perturbation (MP2) level. Energies have been
recalculated at the quadratic configuration interaction QCISD(T) level by using geometries obtained at MP2
level. The energy of the initial acetyl chloride adduct CH<sub>3</sub>COCl (<b>1</b>), formed by barrier-free combination,
lies 78 kcal/mol below the reactants. Two major reaction routes are open to the chemically activated adduct
<b>1</b>: molecular dissociation to H<sub>2</sub>CCO + HCl (<b>3</b>), and the secondary formation of ketene via 1-chlorovinyl
alcohol (<b>2</b>). Both these processes are energetically feasible to the thermal reactants and should hence lead to
a spontaneous emission of a vibrationally hot HCl molecule as observed by Maricq et al. (Int. J. Chem.
Kinet. <b>1997</b>, <i>29</i>, 421). The thermodynamically most stable products, CH<sub>3</sub>Cl + CO, should preferably be
formed via direct displacement of CO from CH<sub>3</sub>CO by Cl; this reaction proceeds via a loose complex between
Cl<sup>δ-</sup> and CH<sub>3</sub>CO<sup>δ+</sup>, which explains the delayed emission of CO in the diode laser study of the Cl + CH<sub>3</sub>CO
reaction. The energy barrier for decarbonylation of the adduct <b>1</b> is quite high and thereby is not accessible
to the thermal reactants. The present potential energy surface reveals this reaction to be a capture-limited
association−elimination reaction with a very high and pressure-independent rate coefficient.
1998-09-25 00:00:00
reactants
MP 2 level
HCl molecule
acetyl chloride adduct CH 3 COCl
adduct 1
reaction proceeds
M øller Plesset perturbation
CH 3 CO reaction
energy surface
transition structures
diode laser study
Theoretical Studies
CO Displacement
CH 3 CO
vibrational frequencies
CH 3 Cl
energy barrier
QCISD
reaction routes
ab initio