scholarly journals Effect of Substitution of Hydrogen Atoms in the Molecules of Anthrone and Anthraquinone

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 502
Author(s):  
Małgorzata Szymańska ◽  
Irena Majerz
Keyword(s):  
Electron Density ◽  
Aromatic Ring ◽  
Significant Influence ◽  
Molecular Geometry ◽  
Plant Origin ◽  
Hydrogen Atoms ◽  
Central Ring ◽  
Crystal State ◽  
Natural Substances

The geometry of anthrone and anthraquinone—natural substances of plant origin—was investigated under the substitution of hydrogen atoms in side aromatic ring and, for anthrone, also in the central ring. A significant influence of substitution on geometry expressed by the angle between the side rings was shown. The geometry changes are connected with the changes of electron density and aromaticity of the anthrone and anthraquinone rings. The flexibility of the investigated compounds was confirmed by comparison of the optimized molecules and the molecules in the crystal state where the packing forces can influence the molecular geometry.

scholarly journals On a Magical Mystery Tour of Green Insecticide Research: Current Issues and Challenges

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5014
Author(s):  
Giovanni Benelli
Keyword(s):  
Cutting Edge ◽  
Plant Origin ◽  
Behavioral Traits ◽  
Modes Of Action ◽  
Natural Substances ◽  
The Impact ◽  
Lethal Doses ◽  
Selection Of

The Editorial outlines recent research advances in green insecticide research. Particular attention is devoted to studies shedding light on the modes of action and non-target toxicity of natural substances of plant origin. Research focusing on the development of new formulations (including those relating to nano-objects) to magnify the effectiveness and stability of green insecticides in the field represents key advances. Herein, a carefully reviewed selection of cutting edge articles about green pesticide development recently published in Molecules is presented. The impact of sub-lethal doses of green insecticides on insect behavioral traits is still overlooked, representing a timely challenge for further research.

Evaluation of in vitro effects of natural substances of plant origin using a model of protein glycoxidation

2005 ◽  
Vol 37 (5) ◽  
pp. 957-962 ◽  
Author(s):  
I. Boušová ◽  
J. Martin ◽  
L. Jahodář ◽  
J. Dušek ◽  
V. Palička ◽  
...  
Keyword(s):  
Plant Origin ◽  
Natural Substances ◽  
In Vitro Effects

Computational analysis of thermal-motion effects on the topological properties of the electron density

2015 ◽  
Vol 71 (2) ◽  
pp. 225-234 ◽  
Author(s):  
J. Robert Michael ◽  
Tibor Koritsanszky
Keyword(s):  
Electron Density ◽  
Probability Distribution Function ◽  
Computational Analysis ◽  
Normal Modes ◽  
Bond Critical Point ◽  
Topological Properties ◽  
Hydrogen Atoms ◽  
Bond Stretching ◽  
Negative Skewness ◽  
Thermal Vibrations

The distributions of bond topological properties (BTPs) of the electron density upon thermal vibrations of the nuclei are computationally examined to estimate different statistical figures, especially uncertainties, of these properties. The statistical analysis is based on a large ensemble of BTPs of the electron densities for thermally perturbed nuclear geometries of the formamide molecule. Each bond critical point (BCP) is found to follow a normal distribution whose covariance correlates with the displacement amplitudes of the nuclei involved in the bond. The BTPs are found to be markedly affected not only by normal modes of the significant bond-stretching component but also by modes that involve mainly hydrogen-atom displacements. Their probability distribution function can be decently described by Gumbel-type functions of positive (negative) skewness for the bonds formed by non-hydrogen (hydrogen) atoms.

Electron densities and the VSEPR model of molecular geometry

1992 ◽  
Vol 70 (3) ◽  
pp. 742-750 ◽  
Author(s):  
R. J. Gillespie
Keyword(s):  
Electron Density ◽  
Present Status ◽  
Electron Pair ◽  
Molecular Geometry ◽  
Physical Basis ◽  
Valence Shell ◽  
Electron Densities ◽  
Total Electron Density ◽  
Total Electron

This paper reviews the present status of the VSEPR model of molecular geometry in relation to electron densities. The discussion is based on the electron pair domain version of this model. The fundamental postulates of the model are summarized and illustrated by a discussion of the structures of some molecules with five and seven electron pair domains in the valence shell, including the recently discovered ions XeF5− and XeOF6−. The total electron density does not provide any obvious support for the model and although electron density deformation maps do provide some support they are not always reliable. The Laplacian of the electron density, however, shows the presence of valence shell charge concentrations that correspond closely in number and properties to the electron pair domains of the VSEPR model. This correspondence between electron pair domains and valence shell charge concentrations provides a physical basis for a better understanding of the VSEPR model. Keywords: VSEPR model, electron densities, molecular geometry, Laplacian of the electron density, electron pair domain.

Solution of organic crystal structures from powder diffraction by combining simulated annealing and direct methods

2003 ◽  
Vol 36 (2) ◽  
pp. 230-238 ◽  
Author(s):  
Angela Altomare ◽  
Rocco Caliandro ◽  
Carmelo Giacovazzo ◽  
Anna Grazia Giuseppina Moliterni ◽  
Rosanna Rizzi
Keyword(s):  
Monte Carlo ◽  
Simulated Annealing ◽  
Electron Density ◽  
Powder Diffraction ◽  
Direct Methods ◽  
Molecular Geometry ◽  
Molecular Structures ◽  
Chemical Information ◽  
Density Map ◽  
Electron Density Map

Theab initiocrystal structure solution from powder diffraction data can be attemptedviadirect methods. If heavy atoms are present, they are usually correctly located; then some crystal chemical information can be exploited to complete the partial structure model. Organic structures are more resistant to direct methods; as an alternative, their molecular geometry is used as prior information for Monte Carlo methods. In this paper, a new procedure is described which combines the information contained in the electron density map provided by direct methods with a Monte Carlo method which uses simulated annealing as a minimization algorithm. A figure of merit has been designed based on the agreement between the experimental and calculated profiles, and on the positions of the peaks in the electron density map. The procedure is completely automatic and has been included inEXPO; its performance has been validated and tested for a set of known molecular structures.

scholarly journals Crystal structure of the 4 + 2 cycloadduct of photooxidized anthracene and C60fullerene

2014 ◽  
Vol 70 (11) ◽  
pp. 444-446
Author(s):  
Gábor Bortel ◽  
Éva Kováts ◽  
Gábor Oszlányi ◽  
Sándor Pekker
Keyword(s):  
Solvent Molecule ◽  
Molecular Geometry ◽  
Close Packing ◽  
Membered Ring ◽  
Solvent Ratio ◽  
Central Ring ◽  
Oxygen Generation ◽  
Thermally Activated ◽  
Singlet Oxygen Generation ◽  
Disordered Carbon

The structure of the title compound, 5,6-[(1R,10S)-2,9-dioxatricyclo[8.6.03,8.011,16]hexadecane-1,10-diyl]-(C60–Ih)[5,6]fullerene methanedithione 0.1-solvate, C74H10O2·0.1CS2, has tetragonal (P42/n) symmetry at 100 K. It has a unique eight-membered ring, with two incorporated O atoms in place of the original central ring of the anthracene. The distortion of the molecular geometry around the cycloadduct bonds corresponds to that seen in related fullerene derivatives. Close packing of the adduct forms cavities partially filled with disordered carbon disulfide solvent molecule. The 41% occupancy of the cavities yields an overall 1:0.103 adduct–solvent ratio. Reaction steps are described as light-assisted singlet-oxygen generation, peroxide, epoxide and dioxocin derivative formation and the final step of thermally activated cycloaddition.

scholarly journals The Expected behaviour of the Hydrogen Lyman Lines in Solar Flares

1972 ◽  
Vol 14 ◽  
pp. 824-824
Author(s):  
Z. Švestka ◽  
L.D. De Feiter
Keyword(s):  
Electron Density ◽  
Solar Flares ◽  
Line Profiles ◽  
Stark Broadening ◽  
Hydrogen Atoms ◽  
Measured Intensity ◽  
Balmer Series ◽  
Model Calculations ◽  
Intensity Measurements

While the merging of the higher lines of the Balmer series emitted by solar flares is solely determined by the electron density, the merging of the high Lyman lines is determined both by the electron density, through Stark broadening of the line absorption coefficient, and by the total number of hydrogen atoms in the flare, through the effect of self-absorption. Preliminary results of model calculations indicate that two or more intensity measurements, each midway between two consecutive lines of the Lyman series (lines 3–4, 4–5, 5–6) allow the determination of the column density of hydrogen atoms in the ground state provided that the electron density is known. One can believe that in between the Lyman lines only the flare elements contribute to the measured intensity since excited interflare matter of much lower electron density produces line profiles of substantially smaller width. Thus the data in between the lines can be reasonably compared to the Ne values deduced from high members of the Balmer series.

Catalysis on evaporated metal films. V Reactions between cyclic hydrocarbons and deuterium

1954 ◽  
Vol 226 (1167) ◽  
pp. 472-489 ◽  
Keyword(s):  
Catalytic Activity ◽  
Molecular Geometry ◽  
Exchange Reactions ◽  
Hydrogen Atoms ◽  
Initial Product ◽  
Product Distributions ◽  
Redistribution Reaction ◽  
Multiple Exchange ◽  
Turn Over ◽  
Catalytic Exchange

Catalytic exchange reactions have been studied by means of a mass spectrometer between deuterium and cyclo Zopentane over palladium and cyclo Zohexane over rhodium, palladium, tungsten, platinum, nickel, oriented nickel and oriented rhodium. Activation energies, frequency factors and distributions of initial products were determined. The reactions involved multiple exchange by repeated second-point adsorption. Half the hydrogen atoms were readily exchanged, and a study of the temperature-dependence of the product distributions showed that it required an activation energy of 4 to 8 kcal/mole in excess of that for adcorption-desorption before the remaining half could be exchanged. Considerations of molecular geometry revealed that in order to exchange the second half of the hydrogen atoms the molecule had to ‘turn over’ on the surface, and for cyclo Zopentane the process for turning over must require second-point adsorption by the same carbon atom, but with cyclo hexane there is the alternative process of exchanging two adjacent equatorial hydrogen atoms. Theories are developed which account satisfactorily for the observed initial product distributions. The pressure-dependence of reaction rate was determined for cyclo hexane over palladium. Deuterium was strongly adsorbed and cyclo hexane weakly adsorbed. Exchange of cyclo hexane over oriented films of nickel and rhodium showed marked differences in distribution compared with unoriented films, suggesting different catalytic activity of different crystal planes. Only exchange was observed with benzene over nickel, but there was simultaneous exchange and deuteration over palladium. The initial product pattern over palladium showed that a redistribution reaction (in the sense of Wagner et al , (1952)) did not occur during deuteration and that benzene was adsorbed mainly as phenyl radicals during the exchange reaction. The reaction between cyclo propane and deuterium was examined over rhodium and simultaneous exchange and deuteration were observed. As determined by the temperature range for reaction the order of reactivity in exchange was cyclo propane > cyclo pentane > cyclo hexane, and the order of catalytic activity of the metals was similar to that observed previously for the exchange of other saturated hydrocarbons.

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