IR characterization of surface hydroxy groups on haematite

The OH stretching absorptions (3670, 3640 and 3460 cm^–1) detected on haematite samples obtained by thermal decomposition of goethite, are assigned to monocoordinated and bridged free surface OH's and to hydrogen bonded OH's in surface micropores, respectively, on the basis of their behavior to successive adsorption of methanol, pyridine and D₂O and surface structural models.

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OH (3670, 3640 3460 ^–1) , . OH, OH, , , , D₂O, .

     

Quantum-chemical study of the optical properties of MgO surface hydroxy groups

Cluster models of MgO surface OH groups have been studied by the semi-empirical CNDO method. The calculated stretching vibration frequencies of OH bonds and localized electron excitation energies on the OH-groups are shown to depend on the oxygen atom coordination.

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OH- MgO. , OH- , OH-, .

     

Size-dependent surface CO stretching frequency investigations on nanodiamond particles

In this work, the spectroscopic properties of surface functionalized nanodiamond particles are investigated via Fourier transform infrared spectroscopy. The functionalization of the nanodiamond surface was achieved chemically using strong acid treatment method. The size dependent C=O stretching frequency (between 1680 and 1820 cm(-1)) are studied for particle diameter sizes from the 5 to 500 nm range. The surface C=O stretching frequencies at approximately 1820 cm(-1), for large particle size (500 nm), down shifted to 1725 cm(-1) (5 nm) with decreasing particle sizes. We attributed the shift as a result of hydrogen bond formation between the COOH groups in the carboxylated nanodiamond surfaces. Particle size was characterized with dynamic light scattering method and surface morphology of the particles was investigated with scanning electron microscopy. The influence of pH value on C=O stretching frequency is also analyzed. This finding affords useful information for the studying of surface functionalized nanodiamonds with implications for their interaction with biomolecules.     

Influence of surface oxygen groups on V(II) oxidation reaction kinetics

The role of surface oxygen groups on the kinetics of the V(II) oxidation reaction was studied on modified glassy carbon (GC) electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The reaction was found to be sensitive to the presence of oxygen groups on the electrode surface. Higher O/C ratios determined by X-ray photoelectron spectroscopy (XPS) corresponded to higher reactivities and lower charge transfer resistances measured in a 1 M V(II) electrolyte. The stability of an oxidised GC surface was also investigated in a 1 M V(II) electrolyte by potential holding and cycling experiments. It was found that after holding and cycling to successively more negative potentials up to − 0.8 V/RHE, the electrode surface lost its initial reactivity.     

Determination of hydroxy and sulfhydryl groups on the surface of sulfided hydrorefining catalysts

Previously proposed methods for the determination of surface hydroxy groups of oxides, based on the reaction of dimethylzinc tetrahydrofuranate with active hydrogen atoms, and for the determination of surface sulfhydryl groups of sulfides, based on the reaction with silver ions, were applied to simultaneous determination of OH and SH groups present on the surface of a sulfided hydrorefining CoMo/Al₂O₃ catalyst.

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, , , , OH SH, -CoMo/Al₂O₃.

     

Determination of the surface hydroxy groups on alumina and silica-alumina catalysts by dimethylzinc

The earlier proposed pulse flow method for the determination of surface OH groups based on the reaction of gaseous dimethylzinc tetrahydrofuranate with active hydrogen was applied to alumina and silica-alumina catalysts. The concentrations of OH groups found by this method are in a good agreement with the published data, obtained by deuterium exchange and gravimetry.

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, , OH, , - . OH, , , .

     

Estimation of proton donor ability of surface hydroxy groups in terms of proton affinity

A method to estimate the proton donor ability of hydroxy groups in terms of proton affinity (PA) is suggested. The PA of hydroxy groups of aerosil and of decationated zeolite type Y have been determined.

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(PA). PA .

     

烷基极化效应与X=O键伸缩振动频率

烷基取代物R'X=O的X=O键伸缩振动频率ν与烷基R的极化效应指PEI(R)的关系可表示为:ν=a+bPEI(R)。研究结果表明,烷基的极化效应使X=O键的伸缩振动频率降低。     

Proton donor ability of surface hydroxy groups from the IR spectra of hydrogen-bonded complexes

The influence of the strength of N-bases on the shift of (OH) in hydrogenbonded complexes upon adsorption on the surface of a decationized zeolite, phosphates and aerosil differing in the proton donor ability of surface hydroxy groups has been investigated. It is shown that the acid-base properties of the adsorbent-adsorbate pair produce additive influence on the above frequency shifts. A method for the determination of the proton donor ability of surface hydroxy groups (in terms of pK_a) from the IR spectra of hydrogen-bonded complexes is suggested.

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- (OH) , , . , - - . ( pK_a) .

     

First structural determination of a trivalent californium compound with oxygen coordination

Single crystals of Cf(IO(3))(3) (1) were synthesized by the hydrothermal reaction of CfCl(3) and H(5)IO(6), and the structure was determined with single-crystal X-ray diffraction. This structural determination of 1 represents the first for a trivalent californium compound containing oxygen coordination. This compound has been further characterized with the use of Raman spectroscopy and emission spectroscopy. Crystallographic data: Cf(IO(3))(3), monoclinic, space group P2(1)/n, a = 8.7994(10) A, b = 5.9388(7) A, c = 15.157(2) A, beta = 96.833(2) degrees , V = 786.43(16) A(3), Z = 4 (T = 295 K).     

Local ordering of hydroxy groups in hydroxyapatite

Density functional theory calculations of hydroxyapatite identified the oxygen and hydrogen positions of the hydroxy groups in the crystal structure to be well defined, alternating in a column in the c-direction, and we predict that the experimentally found oxygen and hydrogen disorder is due to the presence in the crystal of differently oriented locally ordered domains, a finding which is important for studies of crystal growth and surface reactivity.     

Rapid chromatographic method to determine surface concentration of hydroxy groups on silicon and aluminium oxides using dimethylzinc

A rapid chromatographic method to determine the surface concentration of hydroxy groups on silicon and aluminium oxides using dimethylzinc is proposed. The dependence of their concentration over domestic silica gels and -Al₂O₃ on the dehydration temperature has been studied. The results are compared with the literature data.

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. -Al₂O₃ . .

     

Accessibility of hydroxy groups of pectin substances for deuteration

An apparatus for the deuteration of solid samples and for recording their IR spectra in a current of D₂O vapor, and an IR-spectroscopic method of determining the degree of deuteration (q) of the hydroxy groups of pectin substances (PSs) are described. It has been established that there are no zones of structurally different nature in films of derivatives of PSs at the carboxy group. The rate of deuterium-exchange of the water of hydration of PSs is higher than for the hydroxy groups of the pyranose rings. The rate of deuterium exchange depends on the density of packing of the polymer chains of the pectin derivatives.Center for the Automation of Scientific Investigations and Metrology, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Khimiya Priorodnykh Soedinenii, No. 3, pp. 343–348, May–June, 1987.     

含酚羟基Schiff碱化合物的阴离子识别研究

近年来,超分子化学及其应用研究越来越受到科学家的重视[1].许多氢键供体已成功应用于阴离子识别研究中,如酰胺[2]、硫脲[3]及吡咯大环[4]化合物等.含有酚羟基的Schiff碱型化合物常被用于阳离子识别体系中[5,6],而以其为阴离子识别位点的研究相对较少.作为研究超分子化合物的合成、识别性能等工作的一部分[7],我们设计合成了三种具有多位点识别且含有酚羟基的Schiff 碱新型受体.考察了主-客体配合物中所形成的氢键数目对阴离子选择性识别的影响.     

Preparation and structural characterization of organotin(IV) complexes with ligands containing a hetero {N} atom and a hydroxy group or hydroxy and carboxyl groups

Twenty-two n-butyltin(IV) and t-butyltin(IV) complexes of ligands containing an -OH (-CO) group or -OH and -COOH groups and an aromatic {N} donor atom were prepared by metathetical reactions. On the basis of the FT-IR and Mössbauer spectroscopic data, molecular structures were assigned to these compounds. The binding sites of the ligands were identified by means of FT-IR spectroscopic measurements, and it was found that in most cases the organotin(IV) moiety reacts with the phenolic form of these ligands. In the complexes with -OH and -COOH functions, the -COOH group is coordinated to the organotin(IV) centres in a monodentate manner. The ¹¹⁹Sn Mössbauer and the FT-IR studies support the formation of trigonal bipyramidal (TBP) and octahedral (O_h) molecular structures. Furthermore, X-ray diffraction analysis has been performed on the n-butyltin(IV)- and t-butyltin(IV)-8-quinol 8-olato-O,N single crystals. The hexacoordinated tin centres exhibit cis-octahedral geometry in both complexes.     

Selective oxidation of hydroxy groups of phenylthio and phenylseleno alcohols

Various kinds of alcohols bearing phenylthio or phenylseleno moiety were converted into the corresponding carbonyl compounds in good to excellent yields by treating with dimesityl diselenide and $\text{tert}$-butyl hydroperoxide.     

Determination of the content of hydroxy groups in cottonseed oil

IR spectroscopy has been used to determine the content of hydroxy groups in cottonseed oil in relation to the periods of ripening. It has been found that the largest amount of hydroxy groups is present in the oil of the early stages of ripeness.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 300–303, May–June, 1979.