Gas-Phase Ozone Reactions with a Structurally Diverse Set of Molecules: Barrier Heights and Reaction Energies Evaluated by Coupled Cluster and Density Functional Theory Calculations.

Reactions with ozone transform organic and inorganic molecules in water treatment systems as well as in atmospheric chemistry, either in the aqueous phase, at gas/particle interfaces, or in the gas phase. Computed thermokinetic data can be used to estimate the reactivities of molecules toward ozone in cases where no experimental data are available. Although the gas-phase reactivity of olefins with ozone has been characterized extensively in the literature, this is not the case for the richer chemistry of ozone with polar molecules, which occurs in the aqueous phase or in microhydrated environments.

Formation and reactivity of inorganic and organic chloramines and bromamines during oxidative water treatment.

The formation and further reactions of halamines during oxidative water treatment can be relevant for water quality. In this study, we investigated the formation and reactivity of several inorganic and organic halamines (monochloramine, N-chloromethylamine, N-chlorodimethylamine, monobromamine, dibromamine, N-bromomethylamine, N,N-dibromomethylamine, and N-bromodimethylamine) by kinetic experiments, transformation product analysis, and quantum chemical computations. Kinetic model simulations were conducted to evaluate the relevance of halamines for various water treatment scenarios.

Equilibria and Speciation of Chloramines, Bromamines, and Bromochloramines in Water.

The stabilities and speciation of the halamines in water are difficult to characterize experimentally. We provide theoretical estimates of aqueous standard free energies of formation for inorganic chloramines, bromamines, and bromochloramines, based on high-accuracy theoretical standard free energies of formation in gas phase combined with quantum chemical estimates of Henry's law constant. Based on comparisons between several theoretical and experimental datasets, we assign an error of 1.

Correction: Benchmark thermochemistry of chloramines, bromamines, and bromochloramines: halogen oxidants stabilized by electron correlation.

Correction for 'Benchmark thermochemistry of chloramines, bromamines, and bromochloramines: halogen oxidants stabilized by electron correlation' by Daniela Trogolo et al., Phys. Chem.

Molecular mechanism of NDMA formation from N,N-dimethylsulfamide during ozonation: quantum chemical insights into a bromide-catalyzed pathway.

During ozonation of drinking water, the fungicide metabolite N,N-dimethylsulfamide (DMS) can be transformed into a highly toxic product, N-nitrosodimethylamine (NDMA). We used quantum chemical computations and stopped-flow experiments to evaluate a chemical mechanism proposed previously to describe this transformation. Stopped-flow experiments indicate a pK(a) = 10.

Benchmark thermochemistry of chloramines, bromamines, and bromochloramines: halogen oxidants stabilized by electron correlation.

Chloramines, bromamines, and bromochloramines are halogen-containing oxidants that arise from the reaction of hypohalous acids with ammonia in water. Although relevant to both water disinfection chemistry and biochemistry, these molecules are difficult to study in the laboratory, and their thermochemical properties remain poorly established. We developed a benchmark level ab initio calculation protocol, termed TA14, adapted from the Weizmann theory and Feller-Peterson-Dixon approaches to determine the molecular structures and thermochemical properties of these compounds.

First ring formation by radical addition of propargyl to but-1-ene-3-yne in combustion. Theoretical study of the C7H7 radical system.

Combustive formation of a first carbon ring is an important step in the growth of polycyclic aromatic hydrocarbons (PAHs) and soot platelets. Propargyl radical addition to but-1-ene-3-yne (vinylacetylene) can start this process, possibly forming 5-, 6-, and 7-membered rings. A variety of partially intertwined reaction pathways results from density functional theory (DFT), which indicates three C7H7 radicals, benzyl, tropyl, and vinylcyclopentadienyl, as particularly stable.