Ozonolysis of methyl, amino and nitro substituted ethenes: A semi-empirical molecular orbital study

Theoretical studies of atmospheric reaction mechanisms in the troposphere

“…The rate coefficients for the reactions of alkenes with O 3 span many orders of magnitude, depending mostly on the substitution around the double bond. The van der Waals pre-reactive complex, the transition state for cycloaddition, and the formation of the POZ have been characterized theoretically for many compounds; recent examples include (substituted) alkenes, [144][145][146][147][148][149][150][151][152][153] butadiene, 154 cycloalkenes, [155][156][157] terpenoids, 129,[158][159][160][161][162][163][164][165][166][167] and acetylene. 149,150,153 An accurate quantum chemical description of the 1,3-dipolar ozone addition requires particular attention, owing to the strong multi-reference character of the wavefunctions for ozone, pre-reactive complex, and addition transition state.…”

Ozonolysis of Bicyclic 1,2-Dioxines: Initial Scope and Mechanistic Insights

“…It also appears plausible at this stage to propose that one bridgehead phenyl grouping (dioxine 8b ) has little effect on altering the reaction outcome, with normal ozonolysis proceeding, whereas two bridgehead phenyl moieties (dioxine 8c ) remove enough electron density to weaken the peroxide bonds and enable rearrangements to readily occur. Previous research has shown that reactions of alkenes with ozone are sensitive to electronic effects, with electron deficient alkenes having much lower rate constants than those alkenes with greater electron density. − This is believed to be due to the electrophilic nature of ozone, which adds to nucleophilic π-bonds of alkenes that are enriched by lone pair donation by electron donating groups, thereby assisting in the lowering of the activation barrier, and thus enhancing the reaction rate. , When the rate is increased, there is less chance for rearrangements to occur, making it reasonable to suggest that electron withdrawing groups attached to the bridgehead positions of these bicyclic 1,2-dioxines may assist in slowing the rate of reaction and thereby raising the likelihood of rearrangements.…”

Effects of pH value and temperature on the initiation, promotion, inhibition and direct reaction rate constants of natural organic matter in ozonation

“…These values are comparable with those determined for simple organic compounds reacting with ozone. 12,[52][53][54] The E a for promotion and inhibition reactions are 25.6 and 50.1 kJ mol À1 . The difference could result from the different electron densities caused by the hydroxy substitution in the attacked carbon center that differentiates these two types of reaction modes.…”