Clathrate Hydrates in the System Tetraisopentylammonium Iodide-Water

Two clathrate hydrates i-Pent₄NI·36H₂O and i-Pent₄NI·32H₂O were revealed in the system (i-Pent)₄NI-H₂O. The hydrates melt incongruently at 14.2 and 14.8°C, respectively. Along with the polyhydrates, tetraisopentylammonium dihydrate was found.     

New Clathrate Hydrates in the System Triisopentylammonium Bromide-Water

In the system i-Pent₃BuNBr-H₂O, along with the known compound i-Pent₃BuNBr-38H₂O, three new clathrate hydrates were identified: i-Pent₃BuNBr-32H₂O, i-Pent₃BuNBr-26H₂O, and i-Pent₃BuNBr-24H₂O. Crystals of all the hydrates were isolated, and their compositions were determined.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 2, 2005, pp. 192–195.Original Russian Text Copyright © 2005 by Aladko, Dyadin.     

Experimental Modeling of the Processes of Ozone Hydrate Clathrate Formation

The possible formation of ozone hydrates and their interaction with hydrogen chloride under nearstratospheric conditions were investigated. The low-temperature IR spectroscopic technique was used to demonstrate the in situ formation of ozone hydrates that were stable in the temperature range 77–220 K. It was found that HCl reacted with ozone hydrate to destruct clathrate at temperatures above 220 K. This process resulted in compositionally different chlorine oxides. Original Russian Text ? T.A. Vysokikh, T.V. Yagodovskaya, S.V. Savilov, V.V. Lunin, 2008, published in Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 4, pp. 792–795.     

Dicyclohexylamine-Thiourea Clathrate

Abstract

The reaction of dicyclohexylamine (DCHA) with thiourea leads to the formation of the inclusion compound DCHA(6 Thiourea). Room temperature, single crystal X-ray diffraction analysis shows the product has a trigonal structure, α=β=90°, γ=120°, a=b=15.801(2)A, c=12.451(3)A, which may be described as a thiourea matrix defining hexagonal cavities where the di-cyclohexylamine molecules are accommodated. ¹³C-cross polarization magic angle spinning (CP-MAS) NMR study indicates the guest inside the cavities has a relatively free rotation and that the channels are, concerning this amine, perfect van der Waals cavities. Thermal studies indicates that the structural identity of the thiourea matrix endures after a partial loss of amine.     

Benzene Solubility in Ionic Liquids: Working Toward an Understanding of Liquid Clathrate Formation

The solubility of benzene in 15 imidazolium, pyrrolidinium, pyridinium, and piperidinium ionic liquids has been determined; the resulting, benzene‐saturated ionic liquid solutions, also known as liquid clathrates, were examined with ¹H and ¹⁹F nuclear magnetic resonance spectroscopy to try and understand the molecular interactions that control liquid clathrate formation. The results suggest that benzene interacts primarily with the cation of the ionic liquid, and that liquid clathrate formation (and benzene solubility) is controlled by the strength of the cation–anion interactions, that is, the stronger the cation–anion interaction, the lower the benzene solubility. Other factors that were determined to be important in the final amount of benzene in any given liquid clathrate phase included attractive interactions between the anion and benzene (when significant), and larger steric or free volume demands of the ions, both of which lead to greater benzene solubility.     

Clathrate Hydrates of Tetrabutylammonium Dicarboxylates. System Tetrabutylammonium Adipate-Water

In the system tetrabutylammonium adipate-water, two stable and two metastable polyhydrates were identified. The melting points of the polyhydrates were correlated with the anion hydrocarbon chain length in the series H₂O-[(C₄H₉)₄N]₂(CH₂) _n C₂O₄ (n = 0-8).     

反相高效液相色谱检测法测定溴化1-乙基-3-甲基咪唑-水体系中青蒿素

建立了反相高效液相色谱(RP-HPLC)定量检测离子液体溴化1-乙基-3-甲基咪唑-水体系中青蒿素含量的方法.检测条件为:室温(25±1)℃,C18反向柱(250 mm×4.6 mm, 5 μm),以V(甲醇): V(0.01 mol/L HAc-NaAc溶液,pH=5.9)=60: 40混合溶液为流动相,流速0.5 mL/min,检测波长为260 nm.青蒿素浓度在5～30 mg/L之间线性回归方程为y=2.20326×107x-30928.7,相关系数r=0.9990.本方法回收率为100 2%;相对标准偏差(RSD)为0.42%.     

Diisoamyldibutylammonium Bromide Clathrate Hydrates

In the system i-Am₂Bu₂NBr-H₂O, along with the known compound i-Am₂Bu₂NBr·38H₂O, three new clathrate hydrates were revealed: i-Am₂Bu₂NBr·32H₂O, i-Am₂Bu₂NBr·26H₂O, and i-Am₂Bu₂NBr·24H₂O. Crystals of all the hydrates were isolated, and their compositions and melting points were determined.     

Clathrate Formation in the Water–Tetraisoamylammonium Propionate System: X-ray Structural Analysis of the Clathrate Hydrate (i-C5H11)4NC2H5CO2·36H2O

In this work X-ray single crystal structural analysis was carried out on the clathrate hydrate of tetraisoamylammonium propionate with the composition (i-C₅H₁₁)₄NC₂H₅CO₂·36H₂O. The hydrate was found to have an orthorhombic structure in space group Cmc2 ₁ with unit cell parameters: a = 21.281(2) Å, b= 12.010(7) Å, c = 24.768(3) Å (150 K). X-ray powder diffraction studies were performed of the hydrate phase, crystallized in the water–(i-C₅H₁₁)₄NC₂H₅CO₂ system in the concentration range of the salt (10–25 wt%) that is the crystallization region of the studied polyhydrate, according to the phase equilibria data. It was found, that in the given concentration region the same hydrate of orthorhombic structure is formed, unit cell parameters, obtained at 20 °C: a = 21.454(13) Å, b = 12.156(4) Å, c = 25.030(14) Å, are in a good agreement with the data of single crystal structural analysis.     

Ordering and Clathrate Hydrate Formation in Co‐deposits of Xenon and Water at Low Temperatures

Local ordering in co‐deposits of water and xenon atoms produced at low temperatures can be followed uniquely by ¹²⁹Xe NMR spectroscopy. In water‐rich samples deposited at 10 K and observed at 77 K, xenon NMR results show that there is a wide distribution of arrangements of water molecules around xenon atoms. This starts to order into the definite coordination for the structure I, large and small cages, when samples are annealed at ～140 K, although the process is not complete until a temperature of 180 K is reached, as shown by powder Xray diffraction. There is evidence that Xe ? 20 H₂O clusters are prominent in the early stages of crystallization. In xenon‐rich deposits at 77 K there is evidence of xenon atoms trapped in Xe ? 20 H₂O clusters, which are similar to the small hydration shells or cages observed in hydrate structures, but not in the larger water clusters consisting of 24 or 28 water molecules. These observations are in agreement with results obtained on the formation of Xe hydrate on the surface of ice surfaces by using hyperpolarized Xe NMR spectroscopy. The results indicate that for the various different modes of hydrate formation, both from Xe reacting with amorphous water and with crystalline ice surfaces, versions of the small cage are important structures in the early stages of crystallization.     

Hydrogen in Porous Tetrahydrofuran Clathrate Hydrate

The lack of practical methods for hydrogen storage is still a major bottleneck in the realization of an energy economy based on hydrogen as energy carrier. ¹ Storage within solid‐state clathrate hydrates, ² – ⁴ and in the clathrate hydrate of tetrahydrofuran (THF), has been recently reported. ⁵ , ⁶ In the latter case, stabilization by THF is claimed to reduce the operation pressure by several orders of magnitude close to room temperature. Here, we apply in situ neutron diffraction to show that—in contrast to previous reports^{[5, 6]}—hydrogen (deuterium) occupies the small cages of the clathrate hydrate only to 30 % (at 274 K and 90.5 bar). Such a D₂ load is equivalent to 0.27 wt. % of stored H₂. In addition, we show that a surplus of D₂O results in the formation of additional D₂O ice Ih instead of in the production of sub‐stoichiometric clathrate that is stabilized by loaded hydrogen (as was reported in ref. ⁶ ). Structure‐refinement studies show that [D₈]THF is dynamically disordered, while it fills each of the large cages of [D₈]THF?17D₂O stoichiometrically. Our results show that the clathrate hydrate takes up hydrogen rapidly at pressures between 60 and 90 bar (at about 270 K). At temperatures above ≈220 K, the H‐storage characteristics of the clathrate hydrate have similarities with those of surface‐adsorption materials, such as nanoporous zeolites and metal–organic frameworks, ⁷ , ⁸ but at lower temperatures, the adsorption rates slow down because of reduced D₂ diffusion between the small cages.     

Clathrate formation in water-peralkylonium salts systems

We discuss composition, stoichiometry and stability (phase diagrams) of peralkylonium salts and analogues (Alk₃XO, where X=N,P,As) polyhydrates depending on the dimensions and the configuration of the hydrophobic part of a guest-molecule and its ability to interact in a hydrophilic way with the framework.     

Clathrate hydrates of triisoamylbutylammonium iodide

The phase diagram of the (i-C₅H₁₁)₃C₄H₉NI?H₂O system is reported. Triisoamylbutylammonium iodide forms polyhydrates with hydration numbers of 36 (mp 12.5°C) and 32 (mp 13.2°C) and a dihydrate. Crystals of both polyhdrates have been isolated, and their compositions have been determined.     

Clathrate formation in the tetraisoamylammonium propionate-water system

In this paper we examine clathrate formation in the tetraisoamylammonium propionate-water binary system. We have found formation of four polyhydrates, two of which are metastable over the whole temperature range studied. All polyhydrate crystals were isolated and their compositions and densities determined; for (i-C₅H₁₁)₄NC₂H₅COO·36.5H₂O, unit cell parameters were additionally found. The results are compared with data for tetra-n-butylammonium carboxylate polyhydrates, and the structure of the title compounds is suggested. It is confirmed that the isoamyl radical stabilizes the tetradecahedral void of the clathrate hydrate framework better than the n-butyl radical. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 3, pp. 67–71, May–June, 1994. Translated by L. Smolina     

Physicochemical Properties of Ionic Clathrate Hydrates

Ionic clathrate hydrates are known to be formed by the enclathration of hydrophobic cations or anions into confined cages and the incorporation of counterions into the water framework. As the ionic clathrate hydrates are considered for their potential applicability in various fields, including those that involve solid electrolytes, gas separation, and gas storage, numerous studies of the ionic clathrate hydrates have been reported. This review concentrates on the physicochemical properties of the ionic clathrate hydrates and the notable characteristics of these materials regarding their potential application are addressed.     

氮气笼型水合物的激光拉曼光谱

在253K和16MPa的压力下,于实验室内合成了氮气水合物,用显微共焦拉曼光谱对其N-N和O-H键伸缩振动的光谱特征进行了研究．结果表明,氮气水合物中的N-N和O—H键的拉曼峰分别为2322．4和3092．1cm^-1,与天然的空气水合物中的数据十分接近．另外,还测定了液氮和溶解于水中的氮分子中N—N键的拉曼峰值,分别为2326．6和2325．0cm^-1．氮气笼型水合物分解的拉曼谱图表明,氮分子同时进入水合物的大笼和小笼中,但由于氮分子在大、小笼中的环境氛围十分接近,其拉曼位移相差不大,故拉曼谱图只能显示N—N键伸缩振动一个峰．