Radical addition to the vinyl C=C bond: Quantum chemistry model of the reaction
Objects of Investigation: Basic Set of Reactions
To make a background of discussions of reactivity, the following set of reagents was chosen: radicals
HOO• and vinyl monomers
H), propene (Prop,
CH3), styrene (St,
C6H5), vinylacetate (VA,
OCOCH3), methylacrylate (MA,
COOCH3), acrylic nitryl (AN,
CN3), vinylchloride (VCl,
Cl), and vinylidenchloride (VCl2). For these monomers, both positions of attack were considered. In addition, reactivity of monomers with conjugated bonds toward
HOO• were considered *. The total number of calculated TSs was somewhere around 100.
All TSs had the same topology as shown above. Among possible conformations of products those ones were chosen that had a former radical group perpendicular to the former plane of the monomer. Table I presents the main geometric characteristics of TSs of β-attack (attack on the unsubstituted position of the
C=C bond). One may judge from the table that TS geometries within a series remain practically constant. Comparison of rprod/r≠ values shows that the
CH3• addition reaction has the earliest TS and the
HOO• addition the latest, in due agreement with experimental facts.
* Butadiene (Bu2ene), hexatriene (Hex3ene), vinylnaphthalene (ViNaph), 2- and 4-vinylpyridines (ViPy), and 2- and 4-vinylpyrimidines (ViPm).
|r≠, distance between reactive centers in TS (rprod – in product); φ, angle of attack; θ, torsion of |
|r≠ (Å)||1.945 ± 0.01||2.24 ± 0.02||2.05 ± 0.02||2.21 ± 0.01||2.22 ± 0.01|
|RCC (Å)||1.405 ± 0.01||1.385 ± 0.01||1.395 ± 0.01||1.395 ± 0.01||1.395 ± 0.01|
|rprod/r≠||0.735 ±.005||0.685 ±.005||0.689 ±.001||0.702 ±.005||0.721 ±.003|