Theoretical analysis of the structure and intramolecular dynamics of imidazolium halide and N-methylimidazolium halide ion pairs

A plant for the theoretical analysis of the structure and intramolecular dynamics of ion pairs of organic salts based on the combined use of the results of quantum-chemical calculations and molecular mechanics has been proposed. The potential-energy surfaces of the interionic interactions in imidazolium halide and N-methylimidazolium halide ion pairs have been investigated, and the equilibrium geometric parameters and frequencies of the interionic vibrations have been determined. It has been established that these ion pairs should be classified as stereochemically nonrigid molecules.Deceased.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 522–529, September–October, 1985.     

Interionic vibrations and the molecular structure of ion pairs for 1-acetylpyridinium halides

The structure and interionic vibrations of the ion pairs of 1-acetylpyridinium halides have been analysed by the joint use of far-IR spectroscopy, a molecular orbital method and molecular mechanics calculations. It has been found that these ion pairs are non-rigid molecules with large amplitude low-frequency interionic vibrations. The most probable ion pair geometry corresponds to the anion location over the plane of the cation pyridinium ring. The nature of chemical bonding between the anion and cation has been established to be predominantly ionic.     

Complexes of zinc(II), cadmium(II) and mercury(II) halides with ethylenselenourea

Summary Reaction of zinc(II), cadmium(II) and mercury(II) halides with ethylenselenourea yields complexes of general formula ML₂X₂ where X = Cl, Br, I. On the basis of an i.r. comparison of these complexes and their ethylenthiourea analogues in the 4000-200 cm^–1 range, it appears that the ethylenselenourea complexes are monomeric, tetrahedral and Se-bonded to the metals. The metal-halogen and metal-ligand vibrations above 200 cm^–1 are identified.This work was supported by the National Research Council (C.N.R.) of Italy.     

Models having the thermodynamic properties of aqueous alkaline earth halides and NaCl-MgCl2 mixtures

A model studied earlier in relation to aqueous 1–1 electrolytes has been applied to the interpretation of the excess free energies of aqueous solutions of the alkaline earth halides up to 1 M ionic strength. Several variations on the model could be fitted to the data. In the one which seems most consistent with the other observations, the cospheres (hydration layers) on the M⁺⁺ ions were two water molecules thick rather than one as for the alkali metal, tetraalkylammonium, and halide ions. The overlap of cospheres of an M⁺⁺, M⁺⁺ pair was found to make a small attractive contribution to the interionic force, while the overlap of cospheres of an M⁺⁺, X^– pair makes a small positive contribution which is almost the same for X^–=Cl^–, Br^–, or I^–. Thus, ionic hydration shells which are not penetrated by other ions are not required to account for the observed excess free energies. The model is also fitted to NaCl-MgCl₂ mixtures to see whether the new cosphereoverlap parameter which must be determined is consistent with the others. The calculation also shows how the thermodynamic behavior of the mixtures is consistent with the mixture limiting law for unsymmetrical mixtures. The singularities in the mixing coefficients g₀ and w₀ at infinite dilution dominate their concentration dependence only up to ionic strengths of about 0.01 M in models which fit the data.Most of this report is abstracted from a thesis presented by A. Smitherman to the Graduate School of the State University of New York at Stony Brook in partial fulfillment of the requirements for the M.S. degree, August 1972.     

Some Structural and Thermodynamic Aspects of Solvation of Single Ions. 2. Salt Effects in Aqueous Solutions of 1–1 Electrolytes

The ionic coefficients of the pair interionic interaction in aqueous solutions of 1–1 electrolytes at 298 K were determined from the real activity coefficients of single-charged single ions using the McMillan–Mayer formalism. Analysis of the results of calculations revealed that salt effects are stronger in the case of cations. The weakening of cation hydration (increased negative hydration) and the strengthening of anion hydration (increased positive hydration) enhance the mutual salting of cations and anions. It is shown that the structural effects of hydration produce a strong effect on the interionic interaction in solutions.     

Infrared spectra of cyclic ethers and their derivatives

The IR spectra of six monosubstituted and of four 2,6-disubstituted 1,4-dioxanes have been studied in the 650–1800cm^–1 region. The assignment of the bands due to the vibrations of the 1,4-dioxane ring and to the deformation vibrations of the methylene groups of the ring is given. The appearance of a whole series of new absorption bands on passing from unsubstituted 1,4-dioxane to its derivatives is explained by the change in the symmetry of the molecule and the removal of the prohibition from the vibrations previously inactive in the IR spectra connected with this reduction in symmetry. It is proposed to use, in order to confirm the presence of a 1,4-dioxane ring in a molecule from the results of IR spectroscopy, not only the 1126-cm^–1 band but the whole group of bands lying in the frequency ranges 800–950, 1000–1150, and 1200–1300 cm^–1.For part I, see [3].     

Co-deposition of Copper and Tin from Acidic Sulfate Solutions Containing Polyether Laprol 2402C: The Effect of Halides

Voltammetry and x-ray photoelectron spectroscopy data show micromolar amounts of halides to noticeably affect co-deposition of copper and tin from acidic sulfate solutions containing polyether Laprol 2402C as the surface-active substance. The reduction of Cu(II) slows down and that of Sn(II) accelerates in the series Cl^– < Br^– < I^–. Compounds on the surface of bronze coatings are oxides of Cu(I) and Sn(II) and halides of Cu(I).     

IR absorption spectra and association of acridinium salts with hydrogen halide molecules

It was observed that the reaction of acridine with hydrogen halides under heterogeneous conditions proceeds in two steps: An acridinium salt is formed in the first step, while a complex of the salt with hydrogen halide molecules is formed in the second step. The formation of a complex leads to substantial changes in the region of the stretching vibrations of NH⁺ bonds, and this makes it possible to propose the direct participation of these bonds in complexing. The band of the stretching vibrations of NH⁺ bonds of the acridinium ion has a complex structure that changes markedly as a function of the sort of halogen ion and replacement of hydrogen by deuterium and in the case of complexing with the hydrogen halide. It is proposed that the structure of this band is due to Fermi resonance.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 99–101, January, 1981.     

Acetyl transfer from N-acetyloxypyridinium cations to 4-(4′-N,N-dimethylaminostyryl)-pyridine N-oxide and 4-dimethylaminopyridine

Kinetic data are given for the transfer of the acetyl group from the N-acetyloxypyridinium cations of tetraphenylborate salts to 4-(4′-N,N-dimethylaminostyryl)pyridine N-oxide and 4-dimethylaminopyridine in acetonitrile solution. Structural factors were found to affect the rate constants and activation parameters. Correlation equations are given relating the acetyl transfer rate constants with pK_BH+ values of the leaving group and frequencies of the carbonyl vibrations of the salts. Translated from Teoreticheskaya i éksperimental’naya Khimiya, No. 2, pp. 75–77, March–April, 1997.     

Pyridinium Halides and Their Mixtures as Inhibitors of Steel Corrosion in Sulfuric Acid Solutions

Mixtures of 1-acylmethylpyridinium halides with equimolar amounts of pyridinium halides were prepared by the Ortoleva-King reaction. The inhibiting effect of various pyridinium halides and their mixtures on corrosion of steel in sulfuric acid solutions was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 517–519.Original Russian Text Copyright © 2005 by Yurchenko, Ivashchenko, Pilipenko, Pogrebova.     

IR spectroscopic study of adsorption of ammmonia on Brønsted acid centers of a fluorinated surface of silica

The adsorption of aqueous ammonia solution vapor on a fluorinated surface of aerosil was studied by IR spectroscopy. The adsorption of NH₃ is accompanied by the appearance of absorption bands at 740, 1450, and 3330 cm^–1 in the IR spectra. The surface compounds were identified from the results of a study on the thermal degradation of adsorbed complexes and an analysis of literature data. The IR absorption bands at 1450 and 3330 cm^–1 correspond to deformational and stretching vibrations of the N-H bonds of the ammonium cation, The 740 cm^–1 band was assigned to the vibrations of the Si-F bonds in the complex anion, containing a fragment of SiO₂ surface, a fluorine atom, a hydroxyl group and a molecule of water. In this surface-coordinated compound, the silicon atom has a coordination number of six.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 6, pp. 747–751, November–December, 1986.     

Characteristic frequencies in the infrared spectra of pyrazolines

Pyrazolines are characterized by valence vibrations at the following frequencies: C=N (1580–1627 cm^–1), H-C³=N (3040–3063 cm^–1), H-N (3270–3305 cm^–1) and CH₃-N (2780–2805 cm^–1). Lowering of the frequencies of the valence vibrations of C=N in pyrazolines, when compared with the magnitudes characteristic of alkyledene amines and oximes, is regarded as a consequence of coupling with the unshared electron pair of the neighboring nitrogen atom. By means of the IR spectra, it is possible to determine the position of the double bonds in the pyrazoline ring, to distinguish between pyrazolines substituted and nonsubstituted in positions 1 and 3, and to establish the presence of geminate (twin) methyl groups and methyl groups in position 1.     

Friedel-Crafts alkylation of indoles

The alkylation of indole and 2-methylindole with alkyl halides in the presence of a complex catalyst — dipyridinezinc chloride — was investigated. Nitromethane was used as the solvent. 3-Alkylindoles were obtained in 30–80% yields in all cases. The reaction mechanism is discussed. Data from the PMR and mass spectra are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 921–924, July, 1978.     

Temperature dependence of probability of absorption of γ-quanta by Sn(II)-containing complexes of transition metals

A study has been made of the relationship f(T) (T=77–300°K) for platinum-group metal complexes containing Sn(II)-X (X=F, Cl, Br); these data have been used to determine the mean-square amplitudes of vibrations of the Sn atom in the anions and together with the anion, and their temperature dependences have been found. The observed relationships at f(T) depend to a considerable degree on the vibrations of the first type, i.e., on the rigidity of the bonds between the Sn and the immediate enrivonment. The different Sn-X ligands have their own characteristic relationships f(T), so that they can be used for identification of types of Sn(II)-containing complexes. The normal vibrations of the different complexes have been calculated, and it has been established that the observed changes in their f(T) in the series of halides can be explained by the increase in the number of low-frequency vibrations in the series Br>Cl>F and by their effective inclusion in the absorption of the recoil energy given up by the Sn atom. Within the framework of the analysis, an explanation has been found for the increase in f of the complexes when they are supported on the surface of substances containing acidic OH groups.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 21, No. 2, pp. 194–201, March–April, 1985.     

Direct and indirect electrochemical reduction of organic halides in aprotic media

Cyclic voltammetric reduction of 17 different organic halides including alkyl, allyl, and benzyl chlorides, bromides, and iodides in aprotic media (DMF, DMSO, and acetonitrile, AN), containing 0.1 M Bu₄NClO₄, have been reported at glassy carbon (gc) and graphite as working electrodes. A single two-electron irreversible and diffusion-limited reduction of the carbon-halogen bond is observed, the reduction potentials ranging from –1.20 to –2.70 V (versus silver wire quasireference electrode) depending on the halide, the solvent, and the electrode. Indirect reduction of these 17 halides, however, is effected at much lower potentials (–0.79 to –0.92 V versus SCE) depending on the experimental conditions by in situ electrogenerated superoxide ion (O ₂ ^– ) by CPE. The products have been characterized by TLC, GC, CV, or chemical estimation. The diorganic peroxide and the organic hydroperoxide were the major products. In case of tertiary alkyl halides, however, alkenes predominated, due to basic nature of O ₂ ^– in these reactions. These studies indicate sufficient strength of O ₂ ^– as a nucleophile or base depending on the experimental conditions.From Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 350–355.Original English Text Copyright © 2005 by Vasudevan.This article was submitted by the author in English.     

The Raman OH stretching bands of liquid water

In this work, from the discussion on water structure and clusters, it can be deduced that the OH stretching vibration is closely related to local hydrogen-bonded network for a water molecule, and different OH vibrations can be assigned to OH groups engaged in various hydrogen bonding. At ambient condition, the main local hydrogen bonding for a molecule can be classified as DDAA (double donor–double acceptor), DDA (double donor–single acceptor), DAA (single donor–double acceptor) and DA (single donor–single acceptor) and free OH vibrations. As for water at 290 K and 0.1 MPa pressure, the OH stretching region of the Raman spectrum can be deconvoluted into five sub-bands, which are located at 3014, 3226, 3432, 3572, and 3636 cm⁻¹, and can be assigned to ν_DAA-OH, ν_DDAA-OH, ν_DA-OH, ν_DDA-OH, and free OH₂ symmetric stretching vibrations, respectively.     

Ir spectroscopy of 2,3-polymethylene-3,4-dihydroquinazolines and their complexes

We have investigated the IR spectra in the region of stretching vibration of N⁺–H and OH groups of the hydrochlorides of 2,3-trimethylene-3,4-dihydroquinazoline (deoxypeganine, DOP), 2,3-tetramethylene-3,4-dihydroquinazoline (tetrazoline), and 2,3-pentamethylene-3,4-dihydroquinazoline (pentazoline) and peganol and peganine and the corresponding complexes with ZnCl₂, CoCl₂, and MnCl₂. The appearance of two additional absorption bands in the 3100–3300 cm^–1 region in the complexes investigated as compared with the corresponding hydrochlorides witnesses the formation of interionic hydrogen bonds between the quinazoline cation and the (MeCl₄)^2– anion.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6., pp. 854–857, November–December, 1997.     

The origin of the two νCO bands in the infrared spectra of acetophosphides

Conclusions The two intense bands in the infrared spectra of acetophosphides at 1600–1800 cm^–1 are due to valence vibrations of the carbonyl group of the cis-and transisomers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 188–190, January, 1968.     

Fine-structure vibronic fluorescence spectra of meso-substituted porphyrins and their interpretation

Fine-structure fluorescence spectra have been recorded on selective laser excitation at 4.2 K for meso-tetraethylporphyrin (TEP), meso-tetrapropyl-porphyrin (TPP) and their derivatives with deuteriated NH groups. An interpretation of the spectra obtained is proposed on the basis of calculations of the normal vibrations of the molecules. It was noted that the interaction of the ethyl groups of TEP with the solvent leads to different orientations of these groups to the plane of the macrocycle, which leads to an increase in the number of lines in the frequency range 150–400 cm^–1 and to their broadening.Translated from Teoreticheskie i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 664–668, November–December, 1990.     

Calculations of silicooxygen ring vibration frequencies

In the work model calculations of the vibrations of ideally isolated silicooxygen rings (using PM3 method) have been carried out. three-, four-, and six-membered rings have been considered. It has been found that that the three-membered silicooxygen rings are flat and practically undeformed showing D_3h symmetry. The rings of higher number of ring members (i.e. n>3) are deformed to some extent. The deformation reveals itself most significantly in the Si–O–Si bond angles distribution. In the case of all the rings the bridging Si–O–Si bonds are ca. 0.02–0.04 Å shorter than the non-bridging Si–O⁻ bonds. Hypothetical IR spectra for all the rings considered have been also calculated. Analysis of these hypothetical spectra leads to the conclusion that the whole spectrum can be divided into four wavenumbers regions, 1200–1100 cm⁻¹ stretching Si–O(Si) vibrations; 1000–800 cm⁻¹ stretching Si–O⁻ vibrations; 800–600 cm⁻¹; the region in which a band characteristic of silicooxygen rings appears, and below 600 cm⁻¹ bending ⁻O–Si–O⁻ and (Si)O–Si–O(Si). It has been also found that as the number of ring members increases the ‘ring band’ shifts to lower wavenumbers: 725 cm⁻¹ for three-membered rings, 650 cm⁻¹ for four-membered rings and 610 cm⁻¹ for six-membered rings. Calculated spectra have been compared with the experimental spectra of cyclosilicates. They showed good agreement in the 1200–600 cm⁻¹ region. In the experimental spectra as well as in the calculated ones, with increasing the number of ring members the ‘ring band’ shifts towards lower wavenumbers.