DFT Model of Elemental Sulfur in Sulfolane Solutions.

The structure and the thermodynamic and optical (UV) properties of elemental sulfur solution in sulfolane (Sl) have been studied using density functional theory methods. The cyclic molecular form of sulfur (S "crown") was found using PBE1PBE/6-311+G(d,p) approximation in combination with a polarizable continuum model (the integral equation formalism variant) to exist in sulfolane medium as a Sl-S-Sl solvate. It has been theoretically established that sulfur can form stable (S) clusters in concentrated solutions.

Global Kinetics and Spectral Modeling of -Methoxyphenyl Azide Photooxidation.

The kinetics of photooxidation of -methoxyphenyl azide was studied by flash photolysis with spectrophotometric detection of the absorption of active intermediates in an aerated acetonitrile solution at 295 K. The holistic set of experimental data including the consumption of - isomers of -methoxyphenyl nitroso oxide and the accumulation of photooxidation products (2,4)-4-methoxy-6-oxo-hexa-2,4-diene-nitrile oxide and bis--methoxy-azobenzene monitored via the changes in the optical density of the solution in the wavelength range of 300-500 nm was treated to obtain the most complete information about the system under study. Flash photolysis of results in the formation of the corresponding triplet nitrene, which either recombines to azobenzene with a rate constant 2 = (8.

BEP-Like Correction of Nonequilibrium Thermodynamic Parameters of the Solvent-Assisted Reactions: The DFT and Study of Hydration, Peroxidation, and Enolization of Acetone and 1,1,1-Trifluoroacetone in Aqueous Solutions.

The mechanisms of enolization and reactions of nucleophilic addition to carbonyl compounds were analyzed by density functional theory (DFT) (PBE1PBE) and (DLPNO-CCSD(T)) level of theory using the interaction of water and hydrogen peroxide with acetone and 1,1,1-trifluoroacetone (TFA) as the reference reactions. The transition states of the studied reactions were localized within the integrated approach that includes both the dielectric continuum theory (polarizable continuum model (PCM)) and the cyclic or two-cluster explicit solvation models. The considered models provide proton transfer in the enolization, hydration, and peroxidation reactions by the Grotthuss mechanism.

The substituent effects on the [3+2] cycloaddition of nitrile oxides generated by photooxidation of arylazides to acetonitrile.

The DFT approach in M06L/6-311 + G(d,p) approximation was used to study the transformation of unsaturated nitrile oxides (RCNO), which were generated by photooxidation of the corresponding aromatic azide, to oxadiazoles via [3 + 2]cyclization with acetonitrile. It was found that the cycloaddition activation enthalpy was within 60-93 kJ/mol, depending on the structure of the nitrile oxide. A significant mesomeric effect of the substituent and its position in the conjugated molecular system on the activation barrier of the reaction studied was identified.

Nature of Lewis Base Catalysis of 1,3-Dipolar Cycloaddition of Methyl Diazoacetate to Methyl Acrylate; NMR Kinetic Spectroscopy and DFT Study.

The effect of Lewis base (LB) in the domino reaction between methyl diazoacetate and methyl acrylate has been studied. This domino process is initialized by a [3+2]-cycloaddition reaction to generate 3H-pyrazoline followed by a subsequent 1,3-H shift reaction forming 1H-pyrazoline as the more stable isomer. The rate of the first step is not sensitive to the presence of LBs (THF, Py, DMAP, DBU, and triphenylphosphine) as it was evidenced by kinetic nuclear magnetic resonance spectroscopy and quantum chemical modeling.

Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions.

The influence of aerosol concentration on the cloud-droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud-droplet growth and fallout. As aerosol concentration is increased, the cloud-droplet mean diameter decreases, as expected, but the width of the size distribution also decreases sharply.

Acoustic streaming of a sharp edge.

Anomalous acoustic streaming is observed emanating from sharp edges of solid bodies that are vibrating in fluids. The streaming velocities can be orders of magnitude higher than expected from the Rayleigh streaming at similar amplitudes of vibration. Acoustic velocity of fluid relative to a solid body diverges at a sharp edge, giving rise to a localized time-independent body force acting on the fluid.

In situ characterization of cloud condensation nuclei, interstitial, and background particles using the single particle mass spectrometer, SPLAT II.

The aerosol indirect effect remains the most uncertain aspect of climate change modeling, calling for characterization of individual particles sizes and compositions with high spatial and temporal resolution. We present the first deployment of our single particle mass spectrometer (SPLAT II) operated in dual data acquisition mode to simultaneously measure particle number concentrations, density, asphericity, and individual particle size and quantitative composition, with temporal resolution better than 60 s, thus yielding all the required properties to definitively characterize the aerosol-cloud interaction in this exemplary case. We find that particles are composed of oxygenated organics, many mixed with sulfates, biomass burning particles, some with sulfates, and processed sea-salt.