OH Stretching Vibration Band Research Articles

Raman spectra of water in fluid inclusions: II. Effect of negative pressure on salinity measurement

Salinity of fluid inclusions is usually determined by microthermometry, but it becomes unsuitable in case of metastability of the aqueous fluid because of thermodynamics indetermination. Raman microspectrometry of water in individual aqueous fluid inclusions can provide chemical information about fluid composition, in particular the concentration of chloride ions. The regular method consists in correlating the deformation of the OH stretching vibration band of liquid water in the region assigned to hydrogen‐bonded OH groups, with chloride concentration. In order to evaluate the ability of Raman spectroscopy to determine salinity of metastable fluid inclusions, the Raman spectra of water trapped in two natural fluid inclusions were recorded at various temperatures in two physical states of the liquid phase, at equilibrium with vapor or metastable at negative pressure. The difference in salinity measured in the two states increased when temperature decreased, i.e. when the intensity of metastability increased. Metastability was then expressed in negative pressure scale (MPa) by thermodynamic modeling of the fluid trapped in the inclusions and correlated to salinity relative difference. The quantification of this effect led us to conclude that salinity expressed in mass% NaCleq. was overestimated of about 1% per 10–15 MPa of negative pressure. If the negative pressure can be quantified, it is thus possible to determine the salinity of metastable fluid inclusions by Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.

Liquid phase temperature determination in dense water sprays using linear Raman scattering

Linear Raman scattering has been applied for the determination of the temperature of the liquid phase in water sprays under normal and superheated conditions. The envelope of the Raman OH-stretching vibration band of water is deconvoluted into five Gaussian peaks which can be assigned to five different intermolecular interactions (hydrogen bonding). The intensity of each of the peaks is a function of the temperature and the phase of the water under investigation. The interference of the Raman signals originating from the water vapor is eliminated from the Raman signals originating from the liquid water. Consequently the temperature of the liquid water droplets surrounded by water vapor is accessible which is favorable for the investigation of non-equilibrium sprays where the droplet temperature is different to the vapor temperature.

X-Ray Diffraction and Vibrational Spectroscopic Characteristics of Hydroxylclinohumite from Ruby-Bearing Marbles (Luc Yen District, Vietnam)

A honey-yellow hydroxylclinohumite from ruby-bearing marbles of the Luc Yen district in northern Vietnam was characterized by electron microprobe (EPMA), single-crystal X-ray diffraction (XRD), micro-Raman, and Fourier-transform infrared (FTIR) spectroscopy. The studied crystals correspond to nearly ideal clinohumite with the structural formula 4[Mg2SiO4]·[(Mg,Fe,Ti)(OH,F)2] and roughly equal F and OH proportions. Crystal structure analysis showed Ti substitution for Mg only at the Mg3 site. A Fourier-difference map revealed one hydrogen site associated with ninth oxygen atom. The calculated O–H bond distance was shorter than that in other natural clinohumites. FTIR revealed bands corresponding to combination of OH-stretching with Mg–OH and/or Fe–OH bending modes, combinations of OH−and Fe–OH vibrations, combination of fundamental bands of the Si–OH bonding, combination of OH−and Si–OH vibrations, and first (2νOH) and the second (3νOH) overtones of the OH-stretching vibration mode. Two groups of OH-stretching vibration and FTIR absorption bands at 3390–3420 cm−1and 3560–3580 cm−1show reversible temperature-dependent shift. The low-frequency bands absent in pure synthetic hydroxylclinohumites are assigned to OH-planar defects caused by Ti-for-Mg substitution.

Single-step synthesis of a new series of meso di-Mannich bases from the cyclic aminal (2S,7R,11S,16R)-1,8,10,17-tetraazapentacyclo[8.8.1.1.8,170.2,7011,16]icosane and p-substituted phenols

BackgroundThe results presented herein show that the cyclic aminal (2S,7R,11S,16R)-1,8,10,17-tetraazapentacyclo[8.8.1.1.8,170.2,7011,16]icosane (6), derived from cis-(meso)-1,2-diaminocyclohexane and formaldehyde, is a suitable substrate for the preption of a series of cis-meso Mannich bases such as 8a-l by reaction with p-substituted phenols 7a-l in basic media. These compounds are valuable synthetic products and may find application in asymmetric catalysis.ResultsThe products were characterized principally by NMR and IR spectroscopy. Both the benzylic and aminalic protons of the perhydrobenzimidazolidine moiety were diastereotopic due to the presence of stereogenic nitrogen centers. The occurrence of intramolecular hydrogen bonding interactions was confirmed by the broad OH stretching vibration band in the IR spectra. Vibrational spectra were calculated using B3LYP at 6-31G(d,p) level, and the calculated frequencies for the νOH vibrations were compared to those of the experimental spectra. Hydrogen bonding interactions in the solid state were observed through the X-ray crystallography of 8j. Additionally, Mulliken charges and Fukui indices for 6 were calculated as theoretical descriptors of electrophilicity.ConclusionA new series of meso Mannich bases called 4,4′-disubstituted-2,2′-{[(3aR,7aS)-2,3,3a,4,5,6,7,7a-octahydro-1H-1,3-benzimidazole-1,3-diyl]bis(methylene)} diphenols (8a-l) which are derived from cis-(meso)-1,2-diaminocyclohexane, were obtained from cyclic aminal 6. These results confirmed the behavior of 6 as an electrophilic preformed reagent in Mannich reactions in basic media.

Comparison of the sensitivities of IR absorption and raman scattering spectra to hydrogen bonding in methanol

The sensitivity of infrared (IR) absorption and Raman scattering (RS) spectra to hydrogen bonding in methanol is quantified by a comparative sensitivity factor, which can be expressed as the K = (Ib/Iub)IR/(Ib/Iub)RS, where the indices b and ub refer to H-bonded and unbound (free) OH groups, respectively. The resulting value for methanol, K ∼ 20, is identical to that found previously for n-butanol, although the methods of measuring the degree of hydrogen bonding for these two alcohols were quite different. It is shown that, in some cases, Raman spectra can be converted to IR absorption spectra and vice versa. It is important for understanding differences in the shapes of OH stretching vibration bands in IR absorption and Raman spectra.

Brucite, Mg(OH)2におけるOH伸縮振動赤外吸収ピークに及ぼす化学組成の影響

Brucite, Mg(OH)2におけるOH伸縮振動赤外吸収ピークに及ぼす化学組成の影響

Infrared transmission and emission spectroscopic study of selected Chinese palygorskites

Infrared transmission and emission spectroscopy were used to analyze the difference in structure and thermal behavior of two Chinese palygorskites. The position of the main bands identified in the infrared spectra of the palygorskites studied is similar for these two Chinese samples, but there are some differences in their intensity, which is significant. This discrepancy is attributed to the existence of impurities and the geological environments in different regions. The infrared emission spectra clearly show the structural changes and dehydroxylation of the palygorskites when the temperature is raised. The dehydration of the palygorskites is followed by the loss of intensity of the OH stretching vibration bands in the region of 3600–3200 cm −1. Dehydroxylation is followed by the decrease in intensity in the bands between 3700 and 3550 cm −1. Dehydration of pure palygorskite was completed by 600 °C. Partial loss of coordinated water was observed at 400 °C. Infrared emission spectroscopy is an effective method to determine the stability of the mineral.

Synthesis and Thermal Properties of Etherified Konjac Glucomannan

A novel etherified KGM (EKGM) was synthesized with Konjac glucomannan (KGM) and 1-bromopropane in Lithium chloride/dimethyl sulfoxide (LiCl/DMSO). The EKGM was characterized by FT-IR, DSC and TG. The IR of EKGM showed that –OH stretching vibration band decreased and the C–H and C–O–C stretching vibration bands increased comparing with the unmodified KGM, which was indicating that KGM had been etherified. The DSC thermograms showed that an obvious glass transition of EKGM appeared and its glass transition temperature (Tg) decreased with the increasing of Pr/OH ratio. And it was also found that the EKGM had a higher decomposition temperature than unmodified. Meanwhile, it was proved that the EKGM was a good hydrophobic polymer and dissolved in some organic solvent easily.

Perturbations of Water by Alkali Halide Ions Measured using Multivariate Raman Curve Resolution

Polarized Raman spectroscopy, combined with multivariate curve resolution (MCR), is used to measure the influence of dilute alkali halide ions on the OH stretch vibrational band of water. The frequency and integrated intensity of the resulting hydration shell OH bands are found to increase with increasing anion size. Comparisons of results obtained from salt solutions in H(2)O and HOD/D(2)O imply that ion-water interactions reduce the influence of resonance coupling on the OH stretch band of H(2)O. Polarized Raman results indicate that the hydration shell of F(-) gives rise to a nearly perfectly polarized OH stretch band, while large anions produce larger depolarization.

Water speciation in sodium silicate glasses based on NIR and NMR spectroscopy

Water speciation in hydrated Na 2O·2SiO 2 (NS2), Na 2O·4SiO 2 (NS4), and Na 2O·6SiO 2 (NS6) glasses was analyzed by near-infrared (NIR) spectroscopy and low temperature static 1H nuclear magnetic resonance (NMR) spectroscopy. For each composition 6–9 glasses containing between 0.5 and 7.0 wt.% total water (measured by Karl–Fischer titration) were used to calibrate the molar absorption coefficients for the NIR combination bands near 4500 cm − 1 (OH groups) and near 5200 cm − 1 (H 2O molecules). Noticeable disagreement was found between the water speciation derived from NIR spectra using an internally consistent calibration based on total water content and the water speciation determined by 1H NMR spectroscopy. The discrepancies are more pronounced for the evaluation of NIR peak areas (differences up to 55% in OH group content) than for the evaluation of peak heights (differences up to 35% in OH group content). Based on the NMR data we performed a new calibration for the NIR combination bands of the hydrous sodium silicate glasses. The molar absorption coefficients for the 4500 cm − 1 band ( ε 4500) and the 5200 cm − 1 band ( ε 5200) noticeably decrease with increasing Na 2O content of the glasses from NS6 to NS2. The ε values for both bands also decrease with total water content in NS4 and NS6 glasses. The variation of ε values may be due to changes in the relative abundance of water subspecies, i.e. species exposed to strong or weak hydrogen bonding. Another explanation could be an incomplete separation of the combination bands from the tail of the fundamental OH stretching vibration bands and from the unassigned water-related band at 4000 cm − 1 . Using the NMR-supported NIR calibration we calculated water species concentrations in the sodium silicate glasses as a function of total water content. At a total water content of 6.0 wt.%, the amount of water dissolved as OH groups is noticeably higher in the depolymerized glasses NS2 and NS4 (∼ 3.0 wt.%) than in the less depolymerized NS6 (∼ 2.5 wt.%). This observation implies that non-bridging oxygen, charge-compensated by sodium, promotes the formation of OH groups. No significant difference in water speciation was found between rapidly quenched glasses (∼ 150 K/s) and more slowly cooled glasses (∼ 2 K/s).

Quantification of dissolved H 2O in silicate glasses using confocal microRaman spectroscopy

Application of confocal microRaman spectroscopy for quantification of total water content and water speciation was tested for hydrous glasses of various compositions (haplogranite, albite, tonalite, peralkaline rhyolite, dacite, andesite, basalt). Glasses with water contents between 0.5 and 11 wt.% were synthesized in internally heated gas pressure vessels. Total water contents of the glasses were measured by Karl–Fischer titration and IR spectroscopy. To quantify the total water content ( C H 2O t ) by Raman spectroscopy either the integrated intensity of the OH stretching vibration band at 3550 cm − 1 ( A ⁎ 3550) was used directly or A ⁎ 3550 was scaled to low wavenumber Raman bands. A very high reproducibility of A ⁎ 3550 could be achieved with a stand alone Raman microscope LabRam 010. A single regression line reproduces the data of all samples with a 2 σ variation of 1.2 wt.%. However, slightly different trends are observed for polymerized compositions (haplogranite, albite, tonalite), intermediate compositions (dacite, andesite) and depolymerized compositions (basalt) in plots of A ⁎ 3550 vs. water content, implying that the Raman cross section of dissolved hydrous species depends on glass composition. In measurements with a Raman spectrometer T64000, A ⁎ 3550 depends largely on measurement conditions. A good reproducibility could be achieved only by normalizing the OH band intensity with low wavenumber bands. Such an approach has the advantage to eliminate at least partially effects of specific measurement conditions and, hence, opening the possibility to apply the Raman calibration to another spectrometer. For silicic glasses scaling to the area of T–O– T bending band near 500 cm − 1 ( A ⁎ 500) yields the best results. Data for albite, haplogranite and dacite (11 samples, 37 spectra) covering a range of 0.8–7.3 wt.% H 2O are reproduced with a 2 σ standard deviation of 0.16 wt.% H 2O by C H 2 O t ( wt. % ) = 0.28 + 5.135 · A 3550 ⁎ A 500 ⁎ For intermediate and depolymerized compositions the T–O stretching band near 1000 cm − 1 is more intensive than the T–O– T bending band near 500 cm − 1 and, hence, it is more convenient for calibration. Data for andesite and basalt (14 samples, 22 spectra) covering a range of 0.5 to 4.7 wt.% H 2O are reproduced with a 2 σ stand deviation of 0.18 wt.% H 2O by C H 2 O t ( wt. % ) = 3.66 · A 3550 ⁎ A 1000 ⁎ Attempts to determine the relative abundance of OH groups and H 2O molecules in the glasses by decomposing the OH stretching Raman band into 3–5 Gaussians are not consistent with water speciation data derived from near-infrared spectroscopy. We suggest that the intensity growth with water content in the low wavenumber region of the 3550 cm − 1 band reflects only enhanced hydrogen bonding but is not related to the relative abundance of water species.

Solvatochromism of Heteroaromatic Compounds: XXV. Effect of Bifurcate Hydrogen Bond with a Weak Intramolecular Component on the IR, NMR, and UV Spectra of 2,6-Dibromo-4-nitrophenol

Dissolution of 2,6-dibromo-4-nitrophenol in aprotic protophilic solvents forms a three-center solvation H-complex with a sharply weakened intramolecular hydrogen bond. This weakening is associated with a deformation of the bond angle of the hydroxy group. It is only on interaction with weak π-bases that the intramolecular component of the bifurcate hydrogen bond appreciably affects the spectral position of the OH stretching vibration band; this results in a nonlinear dependence between $$\vee$$ OH and the Kamlet-Taft sol-vatochromic parameter.

Influence of molecular hydrogen diffusion on concentration and distribution of hydroxyl groups in silica fibers

To study the hydroxyl (OH)-group contamination mechanisms in silica-based optical fibers, the transmission spectra of substrate tubes and fiber preforms made from various types of silica glasses ("Suprasil F-300," KS-4V, and KUVI) are measured by the method of infrared Fourier spectroscopy in a wavelength region of 2-5 /spl mu/m. Due to the intensity of the fundamental OH stretching vibration band, the absorption coefficient, concentration, and a distribution profile of OH groups across the aforesaid samples are calculated. It is found that using an oxyhydrogen burner in the modified chemical vapor deposition (MCVD) process of manufacturing preforms and fiber drawing, the main source of impurity OH groups can be the molecular hydrogen H/sub 2/ penetrating into glass much deeper than the OH groups diffusing from the substrate tube surface. A simple model explaining the formation and diffusion of OH groups into a fiber core and cladding is proposed. It is shown that heating tubes and preforms in a flame of oxyhydrogen burner during fiber fabrication causes a significant OH-group content growth (almost by two orders of magnitude) near to the outer preform surface. Using substrate tubes made from Suprasil F-300 glass, optical fibers are fabricated having a silica core and fluorosilicate reflecting cladding with optical losses of 0.3 dB/km at 1.55 /spl mu/m and a refractive-index difference between core and cladding /spl sim/1/spl middot/10/sup -2/.

Investigation of Chinese archaic jade by PIXE and μRaman spectrometry

External-beam particle-induced X-ray emission (PIXE) and μRaman spectrometry were used for elemental and structural studies of Chinese archaic nephrite jades of the Guimet Asian Museum in Paris in a non-destructive way. Nephrite is a variety of tremolite–actinolite of the amphibole group, with variable iron and magnesium contents. In the present work, in addition to identification of materials, the cation distribution in nephrite was investigated. Cation order–disorder is related to thermodynamic properties of minerals, and hence associated with geological conditions of the mineral formation. Besides, it plays an important role in the mechanism of coloration. So far, little work has been done on the cation distribution in nephrite. We thus initiated this research expecting to answer open questions concerning art and archaeological issues such as jade provenance and colour. The OH stretching vibration band of nephrite, depending on the electronegativity of the bonded cations, presents a fine structure. The study of this fine structure, together with the total cation content obtained by PIXE, allows estimation of the cation distribution in nephrite. In this study, six jade artefacts, dated from the Neolithic period to the Han dynasty (about 3000 BC to 220 AD), with diverse colours including white, yellow-green, green, dark green and black, were analysed. The data obtained permits establishing a geological database for determination of nephrite provenance and explaining the correlation between colour and cation distribution.

Determination of molar absorptivity of IR fundamental OH-stretching vibration in rhyolitic glasses

Molar absorptivity of the infrared (IR) fundamental OH-stretching vibration band at 3550 cm-1 was determined for rhyolitic glasses. Five obsidian samples, unheated and heated at 500-700 °C using an internally heated pressure vessel, were used to evaluate the dependence of the molar absorptivity and final quenched H2O speciation on H2O contents and temperature. Water contents of the obsidians were measured by Karl-Fischer titration first, then the amount of unextracted H2O was calibrated by IR spectroscopy and a conventional vacuum extraction method. Total H2O contents of the obsidians were determined to be 0.24-1.25 wt%. IR spectra of the unheated and heated obsidian samples were obtained using an FT-IR microspectrometer. We determined the molar absorptivity for the 3550 cm-1 band to be 75 ± 4 L/mol/cm without significant dependence on the H2O contents and heating temperature. This value can be used to determine precise H2O contents up to 1.25 wt% in rhyolitic volcanic glasses.

In situFTIR Assessment of Desiccation-Tolerant Tissues

This essay shows how Fourier transform infrared (FTIR) microspectroscopy can be applied to study thermodynamic parameters and conformation of endogenous biomolecules in desiccation-tolerant biological tissues. Desiccation tolerance is the remarkable ability of some organisms to survive complete dehydration. Seed and pollen of higher plants are well known examples of desiccation-tolerant tissues. FTIR studies on the overall protein secondary structure indicate that during the acquisition of desiccation tolerance, plant embryos exhibit proportional increases inα-helical structures and thatµ-sheet structures dominate upon drying of desiccation sensitive-embryos. During ageing of pollen and seeds, the overall protein secondary structure remains stable, whereas drastic changes in the thermotropic response of membranes occur, which coincide with a complete loss of viability. Properties of the cytoplasmic glassy matrix in desiccation-tolerant plant organs can be studied by monitoring the position of the OH-stretching vibration band of endogenous carbohydrates and proteins as a function of temperature. By applying these FTIR techniques to maturation-defective mutant seeds ofArabidopsis thalianawe were able to establish a correlation between macromolecular stability and desiccation tolerance. Taken together,in situFTIR studies can give unique information on conformation and stability of endogenous biomolecules in desiccation-tolerant tissues.

Hydrothermal Synthesis and Characterization of Sodium Manganese Oxo-Phosphate Na2Mn2O(PO4)2·H2O

Sodium manganese oxo-phosphate Na2Mn2O(PO4)2·H2O (MPOS-3) has been prepared in single-crystal and polycrystalline forms by hydrothermal methods. The crystal structure was determined from a 15 × 15 × 80 μm crystal with synchrotron radiation. In the structure, zigzag edge-sharing MnO6 octahedral chains are connected by PO4 tetrahedra to form two-dimensional planes. A second PO43- group sticks out of the planes by sharing three apexes with three MnO6 octahedra of a zigzag chain. The fourth apex of this PO43- groups interacts strongly with sodium ions that are located between the two-dimensional planes. The sodium ions are exchangeable. Ion exchanging half of the Na+ with Ca2+ expands the surface area from 17 to 45 m2/g. MPOS-3 loses water at about 220 °C. The dehydrated form is stable up to 550 °C, above which O2 is liberated. The FTIR spectrum shows two distinct −OH stretching vibration bands, one at 3627 cm-1 and another at 3437 cm-1. MPOS-3 also demonstrates catalytic activity in oxidation of 2-propanol by air to produce acetone. Carbon dioxide is the only byproduct. Preliminary results show 27% conversion of 2-propanol at 450 °C with 65% selectivity toward acetone.

Organization of water molecules by adhering to oriented layers of dipalmitoylphosphatidyl serine in the presence of varying concentrations of cholesterol

About seven water molecules adhere to one molecule of dipalmitoylphosphatidyl serine (DPPS) in an oriented surface layer as inferred from the increase of the dichroic ratio R of their OH stretching vibration band (3400 cm −1) from 2 in the random bulk state to about 2.8 when adhering to DPPS. In DPPS–cholesterol mixtures the number of water molecules adhering to the phospholipid molecules and oriented by them increases as cholesterol content increases. This increase is very steep between molar fractions of cholesterol X(chol)=0.2–0.4 and at X(chol)=0.6 about 13 water molecules adhere and are oriented by one DPPS molecule.

Properties of proteins and the glassy matrix in maturation‐defective mutant seeds ofArabidopsis thaliana

In situ Fourier transform infrared microspectroscopy was used to study the heat stability of proteins and hydrogen bonding interactions in dry maturation-defective mutant seeds of Arabidopsis thaliana. alpha-Helical, turn and beta-sheet conformations were the major protein secondary structures in all of these seeds. On heating, intermolecular extended beta-sheet structures, typical of protein denaturation, were formed in abscisic acid-insensitive (abi3) and leafy cotyledon (lec) mutant seeds. Proteins in dry wild-type seeds did not denature up to 150 degrees C, but those in dry desiccation-sensitive, lec1-1, lec1-3 and abi3-5 seeds did at 68, 89 and 87 degrees C, respectively. In the desiccation-tolerant abi3-7 and abi3-1 seeds, denaturation commenced above 120 and 135 degrees C, respectively. Seeds of the aba1-1 abi3-1 double mutant showed signs of denaturation already upon drying. The molecular packing in the seeds was studied by observing the shift in the position of the OH-stretching vibration band with temperature. The maximal rate of change of this band with temperature was much higher in the desiccation-sensitive abi3-5, aba1-1 abi3-1, lec1-1, and lec1-3 mutant seeds than in the desiccation-tolerant wild-type, abi3-1, abi3-7, and lec2-1 seeds. We interpret this to mean that the molecular packing density is higher in dry desiccation-tolerant than in dry desiccation-sensitive seeds, which is associated with a higher or lower protein denaturation temperature, respectively. The results are discussed in relation to the physiological and biochemical characteristics of these mutant seeds.

Fourier Transform Infrared Investigation of Water States in Aerosol-OT Reverse Micelles as a Function of Counterionic Nature

A Fourier transform infrared study of the states of water included in reverse micelles made from Aerosol-OT (AOT) in isooctane is carried out for the whole sequence of alkali metal counterions as a function of the water content. The decomposition of the aqueous pool of these micelles into “bound” and “free” water is assumed. Two independent methods are applied for the purpose of interpreting the shape and the intensity of the water OH stretching vibration band. The modelization of the OH stretching band by three Gaussian components is retained as the most efficient decomposition and as an adequate smoothing method. To determine the number of water molecules bound per AOT polar head, three water adsorption models are tested for their ability to fit of the experimental data, to reproduce the effect of the AOT concentration, and to indicate the influence the counterion forming the ion pair with AOT. A Langmuir adsorption isotherm model satisfies best these criteria. The results suggest that the hydration pro...