Synthesis and properties of substituted 10-phenyl-10-hydroxy-10H-pyrido[2,3-b]chromenes

It is shown that 2-aryloxy-3-benzoyl-6-methylpyridines undergo cyclization to the corresponding derivatives of 10-phenyl-10-hydroxy-10H-pyrido[2,3-b]chromenes under the influence of concentrated sulfuric acid in glacial acetic acid. The pK_R+ values of the products, which range from –6.28 to –9.27 and correlate with the _p ⁰ and _R ⁰ meta substituent constants, depending on the position of the substituent, were determined by spectrophotometry.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 798–800, June, 1982.     

Electronic effects of the 1-[CLOSO-3,3,3-(CO)3-3,1,2-ReCaB9H10]− and 1-[CLOSO-3,3,3-(CO)3-3,1,2-.MnC2B9H10]- groups

Conclusions The electronic effects of the 1-[closo-3,3,3-(CO)₃-3,1,2-ReC₂B₉H₁₀]^– (_I=-0.066; _r ^o=0.101) and 1-[closo-3,3,3-(CO)₃-3,1,2-MnC₂B₉H₁₀]^–(_I=0.090; _r ^o=0.165) groups were determined by the Taft method.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2296–2298, October, 1987.     

Tunnel splitting in the Raman spectra for μ-HW2(CO) 10 −

Conclusions The structure of the Raman spectra of -HW₂(CO) ₁₀ ^– complexes in the vicinity of 800 cm^–1 and of -DW₂(CO) ₁₀ ^– in the vicinity of 600 cm^–1 is a result of tunnel splitting.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2145–2146, September, 1984.     

Nucleophilic substitution in dibenz[b,d]iodolium and 11,12-dihydro-10H-dibenz[b,g]iodocinium cations

Treatment of dibenz[b,d]iodolium tetrafluoroborate with NO₂ ^–, Br^–, and N₃ ^– ions gave, along with nucleophilic substitution products, 2-nitro-, 2-bromo-, and 2-azido-2-iodiphenyls, diphenyl, 2-iododiphenyl, and 2,2-diiododiphenyl (products of one electron reduction), whereas 11,12-dihydro-10H-dibenz[b,g]iodocinium tetrafluoroborate underwent nucleophilic substitution with all three nucleophiles to give a single product in each case: 1-(2-nitrophenyl)-, 1-(2-bromophenyl)-, or 1-(2-azidophenyl)-3-(2-iodophenyl)propane.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 405–412, March, 1998.     

Spectral and kinetic characteristics of the α-propionic acid methyl ester radical in cyclohexane and water

The -propionic acid methyl ester radical was produced in dissociative electron capture reaction of 2-chloropropionic acid methyl ester. The absorption maxima of the radical are at 310 and 300 nm in cyclohexane and water with extinction coefficients of 440±50 and 400±50 mol^–1 dm³ cm^–1. The second order decay rate parameter in water is (2.3±0.5)×10⁹ mol^–1 dm³ s^–1. The peroxy radicals have the characteristics: _max=265–270 nm, _max=700–900 mol^–1 dm³ and 2k=(7±2)·10⁸ mol^–1 dm³ s^–1.     

Studies on the kinetics and mechanism of dissociation of copper(II) and nickel(II) complexes of the macrocyclic ligand 1, 5, 9, 13-tetraaza-2, 4, 4, 10, 12, 12-hexamethyl-cyclohexadecane-1, 9-diene in perchloric acid media

Summary Acid catalysed dissociation of the copper(II) and nickel(II) complexes (ML²⁺ of the quadridentate macrocyclic ligand 1, 5, 9, 13-tetraaza-2, 4, 4, 10, 12, 12-hexamethyl-cyclohexadecane-1, 9-diene (L) has been studied spectrophotometrically. Both complexes dissociate quite slowly with the observed pseudo-first order rate constants (k_obs) showing acid dependence; for the nickel(II) complex (k_obs)=k_O+k_H[H⁺], the k_o path is however absent with the copper(II) complex. At 60°C (I=0.1M) the k_H values areca 10^–4 M^–1 s^–1 for both complexes; k _H ^Cu /k _H ^Ni =ca. 3.9, comparable to some other square-planar complexes of these metal ions. The rate difference is primarily due to H values [copper(II) complex, 29.4±0.5 kJ mol^–1; nickel(II) complex, 35.6±1.5 kJ mol^–1] with highly negative S values [for copper(II), –215.5 ±6.1 JK^–1 mol^–1 and for nickel(II), –208.1 ±5.6 JK^–1 mol^–1] which are much higher than the entropy of solvation of Ni²⁺ (ca. –160 JK^–1 mol^–1) and Cu²⁺ (ca. –99 JK^–1 mol^–1) ions; significant solvation of the released metal ions and the ligand is indicated.     

Dissociation quotients of malonic acid in aqueous sodium chloride media to 100°C

The first and second molal dissociation quotients of malonic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. The hydrogen ion molality of malonic acid/bimalonate solutions was measured relative to a standard aqueous HCl solution from 0 to 100°C over 25° intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The molal dissociation quotients and available literature data were treated in the all anionic form by a seven-term equation. This treatment yielded the following thermodynamic quantities for the first acid dissociation equilibrium at 25°C: logK _1a =-2.852±0.003, H _1a ^/o =0.1±0.3 kJ-mol^–1, S _1a ^o =–54.4±1.0 J-mol^–1-K^–1, and C _p,1a ^o =–185±20 J-mol^–1-K^–1. Measurements of the bimalonate/malonate system were made over the same intervals of temperature and ionic strength. A similar regression of the present and previously published equilibrium quotients using a seven-term equation yielded the following values for the second acid dissociation equilibrium at 25°C: logK_2a=–5.697±0.001, H _2a ^o =–5.13±0.11 kJ-mol^–1, S _2a ^o =–126.3±0.4 J-mol^–1-K^–1, and C _p,2a ^o =–250+10 J-mol^–1-K^–1.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991.     

Chemical and Biological Sensors Based on Electrochemical Detection Using Conducting Electroactive Polymers

The electrochemical behavior of composites of conducting electroactive polyaniline (PAn) and polypyrrole (PPy) formulated within cross-linked hydrogel networks was investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Composite PAn gels displayed similar anodic charge density compared to the pristine conducting polymer (80mC/cm² and 84mC/cm², respectively), suggesting a similar degree of electroactivity between the two systems. Composite gels of PAn displayed fast cation transport with K⁺ diffusivity (D_appt= 5.31×10^–7cm²s^–1) that were three orders of magnitude larger than that of pristine PAn (D_appt=3.12×10^–10cm²s^–1), while PPy composite gels showed similar ferrocene anion diffusivity (D_appt=7.05×10^–5cm²s^–1) compared to electropolymerized PPy (D_appt=6.54×10^–5cm²s^–1). The electrochemical interactions between CYP2D6, a cytochrome P450 isoenzyme, and fluoxetine mediated by electroactive polyaniline films on glassy carbon electrodes (GCEs) were investigated. Cyclic voltammograms indicate that PAn is an effective mediator of CYP2D6 activity under anaerobic conditions. An analytical interrogation methodology based on small-amplitude, pulsed DC was developed and incorporated into the Electroconductive Polymer Sensor Interrogation System (EPSIS). Polypyrrole membranes were rendered biospecific by either copolymerization of pyrrole (Py) with 4-(1-pyrrolyl) butyric acid (4PyBA), followed by direct conjugation with 5-(biotinamido)pentyl amine (5BPA), or by reacting 4PyBA with 5BPA to form pyrrolyl-biotin conjugates. The biotinylated PPy was made responsive to glucose or urea by exploiting strong biotin-streptavidin binding to either streptavidin-glucose oxidase or biotin-urease conjugates. These bioactive conducting polymer membranes were demonstrated as conductimetric glucose and urea biosensing layers using the EPSIS. The rate of conductivity of the bioactive PPy membranes was observed to double upon increasing glucose concentration from 100µM (4×10^–6Scm^–1s^–1) to 600µM (9×10^–6Scm^–1s^–1).     

Interaction of singlet oxygen with α-and β-naphthols

The oxidation of - and -naphthol/PhOH/ sensitized by protoporphirin has been studied in benzene and Ccl₄ at 25 °C by a laser flash photolysis apparatus with a time resolution of 10 ns. Kinetics of the¹O₂ decay in the presence and in the absence of PhOH was followed spectrophotometrically by using 1,3-diphenylizobenzofurane /DPBF/ as an acceptor for¹O₂. The effective rate coefficients/k_eff/of the consumption of DPBF were measured as a function of the concentration of PhOH. In CCl₄ the value of k_eff remained practically unchanged after the addition of PhOH at a concentration of 10^–5–10^–4M, at the same time short-lived intermediates were formed which absorb at 400 nm in such solutions. In benzene at [PhOH]<4×10^–2M 5×10⁵M^–1s^–1 and 1×10⁵M^–1s^–1, as it has been calculated. Long-lived intermediates have not been observed in C₆H₆.     

Crystal structure of 1h+, 10h+-1, 10-diazonia-18-crown-6 thiocyanate

An x-ray diffraction structural analysis was carried out for 1H⁺,10H⁺-1,10-diazonia-18-crown-6 thiocyanate. This compound was found to be an ionic H-complex: [H₂DA18C6]²⁺·2SCN^–with unusual N-H...(S=C) interionic hydrogen bonds. The DA18C6 dication has a two-cornered conformation stabilized by weak intracyclic N-H...O hydrogen bonds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 500–502, February, 1991.     

Nitrogen Trioxide in Irradiated Aqueous Nitric Acid Solutions of Hydrazine

The rate constants of reactions of the NO₃ radical with hydrazoic acid (7.6 × 10⁶l mol^–1s^–1) and the hydrazonium ion (2.3 × 10⁶l mol^–1s^–1) in 6 M nitric acid at 290 ± 2 K were measured by a pulse radiolysis technique. The reaction scheme was refined by the computer simulation of the -radiolysis of aqueous nitric acid solutions of hydrazine with the use of the measured rate constants and published data on the reactivity of intermediates. The results of computations were compared with experimental data on the continuous radiolytic degradation of hydrazine in aqueous 2 M nitric acid solutions at 313 K.     

Conductivity Studies of Dilute Aqueous Solutions of Oxalic Acid and Neutral Oxalates of Sodium, Potassium, Cesium, and Ammonium from 5 to 35°C

Conductivity measurements of oxalic acid and neutral oxalates (disodium oxalate, dipotassium oxalate, dicesium, and diammonium oxalate) were performed on dilute aqueous solutions, c < 3 × 10^–3 mol-dm^–3, from 5 to 35°C. These data and those available from the literature were analyzed in terms of dissociation steps of oxalic acid, the Onsager conductivity equation for neutral oxalates, the Quint–Viallard conductivity equation for the acid, and the Debye–Hückel equation for activity coefficients, to give the limiting equivalent conductances of bioxalate anion ;(HC₂O₄ ^–) and oxalate anion (1/2C₂O₄ ^2–) and the corresponding dissociation constants K ₁ and K ₂.     

The effect of pressure on the dissociation of boric acid and sodium borate ion pairs at 25°C

A high pressure UV-visible spectrophotometer was used to determine the dissociation constant of boric acid using an indicator technique. The measurements were made at 25°C and at ionic strengths of 0.1 and 1.0m over a pressure range of 1 to 2000 atm. Extrapolation to I=0 gave a thermodynamic dissociation constant of 5.16×10^–10 at 1 atm. The pressure dependence yielded a partial molal volume change of –28.9 and –31.8 cm³-mol^–1 and a compressibility change of –3.1 and –4.8×10^–3 cm³-mol^–1-atm^–1 for the dissociation at I=0.1 and 1.0m, respectively. The association constant for the formation of the sodium borate ion pair was determined by comparing the acid constants in tetramethylammonium chloride to those in sodium chloride solutions. Extrapolation to I=0 yielded a K_A for [NaB(OH)₄] of 0.64 at 1 atm. The pressure dependence of K_A gave and for the formation of the ion pair.     

Rb[C6H3(COOH)2(COO–)] · [C6H3(COOH)3] · 2H2O: Synthesis,Crystal Structure,and Properties

The salt Rb[C₆H₃(COO)₂(^–)] · [C₆H₃(COOH)₃] · 2H₂O (I) of trimesic acid was synthesized and its thermal stability and conductivity (10^–11 ohm^–1 cm^–1 at 298 K) were measured. Molecular and crystal structures of I were established by X-ray diffraction analysis. Hydrogen bonding system in complex I was detected by IR and Raman spectroscopies. X-ray diffraction data agree with vibration spectroscopy data.     

An evaluation of rate constants for radiation induced decomposition of alkali metal nitrates

Radiation induced decomposition of solid alkali metal nitrates at room temperature has been studied up to an absorbed dose of 300 kGy. [NO ₂ ^– ] increases with absorbed dose. From the kinetic scheme and , rate constants have been evaluated for the overall radiolytic decomposition of alkali metal nitrates. This kinetic scheme is applicable in the low dose range. At higher doses, however, the radiation induced reaction, NO ₂ ^– +1/2 O₂NO ₃ ^– may also contribute. The overall rate constants are 0.13×10^–6 (LiNO₃), 1.05×10^–6 (NaNO₃), 10.10×10^–6 (KNO₃), 9.50×10^–6 (RbNO₃) and 25.50×10^–6 (CsNO₃) kGy^–1.     

Crystal structure of 1H+,10H+-1,10-diazonia-18-crown-6 diethyldithiophosphate

An x-ray diffraction structural analysis was carried out on 1H⁺,10H⁺-1,10-diazonia-18-crown-6 diethyldithiophosphate, which exists in the crystal as isolated ionic hydrogen-bonded complexes [H₂DA18C6]²⁺·2(EtO)₂PS₂ ^– with strong inter-ion N-HS hydrogen bonds. The centrosymmetric DA18C6 dication has an unusual two-cornered conformation stabilized by a pair of weak intra-ring furcated OH(N)O hydrogen bonds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 190–192, January, 1991.     

Cation-exchange separation and colorimetric determination of some elements in trace analysis of platinum-rhodium (10%) alloys

Summary A method of separation and colorimetric determination of trace amounts (10^–4–10^–5%) of Cu, Al, Fe, Bi, Pb, Mn, Cd, Zn, Co, and M in platinum-rhodium (10%) alloys has been developed. The elements to be determined are retained on a column containing the strongly acidic cation-exchanger Amberlite IR-120, from dilute hydrochloric acid medium (p_H 1–1.5), while platinum and rhodium pass through in the form of anionic chloride complexes. The individual metals are eluted and concentrated and then separated by extraction and carrier precipitation. The metals are determined by means of sensitive colorimetrie methods with dithizone (Cu, Bi, Pb, Cd, Zn), eriochromecyanine R (Al), 2-nitroso-1-naphthol (Co),-furildioxime (Ni), 1-(2-pyridylazo)-2-naphthol (Mn), and thiocyanate (Fe). The error of the determination does not exceed 15%.

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Zusammenfassung Eine Trennungs- und Bestimmungsmethode für Spuren (10^–4 bis 10^–5%) von Cu, Al, Fe, Bi, Pb, Mn, Cd, Zn, Co und Ni in PIatm-Rhodium-(10%)-Legierungen wurde ausgearbeitet.Die angeführten Elemente werden mit Amberlit IR-120 aus der verd. salzsauren Lösung (p_H 1 bis 1,5) von Platin und Rhodium getrennt, die als Anionchloridkomplexe im Eluat bleiben. Die einzelnen Metalle werden nach Elution aus ihrer Lösung durch Extraktion bzw. Mitfällung getrennt und kolorimetrisch mit Dithizon (Cu, Bi, Pb, Cd, Zn), Eriochromcyanin R (Al), 2-Nitroso-1-naphthol (Co),-Furildioxim (Ni), 1-(2-Pyridylazo)-2-naphthol (Mn) und Rhodanid (Fo) bestimmt. Der Fehler beträgt weniger als 15%,

     

Dissociation quotients of succinic acid in aqueous sodium chloride media to 225°C

The first and second molal dissociation quotients of succinic acid were measured potentiometrically with a hydrogen-electrode, concentration cell. These measurements were carried out from 0 to 225°C over 25° intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The dissociation quotients from this and two other studies were combined and treated with empirical equations to yield the following thermodynamic quantities for the first acid dissociation equilibrium at 25°C: log K_1a=–4.210±0.003; H _1a ⁰ =2.9±0.2 kJ-mol^–1; S _1a ⁰ =–71±1 J-mol^–1-K^–1; and C _p1a ⁰ =–98±3 J-mol^–1-K^–1; and for the second acid dissociation equilibrium at 25°C: log K_2a=–5.638±0.001; H _2a ⁰ = –0.5±0.1 kJ-mol^–1; S _2a ⁰ =–109.7±0.4 J-mol^–1-K^–1; and C _p2a ⁰ = –215±8 J-mol^–1-K^–1.     

Homolytic dissociation in hydrogen-bonding liquids: energetics of the phenol O–H bond in methanol and the water O–H bond in water

The energetics of the phenol O–H bond in methanol and the water O–H bond in liquid water were investigated by microsolvation modelling and statistical mechanics Monte Carlo simulations. The microsolvation approach was based on density functional theory calculations. Optimised structures for clusters of phenol and the phenoxy radical with one and two methanol molecules are reported. By analysing the differential solvation of phenol and the phenoxy radical in methanol, we predict that the phenol O–H homolytic bond dissociation enthalpy in solution is 24.3±11 kJ/mol above the gas-phase value. The analysis of the water O–H bond dissociation by microsolvation was based on optimised structures of OH–(H₂O)_1–6 and –(H₂O)_1–7 clusters. Microsolvation modelling and statistical mechanics simulations predict that the HO–H bond dissociation enthalpies in the gas phase and in liquid water are very similar. Our results stress the importance of estimating the differences between the solvation enthalpies of the radical species and the parent molecule and the limitations of local models based on microsolvation.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail     

Metal ion catalysed aquation of carboxylatoamine cobalt(III) complexes. Kinetics of copper(II) catalysed aquation ofcis(diformato)bis(ethylenediamine)cobalt(III) ion

Summary The aquation ofcis-[(en)₂Co(CO₂H)₂]⁺ tocis-[(en)₂Co(OH₂)(CO₂H)]²⁺ is catalysed by Cu²⁺ and the rate equation, –d[complex]_t/dt=(k_Cu[Cu²⁺]+k_H [H⁺]) [complex)_T is valid at [Cu²⁺]_T=0.01–0.1, I=0.5 and [HClO₄]=0.005 mol dm^–3. The rate measurements are reported at 30, 35, 40 and 45°C and the rate and activation parameters for the Cu²⁺ and H⁺-catalysed paths are: k_H(35°C)=(2.44±0.09)×10^–2 dm³ mol^–1 s^–1, H=83±13 kJ mol^–1, S=–8±42 JK^–1 mol^–1, k _Cu (35°C)=(3.30±0.09)×10^–3 dm³ mol^–1 s^–1, H=73.2±6.1 kJ mol^–1, S=–55±20 JK^–1 mol^–1. The formate-bridged innersphere binuclear complex,cis-[(en)₂Co{(O₂CH)₂Cu}]³⁺ may be involved as the catalytically active intermediate in the copper(II)-catalysed path, just as the corresponding H⁺-bridged species presumed to be present in the acidcatalysed path.