CALCULATIONS AND EXPERIMENTAL STUDIES OF THE AGGREGATION OF MOLECULES OF LIQUID ACETONE BY SPECTRA OF RAMAN SCATTERING

2013 ◽  
Vol 22 (02) ◽  
pp. 1350022 ◽  
Author(s):  
F. H. TUKHVATULLIN ◽  
U. N. TASHKENBAEV ◽  
A. JUMABAEV ◽  
H. HUSHVAKTOV ◽  
A. ABSANOV ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Oxygen Atom ◽  
Raman Scattering ◽  
Experimental Studies ◽  
Energy Gain ◽  
Half Width ◽  
Hydrogen Atoms ◽  
Aqueous Mixture ◽  
The Difference ◽  
Liquid Acetone

Experimental studies of the Raman scattering of the band of C = O vibrations of acetone (1710 cm–1) showed that the parallel and perpendicular polarized components have a large half-width (respectively, 11.6 and 18 cm–1) and also the bands' maxima of these components are shifted by ~5 cm–1. In the neutral solvent (heptane), the difference of the maxima position of the bands decreases. Calculations showed that the molecules of acetone can aggregate to form a dimer with the energy gain of 10.1 kJ/mole. In the dimer several hydrogen bonds are formed between the oxygen atom of one molecule and the hydrogen atoms of CH3 -group of another molecule. In an aqueous mixture of acetone, according to calculations, there is a possibility for formation of dimers and closed trimer aggregates with the energy gain, respectively, 19.1 and 45.8 kJ/mole. Calculation showed that symmetric and antisymmetric O–H vibrations of water are displaced in the interaction with acetone to lower frequencies, respectively, to 3808.4 and to 3931.8 –1.

A study of α -resorcinol by neutron diffraction

1956 ◽  
Vol 235 (1203) ◽  
pp. 552-559 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Oxygen Atom ◽  
Neutron Scattering ◽  
Benzene Ring ◽  
Unit Cell ◽  
The Other ◽  
Aromatic Molecule ◽  
Hydrogen Atoms ◽  
A Value

The first study of an aromatic molecule by neutron diffraction, leading to a Fourier projection of the neutron scattering density in the unit cell, gives a value of 1·08 ± 0·04 Å for the length of the C—H bonds which link hydrogen atoms to the benzene ring. The spirals of hydrogen bonds which bind together neighbouring molecules are found to consist of typical ‘long bonds’, with the proton much closer to one oxygen atom than to the other. The O—H distance is 1·02 Å, and it appears that the O, H, O atoms are not collinear.

Re-investigation of the crystal structure of whewellite [Ca(C2O4)·H2O] and the dehydration mechanism of caoxite [Ca(C2O4)·3H2O]

2005 ◽  
Vol 69 (1) ◽  
pp. 77-88 ◽  
Author(s):  
T. Echigo ◽  
M. Kimata ◽  
A. Kyono ◽  
M. Shimizu ◽  
T. Hatta
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Structure Refinement ◽  
Structural Features ◽  
Infrared Analysis ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Direct Transformation ◽  
Dehydration Mechanism ◽  
The Difference

AbstractThe crystal structure of whewellite [Ca(C2O4)·H2O] and the dehydration mechanism of caoxite [Ca(C2O4)·3H2O] have been studied by means of differential thermal analysis, X-ray diffraction (powder and single-crystal) analysis and infrared analysis. The first and second analyses confirmed the direct transformation of caoxite into whewellite without an intermediate weddellite [Ca(C2O4)·2H2O] stage. Infrared spectra obtained from caoxite, weddellite and whewellite emphasize the similarity of the O–H-stretching band and O–C–O-stretching band in whewellite and caoxite and the unique bands of weddellite. The structure refinement at low temperature (123 K) reveals that all the hydrogen atoms of whewellite form hydrogen bonds and the two water molecules prop up the crystal structure by the hydrogen bonds that cause a strong anisotropy of the displacement parameter.Comparing the structural features of whewellite with those of weddellite and caoxite suggests that caoxite and whewellite have a sheet structure consisting of Ca2+ ions and oxalate ions although weddellite does not. It is additionally confirmed that the sheets of caoxite are corrugated by hydrogen bonds but whewellite has flat sheets. The corrugated sheets of caoxite would be flattened by dehydration so the direct transformation of caoxite into whewellite would not occur via weddellite. Essential for this transformation is the dehydration of interlayered water molecules in caoxite leading to the building of the crystal structure of whewellite on its intralayered water molecules. The difference in conformation of water molecules between those two crystal structures may explain the more common occurrence of whewellite than of caoxite in nature.

scholarly journals C—H...O contacts in the crystal structure of 1,3-dithiane 1,1,3,3-tetraoxide

2021 ◽  
Vol 77 (2) ◽  
pp. 204-207
Author(s):  
Richard L. Harlow ◽  
Allen G. Oliver ◽  
Michael P. Sammes
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Oxygen Atom ◽  
Complex Network ◽  
Small Molecule ◽  
Monoclinic Space Group ◽  
Hydrogen Atoms ◽  
Adjacent Molecule ◽  
The Many ◽  
Short Contacts

The crystal structure of 1,3-dithiane 1,1,3,3-tetraoxide, C4H8O4S2, has been determined to examine the intermolecular C—H...O hydrogen bonds in a small molecule with highly polarized hydrogen atoms. The crystals are monoclinic, space group Pn, with a = 4.9472 (5), b = 9.9021 (10), c = 7.1002 (7) Å and β = 91.464 (3)° with Z = 2. The molecules form two stacks parallel to the a axis with the molecules being one a translation distance from each other. This stacking involves axial hydrogen atoms on one molecule and the axial oxygen atoms on the adjacent molecule in the stack. None of these C—H...O contacts is particularly short (all are > 2.4 Å). The many C—H...O contacts between the two stacks involve at least one equatorial hydrogen or oxygen atom. Again, no unusually short contacts are found. The whole crystal structure basically consists of a complex network of C—H...O contacts with no single, linear C—H...O contacts, only contacts that involve two (bifurcated), and mostly three or four neighbors.

NEUTRON DIFFRACTION DETERMINATION OF THE HYDROGEN POSITIONS IN NATROLITE

1964 ◽  
Vol 42 (2) ◽  
pp. 229-240 ◽  
Author(s):  
B. H. Torrie ◽  
I. D. Brown ◽  
H. E. Petch
Keyword(s):  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Oxygen Atom ◽  
Water Molecule ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Diffraction Determination

Neutron diffraction data obtained with single crystals of natrolite, Na2Al2Si3O10.2H20, have been analyzed using Fourier difference synthesis arid least squares methods. The details of the aluminosilicate framework were found to be in agreement with the results of earlier X-ray diffraction studies. The oxygen atom of the water molecule is linked by bent hydrogen bonds to two oxygen atoms in the framework, making an O—O—O angle of 134°. Lying almost in the O—O—O plane, the hydrogen atoms are located at distances of 0.94 ± 0.03 and 0.98 ± 0.02 Å from the oxygen of the water molecule and make with it an H—O—H angle of 108°. Natrolite thus provides an excellent example of the ability of the water molecule to resist the influence of the environment in opening the H—O—H angle.

scholarly journals Crystal structure of 5-(dibenzofuran-4-yl)-2′-deoxyuridine

2017 ◽  
Vol 73 (10) ◽  
pp. 1493-1496
Author(s):  
Vijay Gayakhe ◽  
Anant Ramakant Kapdi ◽  
Yulia Borozdina ◽  
Carola Schulzke
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Oxygen Atom ◽  
Crystal Lattice ◽  
Title Compound ◽  
Hydrogen Atoms ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Compound C ◽  
Absolute Structure

The molecule of the title compound, C21H18N2O6, has a bent rather than a linear conformation supported by three intramolecular C—H...O hydrogen bonds. The packing in the crystal lattice is largely determined by interactions between hydrogen atoms with oxygen atom lone pairs with one molecule interacting with neigbouring moleculesviaO—H...O, N—H...O and C—H...O hydrogen bonds. The title compound crystallizes in the chiral orthorhombic space groupP212121. Its absolute structure could not be determined crystallographically and was assumed with reference to that of the reactant 5-iodo-2′-deoxyuridine.

scholarly journals Crystal structures of (E)-2-amino-4-methylsulfanyl-6-oxo-1-(1-phenylethylideneamino)-1,6-dihydropyrimidine-5-carbonitrile and (E)-2-amino-4-methylsulfanyl-6-oxo-1-[1-(pyridin-2-yl)ethylideneamino]-1,6-dihydropyrimidine-5-carbonitrile

2021 ◽  
Vol 77 (5) ◽  
pp. 547-550
Author(s):  
Reham A. Mohamed-Ezzat ◽  
Galal H. Elgemeie ◽  
Peter G. Jones
Keyword(s):  
Nitrogen Atom ◽  
Hydrogen Bonds ◽  
Oxygen Atom ◽  
Crystal Structures ◽  
Layer Structure ◽  
Hydrogen Atoms ◽  
Pyridyl Nitrogen

The title compounds 3a, C14H13N5OS, and 3b, C13H12N6OS, both show an E configuration about the N=C bond and a planar NH2 group. The molecules, which only differ in the presence of a phenyl (in 3a) or pyridyl (in 3b) substituent, are closely similar except for the different orientations of these groups. The amino hydrogen atoms form classical hydrogen bonds; in 3a the acceptors are the oxygen atom and the cyano nitrogen atom, leading to ribbons of molecules parallel to the b axis, whereas in 3b the acceptors are the oxygen atom and the pyridyl nitrogen, leading to a layer structure perpendicular to (\overline{1}01).

Crystal structure of pomalidomide Form I, C13H11N3O4

2021 ◽  
pp. 1-6
Author(s):  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Double Layers ◽  
Carbonyl Groups ◽  
Hydrogen Atoms ◽  
Powder Diffraction File ◽  
Functional Theory ◽  
Amine Hydrogen

The crystal structure of pomalidomide Form I has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Pomalidomide Form I crystallizes in the space group P-1 (#2) with a = 7.04742(9), b = 7.89103(27), c = 11.3106(6) Å, α = 73.2499(13), β = 80.9198(9), γ = 88.5969(6)°, V = 594.618(8) Å3, and Z = 2. The crystal structure is characterized by the parallel stacking of planes parallel to the bc-plane. Hydrogen bonds link the molecules into double layers also parallel to the bc-plane. Each of the amine hydrogen atoms acts as a donor to a carbonyl group in an N–H⋯O hydrogen bond, but only two of the four carbonyl groups act as acceptors in such hydrogen bonds. Other carbonyl groups participate in C–H⋯O hydrogen bonds. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

Distinguishment of Weak Interactions of Hydrogen Atoms Bound to Carbon Atoms: X-Ray Crystal Structural and Hirshfeld Surface Analyses of 2-Hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene with the 2-Methoxylated Homologue

2021 ◽  
Vol 19 ◽  
Author(s):  
Kikuko Iida ◽  
Toyokazu Muto ◽  
Miyuki Kobayashi ◽  
Hiroaki Iitsuka ◽  
Kun Li ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Molecular Conformation ◽  
Weak Interactions ◽  
Carbonyl Oxygen ◽  
Hirshfeld Surface ◽  
Molecular Surface ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Classical Hydrogen Bond

Abstract: X-ray crystal and Hirshfeld surface analyses of 2-hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene and its 2-methoxylated homologue show quantitatively and visually distinct molecular contacts in crystals and minute differences in the weak intermolecular interactions. The title compound has a helical tubular packing, where molecules are piled in a two-folded head-to-tail fashion. The homologue has a tight zigzag molecular string lined up behind each other via nonclassical intermolecular hydrogen bonds between the carbonyl oxygen atom and the hydrogen atom of the naphthalene ring. The dnorm index obtained from the Hirshfeld surface analysis quantitatively demonstrates stronger molecular contacts in the homologue, an ethereal compound, than in the title compound, an alcohol, which is consistent with the higher melting temperature of the former than the latter. Stabilization through the significantly weak intermolecular nonclassical hydrogen bonding interactions in the homologue surpasses the stability imparted by the intramolecular C=O…H–O classical hydrogen bonds in the title compound. The classical hydrogen bond places the six-membered ring in the concave of the title molecule. The hydroxy group opposingly disturbs the molecular aggregation of the title compound, as demonstrated by the distorted H…H interactions covering the molecular surface, owing to the rigid molecular conformation. The position of effective interactions predominate over the strength of the classical/nonclassical hydrogen bonds in the two compounds.

Investigation of Regression-Based Effect Size Methods Developed in Single-Subject Studies

2021 ◽  
pp. 014544552110540
Author(s):  
Nihal Sen
Keyword(s):  
Effect Size ◽  
Experimental Studies ◽  
Single Subject ◽  
Single Subject Design ◽  
Data Set ◽  
Design Studies ◽  
Sample Data ◽  
The Difference ◽  
D Values ◽  
Effect Size Calculation

The purpose of this study is to provide a brief introduction to effect size calculation in single-subject design studies, including a description of nonparametric and regression-based effect sizes. We then focus the rest of the tutorial on common regression-based methods used to calculate effect size in single-subject experimental studies. We start by first describing the difference between five regression-based methods (Gorsuch, White et al., Center et al., Allison and Gorman, Huitema and McKean). This is followed by an example using the five regression-based effect size methods and a demonstration how these methods can be applied using a sample data set. In this way, the question of how the values obtained from different effect size methods differ was answered. The specific regression models used in these five regression-based methods and how these models can be obtained from the SPSS program were shown. R2 values obtained from these five methods were converted to Cohen’s d value and compared in this study. The d values obtained from the same data set were estimated as 0.003, 0.357, 2.180, 3.470, and 2.108 for the Allison and Gorman, Gorsuch, White et al., Center et al., as well as for Huitema and McKean methods, respectively. A brief description of selected statistical programs available to conduct regression-based methods was given.

scholarly journals Crystal structure and Hirshfeld surface analysis of dichlorido(methanol-κO)bis(2-methylpyridine-κN)copper(II)

2020 ◽  
Vol 76 (11) ◽  
pp. 1771-1774
Author(s):  
J. Prakasha Reddy
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Oxygen Atom ◽  
Rotation Axis ◽  
Hirshfeld Surface ◽  
Title Complex ◽  
Complex Molecules ◽  
Crystal Complex ◽  
Tetragonal Pyramidal ◽  
Cl Atoms

In the title complex, [CuCl2(C6H7N)2(CH3OH)], the copper atom is five-coordinated by two nitrogen atoms of 2-methylpyridine ligands, two chloro ligands and an oxygen atom of the methanol molecule, being in a tetragonal–pyramidal environment with N and Cl atoms forming the basal plane. In the crystal, complex molecules related by the twofold rotation axis are joined into dimeric units by pairs of O—H...Cl hydrogen bonds. These dimeric units are assembled through C—H...Cl interactions into layers parallel to (001).

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