共查询到20条相似文献,搜索用时 31 毫秒
1.
Sandra Scherb Christian Nther Wolfgang Bensch 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):m135-m136
In the crystal structure of the title compound, [Ni2(C4H4O6)2(H2O)2]·3H2O, two nickel cations, two tartrate anions and two water molecules form the dimeric complex. Each nickel cation is in a distorted octahedral environment composed of four O atoms of two crystallographically independent tartrate anions, one water molecule and one O atom of a symmetry‐equivalent tartrate anion. The asymmetric unit contains three additional water molecules which are connected via hydrogen bonding. 相似文献
2.
We investigated the effects of NaF, NaCl, NaBr, and NaI on the molecular organization of H2O by a calorimetric methodology developed by us earlier. We use the third derivative quantities of G pertaining to 1-propanol (1P) in ternary 1P-a salt-H2O as a probe to elucidate the effects of a salt on H2O. We found that NaF and NaCl worked as hydration centers. The hydration numbers were 19 +/- 2 for NaF and 7.5 +/- 0.6 for NaCl. Furthermore, the bulk H2O away from the hydration shell was found unaffected by the presence of Na+, F-, and Cl-. For NaBr and NaI, in addition to the hydration to Na+, Br- and I- acted like a hydrophilic moiety such as urea. Namely, they formed a hydrogen bond to the existing H2O network and retarded the fluctuation nature of H2O. These findings were discussed with respect to the Hofmeister ranking. We suggested that more chaotropic anions Br- and I- are characterized as hydrophiles, whereas kosmotropes, F- and Cl-, are hydration centers. 相似文献
3.
采用B3LYP/DZP++的方法研究了第一水化层作用和连续化处理的水溶剂作用对鸟嘌呤-胞嘧啶(GC)碱基对和腺嘌呤-胸腺嘧啶(AT)碱基对质子转移反应的影响. GC和AT碱基对在连续化水溶剂作用下,均发生单质子转移(SPT1)和分步的双质子转移(DPT),而在第一水化层5 个水分子的作用下(GC·5H2O,AT·5H2O)或同时考虑第一水化层作用和连续化水溶剂作用(GC·5H2O+PCM,AT·5H2O+PCM)时,GC和AT碱基对的质子转移均只得到单质子转移反应(SPT1). 单质子转移过程中的活化能变化情况表明:第一水化层对GC和AT碱基对结构和质子转移影响较大,水环境对碱基对的作用主要发生在第一水化层. 相似文献
4.
Zhijing Liu Chao Zhang Ruigang Liu Wushou Zhang Hongliang Kang Pingping Li Yong Huang 《Cellulose (London, England)》2016,23(1):295-305
The effects of chloride salts on the dissolution of cellobiose in aqueous solution were investigated using calorimetry and 1H NMR. The dissolution of cellobiose in salt solutions is a typical entropy-driven process. The activity of ZnCl2 and LiCl hydrated ions is enhanced as the hydration number decreases with increasing temperature. Zn2+ and Li+ hydrates can interact with the oxygen atoms at the O5 and O6 positions of cellobiose and associate with the Cl? anions, leading to the breakage of cellobiose hydrogen bonds. We found that the solubility of cellobiose in aqueous solutions is on the order of ZnCl2 > LiCl > NaCl > H2O > KCl > NH4Cl, which is consistent with the Hofmeister series. For the first time, we recognized the specific ionic effects of the Hofmeister series on the dissolution of cellobiose in salt aqueous solutions. This finding is helpful for understanding the dissolving mechanism of cellulose in aqueous solvents with salts and providing fundamental knowledge for finding and designing new cellulose solvents. 相似文献
5.
Present research compared the effect of chromate reducers such as ferrous sulphate heptahydrate (FeSO4·7H2O) and stannous sulphate dihydrate (SnCl2·2H2O) on the hydration of cement paste, using water?cement ratio of 0.5 and sealed in plastic bags without curing for 28 days. Uncured hydration properties of cement paste are investigated in detail by thermogravimetric analysis (TGA) and verified with the use of scanning electron microscopy (SEM) and X-ray powder diffractometry (XRD). This research concluded that the cement paste with 0.1% additives showed better hydration in the uncured condition than the control.
相似文献6.
Yun Wang Jing Wang Juan Han Shiping Hu Yongsheng Yan 《Central European Journal of Chemistry》2010,8(4):886-891
Binodal data are beneficial to the design of aqueous two-phase extraction and the establishment of thermodynamic models. For
the 2-propanol + Li2SO4/Na2SO4/ (NH4)2SO4/K3PO4 + water systems and 1-propanol + K3PO4/K3C6H5O7/(NH4)3C6H5O7 + water systems, binodal data were determined at 298.15 K. The binodal data were correlated by a theoretical equation on
the basis of statistical geometry. The salting-out abilities of salts and the phase-separation abilities of alcohols were
evaluated by the effective excluded volume of salt and the binodal curves plotted in molality. A simple Hofmeister series
of cations and anions were obtained. The organic salt, K3C6H5O7, shows as high a salting-out ability as K3PO4.
相似文献
7.
A very simple isopiestic method based on that of S. Christian is used for measuring the salting-in of water into nonpolar, low-volatility solvents by tetraalkylammonium salts. The quantity of excess water which is dissolved in such solvents is directly proportional to the salt concentration and is sharply dependent on the nature of the anion but is nearly insensitive to that of the R4N+ cation. The hydration ratioH, which we define as the moles of excess solubilized water per mole of R4N+ X–, is directly relatable to the enthalpy of hydration of the anion X– in several solvents and in the gas phase. The quantityH is also correlated with many free-energy terms including those for the Hofmeister lyotropic series, for the ability of the anions to salt nonelectrolytes out of water, for the free-energy terms for separation of these ions by reverse osmosis membranes, and for their nucleophilicities. A surprising (but not unprecedented) feature of the hydration ratio is that it, rather than its logarithm, behaves as a free-energy term. It is proposed that all these properties have in common the free energy of hydration of the anions, and this notion is supported by a close correspondence between the anionic hydration ratio and their hydrogen-bonding energies with proton donors in aprotic solvents. The results support scattered observations by other workers that isolated water molecules do not have an unusual inherent affinity for anions. Accordingly, large anionic hydration energies in bulk aqueous media reflect extensive cooperative interactions in the solvent. Implications for nucleophilic activity in phase transfer catalysis and enzyme activity are mentioned. 相似文献
8.
It is increasingly being accepted that solvation properties of ions and interfaces (hydration of ions, hydrophobic or hydrophilic character of interfaces) play a fundamental role in ion-surface interaction in water. However, a fundamental understanding of the precise role of solvation in ionic specificity in colloidal systems is still missing, although important progress has been made over the last years. We present in this contribution experimental evidences (including also ions not usually included in specific ion studies) together with Molecular Dynamics (MD) simulations that highlight the importance of the hydration of ions and surfaces in order to understand the origin of ionic specificity. We first show that both surface polarity and ion hydration determine the sorting of ions according to their ability to induce specific effects (the so-called Hofmeister series). We extend these classical series by considering the addition of the inorganic anions IO3−, BrO3− and ClO3−, which present unusual properties as compared with the ions considered in classical Hofmeister series. We also consider big hydrophobic organic ions such as tetraphenylborate anion (Ph4B−) and tetraphenylarsonium cation (Ph4As+) that in the context of the Hofmeister series behave as super-chaotropes ions. 相似文献
9.
Speed of sound and density of 1-propanol + heavy water were measured in the whole concentration range at temperatures from 293 to 313 K. Isentropic compressibility was calculated from the Laplace formula. The partial molar volume of 1-propanol reaches a minimum at the mole fraction of 1-propanol x
1 0.03. At the same concentration, the compressibility isotherms intersect one another. These features of the investigated system are similar to those of 1-propanol + H2O, that points to essential similarity of the two mixtures. A clathrate-like structure was suggested to explain the experimental results for dilute solutions of the alcohol. Somewhat more pronounced hydrophobic hydration in D2O than in H2O is manifested by an effect similar to that resulting from the elongation of the alcohol molecule. 相似文献
10.
Graham Smith Urs D. Wermuth David J. Young 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(7):o345-o348
In the structure of the 1:1 proton‐transfer compound from the reaction of l ‐tartaric acid with the azo‐dye precursor aniline yellow [4‐(phenyldiazenyl)aniline], namely 4‐(phenyldiazenyl)anilinium (2R,3R)‐3‐carboxy‐2,3‐dihydroxypropanoate, C12H12N3+·C4H5O6−, the asymmetric unit contains two independent 4‐(phenyldiazenyl)anilinium cations and two hydrogen l ‐tartrate anions. The structure is unusual in that all four phenyl rings of the two cations have identical rotational disorder with equal occupancy of the conformations. The two hydrogen l ‐tartrate anions form independent but similar chains through head‐to‐tail carboxyl–carboxylate O—H...O hydrogen bonds [graph set C(7)], which are then extended into a two‐dimensional hydrogen‐bonded sheet structure through hydroxy O—H...O hydrogen‐bonded links. The anilinium groups of the 4‐(phenyldiazenyl)anilinium cations are incorporated into the sheets and also provide internal hydrogen‐bonded extensions, while their aromatic tails are layered in the structure without significant association except for weak π–π interactions [minimum ring centroid separation = 3.844 (3) Å]. The hydrogen l ‐tartrate residues of both anions exhibit the common short intramolecular hydroxy–carboxylate O—H...O hydogen bonds. This work provides a solution to the unusual disorder problem inherent in the structure of this salt, as well as giving another example of the utility of the hydrogen tartrate anion in the generation of sheet substructures in molecular assembly processes. 相似文献
11.
Thermal phenomena at the hydration of calcium sulphate hemihydrate (CaSO4·0.5H2O) are investigated in the paper. Time development of hydration heat of β-calcium sulphate hemihydrate prepared from flue
gas desulphurization (FGD) gypsum is determined using two different types of calorimeter, namely the differential calorimeter
DIK 04 and the isothermal heat flow calorimeter KC 01, and the differences in measured data analyzed. Then, the effects of
plasticizers and hydrophobizers on the hydration process of analyzed gypsum mixtures are studied. 相似文献
12.
We studied the intermolecular interactions in ternary glycerol (Gly)–sample (S)–H2O systems at 25 °C. By measuring the excess partial molar enthalpy of Gly, HGlyEH_{\mathrm{Gly}}^{\mathrm{E}}, we evaluated the Gly–Gly enthalpic interaction, HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}, in the presence of various samples (S). For S, tert-butanol (TBA), 1-propanol (1P), urea (UR), NaF, NaCl, NaBr, NaI, and
NaSCN were used. It was found that hydrophobes (TBA and 1P) reduce the values of HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}} considerably, but a hydrophile (UR) had very little effect on HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}. The results with Na salts indicated that there have very little effect on HGly-GlyEH_{\mathrm{Gly}\mbox{--}\mathrm{Gly}}^{\mathrm{E}}. This contrasts with our earlier studies on 1P–S–H2O in that Na+, F− and Cl− are found as hydration centers from the induced changes on HIP-IPEH_{\mathrm{IP}\mbox{--}\mathrm{IP}}^{\mathrm{E}} in the presence of S, while Br−, I−, and SCN− are found to act as hydrophiles. In comparison with the Hofmeister ranking of these ions, the kosmotropes are hydration centers
and the more kosmotropic the higher the hydration number, consistent with the original Hofmeister’s concept of “H2O withdrawing power.” Br−, I− and SCN−, on the other hand, acted as hydrophiles and the more chaotropic they are the more hydrophilic. These observations hint that
whatever effect each individual ion has on H2O, it is sensitive only to hydrophobes (such as 1P) but not to hydrophiles (such as Gly). This may have an important bearing
towards understanding the Hofmeister series, since biopolymers are amphiphilic and their surfaces are covered by hydrophobic
as well as hydrophilic parts. 相似文献
13.
Nada Kouti‐Hulita Miroslav
egarac 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(3):o171-o173
In the crystal structure of (R)‐N,N‐diisopropyl‐3‐(2‐hydroxy‐5‐methylphenyl)‐3‐phenylpropylaminium (2R,3R)‐hydrogen tartrate, C22H32NO+·C4H5O6−, the hydrogen tartrate anions are linked by O—H⋯O hydrogen bonds to form helical chains built from (9) rings. These chains are linked by the tolterodine molecules via N—H⋯O and O—H⋯O hydrogen bonds to form separate sheets parallel to the (101) plane. 相似文献
14.
《Fluid Phase Equilibria》2005,233(1):34-46
A series of bicanonical ensemble Monte Carlo (BC MC) simulations has been performed to calculate Na+ hydration Gibbs energy in aqueous solution. The hydration Gibbs energy of Na+ ion in aqueous solution is the difference between formation free energies of Na+ (H2O)n and (H2O)n clusters at n → α. The convergence of the hydration free energy to bulk water value is fast, and the results at n = 60 turned out to be in good agreement with experimental ones and those calculated using free energy perturbation method [1]. The ion–water interaction has been described by Aqvist's pair potential [1] and SPC model [2] has been used for water–water interactions. The behaviour of the absolute Gibbs energy, the entropy, the internal energy of the clusters and the development of hydration shells’ structure with the increase of the number of water molecules are discussed. 相似文献
15.
Ruggero Caminiti 《Chemical physics letters》1983,96(3):390-394
X-ray diffraction data from a H2SO4 solution were examined. Peaks in the range 3–5 A in the correlation function reveal the presence of sulphate-H2O interactions. Each sulphate ion interacts with eight water molecules. A model of hydration similar to that present in the crystal structure of H2SO4 - 4H2O is shown to be consistent with these results. 相似文献
16.
Ji-min Yang Jing Peng Yu-xia Duan Chong Tian Mei Ping 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(13):1930-1935
The solubilities in the KCl-MgCl2-H2O system were determined at 50 and 75°C and the phase diagrams and the diagram of refractive index vs composition were plotted. Two invariant point, three univariant curves, and three crystallization zones, corresponding to potassium chloride, hexahydrate (MgCl2 · 6H2O) and double salt (KCl · MgCl2 · 6H2O) showed up in the phase diagrams of the ternary system, The mixing parameters ??K, Ca and ??K, Ca, Cl and equilibrium constant K sp were evaluated in KCl-MgCl2-H2O system by least-squares optimization procedure, in which the single-salt Pitzer parameters of KCl and MgCl2 ??(0), ??(1), ??(2), and C ? were directly calculated from the literature. The results obtained were in good agreement with the experimental data. 相似文献
17.
Jacqueline Therese Rajamathi Sylvia Britto Michael Rajamathi 《Journal of Chemical Sciences》2005,117(6):629-633
A mixed-metal hydroxysalt of formula Cu1.6Zn0.4(OH)3(OAc)·H2O has been synthesized by an acetate hydrolysis route. Acetate ions can be exchanged with simple inorganic anions such as
chloride and nitrate, and organic anions such as benzoate and large surfactant anions such as dodecyl sulphate. Structures
of these hydroxysalts are derived from that of Cu2(OH)3NO3·H2O with some of the Cu2+ ions being replaced by Zn2+. 相似文献
18.
Ray L. Frost Sara J. Palmer Ross Pogson 《Journal of Thermal Analysis and Calorimetry》2012,107(2):549-553
Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral ardealite and to ascertain
the thermal stability of this ‘cave’ mineral. The mineral ardealite Ca2(HPO4)(SO4)·4H2O is formed through the reaction of calcite with bat guano. The mineral shows disorder, and the composition varies depending
on the origin of the mineral. Thermal analysis shows that the mineral starts to decompose over the temperature range of 100–150 °C
with some loss of water. The critical temperature for water loss is around 215 °C, and above this temperature, the mineral
structure is altered. It is concluded that the mineral starts to decompose at 125 °C, with all waters of hydration being lost
after 226 °C. Some loss of sulphate occurs over a broad temperature range centred upon 565 °C. The final decomposition temperature
is 823 °C with loss of the sulphate and phosphate anions. 相似文献
19.
Graham Smith Urs D. Wermuth 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(1):o5-o10
The 1:1 proton‐transfer compounds of l ‐tartaric acid with 3‐aminopyridine [3‐aminopyridinium hydrogen (2R,3R)‐tartrate dihydrate, C5H7N2+·C4H5O6−·2H2O, (I)], pyridine‐3‐carboxylic acid (nicotinic acid) [anhydrous 3‐carboxypyridinium hydrogen (2R,3R)‐tartrate, C6H6NO2+·C4H5O6−, (II)] and pyridine‐2‐carboxylic acid [2‐carboxypyridinium hydrogen (2R,3R)‐tartrate monohydrate, C6H6NO2+·C4H5O6−·H2O, (III)] have been determined. In (I) and (II), there is a direct pyridinium–carboxyl N+—H...O hydrogen‐bonding interaction, four‐centred in (II), giving conjoint cyclic R12(5) associations. In contrast, the N—H...O association in (III) is with a water O‐atom acceptor, which provides links to separate tartrate anions through Ohydroxy acceptors. All three compounds have the head‐to‐tail C(7) hydrogen‐bonded chain substructures commonly associated with 1:1 proton‐transfer hydrogen tartrate salts. These chains are extended into two‐dimensional sheets which, in hydrates (I) and (III) additionally involve the solvent water molecules. Three‐dimensional hydrogen‐bonded structures are generated via crosslinking through the associative functional groups of the substituted pyridinium cations. In the sheet struture of (I), both water molecules act as donors and acceptors in interactions with separate carboxyl and hydroxy O‐atom acceptors of the primary tartrate chains, closing conjoint cyclic R44(8), R34(11) and R33(12) associations. Also, in (II) and (III) there are strong cation carboxyl–carboxyl O—H...O hydrogen bonds [O...O = 2.5387 (17) Å in (II) and 2.441 (3) Å in (III)], which in (II) form part of a cyclic R22(6) inter‐sheet association. This series of heteroaromatic Lewis base–hydrogen l ‐tartrate salts provides further examples of molecular assembly facilitated by the presence of the classical two‐dimensional hydrogen‐bonded hydrogen tartrate or hydrogen tartrate–water sheet substructures which are expanded into three‐dimensional frameworks via peripheral cation bifunctional substituent‐group crosslinking interactions. 相似文献
20.
H. M. Patil D. K. Sawant D. S. Bhavsar J. H. Patil K. D. Girase 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1031-1037
The growth of neodymium tartrate crystals was achieved in silica gel by single diffusion method. Optimum conditions were established
for the growth of good quality crystals. Fourier transform infrared (FT-IR) spectroscopic study indicates the presence of
water molecules and tartrate ligands and suggests that tartrate ions are doubly ionised. The thermal behaviour of the material
was studied using thermogravimetry (TG), differential thermal analysis (DTA), derivative thermogravimetry (DTG) and differential
scanning calorimetry (DSC). Thermogravimetric analysis support the suggested chemical formula of the grown crystal to be Nd2(C4H4O6)3·7H2O, and the presence of seven water molecules as water of hydration. It is shown that the material is thermally stable up 45 °C
beyond which it decomposes through many stages till the formation of neodymium oxide (Nd2O3) at 995 °C. The decomposition pattern is reported to be typical of a hydrated metal tartrate. 相似文献