Weak Intermolecular Forces, but High Melting Points

2017 ◽  
Vol 70 (5) ◽  
pp. 538 ◽  
Author(s):  
Jiabin Gao ◽  
Djamal Djaidi ◽  
Christopher E. Marjo ◽  
Mohan M. Bhadbhade ◽  
Alison T. Ung ◽  
...  
Keyword(s):  
Molar Mass ◽  
Intermolecular Forces ◽  
High Melting ◽  
High Melting Point ◽  
Enantiomerically Pure ◽  
X Ray ◽  
Drug Molecules ◽  
Poorly Soluble ◽  
Weak Intermolecular Forces

The poorly soluble racemic compound 6,6a,13,13a-tetrahydropentaleno[1,2-b:4,5-b′]diquinoline (4) has an exceptionally high melting point range of 352–354°C despite its low molar mass (308.38) and a structure containing only 40 atoms (38 of which are C and H). Analysis of the X-ray crystal structure and Hirshfeld surface of 4, along with comparison with its isostructural homologue 2, reveals how this occurs in the absence of Pauling-type hydrogen bonding. Excellent complementarity between homochiral molecules of 4 allows formation of enantiomerically pure layers using C–H⋯π, aromatic π⋯π, and C–H⋯N interactions. The alternating layers of opposite handedness are then crosslinked by means of aza-1,3-peri hydrogen interactions. This bifurcated C–H⋯N⋯H–C motif acts as a molecular clip creating a highly rigid network structure. The role of weaker intermolecular forces in influencing the solubility and bioavailability of potential drug molecules is discussed in the context of the popular Lipinski ‘rule of 5’ guidelines.

3-[(Diphenylphosphinothioyl)oxy]-N-methylpropan-1-aminium diphenylphosphanylthioate

2014 ◽  
Vol 70 (3) ◽  
pp. 320-322
Author(s):  
Merve Karaman ◽  
Sevil İrişli ◽  
Orhan Büyükgüngör
Keyword(s):  
Hydrogen Bond ◽  
Melting Point ◽  
Hydrogen Bonds ◽  
Single Crystals ◽  
Spectroscopic Methods ◽  
High Melting ◽  
Asymmetric Unit ◽  
Slow Evaporation ◽  
High Melting Point ◽  
X Ray

The title salt, C16H21NOPS+·C12H10OPS, was synthesized from the reaction between 3-(methylamino)propan-1-ol and PPh2(S)Cl in the presence of Et3N. Its structure has been identified using spectroscopic methods and X-ray analysis. Single crystals were obtained from ethanol by slow evaporation. In the asymmetric unit, a cation–anion pair is formed through an intermolecular N—H...O [N...O = 2.6974 (18) Å] hydrogen bond. The molecules are packed through N—H...O and N—H...S hydrogen bonds in the crystal and these hydrogen bonds are responsible for the high melting point. The P atoms of the anion and cation both have distorted tetrahedral environments.

Determination of average carbon number of petroleum waxes by X-ray diffraction

2008 ◽  
Vol 41 (5) ◽  
pp. 950-951 ◽  
Author(s):  
Sanat Kumar ◽  
S. P. Srivastava ◽  
H. U. Khan
Keyword(s):  
Melting Point ◽  
Long Range ◽  
Carbon Number ◽  
High Melting ◽  
X Ray Diffraction ◽  
High Melting Point ◽  
X Ray ◽  
Long Range Ordering ◽  
Standard Gas

Eight petroleum waxes, both paraffin as well as microcrystalline, have been analysed by X-ray diffraction. The average carbon number has been estimated by the long-range ordering observed in the diffractograms of these waxes. The average carbon number has also been determined following the standard gas chromatographic (GC) method. The results obtained by X-ray diffractometry compare well with those obtained by the GC method. The former method also permits determination of the average carbon number of high melting point waxes, which is otherwise difficult using GC.

scholarly journals Selectivity of weak intermolecular forces and precursor state of elementary oxidation reactions, a new insight on Ne* + N2 chemiionization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Stefano Falcinelli ◽  
Franco Vecchiocattivi ◽  
Fernando Pirani
Keyword(s):  
Open Shell ◽  
Intermolecular Forces ◽  
Collision Dynamics ◽  
Oxidation Reactions ◽  
Molecular Beam Scattering ◽  
Fundamental Interest ◽  
Precursor State ◽  
New Formulation ◽  
Weak Intermolecular Forces

AbstractThis paper reports on the collision dynamics of N2 with metastable Ne* promoting chemiionizations, prototype of barrier-less oxidation reactions of great interest for fundamental and applied research. Extending guidelines presented in previous papers for the atom–atom case, an innovative treatment of the reaction stereodynamics involving molecules in a quantum state-to-state resolution conditions is proposed that emphasizes the role of structure and stability of the precursor that is here the reaction transition state. A critical test of such treatment, carried out exploiting a new formulation both of real and imaginary parts of the optical potential driving the reaction dynamics, is represented by the detailed-combined description of all relevant findings, provided by high resolution molecular beam scattering experiments carried out in our and other laboratories. The present analysis casts light on basic electronic rearrangements of such prototype oxidation reaction which are expected to be of fundamental interest for many other reactions involving open shell atoms and free radicals.

C–H⋯O (ether) hydrogen bonding along the (110) direction in polyglycolic acid studied by infrared spectroscopy, wide-angle X-ray diffraction, quantum chemical calculations and natural bond orbital calculations

RSC Advances ◽  
2016 ◽  
Vol 6 (20) ◽  
pp. 16817-16823 ◽  
Author(s):  
Harumi Sato ◽  
Mai Miyada ◽  
Shigeki Yamamoto ◽  
Kummetha Raghunatha Reddy ◽  
Yukihiro Ozaki
Keyword(s):  
Molecular Structure ◽  
Hydrogen Bonding ◽  
Quantum Chemical ◽  
Natural Bond Orbital ◽  
Polyglycolic Acid ◽  
Wide Angle ◽  
High Melting ◽  
X Ray Diffraction ◽  
High Melting Point ◽  
X Ray

Polyglycolic acid (PGA), a biodegradable polyester with a simple molecular structure, shows an abnormally high melting point of 220 °C which is the highest among biopolyesters.

Effects of Sb on Microstructure and Mechanical Properties of Mg-5.5Al-1.2Y Alloy

2011 ◽  
Vol 194-196 ◽  
pp. 1374-1377
Author(s):  
Chang Qing Li ◽  
Quan an Li ◽  
Xing Yuan Zhang ◽  
Qing Zhang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Magnesium Alloy ◽  
Room Temperature ◽  
Optical Microscope ◽  
High Melting ◽  
X Ray Diffraction ◽  
High Melting Point ◽  
X Ray ◽  
Microstructure And Mechanical Properties

The microstructure and mechanical properties of aged Mg-5.5Al-1.2Y magnesium alloy with Sb addition are investigated by optical microscope, SEM and X-ray diffraction analyzer. The results show that with proper content of Sb addition,the microstructure of Mg-5.5Al-1.2Y magnesium alloy is refined obviously and high melting point intermetallic compounds Sb3Y5 and Mg3Sb2 are formed. Meanwhile, the β-Mg17Al12 phase is more distributed. With the increase of Sb addition, the mechanical properties of the alloy at room and elevated temperature increase at first, and then decrease. When the content of Sb is up to 0.5%, the values of tensile strength and elongation at room temperature, 150ºC and 175ºC are up to their maxima synchronously, 241MPa /16.84%, 198MPa/20.27.86% and 169MPa/21.21% respectively.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

The role of silicon in forages: A quantitative X-Ray study

1987 ◽  
Vol 45 ◽  
pp. 416-417
Author(s):  
Janet H. Woodward ◽  
D. E. Akin
Keyword(s):  
Sodium Acetate ◽  
Dry Matter ◽  
Acetate Buffer ◽  
Plant Tissues ◽  
Sodium Acetate Buffer ◽  
X Ray ◽  
Dry Matter Digestibility ◽  
Percent Composition

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.

Pathophysiological function of the mitochondria as a calcium reservoir: Quantitative x-ray microanalysis

1990 ◽  
Vol 48 (2) ◽  
pp. 164-165
Author(s):  
K. Teraoka ◽  
N. Kaneko ◽  
Y. Horikawa ◽  
T. Uchida ◽  
R. Matsuda ◽  
...  
Keyword(s):  
Bolus Injection ◽  
Contact Method ◽  
X Ray

The aim of this study was to elucidate the role of the mitochondria as a store of calcium(Ca) under the condition of pathophysiological Ca overload induced by a rise in extracellular Ca concentration and the administration of isoproterenol.Eight rats were employed, and hearts were perfused as in the Langendorff method with Krebs-Henseleit solution gassed with 95% O2 and 5% CO2. Tow specimens were perfused with 2mM Ca for 30 min, and 2 were perfused with 5.5 mM Ca for 20 min. 4 specimens were perfused with 2 mM Ca for 5 min, and of these 4, 2 were infused with 10-7 mM/kg/min. isoproterenol for 5 min, and 2 were given a bolus injection of 3 x 10-7 mM isoproterenol. After rapid-cryofixation by the metal-mirror contact method with a Reichert-Jung KF80/MM80, and cryosectioning at -160 to -180° C with a Reichert-Jung Ultracut Fc-4E, ultrathin specimens (100nm) were free-ze-dreid for several hours at 10-5 Torr in the JEOL FD 7000, and mitochondrial Ca was determined by quantitative x-ray micranalysis (JEOL 1200EX, LINK AN 10000S).

Ionic homeostasis and subcellular element compartmentation

1990 ◽  
Vol 48 (2) ◽  
pp. 150-151
Author(s):  
Ann LeFurgey ◽  
Peter Ingram ◽  
J.J. Blum ◽  
M.C. Carney ◽  
L.A. Hawkey ◽  
...  
Keyword(s):  
Leishmania Major ◽  
Ionic Homeostasis ◽  
X Ray ◽  
Functional Studies ◽  
Cell Compartments ◽  
X Ray Imaging ◽  
Resolution Electron ◽  
Multiple Cell ◽  
Role Of Zn

Subcellular compartments commonly identified and analyzed by high resolution electron probe x-ray microanalysis (EPXMA) include mitochondria, cytoplasm and endoplasmic or sarcoplasmic reticulum. These organelles and cell regions are of primary importance in regulation of cell ionic homeostasis. Correlative structural-functional studies, based on the static probe method of EPXMA combined with biochemical and electrophysiological techniques, have focused on the role of these organelles, for example, in maintaining cell calcium homeostasis or in control of excitation-contraction coupling. New methods of real time quantitative x-ray imaging permit simultaneous examination of multiple cell compartments, especially those areas for which both membrane transport properties and element content are less well defined, e.g. nuclei including euchromatin and heterochromatin, lysosomes, mucous granules, storage vacuoles, microvilli. Investigations currently in progress have examined the role of Zn-containing polyphosphate vacuoles in the metabolism of Leishmania major, the distribution of Na, K, S and other elements during anoxia in kidney cell nuclel and lysosomes; the content and distribution of S and Ca in mucous granules of cystic fibrosis (CF) nasal epithelia; the uptake of cationic probes by mltochondria in cultured heart ceils; and the junctional sarcoplasmic retlculum (JSR) in frog skeletal muscle.

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