Theoretical study of the relative reactivity of chloroethenes with atmospheric oxidants (OH, NO3, O(3P), Cl(2P) and Br(2P))

Abstract

The reactivity of a series of chloroethenes with different electrophiles of tropospheric and stratospheric interest is analyzed by frontier molecular orbital theory and a correlation with calculated orbital energies is investigated. The reactions of CH 2 =CHCl; CH 2 =CCl 2 ; (Z)-CHCl=CHCl; (E)-CHCl=CHCl; CHCl=CCl 2 and CCl 2 =CCl 2 with O( 3 P), Cl( 2 P), Br( 2 P) atoms and with OH and NO 3 radicals were studied using semiempirical methods (AM1 and PM3) and ab initio calculations at the HF and B3LYP levels of theory with the 6-31G ** basis set, using the Gaussian 98 suite of programs. In contrast to the majority of reaction series of small radicals and molecules with alkenes and alkanes, the rate constants for the reactions with halogenated ethenes do not correlate with the ionization potential of the halogenated ethene. The energy and the carbon-carbon p-bonding form of the HOMO change on addition of chlorine atoms as substituents to the carbon-carbon s-bonding framework of the alkenes. For the reactions studied the complete interaction HOMO-SOMO was considered, taking into account the contribution of the different atomic orbitals to the HOMO of the chloroethene through the atomic orbital coefficients, and a good correlation with the experimental values was obtained.

Reactions of chloroethenes with atomic chlorine in air at atmospheric pressure

“…15, 16 This was also confirmed by recent calculations using mo lecular orbital theory. 17 Reaction mechanism. Trichloroacetyl chloride is the major product found in the oxidation process of tetrachlo roethene with Cl atoms (see Table 2).…”

Thermochemical unification of molecular descriptors to predict radical hydrogen abstraction with low computational cost

“…Similar findings were reported for unsaturated organics. 40,41 The inclusion of q via c HOMO (Fig. S8D, ESI †) marginally improved the correlations (Fig.…”

Photoelectron spectroscopy of terpenoids and prediction of their rate constants in atmospheric oxidation reactions

“…Many of these rate constants are unknown, possibly resulting from the variety of these compounds and the inherent expense of deriving these data experimentally. Structure-activity relationship (SAR) analysis [14,15] and perturbation frontier molecular orbital (PFMO) theory have been successfully applied to predict the rate constants for the reactions of some alkenes with OH radical, NO 3 radical, and O 3 in the gas phase [16][17][18]. However, these results are based on theoretical values.…”