Acid–Base Complexes of Tetrahalogentetraazaporphyrins with tert-Butylamine and Tributylamine in Benzene: Synthesis and Stability

Kinetics of formation of acid–base tetrachloro- and tetrabromotetraazaporphyrin complexes with tert-butylamine and tributylamine in benzene was studied. The rate and activation parameters of the process were shown to depend on the nature of protolytes. The mechanism of intermolecular proton transfer from NH groups of tetrahalogentetraazaporphyrins to the nitrogen-containing base is proposed. The structures of acid–base complexes are considered and their kinetic stability is studied.     

Acid–Base Interactions in Complexation of Magnesium Acetylacetonate with Tetraazaporphyrins in Dimethyl Sulfoxide–Benzene System

Complexation of magnesium acetylacetonate with tetraazaporphine, tetrachlorotetraazaporphine, tetrabromotetraazaporphine, octa(p-bromophenyl)tetraazaporphine, or octa(p-nitrophenyl)tetraazaporphine in DMSO–benzene system was studied. The acid properties of tetrapyrrole were shown to affect the rate and activation parameters of the process. The key role of acid–base interactions in the formation of Mg(II) complex with tetraazaporphyrins was established. The mechanism of the processes under study was suggested.     

Acid–Base Interactions in the Dichloroacetic Acid–N,N-Dimethylformamide System as Found from IR Spectroscopic Data

Ion–molecule interactions in the dichloroacetic acid–N,N-dimethylformamide system in the concentration range from pure acid to pure base at 30°C were investigated by multiple attenuated total internal reflectance IR spectroscopy. It was found that, depending on the ratio between components in solution, 1 : 1 or 2 : 1 acid–base complexes with strong hydrogen bonds are formed. With an excess of the acid, protonation of the base does not occur. The intensity of continuous absorption at 2000 cm^–1 is characteristic of quasi-ionic pairs with strong symmetrical hydrogen bonds. However, along with a continuous component, the spectra exhibited individual sharp peaks, which are typical of molecular complexes.     

Titrimetric Determination of Furosemide Using Aqueous–Micellar Solutions of Surfactants

The solubility and acid–base properties of 4-chloro-N-(2-furylmethyl)-5-sulfamoylanthranilic acid (furosemide) were studied in aqueous–micellar solutions of surfactants of different nature. Conditions of the determination of furosemide by acid–base titration in a micellar solution of tridecylpyridinium bromide were found.     

Acid–Base Properties of γ-Al2O3 Suspension Studied by pK Spectroscopy

Theoretic fundamentals of the method of pK spectroscopy are formulated as applied to investigating acid–base properties of suspensions, hydrosols, and solutions of macromolecules. The computer-aided treatment of the data of potentiometric titration of the relevant substrates makes it possible to determine the molar fractions of corresponding acid–base groups (per total number of these groups) as a function of pK values of these groups. An appropriate computer program is tested with a model example and resulted in a pK spectrum meeting the model requirements. The method of pK spectroscopy is used to study acid–base properties of -Al₂O₃ suspension. In the pK spectrum obtained, four bands corresponding to four types of acid–base groups on the oxide surface are observed that appears to be a direct verification of the James–Parks model.     

Strong interactions through the XAu–Y bridge: the Au bond?

The interaction between AuOH and the lone-pair donors (HF, H₂O) is shown to result in well-bound complexes whose structure resembles that of the corresponding H-bonded systems with the gold atom replacing hydrogen. The dissociation energies are estimated to be 10.7 and 27.4 kcal/mol for HFAu–OH and H₂OAu–OH, respectively. However, the interaction between AuOH and the lone pair donors is found to involve significant charge transfer. Furthermore, the Au–O stretching frequency increases upon the complex formation. It is concluded that, in spite of certain similarity to the H-bonded species, the Au-bonded complexes should be considered as Lewis acid–base pairs.     

Surface Properties of Cleaved Mica

The structural characteristics of cleaved mica are studied. Cleavage of phlogopite and muscovite is shown to be accompanied by the deformation of their crystal lattices. The structural charge emerging as a result amounts to 90–95% of the total charge of the mica surface. The acid–base properties of the surfaces of these minerals are studied by the method of potentiometric titration. As is shown using constant capacitance surface complexation model, only deprotonation reactions are characteristic for muscovite, whereas phlogopite undergoes also ion-exchange reactions. The corresponding constants of acid–base equilibrium are determined.     

Role of the Surface Acid–Base Properties of Silver Catalysts in the Partial Oxidation of Ethylene Glycol

The acid–base properties of a bulk silver catalyst and silver catalysts supported on various carriers for the partial oxidation of ethylene glycol were studied. A relationship between the catalytic activity and the concentration of surface acid sites in the catalysts was found. A mechanism was proposed for the participation of Lewis acid sites in the reaction of partial ethylene glycol oxidation to glyoxal.     

Effect of the Acid–Base Properties of the Support on the Activity of Pd–Zeolite Catalysts for CO Oxidation

The effect of the acid–base properties of zeolite Y on the activity of palladium–zeolite catalysts for CO oxidation was studied. The modification of the support with basic additives was found to improve the catalyst activity. A linear correlation between the ratio between the amounts of O₂and CO adsorbed on the surface of palladium and the catalyst activity was established.     

Acid–Base Interactions in the Dichloroacetic Acid–Ethyl Acetate System according to IR Spectroscopic Data

The method of multiple total internal reflection infrared spectroscopy (MTIRIRS) is used to study ion–molecular interactions in the system dichloroacetic acid–ethyl acetate in the range of concentrations from pure acid to pure base at 30°C. Depending on the ratio of components in the solution, molecular complexes with acid : base ratios of 1 : 1 or 2 : 1 are formed in the solutions. In the case of excess acid, base is not protonated and species with a strong symmetric hydrogen bond are not formed. It is shown that the absorption coefficient near 2000 cm^–1 can be used to judge the type of the complex formed and the strength of a hydrogen bond in molecular complexes.     

Ionic Equilibria of Chromophoric Reagents in Microemulsions

Protolytic equilibria of twenty chromophoric acid–base indicators from different classes, namely, sulfophthaleins, hydroxyxanthenes, azo compounds, and others, were studied in direct microemulsions of benzene–pentanol-1–surfactant–water at volume fractions of the dispersed phase of up to 13%. Cetylpyridinium chloride, sodium dodecylsulfate, and certain nonionic surfactants were used. Apparent acidity constants (pK _a) of indicators were determined under the conditions of their complete binding by microdroplets (pK _a ^ac). The strong differentiating effect of the dispersed phase of microemulsions of different types on the acid–base properties of indicators was revealed. The effect of the ionic strength of the continuous phase (0.025–1.0) on the values of pK _a ^ac was studied. The partition constants of Bromothymol Blue anions between water and negatively charged microdroplets were estimated. Similarities and differences were revealed in the action of microemulsions and micellar solutions of the corresponding surfactants on the state of the studied chromophoric reagents.     

Synthesis and spectral and luminescent properties of 3-formyl-7-dialkylaminocoumarins

By means of the Vilsmeier reaction, starting with various 4-substituted 7-dialkylaminocoumarins having an open position 3, the corresponding 3-formyl derivatives have been obtained, and their spectral and luminescence characteristics have been studied. The ¹³C NMR spectra and acid—base properties of a number of the synthesized compounds have been examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1480–1487, November, 1991.     

Reaction of 2,3-Epoxypropyl Ethers with 1-Butanol

Nucleophilic opening of the oxirane ring in 2,3-epoxypropyl ethers with alcohols in the presence of titanium alkoxides and other catalysts was studied. The mechanism of catalysis by titanium alkoxides was discussed on the basis of comparison with acid–base catalysts.     

Calculation of the Cooperativity and Anticooperativity Parameters of the Interaction of a Ligand with an Infinite Homogeneous Polymer

A method for the mathematical processing of experimental titration curves of a homogeneous one-dimensional polynucleotide is described. The method under consideration is based on the modified McGhee–von Hippel conditional probability method. The simulated nonlinear dependences of the effective intrinsic constant on the degree of saturation of the polymer with the ligand are analyzed. The data reported in the literature on the acid–base titration of polycytidylic acid are considered as an experimental example. It is demonstrated that in the analysis of the total of the experimental data, the proposed method provides more accurate treatment of nonlinear deviations from the Scatchard dependences.     

The role of mass spectrometric methods in ionic reaction mechanistic studies

The role of various mass spectrometric methods, including electron ionization, collisional activation, metastable peak shapes, analysis of neutrals from ionic unimolecular dissociations, field ionization kinetics, drift cell, and Fourier transform ion cyclotron resonance spectrometry, in ionic reaction mechanistic studies is described. This is illustrated by selected examples of research performed in the author’s group over the last three decades. They comprise inter alia intramolecular acid–base, anchimeric assistance, nucleophilic attack, isomerization, cycloaddition, S_N2, and hydride ion transfer reactions.     

New Electrodes with Membranes Based on Semiconductor Compounds of the AIIIBV Type

The characteristics of new electrodes with semiconducting membranes based on gallium arsenide and gallium antimonide were studied in solutions of metal salts, halides, and complexing agents. The proposed electrodes can be used as indicator electrodes in acid–base, precipitation, and complexometric potentiometric titration.     

A comparison of the surface properties of lignin and sulfonated lignins by FTIR spectroscopy and wicking technique

The comparison of the FTIR spectra indicated that the sulfonation without caused changes in the main structure of lignin and only in the lignin chains. The surface properties, e.g. the surface free energy and related components, e.g. the Lifshitz–van der Waals and Lewis acid–base interactions components, of lignin and lignosulfonates, LGSs, with different ions, e.g. Na⁺–, Mg²⁺–, and Ca²⁺–, studied and compared by wicking technique indicated that the surface free energy of lignin is lower than that of all used LGSs. This suggests that the sulfonation can enhance the surface property for lignin by increasing of the Lifshitz–van der Waals component and Lewis base component of lignin.     

Studies of the surface wettability and hydrothermal stability of methyl-modified silica films by FT-IR and Raman spectra

Fourier transform infrared (FT-IR) and Raman spectroscopy were employed to study the hydrothermal stability and the influence of surface functional groups on the surface wettability of methyl-modified silica films. The surface free energy parameters of the silica films were determined using the Lifshitz-van der Waals/acid–base approach. The thermal decomposition mechanisms of the CH₃ groups in the methyl-modified silica material are proposed. The results show that with the increase of methyltriethoxysilane (MTES)/tetraethylorthosilicate (TEOS) ratio, the surface free energy and surface wettability of the silica films decrease greatly. This is mainly because of the contribution of the acid–base term; the intensity of Si–CH₃ groups increases at the expense of the intensity of O–H groups in the samples. The surfaces of the methyl-modified silica films exhibited predominantly monopolar electron-donicity. The contact angle on the silica film surface reaches its maximum value when calcination is performed at 350 °C. Thermogravimetric analysis implies that some low molecular weight species, such as H₂, CH₄, and C, are eliminated upon thermal decomposition of the –CH₃ groups. The Si–CH₃ and –CH₃ vibrational bands diminish in intensity as the calcination temperature is increased, disappearing completely when the calcination temperature is increased to 600 °C. When the calcination temperature is increased to 750 °C, the free carbon and CSi₄ species will be formed.     

Acid–Base Properties of 3-Benzazolylcoumarins and Their Imino Analogs

The acid–base equilibria of 3-(N-methyl-2-benzimidazolyl)coumarins and imino chromenes were studied in aqueous ethanol. The major reason for the difference in their proton-acceptor capacity relative to their nonmethylated analogs lies in a loss of planarity of these molecules. The tautomerism of 7-hydroxy-2-iminochromene is discussed.     

Staphylococcus epidermidis adhesion to He, He/O(2) plasma treated PET films and aged materials: contributions of surface free energy and shear rate

Adhesion studies of bacteria (Staphylococcus epidermidis) to plasma modified PET films were conducted in order to determine the role of the surface free energy under static and dynamic conditions. In particular, we investigated the effect of the ageing time on the physicochemical surface properties of helium (He) and 20% of oxygen in helium (He/O₂) plasma treated polyethylene terephthalate (PET) as well as on the bacterial adhesion. Treatment conditions especially known to result in ageing sensitive hydrophilicity (hydrophobic recovery) were intentionally chosen in an effort to obtain the widest possible range of surface energy specimens and also to avoid strong changes in the morphological properties of the surface. Both plasma treatments are shown to significantly reduce bacterial adhesion in comparison to the untreated PET. However, the ageing effect and the subsequent decrease in the surface free energy of the substratum surfaces with time – especially in the case of He treated samples – seem to favor bacterial adhesion and aggregation. The dispersion-polar and the Lifshitz–van der Waals (LW) acid–base (AB) thermodynamic approaches were applied to calculate the Gibbs free energy changes of adhesion (ΔG_adh) of S. epidermidis interacting with the substrates. There was a strong correlation between the thermodynamic predictions and the measured values of bacterial adhesion, when adhesion was performed under static conditions. By decoupling the (ΔG_adh) values into their components, we observed that polar/acid–base interactions dominated the interactions of bacteria with the substrates in aqueous media. However, under flow conditions, the increase in the shear rate restricted the predictability of the thermodynamic models.