Accurately Predicting Barrier Heights for Radical Reactions in Solution Using Deep Graph Networks.

Quantitative estimates of reaction barriers and solvent effects are essential for developing kinetic mechanisms and predicting reaction outcomes. Here, we create a new data set of 5,600 unique elementary radical reactions calculated using the M06-2X/def2-QZVP//B3LYP-D3(BJ)/def2-TZVP level of theory. A conformer search is done for each species using TPSS/def2-TZVP.

Reaction of OH with Aliphatic and Aromatic Isocyanates.

Isocyanates are highly relevant industrial intermediates for polyurethane production. In this work, we used quantum chemistry and transition state theory (TST) to investigate the gas-phase reaction of isocyanates with the OH radical, which is likely one of the most significant chemical sinks for these compounds in the troposphere. -Tolyl-isocyanate (p-tolyl-NCO) was chosen as a proxy substance for the large-volume aromatic diisocyanate species toluene diisocyanate and methylene diphenyl diisocyanate.

Nascent energy distribution of the Criegee intermediate CHOO from direct dynamics calculations of primary ozonide dissociation.

Ozonolysis produces chemically activated carbonyl oxides (Criegee intermediates, CIs) that are either stabilized or decompose directly. This branching has an important impact on atmospheric chemistry. Prior theoretical studies have employed statistical models for energy partitioning to the CI arising from dissociation of the initially formed primary ozonide (POZ).

Theoretical investigation of intersystem crossing in the cyanonitrene molecule, NCN → NCN.

The NCN diradical is an important intermediate of prompt nitric oxide formation in flames. The mechanism of intersystem crossing (ISC) in the NCN molecule formed via pyrolysis or photolysis of NCN is of relevance to the interpretation of experiments that utilize NCN as a precursor for laboratory studies of NCN kinetics. This mechanism has been investigated by means of multi-reference configuration interaction calculations.

endo-Cyclization of unsaturated RO radicals from the gas-phase ozonolysis of cyclohexadienes.

Unsaturated RO radicals from the ozonolysis of cyclodienes can readily undergo an endo-cyclization step under atmospheric conditions forming a new ring-containing RO radical after further O addition. This path represents an extension of the atmospheric autoxidation scheme forming highly oxidized multifunctional organic compounds (HOMs). HOMs play an important role for Earth's organic aerosol burden.

Kinetics of the unimolecular reaction of CH2OO and the bimolecular reactions with the water monomer, acetaldehyde and acetone under atmospheric conditions.

Stabilized Criegee Intermediates (sCIs) have been identified as oxidants of atmospheric trace gases such as SO2, NO2, carboxylic acids or carbonyls. The atmospheric sCI concentrations, and accordingly their importance for trace gas oxidation, are controlled by the rate of the most important loss processes, very likely the unimolecular reactions and the reaction with water vapour (monomer and dimer) ubiquitously present at high concentrations in the troposphere. In this study, the rate coefficients of the unimolecular reaction of the simplest sCI, formaldehyde oxide, CH2OO, and its bimolecular reaction with the water monomer have been experimentally determined at T = (297 ± 1) K and at atmospheric pressure by using a free-jet flow system.

Infrared detection of Criegee intermediates formed during the ozonolysis of β-pinene and their reactivity towards sulfur dioxide.

Recently, direct kinetic experiments have shown that the oxidation of sulfur dioxide to sulfur trioxide by reaction with stabilized Criegee intermediates (CIs) is an important source of sulfuric acid in the atmosphere. So far, only small CIs, generated in photolysis experiments, have been directly detected. Herein, it is shown that large, stabilized CIs can be detected in the gas phase by FTIR spectroscopy during the ozonolysis of β-pinene.