A Clathrate Hydrate of Cyclobutanone: Dielectric Relaxation of the Host and Guest Molecules

1971 ◽  
Vol 49 (8) ◽  
pp. 1243-1251 ◽  
Author(s):  
B. Morris ◽  
D. W. Davidson
Keyword(s):  
Low Frequency ◽  
Clathrate Hydrate ◽  
Water Molecules ◽  
Dielectric Study ◽  
Static Permittivity ◽  
Tetrahedral Symmetry ◽  
Absorption Region ◽  
Guest Molecules ◽  
Arrhenius Energy ◽  
Rotational Oscillations

A low-frequency dielectric study of (CH2)3CO•17H2O shows a water absorption region characteristic of a structure II clathrate hydrate which melts congruently at 0.0 °C. The relatively low Arrhenius energy of 6.5 kcal mol–1 is similar to that of acetone hydrate, for which new results are given. At low temperatures reorientation of encaged cyclobutanone molecules gives a very broad absorption region and a contribution to the static permittivity which falls with decrease of temperature. These properties are attributed to the effects of the electrostatic fields of the orientationally-disordered water molecules, which form the cages. Such fields distort the tetrahedral symmetry of the cages to an extent which varies greatly from cage to cage. The high permittivity (~3.6) at 4.2 °K probably arises from rotational oscillations at frequencies near 20 cm−1 of the guest molecules in shallow potential minima. This enhancement of polarizability removes the difficulty previously noted in the applicability of the Onsager cavity model to structure II hydrates. The dipole moment of cyclobutanone in cyclohexane solution was found to be 2.78 ± 0.02 D.

The Rotational Oscillations of Tetrahydrofuran in Tetrahydrofuran Clathrate Hydrate

1973 ◽  
Vol 51 (24) ◽  
pp. 4062-4071 ◽  
Author(s):  
D. D. Klug ◽  
E. Whalley
Keyword(s):  
Gas Phase ◽  
Low Frequency ◽  
Clathrate Hydrate ◽  
Water Molecules ◽  
Dielectric Measurements ◽  
Effective Dipole Moment ◽  
Orientational Disorder ◽  
Guest Molecules ◽  
Rotational Oscillations ◽  
Good Agreement

The absorptivity of tetrahydrofuran clathrate hydrate in the range 70–7 cm−1 has been measured at several temperatures in the range 17–80 K. There are two broad bands with maxima at 25 and 38 cm−1 which are due to the rotational oscillations of tetrahydrofuran molecules in their cages. The integrated absorptivity yields an effective dipole moment for the oscillation of 1.63 D, which is close to the gas-phase value. The negative second moment of the absorptivity yields the contribution 0.105 ± ~0.007 to the low-frequency refractive index, in good agreement with a less accurate value from dielectric measurements. The orientational disorder of the water molecules causes a distribution of potentials hindering the rotational oscillations of the guest molecules, and a detailed analysis of the shapes of the bands yields directly the distribution of force constants for the oscillations.

THE LOW-FREQUENCY DIELECTRIC PROPERTIES OF ETHYLENE OXIDE AND ETHYLENE OXIDE HYDRATE

1963 ◽  
Vol 41 (6) ◽  
pp. 1424-1434 ◽  
Author(s):  
D. W. Davidson ◽  
G. J. Wilson
Keyword(s):  
Ethylene Oxide ◽  
High Frequency ◽  
Low Temperatures ◽  
Low Frequency ◽  
Dielectric Constants ◽  
Water Molecules ◽  
Kcal Mole ◽  
Absorption Region ◽  
Experimental Values ◽  
Static Dielectric Constants

The static dielectric constant of liquid ethylene oxide has been measured between 158 and 286 °K. The hydrate of ethylene oxide exhibits a dispersion–absorption region characterized by static dielectric constants about one-third as large as those of ice and by relatively large "high-frequency" dielectric constants (ε1 = 7.5 at 0 °C). This region may be approximately described as a circular arc locus, but may be represented somewhat better by a superposition of two (or three) semicircular dispersions. In either case, the activation energy for the relaxation of water molecules, to which this region is ascribed, is ca. 6.7 kcal/mole, except at low temperatures, where it becomes smaller. Experimental values of ε1 agree roughly with those calculated for comparatively rapid orientation of ethylene oxide molecules in the cavities of the hydrate. Such orientation may account for absorption maxima observed at 11 Mc/sec and above 100 Mc/sec at 90 °K.

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.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Shelby C. Straight ◽  
Francesco Paesani
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Potential Energy Function ◽  
Md Simulations ◽  
Sum Frequency Generation ◽  
Water Molecules ◽  
Water Interface ◽  
Sum Frequency ◽  
Air Water Interface ◽  
Frequency Generation

<div> <div> <div> <p>The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The total vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular auto-correlation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating 0, 1, or 2 hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm−1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules. </p> </div> </div> </div>

Dielectric and nuclear magnetic resonance study of the hydrate of sulphur hexafluoride

1968 ◽  
Vol 46 (10) ◽  
pp. 1683-1690 ◽  
Author(s):  
Y. A. Majid ◽  
S. K. Garg ◽  
D. W. Davidson
Keyword(s):  
Magnetic Resonance ◽  
Lattice Structure ◽  
Nuclear Magnetic Resonance Study ◽  
Water Molecules ◽  
Activation Entropy ◽  
Sulphur Hexafluoride ◽  
Rigid Lattice ◽  
Second Moment ◽  
Resonance Behavior ◽  
Arrhenius Energy

In its dielectric and proton magnetic resonance behavior (except T1) the clathrate hydrate of SF6 is similar to ice I. Reorientation of water molecules appears to be little affected by the guest SF6 molecules and probably depends on the diffusion of rotational Bjerrum defects formed in numbers intrinsic to the lattice structure. The Arrhenius energy and activation entropy for dielectric relaxation are 12.3 + 0.5 kcal mole−1 and 6.8 + 2.0 cal deg−1 mole−1, respectively. The proton rigid-lattice second moment is 32.8 ± 0.5 G2 at −180 °C. The 19F second moment agrees with the value calculated for rapid isotropic rotation of SF6 molecules in the large cages only. Diffusion of water molecules in the hydrate is slower than in ice, which suggests that diffusion in ice occurs by migration of interstitial molecules through the channels in ice rather than by migration of lattice vacancies.

Clathrate and other solid phases in the tetrahydrofuran–water system: thermal conductivity and heat capacity under pressure

1982 ◽  
Vol 60 (7) ◽  
pp. 881-892 ◽  
Author(s):  
Russell G. Ross ◽  
Per Andersson
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Water System ◽  
Clathrate Hydrate ◽  
Transient Hot Wire ◽  
Guest Molecules ◽  
Hydrate Phase ◽  
Wire Method ◽  
Solid Phases ◽  
Thermal Conductivity Λ

Solid phases in the tetrahydrofuran–water (THF–H2O) system were investigated in the temperature range 100–260 K and at pressures up to 1.5 GPa. Thermal conductivity, λ, and heat capacity per unit volume, ρcp, were measured, using the transient hot-wire method. We made measurements on solid phases having nominal compositions THF•17H2O, THF•7•1H2O, and THF•4•6H2O, which we refer to as phases α, β, and γ, respectively. Phase α is known to be a structure II clathrate hydrate, and λ for this phase was found to be similar to other crystalline solids which are glass-like in relation to their thermal properties. Low-energy excitations are known to be relevant to the properties of glass-like solids, and, in the case of phase α, were probably rotational vibrations of the THF guest molecules. Phase β was similar, and we inferred that it was probably a structure I clathrate hydrate. Phase γ behaved nearly like a normal crystal phase at low temperatures, but λ became almost independent of temperature near melting. At 1.1 GPa and 130 K, we found evidence that phase α transformed, on pressurization, to a metastable modification which may be a new high-density form of clathrate hydrate. The astrophysical implications of our results were mentioned briefly.

scholarly journals Supramolecular Complexes of Cucurbiturils with Second Group Metal Salts and Hydrates and Histamine

INEOS OPEN ◽  
2021 ◽  
Vol 4 ◽  
Author(s):  
Yu. A. Borisov ◽  
◽  
S. S. Kiselev ◽  
Keyword(s):  
Aqueous Solution ◽  
Density Functional Theory ◽  
Density Functional ◽  
Metal Salts ◽  
Supramolecular Complexes ◽  
Water Molecules ◽  
Functional Theory ◽  
Guest Molecules ◽  
First Time ◽  
Formation Energies

The interaction of cucurbiturils (Q6, Q7, and Q8) with Ca and Ba chlorides and iodides are studied for the first time by density functional theory. The thermodynamic parameters for the formation of host–guest complexes are calculated. The structures of complexes of Q6 and Q7 with one and two guest molecules are established. The energy parameters for the transfer of Be2+ and Ba2+ cations from an aqueous solution into the cavity of Q7 containing n water molecules are defined. The dependences of the formation energies for complexes Q7WnBe2+ and Q7WnBa2+ on the number of water molecules are shown to be parabolic, with the energy minima at n = 5 and n = 6, respectively. It is found that Q7 can form in an aqueous solution supramolecular complexes with protonated histamine (HA) and neutral histamine in the presence of Ca2+ ions.

scholarly journals Phase transformations in cucurbituril host-guest complexes

2014 ◽  
Vol 70 (a1) ◽  
pp. C646-C646
Author(s):  
Oksana Danylyuk ◽  
Karolina Kedra-Krolik ◽  
Marta Worzakowska ◽  
Joanna Osypiuk-Tomasik ◽  
Vladimir Fedin
Keyword(s):  
Single Crystal ◽  
Crystal Lattice ◽  
Supramolecular Assembly ◽  
Water Molecules ◽  
Guest Molecules ◽  
X Ray ◽  
Host Guest Complex ◽  
Crystallographic Study ◽  
Partial Dehydration ◽  
Structure Changes

The retention of crystallinity upon desolvation of molecular crystals is not common, as the molecules are rigidly and densely packed in the crystals and the original framework usually collapses once solvent is removed from the structure. However, in rare cases the host framework remains substantially unaffected by solvent (guest) removal yielding structure with open channels or discrete lattice voids that can show permanent porosity. [1] Furthermore, sometimes happens, the desolvation process proceeds as single-crystal to single-crystal transformation resulting in distortion and sliding of the structure, changes in conformation, coordination modes and/or space group. Here we would like to present crystallographic study and thermal analysis on the dehydration process of the crystalline supramolecular complex between macrocyclic host cucurbit[6]uril and dopamine. In the solid state the 1:1 host-guest complex assembles into hexameric tubes with water-filled interior channels. Another set of water channels is created between three neighboring tubes in the crystal lattice. The crystals of such supramolecular assembly are not stable when out from mother solution and immediately start to loose water upon exposure to air. However, despite severe cracking the crystals dried in air maintained their integrity and still gave satisfactory diffraction pattern. The X-ray analysis showed significant decrease in the unit cell volume of the partially dehydrated crystals that corresponds to the liberation of some of the water molecules from the channels. Moreover, the reorganization of dopamine guest molecules has occurred in the crystal lattice as a response to the escape of water molecules from the structure. The partial dehydration and reorganization of the supramolecular framework proceeds via a single-crystal to single-crystal mechanism.

The Far Infrared Spectra of Partially Orientationally Ordered Water Molecules: Hexamethylenetetramine Hexahydrate at 95 K

1975 ◽  
Vol 53 (17) ◽  
pp. 2642-2645 ◽  
Author(s):  
John E. Bertie ◽  
Marco Solinas
Keyword(s):  
Infrared Spectrum ◽  
Infrared Spectra ◽  
Far Infrared ◽  
Clathrate Hydrate ◽  
Factor Group ◽  
Water Molecules ◽  
Disordered Solids ◽  
Ordered Water ◽  
Far Infrared Spectra ◽  
Three Phases

The far infrared spectra of four isotopic modifications of the partially orientationally ordered clathrate hydrate hexamethylenetetramine hexahydrate at 95 K are reported. The spectra are assigned to absorption allowed under the diffraction factor group, and to disorder-allowed absorption, following the theory for absorption by translational vibrations in orientationally disordered solids. Three phases formed primarily by hydrogen-bonded water molecules are known to be significantly, but only partially, orientationally ordered, hexamethylenetetramine hexahydrate, ice V, and ice VI. Of these phases, only ice VI fails to show sharp absorption in its far infrared spectrum in addition to the broad, disorder-allowed absorption.

ChemInform Abstract: Complexes of Macrocyclic Polyethers and Neutral Guest Molecules: A Systematic Approach to the Complexation of Water Molecules by 2,6-Pyridinium Crown Ethers.

1986 ◽  
Vol 17 (25) ◽  
Author(s):  
P. D. J. GROOTENHUIS ◽  
J. W. H. M. UITERWIJK ◽  
D. N. REINHOUDT ◽  
C. J. VAN STAVEREN ◽  
E. J. R. SUDHOELTER ◽  
...  
Keyword(s):  
Crown Ethers ◽  
Systematic Approach ◽  
Water Molecules ◽  
Macrocyclic Polyethers ◽  
Guest Molecules
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