Application of IR spectroscopy in the analysis of the woody-fibrous mass in the process of hydrolysis

The possibility has been shown of using IR spectroscopy in the investigation of the changes in the polysaccharide component of wood in the process of acid hydrolysis. The method of determining the relative optical density (ROD) was used for the quantitative evaluation of the changes in the functional groups of the lignocellulose.     

Kinetics of the hydrolysis of woody-fibrous mass

The possibility has been shown of obtaining fodder additives by the hydrolysis of woody-fibrous mass with dilute sulfuric acid solutions. The kinetics of hydrolysis have been studied, a calculation has been made of the effective rate constants of hydrolysis of the polysaccharide part of the woody-fibrous mass, and the range of variation of the effective activation energy of the process has been determined.     

Kinetics of the hydrolysis of woody-fibrous mass

The possibility has been shown of obtaining fodder additives by the hydrolysis of woody-fibrous mass with dilute sulfuric acid solutions. The kinetics of hydrolysis have been studied, a calculation has been made of the effective rate constants of hydrolysis of the polysaccharide part of the woody-fibrous mass, and the range of variation of the effective activation energy of the process has been determined.Deceased.Siberian Scientific Research Institute of Cellulose and Board, Bratsk. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 687–690, September–October, 1990.     

Identification of the products of partial hydrolysis of silicon tetrafluoride by matrix isolation IR spectroscopy

Matrix isolation Fourier transform IR spectroscopy has been used for studying the products and mechanism of the silicon tetrafluoride reaction with water at various component ratios and reaction durations. Assignment of new bands in the spectrum confirms the earlier assumptions of first the formation of a molecular complex with water and later of trifluorosilanol, which finally condenses to give hexafluorodisiloxane.     

Photoacoustic spectroscopy for process analysis

Photoacoustic spectroscopy (PAS) is based on the absorption of electromagnetic radiation by analyte molecules. The absorbed energy is measured by detecting pressure fluctuations in the form of sound waves or shock pulses. In contrast to conventional absorption spectroscopy (such as UV/Vis spectroscopy), PAS allows the determination of absorption coefficients over several orders of magnitude, even in opaque and strongly scattering samples. Small absorption coefficients, such as those encountered during trace gas monitoring, can be detected with cells with relatively short pathlengths. Furthermore, PA techniques allow absorption spectra of solid samples (including powders, chips or large objects) to be determined, and they permit depth profiling of layered systems. These features mean that PAS can be used for on-line monitoring in technical processes without the need for sample preparation and to perform depth-resolved characterization of industrial products. This article gives an overview on PA excitation and detection schemes employed in analytical chemistry, and reviews applications of PAS in process analytical technology and characterization of industrial products.     

Fourier self-deconvolution in IR spectroscopy

Fourier self-deconvolution (FSD) is a mathematical means for reducing bandwidths, so that overlapped bands can be resolved from one another. The principles of FSD are described briefly, and examples are shown of how overlapped infrared spectra can be enhanced so as to greatly improve their information content. The disadvantages of FSD are discussed and it is shown how the method can be extended to extract individual components from a composite envelope of bands.     

Electrospray ionization mass spectrometry for the hydrolysis complexes of cisplatin: implications for the hydrolysis process of platinum complexes

Non‐enzyme‐dependent hydrolysis of the drug cisplatin is important for its mode of action and toxicity. However, up until today, the hydrolysis process of cisplatin is still not completely understood. In the present study, the hydrolysis of cisplatin in an aqueous solution was systematically investigated by using electrospray ionization mass spectrometry coupled to liquid chromatography. A variety of previously unreported hydrolysis complexes corresponding to monomeric, dimeric and trimeric species were detected and identified. The characteristics of the Pt‐containing complexes were investigated by using collision‐induced dissociation (CID). The hydrolysis complexes demonstrate distinctive and correlative CID characteristics, which provides tools for an informative identification. The most frequently observed dissociation mechanism was sequential loss of NH₃, H₂O and HCl. Loss of the Pt atom was observed as the final step during the CID process. The formation mechanisms of the observed complexes were explored and experimentally examined. The strongly bound dimeric species, which existed in solution, are assumed to be formed from the clustering of the parent compound and its monohydrated or dihydrated complexes. The role of the electrospray process in the formation of some of the observed ions was also evaluated, and the electrospray ionization‐related cold clusters were identified. The previously reported hydrolysis equilibria were tested and subsequently refined via a hydrolysis study resulting in a renewed mechanistic equilibrium system of cisplatin as proposed from our results. Copyright © 2017 John Wiley & Sons, Ltd.     

Vibronic spectroscopy of the peroxyacetyl radical in the near IR

The A 2A'<--X 2A" electronic transition of the peroxyacetyl radical (PA) is observed employing NIR/VUV ion enhancement, supersonic jet spectroscopy. Rotational envelope simulations yield a rotational temperature for ground state PA of ca. 55 K. Ab initio calculations of transition energies and vibrational frequencies for the A<--X transition assist in the assignment of the observed spectrum. A number of the vibrational modes of the A state are assigned to observed transitions (the O-O stretch 2(1), the COO bend 5(1), and the CCOO backbone bend 6(1)). The calculations and mass spectra suggest that the ground state of the PA ion is repulsive. An increase in rotational linewidth of the overtone of the O-O stretch (2(1)) is observed and discussed in terms of A state dynamics. The O-O stretch anharmonicity is estimated to be 13.35 cm(-1).     

A study of the interaction of dimethylcadmium and diethylcadmium with the Aerosil surface by IR spectroscopy and mass spectrometry

Dimethyl- and diethylcadmium interact with both free hydroxyl and siloxane groups of the Aerosil surface to form ≡Si-O-Cd-C≡ and ≡Si-H fragments. At 200 °C these structures undergo β-elimination to form surface ≡Si-O-Cd-H groups. It has been established that on heating to 600 °C, these groups decompose to afford metallic cadmium with the regeneration of the ≡Si-OH surface groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1717–1720, October, 1993.     

IR spectroscopy investigation of molecular association in the acetone-trichlormethane mixture

A significant increase in the stretching band intensity of trichloromethane in IR spectra of its solutions in acetone with increasing acetone mole fraction indicates the formation of hydrogen bonds between their molecules. The integral absorption coefficient (α) of this vibration is calculated. Experimental values of α are approximated by a theoretical dependence using the nonlinear least-squares method; association parameters are obtained. The relative volume fractions of H-bonded and free trichloromethane molecules are calculated depending on the total trichloromethane volume fraction in solution. The structure of the H-bonded associate is determined by quantum chemical calculations.     

Quantitative inorganic analysis by Q-switched laser mass spectroscopy

The authors use a Q-switched laser for the vaporization and ionization of sample materials. The ions thus formed are separated according to energy and mass-charge ratio and finally detected with a double-focusing mass spectrometer. It is shown that this method permits semiquantitative analysis of both conducting and non-conducting inorganic materials, without the use of reference samples. The samples may be in the form of solid, powdered or liquid bulk materials, thin layers, deposits or inclusions.     

The analysis of the near IR of some organic and organometallic compounds by photoacoustic spectroscopy

The photoacoustic spectrum (PAS) was measured in the near IR region (1000 to 2600 nm) for organic compounds (C₆H₆, C₆D₆, C₇H₈, and C₆H₁₂) and organometallic compounds (Cp₂Fe, Cp₂Fe₂(CO)₄, Cp₄Fe₄(CO)₄, Cp₄Fe₄S₄, C₆H₆Cr(CO)₃, CpCo(C₄Ph₄) and CpCo(CO)₂). Band assignments were made by comparison to the infrared spectra. The bands were assigned as the CH overtone stretch and combinations of CH and other IR fundamentals. These bands provide fingerprint spectra for these compounds.     

Investigation of the conformation of epoxychalcones by IR spectroscopy

Molecules of ketone oxides in the solid phase exist exclusively in the gauche form, whereas compounds of the open type form a mixture of cis and gauche conformers in solution. The effect of temperature on the conformational equilibrium was investigated.     

Study of the structure of benzazolylhydrazones by IR spectroscopy

Benzazolylhydrazones may exist in amino and imino tautomeric forms in carbon tetrachloride and chloroform solutions. The investigated hydrazones are associated in carbon tetrachloride solutions through intermolecular hydrogen bonds.     

Investigation of the ring-chain tautomerism of alkyl-substituted 6-hydroxytetrahydro-1,3-thiazine-2-thiones by IR spectroscopy and mass spectrometry

The ring-chain tautomerism of alkyl-substituted 6-hydroxytetrahydro-1,3-thiazine-2-thiones was studied by IR spectroscopy and mass spectrometry. The dependence of the tautomeric equilibrium on the number and location of the methyl groups in the molecule and the aggregate state of the substance was ascertained. Substituted 3,4-dihydro-2H-1,3-thiazine-2-thiones were obtained by the dehydration of the 6-hydroxytetrahydro-1,3-thiazine-2-thionesTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 985–990, July, 1992.     

IR spectroscopy of hydrogen-bonded 2-fluoropyridine-methanol clusters

The electronic and infrared spectra of 2-fluoropyridine-methanol clusters were observed in a supersonic free jet. The structure of hydrogen-bonded clusters of 2-fluoropyridine with methanol was studied on the basis of the molecular orbital calculations. The IR spectra of 2-fluoropyridine-(CH3OH)n(n = 1-3) clusters were observed with a fluorescence-detected infrared depletion (FDIR) technique in the OH and CH stretching vibrational regions. The structures of the clusters are similar to those observed for 2-fluoropyridine-(H2O)n (n = 1-3) clusters. The existence of weak hydrogen bond interaction through aromatic hydrogen was observed in the IR spectra. The theoretical calculation also supports the result. The vibrational frequencies of CH bonds in CH3 group are affected by hydrogen bond formation although these bonds do not directly relate to the hydrogen bond interaction. The B3LYP/6-311 ++G(d,p) calculations reproduce well the vibrational frequency of the hydrogen-bonded OH stretching vibrations. However, the calculated frequency of CH stretching vibration could not reproduce the IR spectra because of anharmonic interaction with closely lying overtone or combination bands for nu3 and nu9 vibrations. The vibrational shift of nu2 vibration is reproduced well with molecular orbital calculations. The calculation also shows that the frequency shift of nu2 vibration is closely related to the CH bond length at the trans position against the OH bond in hydrogen-bonded methanol.     

A study of gelatin by IR spectroscopy

Samples of freshly prepared soluble, naturally aged soluble, and insoluble gelatins (an accumulation of glue taken from a wooden sculpture of the XVth century) before and after heating at 210°C have been investigated by IR spectroscopy. The IR spectra of the samples before heating consisted of the characteristic spectra of collagen or gelatin although there were differences in the 1380–1460 cm^?1 region of the spectra. After the samples had been heated, the IR spectra of the soluble gelatins differed from those of the unheated samples. The changes in the IR spectra are discussed in connection with the probable structural rearrangements taking place in the natural ageing of gelatin.