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Articles 1 - 16 of 16
Full-Text Articles in Physical Sciences and Mathematics
Emissions Of Organic Compounds From Produced Water Ponds, Seth Lyman
Emissions Of Organic Compounds From Produced Water Ponds, Seth Lyman
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We measured fluxes of methane, a suite of non-methane hydrocarbons (C2-C11), light alcohols, and carbon dioxide from oil and gas produced water storage and disposal ponds in Utah (Uinta Basin) and Wyoming (Upper Green River Basin) United States during 2013-2016. In this paper, we discuss the characteristics of produced water composition and air-water fluxes, with a focus on flux chamber measurements. In companion papers, we will (1) report on inverse modeling methods used to estimate emissions from produced water ponds, including comparisons with flux chamber measurements, and (2) discuss the development of mass transfer coefficients to estimate emissions and place …
Comparison Of Various Means Of Evaluating Molecular Electrostatic Potentials For Noncovalent Interactions, Steve Scheiner
Comparison Of Various Means Of Evaluating Molecular Electrostatic Potentials For Noncovalent Interactions, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The various heterodimers formed by a series of Lewis acids with NH3 as Lewis base are identified. Lewis acids include those that can form chalcogen (HSF and HSBr), pnicogen (H2PF and H2PBr), and tetrel (H3SiF and H3SiBr) bonds, as well as H‐bonds and halogen bonds. The molecular electrostatic potential (MEP) of each Lewis acid is considered in a number of ways. Pictorial versions show broad regions of positive and negative MEP, on surfaces that vary with respect to either the value of the chosen isopotential, or their distance from the nuclei. Specific points are identified where the MEP reaches a …
Can Hcch/Hbnh Break B=N/C=C Bonds Of Single-Wall Bn/Carbon Nanotubes At Their Surface?, Tapas Kar, Peter Grüninger, Steve Scheiner, Holger F. Bettinger, Ajit K. Roy
Can Hcch/Hbnh Break B=N/C=C Bonds Of Single-Wall Bn/Carbon Nanotubes At Their Surface?, Tapas Kar, Peter Grüninger, Steve Scheiner, Holger F. Bettinger, Ajit K. Roy
Chemistry and Biochemistry Faculty Publications
The iminoborane (HBNH) molecule, which prefers cycloaddition reactions, selectively breaks a B=N bond of smaller diameter single-wall BNNTs and expands a ring at their surface, either at the edges or at the middle of the tube. Density functional theory (DFT) is used to test whether its organic counterpart HCCH can do the same with BNNTs. HCCH-BNNT complexes are identified and transition states located for these combination reactions. Also explored are possible reactions of HBNH with SWNTs and HCCH with SWNTs. Data suggest that B=N (C=C) bond breaking, followed by ring expansion at the surface may be possible. Although [2+2] cycloaddition …
Halogen Bonds Formed Between Substituted Imidazoliums And N Bases Of Varying N-Hybridization, Steve Scheiner
Halogen Bonds Formed Between Substituted Imidazoliums And N Bases Of Varying N-Hybridization, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Heterodimers are constructed containing imidazolium and its halogen-substituted derivatives as Lewis acid. N in its sp3, sp2 and sp hybridizations is taken as the electron-donating base. The halogen bond is strengthened in the Cl < Br < I order, with the H-bond generally similar in magnitude to the Br-bond. Methyl substitution on the N electron donor enhances the binding energy. Very little perturbation arises if the imidazolium is attached to a phenyl ring. The energetics are not sensitive to the hybridization of the N atom. More regular patterns appear in the individual phenomena. Charge transfer diminishes uniformly on going from amine to imine to nitrile, a pattern that is echoed by the elongation of the C-Z (Z=H, Cl, Br, I) bond in the Lewis acid. These trends are also evident in the Atoms in Molecules topography of the electron density. Molecular electrostatic potentials are not entirely consistent with energetics. Although I of the Lewis acid engages in a stronger bond than does H, it is the potential of the latter which is much more positive. The minimum on the potential of the base is most negative for the nitrile even though acetonitrile does not form the strongest bonds. Placing the systems in dichloromethane solvent reduces the binding energies but leaves intact most of the trends observed in vacuo; the same can be said of ∆G in solution.
Special Issue: Intramolecular Hydrogen Bonding 2017, Steve Scheiner
Special Issue: Intramolecular Hydrogen Bonding 2017, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Even after more than a century of study [1–6], scrutiny, and detailed examination, the H-bond continues [7–12] to evoke a level of fascination that surpasses many other phenomena. Perhaps it is the ability of the simple H atom, with but a single electron, to act as a glue that maintains contact between much more complicated species. Or it might be its geometry, which prefers to hold the bridging proton on a direct line between the two heavy atoms. Not to be ignored are the spectral features of the H-bond: the large red shift of the stretching frequency of the covalent …
Universal Surface Engineering Of Transition Metals For Superior Electrocatalytic Hydrogen Evolution In Neutral Water, Bo You, Xuan Liu, Guoxiang Hu, Sheraz Gul, Junko Yano, De-En Jiang, Yujie Sun
Universal Surface Engineering Of Transition Metals For Superior Electrocatalytic Hydrogen Evolution In Neutral Water, Bo You, Xuan Liu, Guoxiang Hu, Sheraz Gul, Junko Yano, De-En Jiang, Yujie Sun
Chemistry and Biochemistry Faculty Publications
The development of low-cost hybrid water splitting-biosynthetic systems that mimic natural photosynthesis to achieve solar-to-chemical conversion is of great promise for future energy demands, but often limited by the kinetically sluggish hydrogen evolution reaction (HER) on the surface of nonprecious transition metal catalysts in neutral media. It is thus highly desirable to rationally tailor the reaction interface to boost the neutral HER catalytic kinetics. Herein, we report a general surface nitrogen modification of diverse transition metals (e.g. iron, cobalt, nickel, copper, and nickel-cobalt alloy), accomplished by a facile low-temperature ammonium carbonate treatment, for significantly improved hydrogen generation from neutral water. …
Deciphering Delocalized Bonding In Excited States, Solvated Species And Novel 0-, 1-, 2-, And 3-Dimensional Chemical Systems, Alexander Boldyrev
Deciphering Delocalized Bonding In Excited States, Solvated Species And Novel 0-, 1-, 2-, And 3-Dimensional Chemical Systems, Alexander Boldyrev
Funded Research Records
No abstract provided.
New Strategies For Investigating Oxidative Aliphatic Carbon-Carbon Bond Cleavage Reactions, Lisa Berreau
New Strategies For Investigating Oxidative Aliphatic Carbon-Carbon Bond Cleavage Reactions, Lisa Berreau
Funded Research Records
No abstract provided.
Chemical Tools For Delivery Of Carbon Monoxide, Lisa Berreau
Chemical Tools For Delivery Of Carbon Monoxide, Lisa Berreau
Funded Research Records
No abstract provided.
Systematic Elucidation Of Factors That Influence The Strength Of Tetrel Bonds, Steve Scheiner
Systematic Elucidation Of Factors That Influence The Strength Of Tetrel Bonds, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Quantum calculations are used to examine the properties of heterodimers formed by a series of tetrel-containing molecules with NH3 as universal Lewis base. TH4 was taken as a starting point, with T= C, Si, Ge, and Sn. The H atoms were replaced by various numbers of F atoms: TH3F, TF3H, and TF4 so as to monitor the effects of adding electron-withdrawing substituents. Unsubstituted TH4 molecules form the weakest tetrel bonds, only up to about 2 kcal/mol. The bond is strengthened when the H opposite NH3 is replaced by F, rising up …
Collaborative Research: Refining And Testing Methods For Identifying And Quantifying Gaseous Oxidized Mercury In Air, Seth Lyman
Funded Research Records
No abstract provided.
Assembly Of Effective Halide Receptors From Components. Comparing Hydrogen, Halogen, Tetrel Bonds, Steve Scheiner
Assembly Of Effective Halide Receptors From Components. Comparing Hydrogen, Halogen, Tetrel Bonds, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Receptors for halide anions are constructed based on the imidazolium unit, and then replacing the H-bonding C-H group firstby halogen-bonding C-I and then by tetrel-bonding C-SnH3 and C-SiF3.Attaching a phenyl ring to any of these species has little effect on its ability to bind a halide, but incorporation of a second imidazolium to the benzene connector, forming a bidentate dicationic receptor, greatly enhances the binding. Addition of electron-withdrawing F atoms to each imidazolium adds a further increment. F- consistently binds more strongly to the various receptor models than does Cl-. Whereas replacement of the H atom on the imidazolium groups …
Solvation Enhances The Distinction Between Carboxylated Armchair And Zigzag Single-Wall Carbon Nanotubes (Swnt-Cooh), Tapas Kar, Upendra Adhikari, Steve Scheiner, Ajit K. Roy, Renato L. T. Parreira, Pedro A. De S. Bergamo, Giovanni F. Caramori, Felipe S. S. Schneider
Solvation Enhances The Distinction Between Carboxylated Armchair And Zigzag Single-Wall Carbon Nanotubes (Swnt-Cooh), Tapas Kar, Upendra Adhikari, Steve Scheiner, Ajit K. Roy, Renato L. T. Parreira, Pedro A. De S. Bergamo, Giovanni F. Caramori, Felipe S. S. Schneider
Chemistry and Biochemistry Faculty Publications
The effect of various solvents on the structures and properties of carboxylated SWNTs has been explored using the Same Level Different Basis Set approach (SLDB), where B3LYP functional of density functional theory (DFT) was applied. Armchair (4,4) and zigzag (8,0) and (9,0) tubes were considered as the test bed. In order to simulate varying concentration of –COOH groups, one to five acids groups were placed at one end of these tubes. These samples were placed in different solvents (namely, CS2, THF and water) with varying polarity and results were compared with gas-phase properties. Similar to the gas-phase, zigzag tubes also …
Comparison Of Halide Receptors Based On H, Halogen, Chalogen, Pnicogen, And Tetrel Bonds, Steve Scheiner
Comparison Of Halide Receptors Based On H, Halogen, Chalogen, Pnicogen, And Tetrel Bonds, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
A series of halide receptors are constructed and the geometries and energetics of their binding to F-, Cl-, and Br- assessed by quantum calculations. The dicationic receptors are based on a pair of imidazolium units, connected via a benzene spacer. The imidazoliums each donate a proton to a halide in a pair of H-bonds. Replacement of the two bonding protons by Br leads to binding via a pair of halogen bonds. Likewise, chalcogen, pnicogen, and tetrel bonds occur when the protons are replaced, respectively, by Se, As, and Ge. Regardless of the binding group considered, F- is bound much more …
Comparison Of Tetrel Bonds In Neutral And Protonated Complexes Of Pyridinetf3 And Furantf3 (T = C, Si, And Ge) With Nh3, Mingxiu Liu, Qing-Zhong Li, Steve Scheiner
Comparison Of Tetrel Bonds In Neutral And Protonated Complexes Of Pyridinetf3 And Furantf3 (T = C, Si, And Ge) With Nh3, Mingxiu Liu, Qing-Zhong Li, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Ab initio calculations have been performed for the complexes H+–PyTX3⋯NH3 and H+–furanTF3⋯NH3 (T = C, Si, and Ge; X = F and Cl) with focus on geometries, energies, orbital interactions, and electron densities to study the influence of protonation on the strength of tetrel bonding. The primary interaction mode between α/β-furanCF3/p-PyCF3 and NH3 changes from an F⋯H hydrogen bond to a C⋯N tetrel bond as a result of protonation. Importantly, the protonation has a prominent enhancing effect on the strength of tetrel bonding with an increase in binding energy from 14 to 30 kcal mol−1. The tetrel bonding becomes stronger …
Flipped Learning In Synchronously-Delivered, Geographically-Dispersed General Chemistry Classrooms, Michael A. Christiansen, Louis Nadelson, Lianna K. Etchberger, Marilyn M. Cuch, Trish A. Kingsford, Leslie O. Woodward
Flipped Learning In Synchronously-Delivered, Geographically-Dispersed General Chemistry Classrooms, Michael A. Christiansen, Louis Nadelson, Lianna K. Etchberger, Marilyn M. Cuch, Trish A. Kingsford, Leslie O. Woodward
Chemistry and Biochemistry Faculty Publications
In synchronously-delivered, multi-site classrooms, the physical separation between distance students and instructors may create a perceived divide that negatively affects learning. Building on prior experience in flipping organic chemistry in single-site face-to-face (F2F) classes, we decided to extend our approach to multi-site, synchronously-delivered general chemistry courses. Our thought was to narrow the perceived instructor-student divide in distance teaching by using the flexible in-class time that flipping affords to increase the number of positive teacher/distance-student interactions. In this effort, we gradually developed a technique called “bridging questions,” through which the instructor becomes more familiar with student interests and then connects those …