Isoxazole Hydrate

1974 ◽  
Vol 52 (18) ◽  
pp. 3193-3195 ◽  
Author(s):  
S. R. Gough ◽  
S. K. Garg ◽  
J. A. Ripmeester ◽  
D. W. Davidson
Keyword(s):  
Clathrate Hydrate ◽  
Type Ii ◽  
Dielectric Studies ◽  
Guest Molecules ◽  
X Ray ◽  
Typical Type

X-Ray, n.m.r., and dielectric studies show that the hydrate of isoxazole is a typical type II clathrate hydrate in structure, in reorientation rates of host and guest molecules, and in composition.

Structural Transition of Trimethylamine Hydrate by Methane or Hydrogen Inclusion

2020 ◽  
Author(s):  
Minjun Cha
Keyword(s):  
Structural Transition ◽  
Guest Molecule ◽  
Clathrate Hydrate ◽  
Hydrogen Gas ◽  
Time Dependent ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Inclusion Process ◽  
Diffraction Patterns

<p>Recently, several alkylamine hydrates have been studied in an effort to reveal the structural transitions from semi- to ‘canonical’ clathrate hydrate in the presence of secondary guest molecules. Trimethylamine (TMA) is known to form the semi-clathrate hydrate, and it has been reported that the structural transition of the TMA semi-clathrate hydrate may not occur in the presence of hydrogen gas as a secondary guest molecule. This paper reports the structural transition of trimethylamine(TMA) hydrate induced by the type of guest molecules. Powder X-ray diffraction patterns of (TMA + H<sub>2</sub>) hydrates show the formation of hexagoanl P6/mmm hydrate, but those of (TMA + CH<sub>4</sub>) hydrates indicate the formation of cubic Fd3m hydrate. Without gaseous guest molecule, the crystal structure of pure TMA hydrate is identified as hexagonal P6/mmm. Therefore, inclusion of gaseous methane in TMA hydrate can induce the structural transition from hexagonal to cubic hydrate or the formation of metastable cubic hydrate. To clearly reveal this possibility, we also check the time-dependent structural patterns of binary (TMA + CH<sub>4</sub>) hydrates from 1 to 14 days, and the results show that the structural transition of TMA hydrate from hexagonal P6/mmm to cubic Fd3m hydrate structure can occur during the methane inclusion process.</p>

The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates

2017 ◽  
Vol 203 ◽  
pp. 61-77 ◽  
Author(s):  
Hana Dureckova ◽  
Tom K. Woo ◽  
Konstantin A. Udachin ◽  
John A. Ripmeester ◽  
Saman Alavi
Keyword(s):  
Ab Initio ◽  
Halogen Bonding ◽  
Chem Phys ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Water Molecules ◽  
Guest Molecules ◽  
X Ray ◽  
Covalent Interaction ◽  
Water Oxygen

Clathrate hydrate phases of Cl2 and Br2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen–halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen–halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme–substrate compounds. The nature of the halogen–water interactions for the Cl2 and Br2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl2 and Br2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.

scholarly journals Type II Clathrate Hydrate Formation in Cometary Ice Analogs in Vacuo

1992 ◽  
Vol 150 ◽  
pp. 437-438
Author(s):  
D. F. Blake ◽  
L. Allamandola ◽  
S. Sandford ◽  
D. Hudgins ◽  
F. Freund
Keyword(s):  
High Vacuum ◽  
Hydrate Formation ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Type Ii ◽  
State Transformation ◽  
Solid State Transformation ◽  
Guest Molecules ◽  
Amorphous Ices ◽  
Analog Experiments

Clathrate Hydrates can be formed under high vacuum conditions by annealing vapor-deposited amorphous ices of the appropriate composition. When astrophysically significant H2O:CH3OH ices are deposited and annealed, Type II Clathrate Hydrates are formed which can hold up to 6 mole % large guest molecules such as methanol and 12 mole % small guest molecules such as CO2 and CO. The solid state transformation of amorphous mixed molecular ice into crystalline clathrate hydrate and its sublimation at higher temperatures may serve to explain heretofore anomalous mechanical and gas release properties observed in cometary ices and laboratory ice analog experiments.

Synthesis and Structure of a Clathrated Two-Dimensional Metal-Organic Framework: [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2·H2O (L = Bis(1-pyrazinylethylidene)hydrazine)

2008 ◽  
Vol 73 (1) ◽  
pp. 24-31
Author(s):  
Dayu Wu ◽  
Genhua Wu ◽  
Wei Huang ◽  
Zhuqing Wang
Keyword(s):  
Metal Organic Framework ◽  
Channel Structure ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Square Planar ◽  
Metal Organic ◽  
Aqueous Meoh ◽  
Organic Framework

The compound [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2 was obtained by the reaction of Cd(ClO4)2, bis(1-pyrazinylethylidene)hydrazine (L) and 4,4'-bipyridine in aqueous MeOH. Single-crystal X-ray diffraction has revealed its two-dimensional metal-organic framework. The 2-D layers superpose on each other, giving a channel structure. The square planar grids consist of two pairs of shared edges with Cd(II) ion and a 4,4'-bipyridine molecule each vertex and side, respectively. The square cavity has a dimension of 11.817 × 11.781 Å. Two guest molecules of bis(1-pyrazinylethylidene)hydrazine are clathrated in every hydrophobic host cavity, being further stabilized by π-π stacking and hydrogen bonding. The results suggest that the hydrazine molecules present in the network serve as structure-directing templates in the formation of crystal structures.

scholarly journals Hydrogen Inter-Cage Hopping and Cage Occupancies inside Hydrogen Hydrate: Molecular-Dynamics Analysis

2020 ◽  
Vol 11 (1) ◽  
pp. 282
Author(s):  
Yogeshwaran Krishnan ◽  
Mohammad Reza Ghaani ◽  
Arnaud Desmedt ◽  
Niall J. English
Keyword(s):  
Molecular Dynamics ◽  
Energy Barrier ◽  
Guest Molecule ◽  
Arrhenius Equation ◽  
Dynamics Simulation ◽  
Type Ii ◽  
Large Cage ◽  
Guest Molecules ◽  
Simulation Time ◽  
Average Occupancy

The inter-cage hopping in a type II clathrate hydrate with different numbers of H2 and D2 molecules, from 1 to 4 molecules per large cage, was studied using a classical molecular dynamics simulation at temperatures of 80 to 240 K. We present the results for the diffusion of these guest molecules (H2 or D2) at all of the different occupations and temperatures, and we also calculated the activation energy as the energy barrier for the diffusion using the Arrhenius equation. The average occupancy number over the simulation time showed that the structures with double and triple large-cage H2 occupancy appeared to be the most stable, while the small cages remained with only one guest molecule. A Markov model was also calculated based on the number of transitions between the different cage types.

X‐Ray, Optical, and Radio Observations of the Type II Supernovae 1999em and 1998S

2002 ◽  
Vol 572 (2) ◽  
pp. 932-943 ◽  
Author(s):  
David Pooley ◽  
Walter H. G. Lewin ◽  
Derek W. Fox ◽  
Jon M. Miller ◽  
Christina K. Lacey ◽  
...  
Keyword(s):  
Type Ii ◽  
Radio Observations ◽  
X Ray

Structural properties of the guest species in diacyl peroxide/urea inclusion compounds: an X-ray diffraction investigation

1990 ◽  
Vol 431 (1882) ◽  
pp. 245-269 ◽  
Keyword(s):  
Single Crystal ◽  
Structural Properties ◽  
Inclusion Compounds ◽  
X Ray Diffraction ◽  
Channel Axis ◽  
Guest Molecules ◽  
X Ray ◽  
Urea Inclusion Compounds ◽  
Diacyl Peroxide ◽  
Urea Inclusion

In this paper we report single crystal X-ray diffraction studies of urea inclusion compounds containing diacyl peroxides (dioctanoyl peroxide (OP), diundecanoyl peroxide (UP), lauroyl peroxide (LP)) as the guest component. In these inclusion compounds, the host (urea) molecules crystallize in a hexagonal structure that contains linear, parallel, non-intersecting channels (tunnels). The guest (diacyl peroxide) molecules are closely packed inside these channels with a periodic repeat distance that is incommensurate with the period of the host structure along the channel axis. Furthermore, there is pronounced inhomogeneity within the guest structure: within each single crystal, there are regions in which the guest molecules are three-dimensionally ordered, and other regions in which they are only one-dimensionally ordered (along the channel axis). Although it has not proven possible to ‘determine’ the guest structures in the conventional sense, substantial information concerning their average periodicities and their orientational relationships with respect to the host has been deduced from single crystal X-ray diffraction photographs recorded at room temperature. For OP/urea, UP/urea and LP/urea, the guest structure in the three-dimensionally ordered regions is monoclinic, and six types of domain of this monoclinic structure can be identified within each single crystal. The relative packing of diacyl peroxide molecules is the same in each domain, and the different domains are related by 60° rotation about the channel axis. For each of these inclusion compounds, the offset between the ‘heights’ of the guest molecules in adjacent channels is the same ( ca . 4.6 Å (4.6 x 10 -10 m)) within experimental error, suggesting that the relative interchannel packing of the guest molecules is controlled by a property of the diacyl peroxide group. In addition to revealing these novel structural properties, the work discussed in this paper has more general relevance concerning the measurement and interpretation of single crystal X-ray diffraction patterns that are based on more than one three-dimensionally periodic reciprocal lattice. Seven separate reciprocal lattices are required to rationalize the complete X-ray diffraction pattern from each diacyl peroxide/urea crystal studied here.

Developing structure-based models to predict substrate specificity of D-group (Type II) molybdenum enzymes: application to a molybdo-enzyme of unknown function from Archaeoglobus fulgidus

2006 ◽  
Vol 34 (1) ◽  
pp. 118-121 ◽  
Author(s):  
E.J. Dridge ◽  
D.J. Richardson ◽  
R.J. Lewis ◽  
C.S. Butler
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Sequence Analysis ◽  
Archaeoglobus Fulgidus ◽  
Substrate Selectivity ◽  
Type Ii ◽  
Amino Acid Residues ◽  
Sequence Alignments ◽  
X Ray ◽  
Group Type

The AF0174–AF0176 gene cluster in Archaeoglobus fulgidus encodes a putative oxyanion reductase of the D-type (Type II) family of molybdo-enzymes. Sequence analysis reveals that the catalytic subunit AF0176 shares low identity (31–32%) and similarity (41–42%) to both NarG and SerA, the catalytic components of the respiratory nitrate and selenate reductases respectively. Consequently, predicting the oxyanion substrate selectivity of AF0176 has proved difficult based solely on sequence alignments. In the present study, we have modelled both AF0176 and SerA on the recently determined X-ray structure of the NAR (nitrate reductase) from Escherichia coli and have identified a number of key amino acid residues, conserved in all known NAR sequences, including AF0176, that we speculate may enhance selectivity towards trigonal planar (NO3−) rather than tetrahedral (SeO42− and ClO4−) substrates.

Detailed X-ray diffraction studies on optically pumped mid-infrared InAs/Ga(In)Sb/AlSb type-II lasers

2003 ◽  
Vol 257 (1-2) ◽  
pp. 42-50 ◽  
Author(s):  
G. Hoffmann ◽  
H.J. Schimper ◽  
C. Schwender ◽  
N. Herhammer ◽  
G.F. West ◽  
...  
Keyword(s):  
Type Ii ◽  
X Ray Diffraction ◽  
Optically Pumped ◽  
Mid Infrared ◽  
X Ray
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