IR study of isopropanol adsorption on haematite

The IR study shows that isopropanol interacts with haematite at IR beam temperature both as a physisorbed form, hydrogen bonded to basic sites of the surface, and as isopropoxide groups. At 423 K a decomposition of isopropoxide groups produces enolate anions of acetone.

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, , - , . 150 °C .

     

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) .

     

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-, .

     

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, , , .

     

Quantitative IR characterization of urea groups in waterborne polyurethanes

The purpose of this study is to propose a correlation between IR spectra and the urea fraction of waterborne polyurethanes (PUs) to investigate the side reaction, that is, isocyanate–water reaction, during polymerization. This method is based on the decomposition of the spectrum in amide I range, that is, 1600–1800 cm^?1, where the bands of interest overlap. Several individual bands present in this region were resolved by employing Fourier self‐deconvolution (FSD) and Gaussian curve‐fitting techniques, and the intensity ratio of urethane's C?O to urea's C?O was determined. To realize some quantitative measurements, a calibration curve was established with some polyurethane‐urea samples, characterized by ¹H NMR, which were used as standards. The concentration ratios of urethane groups to urea groups were determined from ¹H NMR. A good correlation was evidenced between IR and ¹H NMR measurements. Moreover, waterborne PUs were prepared by miniemulsion polymerization of IPDI with diols. From quantitative IR analysis, it was shown that a vinylic monomer, as a solvent of polyaddition, restrained the isocyanate–water reaction, and this side reaction was influenced by the hydrophilicity of the vinylic monomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2433–2444, 2008     

Influence of oxygen compound structural elements of stretching vibration frequency of surface hydroxy groups

Stretching vibration frequencies of OH groups ( OH) in acidic oxygen compounds are determined by the electrostatic characteristics (E_p) of the polyhedron containing this group. Empirical dependence of OH various hydroxy groups on the number and nature of their binding cations is suggested.

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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 .

     

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 . .

     

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.     

Effect of hydroxy groups on conformational equilibrium in bis-quinolizidine systems

A review of the 99 ¹³C NMR spectra of 72 hydroxy, methoxy or ester derivatives of alkaloids with the sparteine skeleton has been made. An improved method of determination of the conformer fractions in conformational equilibria in bis-quinolizidine compounds of sparteine type has been used to estimate the energy of the hydroxy group effect at various positions. The effect can be explained by intermolecular hydrogen bonds.     

原位红外光谱法研究脱铝Y型沸石表面羟基及异丙苯裂解反应

本文用原位红外光谱法, 以自行设计的红外池, 采用流动体系研究了NH4Y及用EDTA配位脱铝的Y型沸石上的表面羟基, 苯及异丙苯在不同温度下的吸附, 以及用脉冲进样原位红外研究了异丙苯裂解反应。发现在脱铝Y型沸石(DAIY)中除Y型沸石有的3620和3535cm^-^1表面羟基峰外, 在3724cm^-^1处又出现一个与脱铝“空穴"Si-OH有关的吸收峰, 且此峰随脱铝量增加而增加, 脱氨过程的研究表明超笼中羟基具有酸性, 苯及异丙苯Y型或DNIY型沸石上均与超笼中羟基作用。在360℃时异丙苯裂解反应的活性中心主要是超笼中羟基, 催化剂失活主要是由于炭沉积在活性位上所致。     

On the characterization of chemical surface groups of carbon materials

This paper deals with the use of several methods to characterize the chemical surface groups of carbon materials. Several samples embracing a wide range of acidic and basic characteristics have been used for this purpose. The quantitative determinations have been carried out by selective titrations in aqueous solutions, thermal programmed desorption connected to mass spectrometry (TPD-MS), and ammonia adsorption-desorption, measured by thermogravimetry (TG). The results show some inconsistencies between the different experimental methods. These mainly arise because chemical transformations can be produced during the experiments. Moreover, the textural characteristics of the carbon materials and the existence of pi electrons on the graphitic planes are important factors to be considered in the discussion of the results.     

Preparation and characterization of polystyrene latexes bearing disaccharide surface groups

Emulsifier-free polystyrene latexes covered with disaccharide species have been prepared by a seed (co)polymerization method in the presence of a hexylmethacrylate-terminated oligosaccharide 6-(2-methylpropenoyloxy)hexyl -d-cellobioside (CHMA). First, the surface activity of this macromonomer was studied using ring and drop volume methods, respectively. Then, its polymerization onto polystyrene seed latexes was carried out upon varying experimental conditions: particle size, solid contents of the seed and type of comonomer. Analysis of the macromonomer distribution between aqueous and polymer phases suggested that an optimal surface yield can be reached upon increasing the overall surface area of particle and or using methylmethacrylate as comonomer. Finally, the presence of the disaccharide residues at the particle surface was shown, either directly using NMR and ESCA analysis, or indirectly through the comparison of the electrophoretic mobility behavior of the seed polystyrene and functionalized latexes.     

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.     

Catalytic effect of hydroxy groups on reaction of polyamine with tert-butyl acrylate

The reaction of N-cyclohexyl-1,3-propanediamine with tert-butyl acrylate and the catalytic effect of hydroxy groups on the reaction course was investigated by Near Infrared spectroscopy. The reaction was found to be bimolecular and of second order. The dependence of rate constant on catalyst concentration (diols) is linear and the structure of diol used has no effect.

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N--1,3- -. . . () , .

     

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.