Mechanism of Formation and Molecular Structure of α-Halothioacetones

10.1007/s11178-008-1003-1

“…1). The enrgies of activation for the systems including structures Ia-Ic were estimated at 179.0, 183.4, and 187.6 kJ/mol, respectively (Table 2); these values are lower by about 50 kJ/mol than the activation barrier to the formation of geminal hydroxy thiols from monohaloacetones [20]. It was found that the stability weakly depends on the halogen nature: it slightly increases with rise in the halogen atom number (28.1, 31.3, and 39.6 kJ/mol for X = F, Cl, and Br, respectively).…”

“…The depth of the corresponding potential well relative to those for the nearest rotamers increases with rise in the halogen atom number (Table 1). According to the calculations performed at the B3LYP/LANL2DZ level, reactions of α-haloacetones with hydrogen sulfide involve intermediate formation of the corresponding enol [20], while hydrogen chloride mediates the enolization process (Scheme 2). According to the calculations performed at the B3LYP/LANL2DZ level, reactions of α-haloacetones with hydrogen sulfide involve intermediate formation of the corresponding enol [20], while hydrogen chloride mediates the enolization process (Scheme 2).…”

“…According to the calculations performed at the B3LYP/LANL2DZ level, reactions of α-haloacetones with hydrogen sulfide involve intermediate formation of the corresponding enol [20], while hydrogen chloride mediates the enolization process (Scheme 2). Direct attack on the substrate by hydrogen sulfide molecule with formation of a four-center transition state is less favorable by about 80-90 kJ/mol [20]. Its activation energy is 230.…”

10.1007/s11178-008-1004-0

“…According to the experimental data, the mechanism of formation of hydroxy thiols in reactions of halogenated ketones with hydrogen sulfide in the presence of hydrogen chloride is determined on the number of halogen atoms in the α-positions with respect to the carbonyl group and is almost independent of the halogen nature (F, Cl, Br) [7,8]. Therefore, the calculations were performed for chlorinated acetones.…”

“…The potential energy surface for the reaction of ketone I with H 2 S and HCl was analyzed following the pro- cedures described in [7,8] for trimolecular system I · HCl · H 2 S (V). It includes intermolecular proton shifts.…”