Infrared studies of water in crystalline hydrates: gypsum, CaSO4•2H2O

1969 ◽  
Vol 47 (8) ◽  
pp. 1361-1368 ◽  
Author(s):  
V. Seidl ◽  
Osvald Knop ◽  
Michael Falk
Keyword(s):  
Hydrogen Bonds ◽  
Isotopic Dilution ◽  
Water Molecules ◽  
Spectral Features ◽  
Vibrational Coupling ◽  
Fundamental Frequencies ◽  
Infrared Studies ◽  
The Difference ◽  
Crystalline Hydrates

Infrared spectra of partially deuterated hydrates yield the fundamental frequencies of isotopically dilute H2O, D2O, and HDO molecules. Isotopic dilution eliminates vibrational coupling and allows the determination of the total number of crystallographically distinct water molecules in the crystal. It also yields the number of distinct symmetric (C2v) and asymmetric (Cs) water molecules. The results for gypsum show that all the water molecules are equivalent and that they are asymmetric, in agreement with crystallographic results. The extent of asymmetry is measured by the difference between the two OH stretching frequencies of HDO molecules, which is 90 cm−1. This corresponds to an estimated difference of 0.02 Å in the [Formula: see text] distances of the two hydrogen bonds. The spectra of partially deuterated gypsum show clearly that spectral features previously explained by the presence of two sets of distinct water molecules or by proton tunnelling, are in fact due to vibrational coupling.

Infrared Studies of Water in Crystalline Hydrates: Sodium Nitroprusside Dihydrate, Na2[Fe(CN)5NO]•2H2O

1971 ◽  
Vol 49 (9) ◽  
pp. 1413-1424 ◽  
Author(s):  
Michaela Holzbecher ◽  
Osvald Knop ◽  
Michael Falk
Keyword(s):  
Water Molecule ◽  
Sodium Nitroprusside ◽  
Infrared Spectra ◽  
Structure Determination ◽  
The Other ◽  
Water Molecules ◽  
Infrared Studies ◽  
Increasing Temperature ◽  
Crystalline Hydrates ◽  
The Ideal

Infrared spectra of polycrystalline Na2[Fe(CN)5NO] 2H2O at different degrees of deuteration were studied as a function of temperature. The single peaks observed for the bending fundamentals of isotopically dilute H2O and D2O show that all the water molecules are equivalent, as required by Manoharan and Hamilton's structure determination; the doublets observed for the three fundamentals of isotopically dilute HDO show that the water molecules are asymmetric. Doublet separation decreases gradually with increasing temperature, indicating decreasing asymmetry. The water molecule appears to orient itself so as to maximize the strength of one [Formula: see text] bond, while the other OH group interacts only very weakly with another CN group. The hitherto unknown extent to which the nitroprusside ion deviates from the ideal C4v symmetry has been estimated from the 13C14N stretching spectrum. The 15N16O and 14N18O stretching spectrum was used to confirm that only one type of NO group is present in the crystal, and hence that all nitroprusside ions are equivalent.

Infrared studies of water in crystalline hydrates: NaClO4•H2O, LiClO4•3H2O, and Ba(ClO4)2•3H2O

1970 ◽  
Vol 48 (13) ◽  
pp. 2096-2103 ◽  
Author(s):  
George Brink ◽  
Michael Falk
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Room Temperature ◽  
Water Molecules ◽  
Weak Hydrogen Bond ◽  
Kcal Mole ◽  
Hydrogen Bond Energy ◽  
Weak Hydrogen Bonds ◽  
Infrared Studies ◽  
Crystalline Hydrates

Infrared spectra of undeuterated and partially deuterated NaclO4•H2O, LiClO4•3H2O, and Ba(ClO4)2•3H2O were examined. Crystallographic data point to a weak hydrogen bond between water molecules and the perchlorate ions in LiClO•3H2O. This is confirmed by the high HDO stretching frequencies for this compound. The nearly identical HDO stretching frequencies in LiClO4•3H2O, NaClO4•H2O, Ba(ClO4)2•3H2O, and in aqueous solutions of these salts show that similar weak hydrogen bonds occur in all three hydrates and in solution. The hydrogen bond energy is of the order of 2 kcal/mole. In all three compounds the water molecules are symmetric at room temperature. At −165° the water molecules become highly distorted in the sodium compound, slightly distorted in the barium compound, and remain undistorted in the lithium compound. Very narrow OD stretching bands are observed, showing that the hydrogen atom positions are ordered in all three hydrates.

Re-investigation of the crystal structure of whewellite [Ca(C2O4)·H2O] and the dehydration mechanism of caoxite [Ca(C2O4)·3H2O]

2005 ◽  
Vol 69 (1) ◽  
pp. 77-88 ◽  
Author(s):  
T. Echigo ◽  
M. Kimata ◽  
A. Kyono ◽  
M. Shimizu ◽  
T. Hatta
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Structure Refinement ◽  
Structural Features ◽  
Infrared Analysis ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Direct Transformation ◽  
Dehydration Mechanism ◽  
The Difference

AbstractThe crystal structure of whewellite [Ca(C2O4)·H2O] and the dehydration mechanism of caoxite [Ca(C2O4)·3H2O] have been studied by means of differential thermal analysis, X-ray diffraction (powder and single-crystal) analysis and infrared analysis. The first and second analyses confirmed the direct transformation of caoxite into whewellite without an intermediate weddellite [Ca(C2O4)·2H2O] stage. Infrared spectra obtained from caoxite, weddellite and whewellite emphasize the similarity of the O–H-stretching band and O–C–O-stretching band in whewellite and caoxite and the unique bands of weddellite. The structure refinement at low temperature (123 K) reveals that all the hydrogen atoms of whewellite form hydrogen bonds and the two water molecules prop up the crystal structure by the hydrogen bonds that cause a strong anisotropy of the displacement parameter.Comparing the structural features of whewellite with those of weddellite and caoxite suggests that caoxite and whewellite have a sheet structure consisting of Ca2+ ions and oxalate ions although weddellite does not. It is additionally confirmed that the sheets of caoxite are corrugated by hydrogen bonds but whewellite has flat sheets. The corrugated sheets of caoxite would be flattened by dehydration so the direct transformation of caoxite into whewellite would not occur via weddellite. Essential for this transformation is the dehydration of interlayered water molecules in caoxite leading to the building of the crystal structure of whewellite on its intralayered water molecules. The difference in conformation of water molecules between those two crystal structures may explain the more common occurrence of whewellite than of caoxite in nature.

Infrared Studies of Water in Crystalline Hydrates: K2CuCl4•2H2O

1974 ◽  
Vol 52 (7) ◽  
pp. 1029-1041 ◽  
Author(s):  
Gwen H. Thomas ◽  
Michael Falk ◽  
Osvald Knop
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Infrared Spectra ◽  
Vibrational Spectra ◽  
Distinct Type ◽  
Vibrational Coupling ◽  
Infrared Studies ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline K2CuCl4•2H2O at different degrees of deuteration were recorded, between 4000 and 300 cm−1, at temperatures from −160 to 90 °C. The spectra confirm the existence of only one crystallographically distinct type of water molecule in the structure, on sites of symmetry C2r. Vibrational coupling of the bending fundamentals of the water molecule has been analyzed in detail. It is shown that the existence and magnitude of such coupling may be used to predict, from the spectrum of a hydrate, the manner in which a water molecule participates in the crystal structure. The structure and the vibrational spectra of K2CuCl4•2H2O are compared with those of the closely related CuCl2•2H2O.

Determination of Interproton Distances in Water Molecules of Crystalline Hydrates by IRS Data

1977 ◽  
Vol 10 (7) ◽  
pp. 603-607
Author(s):  
R. N. Pletnev ◽  
O. V. Koryakova ◽  
V. V. Gorshkov ◽  
L. A. Perelyaeva
Keyword(s):  
Water Molecules ◽  
Interproton Distances ◽  
Crystalline Hydrates

Infrared Spectra of Water in Crystalline Hydrates: KSnCl3•H2O, an Untypical Monohydrate

1974 ◽  
Vol 52 (16) ◽  
pp. 2928-2931 ◽  
Author(s):  
Michael Falk ◽  
Chung-Hsi Huang ◽  
Osvald Knop
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Room Temperature ◽  
Water Molecules ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline KSnCl3•H2O were recorded between 4000 and 300 cm−1 at different degrees of deuteration and at temperatures between 30 and −160 °C. At low temperatures the spectra show a complexity indicative of the presence of several crystallographically distinct water molecules. These molecules occupy sites with nearly identical environments and at room temperature are spectroscopically indistinguishable. The environment of each of these molecules is asymmetric. Hydrogen bonds are very weak and probably highly bent. The water molecules are less separated from one another than in K2SnCl4•H2O and may share their potassium neighbors.

scholarly journals X-Ray Determination of the Structure of Ice IV

1978 ◽  
Vol 21 (85) ◽  
pp. 51-53 ◽  
Author(s):  
Hermann Engelhardt ◽  
Barclay Kamb
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Structural Feature ◽  
Unit Cell ◽  
Water Molecules ◽  
X Ray ◽  
Rhombohedral Unit Cell ◽  
Bond Network ◽  
Ice Phase

AbstractIce IV, a wholly metastable ice phase, has a structure based on a framework of tetrahedrally hydrogen-bonded water molecules in a rhombohedral unit cell. The structure involves two non-equivalent types of water molecules and four non-equivalent types of hydrogen bonds. A novel structural feature is a hydrogen bond that passes through the center of a 6-ring of water molecules and links non-adjacent structural layers. The bond network is proton-disordered, even after quenching.

scholarly journals Redetermination of nickel(II) formate dihydrate

IUCrData ◽  
2018 ◽  
Vol 3 (3) ◽  
Author(s):  
Matthias Weil
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Structure Determination ◽  
Three Dimensional ◽  
The Other ◽  
Water Molecules ◽  
Hydrogen Bonding Pattern ◽  
Medium Strength

In comparison with the previous structure determination of poly[diaquadi-μ-formato-nickel(II)], [Ni(HCOO)2(H2O)2]n, based on Weissenberg film data [Krogmann & Mattes (1963).Z. Kristallogr.118, 291–302], the current redetermination from modern CCD data revealed the positions of the H atoms, thus making a detailed description of the hydrogen-bonding pattern possible. Both Ni2+cations in the crystal structure are located on inversion centres and are octahedrally coordinated. One Ni2+cation is bound to six O atoms of six formate anions whereas the other Ni2+cation is bound to four O atoms of water molecules and to two formate O atoms. In this way, the formate anions bridge the two types of Ni2+cations into a three-dimensional framework. O—H...O hydrogen bonds of medium strength between water molecules and formate O atoms consolidate the packing.

Infrared studies of water in crystalline hydrates: K2HgCl4.H2O

1977 ◽  
Vol 55 (10) ◽  
pp. 1736-1744 ◽  
Author(s):  
Michael Falk ◽  
Osvald Knop
Keyword(s):  
Hydrogen Bond ◽  
Neutron Diffraction ◽  
Bond Distance ◽  
Single Type ◽  
Water Molecules ◽  
Dynamic Coupling ◽  
X Ray ◽  
Hydrogen Bond Distance ◽  
Infrared Studies ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline K2HgCl4.H2O at different degrees of deuteration were recorded, in the 4000–250 cm−1 region, at temperatures between liquid-nitrogen and 130 °C. The spectra confirm the existence of a single type of water molecule, engaged in two equivalent hydrogen bonds. The value of 2548 cm−1 for the isolated O—D stretching frequency leads to an estimate of 3.25(3) Å for the O … Cl hydrogen-bond distance, in excellent agreement with the results of X-ray and neutron diffraction. Dynamic coupling is appreciable for stretch, bend, and librational fundamentals but is weaker than in CuCl2.2H2O or K2CuCl4.2H2O, in which the water molecules in the crystal are more tightly bonded.A number of corrected values are reported of isolated O—D stretching frequencies in hydrates studied previously.

scholarly journals VERY LOW H–O–H BENDING FREQUENCIES. VI. VIBRATIONAL SPECTRA OF CdCl2·H2O

2017 ◽  
Vol 38 (1) ◽  
pp. 91
Author(s):  
Viktor Stefov ◽  
Metodija Najdoski ◽  
Bernward Engelen ◽  
Zlatko Ilievski ◽  
Adnan Cahil
Keyword(s):  
Hydrogen Bonds ◽  
Water Molecule ◽  
Gas Phase ◽  
Raman Spectra ◽  
Structural Data ◽  
Liquid Nitrogen Temperature ◽  
Water Molecules ◽  
Deuterium Content ◽  
Infrared And Raman Spectra ◽  
The Difference

The infrared and Raman spectra of CdCl2·H2O as well as those of a series of its partially deuterated analogues were recorded at room and at liquid-nitrogen temperature (RT and LNT, respectively). The combined results from the analysis of the spectra were used to assign the observed bands. In the difference IR spectrum of the compound with low deuterium content (≈ 4 % D) recorded at RT, one broad bands is observed at around 2590 cm–1 while in the LNT spectrum two bands appear (at 2584 cm–1 and 2575 cm–1). The appearance in the LNT spectrum of these two bands which are due to the stretching OD modes of the isotopically isolated HDO molecules points to the existance of two crystallographically different hydrogen bonds and is in accordance with the structural data for this compound. In the LNT infrared and Raman spectra of the protiated compound, one band, at 1583 cm-1, is observed in the region of the bending НОН vibrations with a frequency that is decreasing with lowering the temperature. An interesting finding related to this band is that its frequency is lower than that for the water molecule in the gas phase (1594 cm–1). In the RT and LNT IR spectra, only one strong band (at 560 cm–1) is observed in the region of the librations of water molecules (700 cm–1 – 400 cm–1).

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