Reaction mechanisms for methyl isocyanate (CHNCO) gas-phase degradation.

Methyl isocyanate (MIC) is a toxic chemical found in many commercial, industrial, and agricultural processes, and was the primary chemical involved in the Bhopal, India disaster of 1984. The atmospheric environmental chemical reactivity of MIC is relatively unknown with only proposed reaction channels, mainly involving OH-initiated reactions. The gas-phase degradation reaction pathways of MIC and its primary product, formyl isocyanate (FIC), were investigated with quantum mechanical (QM) calculations to assess the fate of the toxic chemical and its primary transformation products.

Atomistic insights into the hydrodefluorination of PFAS using silylium catalysts.

Fluorochemicals are a persistent environmental contaminant that require specialized techniques for degradation and capture. In particular, recent attention on per- and poly-fluoroalkyl substances (PFAS) has led to numerous explorations of different techniques for degrading the super-strong C-F bonds found in these fluorochemicals. In this study, we investigated the hydrodefluorination mechanism using silylium-carborane salts for the degradation of PFAS at the density functional theory (DFT) level.

High-temperature decomposition chemistry of trimethylsiloxane surfactants, a potential Fluorine-Free replacement for fire suppression.

Per- and polyfluoroalkyl substances (PFAS) have become global environmental contaminants due to being notoriously difficult to degrade, and it has become increasingly important to employ suitable PFAS alternatives, especially in aqueous film-forming foams (AFFF). Trimethylsiloxane (TriSil) surfactants are potential fluorine-free replacements for PFAS in fire suppression technologies. Yet because these compounds may be more susceptible to high-temperature decomposition, it is necessary to assess the potential environmental impact of their thermal degradation products.

Periodic Trends behind the Stability of Metal Catalysts Supported on Graphene with Graphitic Nitrogen Defects.

This study explored the fundamental chemical intricacies behind the interactions between metal catalysts and carbon supports with graphitic nitrogen defects. These interactions were probed by examining metal adsorption, specifically, the location of adsorption and the electronic structure of metal catalysts as the basis for the metal-support interactions (MSIs). A computational framework was developed, and a series of 12 transition metals was systematically studied over various graphene models with graphitic nitrogen defect(s).

Structure and Reactivity of Alloxan Monohydrate in the Liquid Phase.

Alloxan is an important toxic glucose analogue used to induce diabetes in lab test animals. Once regarded as a "problem structure," the condensed-phase structure of anhydrous alloxan has largely been settled, but literature inconsistencies remain for the structure of the typically employed reagent alloxan monohydrate. Due to the criticality of structure-function relationships, we have used H/C{H} NMR, IR spectroscopy, as well as quantum mechanical (QM) calculations to probe the liquid-phase structure and reactivity of alloxan monohydrate.

Quantum chemical calculations for over 200,000 organic radical species and 40,000 associated closed-shell molecules.

The stabilities of radicals play a central role in determining the thermodynamics and kinetics of many reactions in organic chemistry. In this data descriptor, we provide consistent and validated quantum chemical calculations for over 200,000 organic radical species and 40,000 associated closed-shell molecules containing C, H, N and O atoms. These data consist of optimized 3D geometries, enthalpies, Gibbs free energy, vibrational frequencies, Mulliken charges and spin densities calculated at the M06-2X/def2-TZVP level of theory, which was previously found to have a favorable trade-off between experimental accuracy and computational efficiency.

A perspective on biomass-derived biofuels: From catalyst design principles to fuel properties.

The hazards to health and the environment associated with the transportation sector include smog, particulate matter, and greenhouse gas emissions. Conversion of lignocellulosic biomass into biofuels has the potential to provide significant amounts of infrastructure-compatible liquid transportation fuels that reduce those hazardous materials. However, the development of these technologies is inefficient, due to: (i) the lack of a priori fuel property consideration, (ii) poor shared vocabulary between process chemists and fuel engineers, and (iii) modern and future engines operating outside the range of traditional autoignition metrics such as octane or cetane numbers.

Reactive Molecular Dynamics Simulations and Quantum Chemistry Calculations To Investigate Soot-Relevant Reaction Pathways for Hexylamine Isomers.

Sooting tendencies of a series of nitrogen-containing hydrocarbons (NHCs) have been recently characterized experimentally using the yield sooting index (YSI) methodology. This work aims to identify soot-relevant reaction pathways for three selected CHN amines, namely, dipropylamine (DPA), diisopropylamine (DIPA), and 3,3-dimethylbutylamine (DMBA) using ReaxFF molecular dynamics (MD) simulations and quantum mechanical (QM) calculations and to interpret the experimentally observed trends. ReaxFF MD simulations are performed to determine the important intermediate species and radicals involved in the fuel decomposition and soot formation processes.

Investigating the Photochemistry of C7 and C8 Functionalized N(5)-Ethyl-flavinium Cation: A Computational Study.

Flavins are a diverse set of compounds with a wide variety of biological and nonbiological applications. Applications of flavins receiving attention recently consist of electro- and photocatalytic oxidation of substrates for organic synthesis, bioengineered nanotechnology, and water splitting catalysts, among others. While there is vast knowledge regarding the structure-property relationships of flavins and their electrochemistry, there is much less work elucidating the structure property relationships as they pertain to flavinium photochemistry.

Characterization of the ALSEP Process at Equilibrium: Speciation and Stoichiometry of the Extracted Complex.

We have determined the identity of the complexes extracted into the ALSEP process solvent from solutions of nitric acid. The ALSEP process is a new solvent extraction separation designed to separate americium and curium from trivalent lanthanides in irradiated nuclear fuel. ALSEP employs a mixture of two extractants, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and ,,','-tetra(2-ethylhexyl)diglycolamide (TEHDGA) in -dodecane, which makes it difficult to ascertain the nature of the extracted metal complexes.

Solvation Dynamics of HEHEHP Ligand at the Liquid-Liquid Interface.

Actinide-lanthanide separation (ALSEP) has been a topic of interest in recent years as it has been shown to selectively extract problematic metals from spent nuclear fuel. However, the process suffers from slow kinetics, prohibiting it from being applied to nuclear facilities. In an effort to improve the process, many fundamental studies have been performed, but the majority have only focused on the thermodynamics of separation.