C-H···H-C interactions in organoammonium tetraphenylborates: another look at dihydrogen bonds

2003 ◽  
Vol 81 (6) ◽  
pp. 727-743 ◽  
Author(s):  
Katherine N Robertson ◽  
Osvald Knop ◽  
T Stanley Cameron
Keyword(s):  
Closed Shell ◽  
Relative Strength ◽  
Critical Parameters ◽  
Bond Critical Point ◽  
Dipole Interactions ◽  
Dihydrogen Bonds ◽  
Induced Dipole ◽  
Bond Topology ◽  
Multipole Refinement ◽  
The Difference

The crystal structures of the tetraphenylborates of the dabcoH+, guanidinium (MeCN solvate), and biguanidinium cations are shown to contain a variety of C-H···H-C dihydrogen (DB) bonds of nominally zero polarity, as well as a variety of N-H···N, C-H···N, N-H···Ph, and C-H···Ph hydrogen (HB) bonds. These intermolecular bonds have been characterized topologically after multipole refinement of the structures. The coexistence of the DBs and HBs in each of the structures makes it possible to establish their relative strength hierarchy. It also illustrates the importance of the DBs in satisfying the tendency of these structures to maximize the total intermolecular bonding engagement. To compare the above DBs with other DBs, the results of an extensive set of MP2/6-31G(d,p) calculations (supplied by I. Alkorta) were analyzed for reference correlations between the bond-critical parameters. Thus, for an X-H···H-Y bond, the difference Δε(H)m between the Mulliken charges on the H atoms in the uncomplexed X-H and H-Y components correlates quite well with the X-H···H-Y parameters and can be used for predicting the topological strength of an X-H···H-Y bond. The use of the difference Δε(H)c in the bond does not appear to change the correlation significantly; closer correlations are observed when the amount of charge transferred on formation of the H···H bond is used instead of Δε(H)m or Δε(H)c. Bonding interactions are obtained even between like or symmetry-related H atoms as a consequence of induced-dipole interactions, which accounts for the existence of the above intermolecular C-H···H-C bonds with d(H···H) = 2.18–2.57 Å, electron density at the bond-critical point of ~0.05–0.08 e/Å3, and a rough estimate of the H···H binding energy of ~1-5 kcal/mol. Examination of the bond-critical parameters of X-H···H-Y bonds also suggests a criterion of stability of these bonds with respect to the transition from non-shared (closed-shell) X-H···H-Y interaction to covalent (shared-shell) X···H-H···Y interaction. This transition appears to be discontinuous.Key words: bond-critical parameters, bond topology, dihydrogen bonds, hydrogen bonds, organoammonium tetraphenylborates.

Large Stroke Series Compliant Mechanism

2012 ◽  
Vol 490-495 ◽  
pp. 1104-1108 ◽  
Author(s):  
Ming Cai Shan ◽  
Wei Ming Wang ◽  
Shu Yuan Ma ◽  
Shuang Liu
Keyword(s):  
Theoretical Model ◽  
Maximum Stress ◽  
Compliant Mechanism ◽  
Critical Parameters ◽  
Element Analysis ◽  
Flexure Hinges ◽  
Body Model ◽  
System A ◽  
Rigid Body Model ◽  
The Difference

To increase the stroke of precision positioning system, a novel series compliant mechanism is presented which is based on elliptical flexure hinges. Pseudo-rigid-body model and energy method are applied to establish the theoretical model of stiffness and maximum stress, which are critical parameters for the large stroke compliant mechanism. The relationships are analyzed between geometric parameters of the series complaint mechanism, stiffness and maximum stress. According that, the series compliant mechanism is designed with the stroke more than 5mm and stiffness less than 3.2N/mm. The difference is less than 5% between the results of finite element analysis and theoretical model computation, which proves the correctness of the application design.

scholarly journals Theoretical Prediction on the New Types of Noble Gas Containing Anions OBONgO− and OCNNgO− (Ng=He, Ar, Kr and Xe)

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5839
Author(s):  
Cheng-Cheng Tsai ◽  
Yu-Wei Lu ◽  
Wei-Ping Hu
Keyword(s):  
Density Functional Theory ◽  
Electron Density Distribution ◽  
Density Functional ◽  
Noble Gas ◽  
Structure Calculation ◽  
Molecular Structures ◽  
Fluoride Ion ◽  
Functional Theory ◽  
Dipole Interactions ◽  
Induced Dipole

The fluorine-less noble gas containing anions OBONgO− and OCNNgO− have been studied by correlated electronic structure calculation and density functional theory. The obtained energetics indicates that for Ng=Kr and Xe, these anions should be kinetically stable at low temperature. The molecular structures and electron density distribution suggests that these anions are stabilized by ion-induced dipole interactions with charges concentrated on the electronegative OBO and OCN groups. The current study shows that in addition to the fluoride ion, polyatomic groups with strong electronic affinities can also form stable noble gas containing anions of the type Y−…NgO.

Hemispheric asymmetry of the ionospheric variation during major sudden stratospheric warming events

2020 ◽  
Author(s):  
Donghe Zhang ◽  
Jing Liu
Keyword(s):  
Hemispheric Asymmetry ◽  
Relative Strength ◽  
Magnetic Equator ◽  
Electron Content ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Total Electron ◽  
The North ◽  
Latitudinal Variations ◽  
The Difference

<p>The hemispheric asymmetry of the ionospheric variation in the American sector (45°N~45°S, MLAT; 80°~60°W) is studied with total electron content (TEC) data during major sudden stratospheric warming events. The amplitude (A<sub>M2</sub>) and relative strength (RS<sub>M2</sub>) of the semi-diurnal lunar tidal component (M2) of TEC are analyzed. RS<sub>M2</sub> is the ratio between the energy of M2 and the energy of all the studied tidal components. The magnitudes of A<sub>M2</sub> and RS<sub>M2</sub> exhibit clear hemispheric and latitudinal variations. The A<sub>M2</sub> in the north of the magnetic equator tends to occur at lower magnetic latitudes than the A<sub>M2</sub> in the south of the magnetic equator. The RS<sub>M2</sub> exhibits similar features as the A<sub>M2</sub> but the difference is more distinct. We suggest that such hemispheric asymmetry of M2 parameters is related to the hemispheric asymmetry of the EIA and the latitudinal variation of the amplitude of the solar tidal components in winter.</p>

Biomechanical Analysis of Tendon Suture Techniques

Hand Surgery ◽  
1997 ◽  
Vol 02 (02) ◽  
pp. 93-100
Author(s):  
Kwang Suk Lee ◽  
Kyung Jo Woo ◽  
Jae Young Jeon
Keyword(s):  
Tensile Strength ◽  
Modulus Of Elasticity ◽  
Maximum Stress ◽  
Statistical Significance ◽  
Relative Strength ◽  
Suture Technique ◽  
Biomechanical Analysis ◽  
Suture Techniques ◽  
The Difference ◽  
Group 2

The relative strength of three suture methods of lacerated tendon were measured by mechanical disruption in effort to determine the strength of suture technique. Fifty-four calcaneal tendons of 27 New Zealand white rabbits were transected at mid-portion and repaired with the three suture techniques: group 1: Kessler suture; group 2: Pennington's modified-Kessler suture; and group 3: augmented-Becker suture technique. Each group was composed of 18 calcaneal tendons. Three groups of rabbits, 9 in each, were, respectively, sacrificed immediately after suture, at 2 weeks postoperatively and at 4 weeks postoperatively. The augmented-Becker repair was strongest in tensile strength and maximum stress at immediate operation, 2 weeks postoperatively and 4 weeks postoperatively. The augmented-Becker repair had the highest modulus of elasticity at time of suture, at 2 and at 4 weeks postoperatively. Tensile strength, maximum stress and modulus of elasticity gradually increased from the time of operation to 4 weeks, but the difference was not of statistical significance at 4 weeks.

THE CRYSTAL SPECTRUM OF PERYLENE

1961 ◽  
Vol 39 (3) ◽  
pp. 451-458 ◽  
Author(s):  
Robin M. Hochstrasser
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption ◽  
Weak Coupling ◽  
Room Temperature ◽  
Excited Level ◽  
Vibrational Structure ◽  
Factor Group ◽  
Electronic Band ◽  
Dipole Interactions ◽  
Induced Dipole

The electronic absorption spectrum of crystalline perylene has been examined in the spectral region 3000–4700 Å. The lowest energy electronic state of perylene has a large oscillator strength and the crystal spectrum deviates considerably from that calculated from a weak coupling (Davydov) model.The sublimation flakes were examined at room temperature and at the temperature of boiling nitrogen. The lowest energy crystal state was polarized along the crystallographic a-axis (Bu) and the factor group splitting of lowest vibrational envelope of the electronic band was 800 cm−1. The whole spectrum was more intense along the a- than along the b-axis of the crystal. These results are consistent with the notion that the crystal spectrum is derived from dipole-induced dipole interactions between molecular B2u levels of perylene and neighboring unexcited molecules. This assignment of the lowest excited level of perylene is in agreement with theory.The molecular vibrational structure is severely altered in the crystal and the observed crystal shift is much smaller than that predicted by the Davydov theory.

scholarly journals Bimolecular Reactions of Trapped Ions. VI. Ion–Molecule Reactions Involving CH5+ and C2H5+

1973 ◽  
Vol 51 (10) ◽  
pp. 1645-1654 ◽  
Author(s):  
A. S. Blair ◽  
A. G. Harrison
Keyword(s):  
Proton Transfer ◽  
Trapped Ions ◽  
Rate Coefficients ◽  
Polar Molecules ◽  
Large Role ◽  
Bimolecular Reactions ◽  
Trapped Ion ◽  
Ion Molecule Reactions ◽  
Dipole Interactions ◽  
Induced Dipole

The ion–molecule reactions in mixtures of methane with the polar molecules dimethyl-d6 ether, ethylene-d4 oxide, acetaldehyde-d4, acetone, and acetonitrile have been studied using the trapped-ion technique. The CH5+ and C2H5+ ions produced by ion–molecule reactions in methane react rapidly (predominantly by proton transfer) with the polar molecules; the rate coefficients range from 1.98 × 10−9 cm3 molecule−1 s−1 (C2H5+ + C2D4O) to 5.26 × 10−9 cm3 molecule−1 s−1 (CH5+ + (CH3)2CO). The rate coefficients are much larger than those predicted from ion – induced dipole interactions only indicating that ion–dipole interactions play a large role in the collision process.Rate coefficients for reaction of CH3+ and CH4+ with the polar molecules also have been measured. Most of these also are larger than predicted from ion – induced dipole interactions indicating in this case as well substantial effects due to ion–dipole interactions.

Ion–molecule reactions in formic-d acid and methyl formate

1968 ◽  
Vol 46 (12) ◽  
pp. 2141-2146 ◽  
Author(s):  
Howard Pritchard ◽  
J. C. J. Thynne ◽  
A. G. Harrison
Keyword(s):  
Rate Constants ◽  
Methyl Formate ◽  
Ion Molecule Reactions ◽  
Dipole Interactions ◽  
Induced Dipole ◽  
Energy Formula ◽  
Good Agreement

The following ion–molecules reactions have been found to occur in DCOOH for ions produced by bombardment with electrons of 10–15 eV energy (all rate constants in cm3 molecule−1 units).[Formula: see text]In methyl formate the following reactions have been identified and rate constants measured for ions formed by bombardment with electrons of 10–15 eV energy.[Formula: see text]Experiments using DCO2CH3 show that reaction [f] involves transfer of the methyl hydrogen at a rate 1.5 times that of the formyl hydrogen while reaction [g] involves transfer from only the methyl position of CH3OH+. The rate constants for all reactions are considerably higher than predicted on the basis of ion–induced dipole interactions only but are in good agreement with values calculated by including ion–dipole interactions.

scholarly journals Parametric Study on the Response of Composite Single Piles to Lateral Load by Numerical Simulation (FDM)

2018 ◽  
Vol 3 (10) ◽  
pp. 16-20
Author(s):  
Alex Otieno Owino ◽  
Zakaria Hossain ◽  
Jim Shiau
Keyword(s):  
Parametric Study ◽  
Primary Component ◽  
Critical Parameters ◽  
Foundation Design ◽  
Material Stiffness ◽  
Single Piles ◽  
The Difference ◽  
Lateral Behavior ◽  
Ultimate Loading Capacity ◽  
The Given

This paper entails a detailed numerical and parametric study on the lateral behavior of piles in foundation designs. Single-piles are one of the major components of a foundation as they act as the primary component in the transmission of the weights above the structure into the ground for stability to be attained. For this reason, a detailed study on the influence generated on the p-y curves is mandatory to create a numerically valid model for use in the process of foundation design without much ado. Modeling procedure under consideration employs the use of the finite difference method (FMD) embedded in FLAC2D. FDM is used to implement a solution to the coded input for example soil and pile element parameters. The model validation process done in this paper involves the variation of some of the critical parameters such as the variation on the type of soil in the area under consideration. Next, modification of the elastic modulus of the given soil as a check on the cohesiveness, change on the loading velocity at the top of the pile, a variation of the pile material stiffness and the difference of the pile eccentricity. The results obtained from the p-y curves generated from the parameters undergo sifting through for any effects on the ultimate loading capacity of the pile to the allowed design loading limits upon full structural installation. This variation is necessary for the approval of the validity of the model in engineering design. The parametric study from this study shows that the structure is of functional strength and a tolerable factor of safety.

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