Reactivity and Regioselectivity of Hydroxyl Radical Addition to Halogenated Ethenes

Abstract

The reactions of hydroxyl radical with ethene, fluoroethene, and chloroethene have been studied by quantum chemical methods. Reactants, prereaction complexes, transition-state structures, and products were optimized and vibrational frequencies were calculated at the UMP2/6-311+G(2d,p) level. Transition-state structures are significantly different from the prereaction complexes formed on the reactant side of the MEP. The convergence of barrier heights and reaction enthalpies has been systematically investigated with respect to the size and quality of basis set and the treatment of correlation energy. The best agreement with experimental results is found at the MP2/aug-cc-pVTZ level of theory. Regioselectivity is discussed in terms of two properties of the radical and the investigated alkenes. The first factor is the relative spin density in the 3ππ* state of the alkene. The second factor is the relative strengths of the product C−O bond, i.e., relative stability of the corresponding radical product. In the case of fluoroethene these two effects oppose each other and regioselectivity is negligible. In the case of chloroethene spin density is the dominant factor and the addition of OH radicals to the unsubstituted carbon atom is preferred.

Modeling lifetime and degradability of organic compounds in air, soil, and water systems (IUPAC Technical Report)

“…The tremendously fast developments in computing technology, hardware, and software have enabled the calculation of the energy profiles of gas-phase reactions with OH radicals. The abstraction of hydrogen atoms by hydroxyl radicals, as well as its addition to the double bonds, have been a subject of theoretical investigations with semiempirical [38][39][40] and accurate ab initio [41][42][43][44][45][46][47][48][49][50][51][52] MO calculations during the last decade. The early efforts have focused on studying structural and energetic properties of reactants, products, and transition-state structures of hydroxyl radical reactions with small hydrocarbons and their halogenated derivatives [41][42][43][48][49][50][51]53].…”

Anharmonic theoretical simulations of infrared spectra of halogenated organic compounds

“…With these premises, it is not surprising that the last years have seen a renewed interest in the spectroscopic studies of halogenated organic compounds, motivated not only by their role as air pollutants, but also because these investigations are useful to improve the modeling of the atmospheric chemistry of these compounds. [22][23][24][25] In this context, the prediction of molecular properties by state-of-the-art quantummechanical (QM) methods has been proved of paramount relevance for the study of molecular systems. In the last years, theoretical computations have become powerful and widespread tools for the assignment and prediction of the experimental spectra, as well as to get deeper insight into the different effects which determine the observed spectroscopic properties.…”

A Two Transition State Model for Radical−Molecule Reactions: Applications to Isomeric Branching in the OH−Isoprene Reaction

“…The addition of OH to ethylene represents the simplest example of this class of reactions and is, therefore, a benchmark system for understanding the underlying nature of these reactions. As a consequence, there have been numerous experimental and theoretical [54][55][56][57][58][59][60][61][62] studies of this reaction.…”

“…Theoretical studies of the C 2 H 4 + OH reaction have considered quantum chemical analyses of the stationary points on the potential energy surface [54][55][56][57][58][59][60][61][62] as well as transition state theory based analyses of the kinetics. 56,[58][59][60]62 The quantum chemical analyses have provided fairly detailed descriptions of the saddle point connecting the entrance van der Waals complex with the CH 2 CH 2 OH adduct, as well as mapping out the full reactive potential energy surface.…”