DFT study and NBO analysis of the mutual interconversion of cumulene compounds

The B3LYP/6‐31G* method was used to investigate the configurational properties of allene (1,2‐propadiene) ( 1 ), 1,2,3‐butatriene ( 2 ), 1,2,3,4‐pentateriene ( 3 ), 1,2,3,4,5‐hexapentaene ( 4 ), 1,2,3,4,5,6‐heptahexaene ( 5 ), 1,2,3,4,5,6,7‐octaheptaene ( 6 ), 1,2,3,4,5,6,7,8‐nonaoctaene ( 7 ), and 1,2,3,4,5,6,7,8,9‐decanonaene ( 9 ). The calculations at the B3LYP/6‐31G* level of theory showed that the mutual interconversion energy barrier in compounds 1 – 8 are: 209.73, 131.77, 120.34, 85.00, 80.91, 62.19, 55.56, and 46.83 kJ mol^?1, respectively. The results showed that the difference between the average C?C double bond lengths ( ) values in cumulene compounds 1 and 2 , is larger than those between 7 and 8 , which suggest that with large n (number of carbon atoms in cumulene chain), the values approach a limiting value. Accordingly, based on the plotted data, the extrapolation to n = ∞, gives nearly the same limiting (i. e., ). Also, NBO results revealed that the sum of π‐bond occupancies, , decrease from 1 to 8 , and inversely, the sum of π‐antibonding orbital occupancies, , increase from compound 1 to compound 8 . The decrease of values for compounds 1 – 8 , is found to follow the same trend as the barrier heights of mutual interconversion in compounds 1 – 8 , while the decrease of the barrier height of mutual interconversion in compounds 1 – 8 is found to follow the opposite trend as the increase in the number of carbon atom. Accordingly, besides the previously reported allylic resonant stabilization effect in the transition state structures, the results reveal that the values, , Δ(E_HOMO ? E_LUMO), and the C atom number could be considered as significant criteria for the mutual interconversion in cumulene compounds 1 – 8 . This work reports also useful predictive linear relationships between mutual interconversion energy barriers ( ) in cumulene compounds and the following four parameters: , , Δ(E_HOMO ? E_LUMO), and C_Number. Copyright © 2007 John Wiley & Sons, Ltd.     

Epitaxy of m ‐plane ZnO on (112) LaAlO3 substrate

Heteroepitaxial growth of non‐polar m ‐plane (10 0) ZnO has been demonstrated on (112) LaAlO₃ single crystal substrates using the pulsed laser deposition method. X‐ray diffraction, reflection high energy electron diffraction, and cross‐sectional transmission electron microscopy with selected‐area diffraction, have been used to characterize the structural properties of deposited ZnO films. The epitaxial relationship between ZnO and LAO is shown to be (10 0)_ZnO ∥ (112)_LAO, (11 0)_ZnO ∥ ( 1)_LAO and [0001]_ZnO ∥ [ 10]_LAO. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Na‐site energy of P2‐type NaxM O2 (M = Mn and Co)

P2‐type Na_xM O₂ (M = Mn and Co) is a promising cathode material for low‐cost sodium ion secondary batteries. In this structure, there are two different crystallographic Nai (i = 1 and 2) sites with different Coulomb potential $ (\varphi _i)$ provided by M^4–x and O^2–. Here, we experimentally determine a difference ${(\rm \Delta }\varepsilon \equiv \varepsilon _1 - \varepsilon _2)$ of Na‐site energies ${(}\varepsilon _i \equiv e\varphi {\kern 1pt} _i)$ based on the temperature dependence of the site occupancies. We find that ${\rm \Delta }\varepsilon \;{=}\;56\;{K}$ for Na_0.52MnO₂ is significantly smaller than 190 K for Na_0.59CoO₂. We interpret the suppressed ${\rm \Delta }\varepsilon $ in Na_0.52MnO₂ in terms of the screening effect of the Na⁺ charge. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The mechanisms of the homogeneous,unimolecular, elimination kinetics of several β‐substituted diethyl acetals in the gas‐phase

The rates of gas‐phase elimination of several β‐substituted diethyl acetals have been determined in a static system and seasoned with allyl bromide. The reactions, inhibited with toluene, are homogeneous, unimolecular, and follow first‐order law kinetics. These elimination processes involve two parallel reactions. The first parallel reaction yields ethanol and the corresponding ethyl vinyl ether. The latter product is an unstable intermediate and further decomposes to ethylene and the corresponding substituted aldehyde. The second parallel reaction gives ethane and the corresponding ethyl ester. The kinetics has been measured over the temperature range of 370–441 °C and pressure range of 23–160 torr. The rate coefficients are given by the following Arrhenius equations: The differences in the rates of ethanol formation may be attributed to electronic transmission of the β‐substituent. The comparative kinetic and thermodynamic parameters of the parallel reactions suggest two different concerted polar four‐membered cyclic transition state types of mechanisms. Copyright © 2010 John Wiley & Sons, Ltd.     

Substituent effect on the UV spectra of p‐disubstituted compounds XPh(CHCHPh)nY (n = 0, 1, 2)

Three parameters, , and , are developed to express the substituent effect and the effect of the parent molecular structure of p‐disubstituted compounds XPh(CH?CHPh)_nY (n = 0, 1, 2). The investigated result shows a good correlation between the UV absorption wavenumbers (υ_max) and the three parameters for a diverse set of title compounds, and the correlation equation can be used to predict the UV absorption energy of compounds with the mentioned structure. This approach provides a new insight for the quantitative structure‐property relationship (QSPR) correlation of the UV absorption energy of p‐disubstituted homologues. Copyright © 2010 John Wiley & Sons, Ltd.     

Kinetics and mechanisms of gas‐phase elimination of 2,2‐diethoxyethyl amine and 2,2‐diethoxy‐N,N‐diethylethanamine

The gas‐phase elimination kinetics of 2,2‐diethoxyethyl amine and 2,2‐diethoxy‐N,N‐diethylethanamine (320–380 °C; 40–150 Torr) in a seasoned reaction vessel are homogeneous, unimolecular and obey a first‐order rate law. These elimination processes involve two parallel reactions. The first gives ethanol and the corresponding 2‐ethoxyethenamine. The latter compound further decomposes to ethylene, CO and the corresponding amine. The second parallel reaction produce ethane and the corresponding ethyl ester of an α‐amino acid. The following Arrhenius expressions are given as: For 2,2‐diethoxyethyl amine For 2,2‐diethoxy‐N,N‐diethylethanamine Comparative kinetic and thermodynamic parameters of the overall, the parallel and the consecutive reactions lead to consider two types of mechanisms in terms of a concerted polar cyclic transition state structures. Copyright © 2008 John Wiley & Sons, Ltd.     

An ab initio study of CX3‐substitution (X = H,F, Cl,Br, I) effects on the static electric polarizability and hyperpolarizability of diacetylene

We report a systematic ab initio and density functional theory (DFT) study of the electric properties of the X₃C? C≡C? C≡C? H (X = H, F, Cl, Br, and I) sequence of substituted diacetylenes. We rely on finite‐field Møller–Plesset perturbation theory and coupled‐cluster calculations with large, flexible basis sets. Our best values at the second‐order Møller–Plesset perturbation theory level for the mean dipole polarizability and second hyperpolarizability are $\overline {{\alpha} } $ /e²aE = 64.46 (? CH₃), 65.59 (? CF₃), 110.11 (? CCl₃), 138.90 (? CBr₃), 184.98 (? CI₃) and $\overline {{\gamma} } $ /e⁴aE = 21020 (? CH₃), 13469 (? CF₃), 32708 (? CCl₃), 57599 (? CBr₃), and 105251 (? CI₃). For comparison, the analogous MP2 values for diacetylene [P.Karamanis and G.Maroulis, Chem. Phys. Lett. 2003 , 376, 403.] are $\overline {{\alpha} } $ /e²aE = 49.17, and $\overline {{\gamma} } $ /e⁴aE = 16227. For the mean first hyperpolarizability we report $\overline {{\beta} } $ /e³aE = ?205.8 (? CH₃), ?55.7 (? CF₃), 120.8 (? CCl₃), 443.8 (? CBr₃), and 725.4 (? CI₃). Copyright © 2010 John Wiley & Sons, Ltd.     

Computational characterization of the hydroxylamino (?NH?OH) group

We have examined computationally some properties of the hydroxylamino group, ? N(H)? OH, in different molecular environments. Geometries were optimized at the B3LYP/6‐31G** level and used to calculate B3LYP/6‐311G(3df,2p) energy differences and HF/6‐31G* electrostatic potentials V( r ) and local ionization energies . V( r ) and were evaluated on the molecular surfaces defined by the 0.001 au contours of the electronic densities. Two important factors in determining the ? N(H)? OH structure are lone pair repulsion and possible intramolecular hydrogen bonding involving the remainder of the molecule, which can affect the pyramidal character of the nitrogen. The nitrogen and oxygen lone pairs produce regions of negative potential, those of the oxygen being stronger. These should function as hydrogen bond acceptors, although not as well as NH₃ and H₂O. The nitrogen lone pairs, although less negative, are expected to be the more basic, often roughly similar to pyridine. The amine and hydroxyl hydrogens tend to have quite positive potentials, and should be potent in hydrogen bonding. Depending upon the remainder of the molecule, the hydroxyl and the amine protons can range from essentially no acidity to weak to quite strong. The hydroxylamino group is estimated to have an average polarizability of 2.38 ų and as a substituent on aromatic rings to be activating and ortho, para‐directing, with Hammett δ_p = ?0.37. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydration,entropy, and energy relationships for periodate oxidations

Periodate oxidations of ethanediol and pinacol each occur in two phases; these are (1) formation and (2) decomposition of the intermediate complex. In phase (1), an increase in acidity gives . The rate of oxidation of ethanediol decreases with increasing acidity, whereas the rate of oxidation of pinacol maximizes with H₅IO₆. For both glycols, the activation energy increases and ΔS_act decreases with increasing acidity. In phase (2), the energy of activation is essentially constant with pH, whereas the rate decreases, and the entropy of activation decreases modestly as pH decreases. The latter correlates with the nonhomogeniuty of product formation. Rates for 3‐chloro‐1,2‐propanediol are also listed. Pentaerythritol forms an inactive complex with or H₅IO₆ indicating the importance of chelation in the formation of the intermediate complex. Copyright © 2007 John Wiley & Sons, Ltd.     

Hierarchy of the non‐covalent interactions in the alanine‐based secondary structures. DFT study of the frequency shifts and electron‐density features

The alanine (Ala)‐based cluster models of C5, C7, and C10 H‐bonds are studied at the DFT/B3LYP level. CPMD/BLYP simulations of the infinite polyalanine α‐helix (C13 H‐bond) and the two‐stranded β‐sheets are performed. Combined use of frequency shifts and electron‐density features enable us to detect and describe quantitatively the non‐covalent interactions (H‐bonds) defining the intrinsic properties of Ala‐based secondary structures. The energies of the primary N? H O H‐bonds are decreasing in the following way: C13 > C5 ≥ C7 > C10. The energies of the secondary N? H O, N?H N, and H H interactions are comparable to those of the primary H‐bonds (～4.5 kcal/mol). Side chain–backbone C? H O interaction is found to be the weakest non‐covalent interaction in the considered species. Its energy is ～0.5 kcal/mol in the infinite polyalanine α‐helix. Quantum‐topological electron‐density analysis is found to be a powerful tool for the detection of secondary non‐covalent interactions (C?O H? C and H H) and bifurcated H‐bonds, while the frequency shift study is useful for the identification and characterization of primary or secondary H‐bonds of the N? H O type. Copyright © 2008 John Wiley & Sons, Ltd.     

Room‐temperature epitaxial growth of high‐quality m ‐plane InGaN films on ZnO substrates

The authors have grown high‐quality m ‐plane In_0.36Ga_0.64N (1 00) films on ZnO (1 00) substrates at room temperature (RT) by pulsed laser deposition (PLD) and have investigated their structural properties. m ‐plane InGaN films grown on ZnO substrates at RT possess atomically flat surfaces with stepped and terraced structures, indicating that the film growth proceeds in a two‐dimensional mode. X‐ray diffraction measurements have revealed that the m ‐plane InGaN films grow without phase separation reactions at RT. The full‐width at half‐maximum values of the 1 00 X‐ray rocking curves of films with X‐ray incident azimuths perpendicular to the c ‐ and a‐axis are 88 arcsec and 78 arcsec, respectively. Reciprocal space‐mapping has revealed that a 50 nm thick m ‐plane In_0.36Ga_0.64N film grows coherently on the ZnO substrate, which can probably explain the low defect density that is observed in the film. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetics and thermodynamics of the Li/Li+ couple in tetrahydrofuran at low temperatures (195–295 K)

Kinetic and thermodynamic (formal potential) data relating to the synthetically useful Li/Li⁺ couple in tetrahydrofuran (THF) solvent at a range of temperatures (196–295 K) are reported. Formal potentials, have been measured versus the standard reference electrode, in THF. At 295 K the following data have been obtained using a mathematical model to simulate the electro‐deposition (metal deposition and growth kinetics) processes of lithium (Li) on a platinum microelectrode; a of ?3.48 ± 0.005 V, = ?9.2 (±0.5) × 10^?4 V K^?1, the standard electrochemical rate constant, k₀ = 1 (± 0.1) × 10^?4 cm s^?1, transfer coefficient, α = 0.57 ± 0.03 and diffusion coefficient, D = 8.7 ± 0.1 × 10^?6 cm² s^?1. Copyright © 2007 John Wiley & Sons, Ltd.     

Silver: a novel growth catalyst for Ge nanoislands on Si(113)

The impact of silver pre‐adsorption on germanium growth on Si(113) was investigated using in‐situ low‐energy electron microscopy (LEEM) as well as low‐energy electron diffraction (LEED). The adsorption of silver leads to the formation of a regular pattern of nanofacets along the [1 0] direction. The periodicity of this pattern in [33 ] direction was determined to (44 ± 4) nm. From LEED series at different energies the facets were identified to be of (111) and (115) orientation. While the (111) facets show a (√3 × √3)‐R30° reconstruction, the (115) facets exhibit a (2 × n) superstructure. The subsequent growth of Ge results in the formation of nanoislands that are aligned along the facets. These Ge islands have an anisotropic shape with typical sizes of about 100 nm in [33 ] direction and 400 nm in [1 0] direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Single domain nonpolar (13$ \bar 4 $0) ZnO on (114) LaAlO3

An unconventional nonpolar plane (13$ \bar 4 $ 0) ZnO epitaxial film was grown on a 2‐inch (114) LaAlO₃ (LAO) substrate by pulsed laser deposition. Reflection high energy electron diffraction (RHEED) patterns of the grown ZnO surface demonstrate single crystalline characteristics with the orientation inclined with the a‐axis. Atomic force microscopy (AFM) shows that the grown ZnO film exhibits a stripe‐like surface morphology with the longitudinal direction parallel to the c‐axis. Cross‐sectional transmission electron microscopy (TEM) with selected area electron diffraction (SAED) was used to characterize the microstructure and to determine the growth plane of ZnO grown film as (13$ \bar 4 $ 0). In addition, XRD pole‐figure measurements confirm the single domain growth of (13$ \bar 4 $ 0) ZnO on (114) LAO. Room temperature photoluminescence spectra of the ZnO film measured across the substrate show the same near band edge emission peak at 3.29 eV, indicating that the nonpolar (13$ \bar 4 $ 0) ZnO film has excellent uniform optical properties. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

DFT study of the biphenylene–NO complexes formed in nitration mechanism

The most probable complexes formed in biphenylene (BP) nitration pathway have been investigated at B3LYP/6‐31+G(d,p) level of theory in the gas phase. To obtain more accurate energies, single point calculations were carried out at B3LYP/6‐31++G(2d,2p), B3PW91/6‐31+G(d,p), and B3PW91/6‐31++G(2d,2p) levels using B3LYP/6‐31+G(d,p) optimized geometry. The six intermediates and one transition state were found before the subsequent formation of the arenium ion on the potential energy surface of the electrophilic nitration of BP. It was also shown that the position β in the BP is much more susceptible to electrophilic attack than the competing position α. The Natural Bond Orbital (NBO), Charges from Electrostatic Potentials using a Grid based method (CHelpG), and Merz–Singh–Kollman (MK) charges and s‐characters of atoms involved in the reaction mechanism were calculated. Inspection of charges in the moieties indicates that the positive charge in all complexes is chiefly located on the BP, which means that theNO₂ moiety received the electron from the BP. To investigate the nature of BP– interaction in the five π‐complexes, atoms in molecules (AIM) analysis was performed. The AIM results suggested that the BP– interactions have an electrostatic characteristic. In addition, high electrostatic interactions were predicted in π‐complexes in which one of the oxygen atoms of interacts with the BP. Nucleus‐independent chemical shift (NICS) methodology has been applied to study the change of antiaromaticity in four‐membered ring of BP upon complexation with . The results based on NICS calculations show that antiaromaticity of four‐membered ring decreases upon complexation. Copyright © 2008 John Wiley & Sons, Ltd.     

Crystal structures of 3‐methyl‐2(1H)‐quinoxalinone and three substituted derivatives

3‐Methyl‐2(1H)‐quinoxalinone and three derivatives (3,7‐dimethyl‐2(1H)‐quinoxalinone, 3‐methyl‐6,7‐dichloro‐2(1H)‐quinoxalinone and 3‐methyl‐7‐nitro‐2(1H)‐quinoxalinone) have been synthesised and analysed by ¹H NMR and IR spectral spectroscopies. The crystal structures have been determined at room temperature from X‐ray single crystal diffraction data for three of them and from powder diffraction data for the nitro derivative. 3‐Methyl‐2(1H)‐quinoxalinone crystallises in the P2₁/c monoclinic system, 3,7‐dimethyl‐2(1H)‐quinoxalinone in the Pbca orthorhombic system and the two others compounds in the P$\overline {1} $ triclinic system. For the nitro derivative, C? H$\cdots $ N short contacts are established between the carbon of the methyl and the double bounded nitrogen of the ring. For the three other compounds N? H$\cdots $ O hydrogen bonds involve the atoms of the heterocyclic ring. Copyright © 2011 John Wiley & Sons, Ltd.     

Structure and reactivity in the hydrolyses of aliphatic carboxylic acid esters and chlorides

For hexanoic acid and its seven isomers, relative rates have been determined for acid catalysed esterification with methanol, and compared with those for saponification of the methyl esters. A good correlation between logarithms of relative rates for the two reactions is obtained, and it is suggested that the eight isomers provide a test set of compounds in which steric effects alone act on reactivity at the acyl carbon. A full set of steric parameters ( values) are presented. Rates of solvolyses of the acid chlorides of the isomers have been determined conductometrically in 3:1 wt:wt acetonitrile water. Logarithms of relative rates show a poor correlation with , and, taking into account the solvent dependence of the rates, the pattern excludes both rate‐limiting formation of a tetrahedral intermediate and rate‐limiting dissociation of chloride to form acylium ions. The remaining possibilities, a concerted process (A_ND) and rapid reversible formation of a hydrate followed by rate‐limiting dissociation of chloride (A_N + D) are considered. Copyright © 2007 John Wiley & Sons, Ltd.     

Ionic equilibrium in mixtures of protophobic and protophilic polar non‐hydrogen bond donor solvents: acids,salts, and indicators in acetone containing 5 mol% DMSO

Properties of a protophobic polar non‐HBD solvent can be strongly modified by introduction of a small amount of a protophilic polar non‐HBD solvent. In this paper, acetone (AC) with 5 mol% additive of DMSO, a solvent with , was considered as a media for acid–base reactions. Conductance was used for determination of dissociation constants of a set of salts, hydrogen chloride, and picric acid. The last‐named was also studied by UV‐vis spectroscopy. The introduction of 5 mol% of DMSO results in suppressing, to some extent, the homoconjugation processes in AC media as well as of proton hydration by (possible) traces of water. The dissociation of salicylic acid and 2,4‐dinitrophenol was examined utilizing quinhydrone electrodes in a cell with liquid junction. The pK_a values of buffer acids and values of buffer solutions were calculated by taking into account the incomplete dissociation of salts. The response of the glass electrode appeared to be satisfactory, which allowed the estimation of the pK_a value of benzoic acid. The apparent ionization constants of 22 acid–base indicators in buffer mixtures and perchloric acid solutions were determined in (AC + 5 mol% DMSO) using the spectrophotometric procedure. Copyright © 2009 John Wiley & Sons, Ltd.     

Zur unitarisierten Gravitationstheorie mit lang- und kurzrechweitigen Termen (mit ruhmasselosen und schweren Gravitonen)

In our papers, TREDER [1, 2] we have formulated a unified electrodynamics of the fourth order with bi-wave equations for the vector potential A. In this electrodynamics EINSTEIN ian photon and heavy W-mesons are the field quanta. In correspondence to this field theory we are able to formulate a unified theory of gravitation, too. The field equations for the gravitational metrics grr in this theory are corresponding with the EINSTEIN equations of General Relativity in the same way like the electromagnetic bi-wave equations are corresponding with the MAXWELL equations. The metric g_μν is a linear functional of an EINSTEIN ian long-range potential g_μν and of a subatomic short-range potential definierte Materie-Tensor die gemeinsame Quelle für alle drei Felder ist. Dann ist g1_μν, g2_μν und g_μν und es gelten die Funktional-Bedingungen wobei hier g2_μν Feldgleichungen vom “kosmologischen Typ” befriedigt. By these conditions, the short-range interaction becomes a repulsive force and the action of the NEWTON -EINSTEIN ian attraction and of the subatomic repulsion makes the matter point-like (as in the E.-I.-H.-method) but self-consistent. The gravitational metrics g2_μν become regulary. P. e., in the EINSTEIN approximation the field of a point-like mass M is given by a SCHWARZSCHILD     

Effects of ortho‐substituents in SE1 protonolysis of phenylmercuric chloride

The kinetics of the reactions of o‐substituted phenylmercuric chlorides, o‐RC₆H₄HgCl (R = CH₃, H, C₂H₅O, CH₃O, C₆H₅, F, COOC₂H₅, Cl, Br, CF₃, NO₂), with hydrochloric acid in 80% aqueous dioxane in the presence of NaI were studied. The reactions are of the first order. The rate constant at 40°C decreases in the order of R: CH₃ > H > C₂H₅O > CH₃O > C₆H₅ > F > COOC₂H₅ > Cl > Br > CF₃ > NO₂. The analysis of effects of those o‐substitutes is carried out through multiple regression of log k/k_H with the corresponding inductive substituent constants σ_I and the various resonance substituent constants σ, σ_R(BA), σ, σ and σ_x, and the corresponding Swain–Lupton field effect constant and resonance effect constant . The results showed that o‐substituent intramolecular coordination with the neighbor mercury (field effect) is the main effect in effects of o‐substituents on rate of the S_E1 protonolysis. Copyright © 2007 John Wiley & Sons, Ltd.