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.     

A study of the chemiluminescence behavior of myoglobin with luminol and its analytical applications

A chemiluminescence signal at 425 nm was observed when ferric state myoglobin was mixed with luminol in alkaline medium. Because the signal was remarkably enhanced in the presence of Fe(CN)₆ ^4–, analytical applications were investigated in a flow-injection system. The increase in chemiluminescence was linearly dependent on myoglobin concentration in the range 0.1 to 100 nmol L^–1, and the limit of detection was 0.04 nmol L^–1 with relative standard deviation 3.2% (3). It was also found that binding of Mb with the ligands CN^–, SCN^–, and F^– significantly inhibited the chemiluminescence reaction. The linear dynamic ranges for the ligands were 1.0–300.0, 0.1–3.0, and 0.5–100.0 nmol L^–1, and the limits of detection (S/N=3) 0.4, 0.04, and 0.2 nmol L^–1, for F^–, CN^–, and SCN^–, respectively. The relative standard deviations were 5.32%, 6.13%, and 3.38% for 0.1 nmol L^–1 CN^–, 0.5 nmol L^–1 SCN^–, and 1.0 nmol L^–1 F^–, respectively. At a flow rate of 2.0 mL min^–1 the assay could be accomplished in 1 min, including sampling and washing. The method has been successfully applied to the determination of myoglobin in human urine and F^– in water samples. A possible mechanism of chemiluminescence production by myoglobin and luminol is presented.     

Activation Parameters for the Formation and Decay of Partial-Charge-Transfer Exciplexes of 9-Cyanoanthracene, 1,12-Benzperylene, and Pyrene

The factors affecting the rate of formation and decay of exciplexes with partial charge transfer, which form in the kinetic region of photoinduced electron transfer (G ^* _et > –0.2 eV), were studied. The rate of formation of exciplexes is controlled mainly by the diffusion of reactants and the low steric factor (0.15–1.0). The activation enthalpy and entropy for the exciplex formation (9–13 kJ mol^–1 and –(12–28) J mol^–1 K^–1) are close to the activation enthalpy and entropy of diffusion, respectively. Charge transfer in an exciplex and polarization of the medium generally occur after passing the transition state. In contrast, the activation enthalpy of exciplex decay (its conversion into the reaction products) is close to zero (±6 kJ mol^–1) and the activation entropy is strongly negative –(80–130) J mol^–1 K^–1.     

Kinetic study of the reaction betweentrans-tetracyanodioxomolybdate(IV) and fluoride ions

Summary The kinetics of the reaction between [MoO₂(CN)₄]^4– and F^– have been studied in the pH range 8 to 11. The results indicated that the diprotonated form, [MoO(OH₂)(CN)₄]^2–, is the only reactive species and that the aqua-ligand is substituted by the F^– ion according to the following reaction. The k₁ and k_–1 values are 8.8(2) M^–1 s^–1 and 0.6(1)s^–1, respectively, at 15°C. A dissociative substitution process is proposed.     

Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L=Cysteine and related thiolates

Complexes of the [RuIII(edta)SR]n series, with SR–= deprotonated cysteine, N- acetylcysteine, 2–mercaptoethanol, glutathione and penicilamine, were prepared from [Ru(edta)H2O]– and the corresponding RSH thiols, at pH=5.5. The complexes exhibit intense visible absorption bands at ca. 520nm (3500M–1 cm–1), associated with LMCT from the sulfur ligands bound to RuIII. The kinetics of the formation reactions were first order in [RuIII(edta)H2O]– and thiol reactants, with k1 values ca. 1–5×102 M–1s–1 (25°C) for all the sulfur ligands except penicilamine, which reacted slower by a factor of 10. Activation parameters suggest an associative mechanism, as for the coordination of other S- and N-bound ligands to [RuIII(edta)H2O]–. A reactivity decrease is apparent at low and high pH's (ranges 1–3 and 8–10, respectively), associated with acid-base equilibria involving the less reactive [RuIII(Hedta)H2O] and [RuIII(edta)OH]2– species. A significant rate increase was found for cysteine and penicilamine at ca. pH=8.0, because the thiol reactants deprotonate. The equilibrium constants for all the ligands showed that robust complexes were formed, with K=ca. 1×105 M–1 (25°C). The dissociation rate constants, k–1, were in the 10–3–10–4 s–1 range. The influence of nucleophilic and steric effects increasing and decreasing the formation rates, respectively, is discussed for the thiolate ligands, with adequate comparisons with other L species bound to [RuIII(edta)H2O]–.     

The nature of the splitting of the bands in the infrared spectra of phosphorus dithioacids

Conclusions The IR spectra of a series of phosphorus dithioacids were studied under different conditions. The splitting of bands in the regions 490–550 and 2500–2600 cm^–1 is explained by rotational isomerism.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 672–673, March, 1968.     

Cyclodextrin Complexation of the Stilbene 4-(2-(4-Tert-butylphenyl)ethen-1-yl)- benzoate and the Self-assembly of Molecular Devices

E-4-(2-(4- tert - butylphenyl) ethen-1- yl)benzoate, E-1^–, photoisomerizes to the Z-1^– isomer and vice versa in the free state and in the binary complexes 2·E-1^–, 2·Z-1^–, 3·E-1^– and 3·Z-1^– where 2 is the urea-linked cyclodextrin N-(6 ^A -deoxy--cyclodextrin-6 ^A - yl)-N-(6 ^A -deoxy--cyclodextrin-6 ^A - yl)urea and 3 is N,N- bis(6 ^A -deoxy--cyclodextrin-6 ^A - yl)urea. In 2·E-1^–and 3·E-1^– the stilbene occupies both cyclodextrin (CD) components of 2 and 3, whereas in 2·Z-1^– and 3·Z-1^– it only occupies one CD component while the other CD component is unoccupied. 4- tert - Butylphenolate, 4^–, and its carboxylate, 5^–, and sulfonate, 6^–, analogues form the ternary complex 2·Z-1^–·4^– and its analogues and also 3·Z-1^–·4^– and its analogues. These photoisomerize to 2·E-1^–and 3·E-1^– and either free 4^–, 57^– or 6^– and thereby function as molecular devices.     

FTIR-ATR-spectroscopic investigation of the silanization of germanium surfaces with 3-aminopropyltriethoxysilane

Summary The adsorption of 3-aminopropyltriethoxysilane (3-APTS) on germanium crystals was investigated using Attenuated Total Reflection (ATR) spectroscopy. Ethanol, which is produced by the hydrolysis of 3-APTS in water, adsorbs on germanium prior to 3-APTS. This can be checked by the CH₃-modes at 1150 cm^–1 and 2975 cm^–1. The structure differences between chemisorbed and physisorbed 3-APTS can be observed by the shift of the Si-O-Si bands of the silane molecules. The asymmetric and symmetric stretch bands for chemisorbed 3-APTS occurs at 1096 cm^–1 and 1022 cm^–1, whereas, the bands for physisorbed 3-APTS are found at 1115 cm^–1 and 1038 cm^–1. The amino groups of physisorbed 3-APTS display two strong bands at 1566 cm^–1 and 1485 cm^–1 which result from amino groups strongly hydrogen bonded to free silanols. The deformation modes of the amino groups in chemisorbed layers can be found at 1609 cm^–1 and 1512 cm^–1, which is due to the deformation modes of the free amino groups. A controlled chemisorption is important for the development of chemical IR-sensors [15].

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FTIR-ATR-Spektroskopische Untersuchung der Silanisierung von Germaniumoberflächen mit 3-Aminopropyltriethoxysilan

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Dedicated to Prof. Dr. G. Tölg at the occasion of his 60. birthday     

The effect of pressure on the dissociation constant of hydrofluoric acid and the association constant of the NaF ion pair at 25°C

The effect of pressure on the dissociation constant of hydrofluoric acid was determined by using the indicator technique at 25°C at an ionic strength of 0.1m over a pressure range of 1 to 2000 atm. A value of 3.14 for pK _a ^* at I =0 was obtained by extrapolation to zero ionic strength at 1 atm. The pressure dependence yielded a partial molar volume change of –9.6 cm³-mol^–1 and a compressibility change of — 35×10^–3 cm³-mol^–1 –atm^–1 for the dissociation. The dependence of ionic strength on the association constant K _A ^* of NaF was studied at 25°C and 1 atm. Extrapolation to I=0 yielded a pK _A ^* of –0.78. The pressure dependence of K _A ^* gave a change of volume of 3.26 cm³-mol^–1 and a change in compressibility of 6×10^–3 cm³-mol^–1-atm^–1 for the formation of the ion pair.     

An ab initio quantum chemical study of the electronic structure and stability of the pyrrolyl radical: Comparison with the isoelectronic cyclopentadienyl radical

The electronic structure and stability of pyrrolyl are investigated using CASSCF, CASPT2 and G2(MP2) techniques. The ground state of pyrrolyl is found to be ²A₂, with five π-electrons, as in cyclopentadienyl. The computed N–H bond energy of pyrrole is 94.8 kcal mol⁻¹, while the heat of formation Δ_fH₂₉₈^o of pyrrolyl is deduced to be 70.5±1 kcal mol⁻¹. The Arrhenius parameters of N–H and C–H bond fission in pyrrole and cyclopentadiene and hydrogen abstraction reactions (by hydrogen) were also computed, indicating that pyrrolyl forms predominantly by C–H bond fission of pyrrolenine rather than by direct N–H bond fission.     

Heavy metals in selected soils of the semi-arid region of Nigeria

Eight soil profiles developed on crystalline basement complex rocks in the semi-arid region of Nigeria were analyzed for total contents of cesium (Cs), chromium (Cr), cobalt (Co), hafnium (Hf), iron (Fe), lanthanum (La), lutetium (Lu), scandium (Sc), thorium (Th), uranium (U) and ytterbium (Yb). The contents range from 50.3–95.4 Cs, 16.1–58.1 Cr, 0.6–9.0 Co, 9.0–34.8 g g^–1 Hf, 0.31–3.69% Fe, 17.2–60.7 La, 60.4–90.6 Lu, 2.6–12.6 Sc, 8.3–21.5 Th, 4.7–9.2 U and 3.6–92 g g^–1, Yb. Their corresponding means were 68.4, 35.1, 4.0, 19.9 g g^–1, 1.70%, 37.1, 79.4, 6.5, 14.7, 6.7 and 5.0 g g^–1. In general, total Cs, Co, Fe, La, U and Yb increased with further increase with depth. On the other hand, Lu, Sc and Th showed no distinct vertical distribution within the profiles. All eleven elements were correlated with the amounts of clay present in the soils, the correlation being stronger for Cs, Th, Yb, Cr and Lu.     

Immobilization of Urease and Cholinesterase on the Surface of Semiconductor Transducer for the Development of Light-Addressable Potentiometric Sensors

Various methods for the immobilization of urease and butyrylcholinesterase on the insulator surface of a laser-scanned semiconductor transducer (LSST) have been tested and compared for the development of an enzyme-based light-addressable potentiometric sensor (LAPS). The method of preparing photocurable membranes on LAPS is presented, and a new type of enzyme LAPS with photocurable polymeric enzyme membranes has been elaborated. It was found that sensors prepared by means of covalent bonding and cross-linking with inactive protein (type SIII) and with photocurable membrane matrices (type SIV) are more prospective. The enzyme LAPSensors with photocurable membranes demonstrate a degree of sensitivity close to the theoretical value and working ranges of 6.3·10^–5–1.1·10^–2 and 1·10^–4–1·10^–1molL^–1 urea for acrylamide and acrylate-based membrane matrices, respectively, and 2.5·10^–4–2·10^–1molL^–1 butyrylcholine for an acrylamide membrane matrix. It is shown that such sensors can be also used for the analysis of enzyme inhibitors.     

Rapid determination of telmisartan in pharmaceuticals and serum by the parallel catalytic hydrogen wave method

The polarographic characteristics of telmisartan have been investigated in 0.8 mol L^–1 NH₃.H₂O–NH₄Cl (pH 8.9)–0.01 mol L^–1 H₂O₂ as supporting electrolyte. The results demonstrate that the polarographic reduction wave at ca. –1.30 V in the absence of H₂O₂ is a catalytic hydrogen wave, and the reduction wave enhanced by H₂O₂ is a so-called parallel catalytic hydrogen wave. The analytical sensitivity of the parallel catalytic hydrogen wave is ca. 60 times higher than that of the corresponding catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave a novel method has been developed for determination of telmisartan by linear sweep polarography. The calibration curve is linear in the range 2.0×10^–8–2.0×10^–6 mol L^–1 and the detection limit is 1.0×10^–8 mol L^–1. The precision is excellent with relative standard deviations of 2.6% at a concentration of 1.0×10^–7 mol L^–1 telmisartan. The proposed method has been applied to the direct determination of the telmisartan in capsule forms and biological samples. The proposed method has been proved to be advantageous over existing CZE and MEKC methods in simplicity, rapidity, and reproducibility.     

Buffer Standards for the Physiological pH of Zwitterionic Compounds,MOBS and TABS from 5 to 55°C

The values of the second dissociation constant, pK₂, and related thermodynamic quantities of 4-(N-morpholino)butanesulfonic acid (MOBS) and N-tris(hydroxymethyl)-4-aminobutanesulfonic acid (TABS) have already been reported over the temperature range 5–55°C including 37{°}C. This paper reports the pH values of twelve equimolal buffer solutions at designated pH (s) with the following compositions: (a) mixtures of MOBS (0.05 mol-kg^–1) + NaMOBS (0.05 mol-kg^–1); (b) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1); (c) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1); (d) TABS (0.05 mol-kg^–1) + NaTABS (0.05 mol-kg^–1); and (e) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1); and (f) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1). Two buffer solutions have ionic strengths I= 0.05 mol-kg^–1, another two have I=0.08 mol-kg^–1, and the remaining two buffer solutions have I= 0.16 mol-kg^–1, which is close to that of the clinical fluids (blood serum). These buffers have been recommended as a useful pH standard for the measurements of physiological solutions. Conventional pH values of all six buffer solutions from 5–55°C, as well as those obtained from the liquid junction potential correction at 25 and 37{°}C have been calculated. The flowing-junction calomel cell has been utilized to measure E_j, the liquid junction potential.     

The unusual influence of the acidity of the medium on the rate of isotopic exchange of hydrogen of C6H6Cr(CO)2P(C6H5)3

Conclusions When the acidity function H₀ is varied from +1 to –2.5, the rate of the isotopic exchange of hydrogen of benzenechromiumdicarbonylphenylphosphine is directly proportional to the acidity of the medium, while in the case of higher acidities from –2.5 to –7.1, an inverse dependence is observed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 756–758, April, 1974.     

Mass spectrometic investigation of the structure and formation mechanism of ions in the autoionization of aliphatic alcohols

The structure and formation mechanism of ions in the field ionization of methanol and ethanol have been studied by isotopic labeling with O¹⁸ and deuterium, and mass spectrometric analysis. It is shown that these alcohols give identical mass spectra in the molecular ion region, these consisting of four lines: M+1, M, M–1, and M–2. The M+2 ions have the structure ROH·H⁺ while the M–1 ions are (R–H)·OH⁺. For methanol the M–2 ions have the structure of formaldehyde, and for ethanol they have those of both an aldehyde and a vinyl alcohol. It is also shown that field ionization may be used to study the catalytic oxidation of alcohols over platinum by free oxygen.     

Solubility of Solid 1-Hexyne in Liquid Argon and Nitrogen at the Standard Boiling Points of the Solvents

The solubilities of solid 1-hexyne in liquid argon at 87.3 and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in 1-hexyne. The experimental value of the mole fraction solubility of solid 1-hexyne in liquid argon at 87.3 K is (0.85 ± 0.19) × 10^–7 and (1.25 ± 0.08) × 10^–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbon in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l ₁₂ were also calculated. At 90.0 K liquid argon is a better solvent for solid 1-hexyne than is liquid nitrogen.     

Flow injection chemiluminescence determination of naftopidil based on potassium permanganate oxidation in the presence of formaldehyde or formic acid

A flow injection method is proposed for the determination of naftopidil based upon the oxidation by potassium permanganate in a sulfuric acid medium and sensitized by formaldehyde and formic acid. The optimum chemical conditions for the chemiluminescence emission were 0.25 mM potassium permanganate and 4.0 M sulfuric acid. Two manifolds were tested and instrumental parameters such as the length of the reactor, injection volume and flow rate were compared. When using the selected manifold in the presence of 0.4 M formaldehyde, naftopidil gives a second-order calibration graph over the concentration range 0.1–40.0 mg L^–1 with a detection limit calculated (as proposed by IUPAC) of 92.5 ng mL^–1 and a standard deviation of 0.12 mg mL^–1 for ten samples of 10.0 mg L^–1 naftopidil. In the presence of 1.15 M formic acid, naftopidil gives a second-order calibration graph over the concentration range 0.05–40.0 mg L^–1 with a detection limit of 14.2 ng mL^–1 and a standard deviation of 0.37 mg mL^–1 for ten samples of 10.0 mg L^–1 naftopidil. In both cases, the determination is free from interferences from common excipients such as sucrose, glucose, lactose, starch and citric acid.     

Determination of traces of vanadium with the catalytic maximum wave in differential pulse polarography

Summary A differential pulse-polarographic method has been studied for the determination of vanadium employing the catalytic maximum wave. A well-defined differential pulse polarographic peak is observed in the potential range from –0.2 to –0.7 V vs. SCE for vanadium(V) in 10 mmol 1^–1 NaCl containing 10 mmol 1^–1 acetic acid, 40 mmol 1^–1 pyrocatechol, and 2.5 mmol 1^–1 KBrO₃. The peak current is very large and proportional to the concentration of vanadium(V) between 1×10^–7 and 1×10^–6 mol 1^–1. The relative standard deviation at 0.5 mol l^–1 vanadium(V) was 2.06% (n=7). This method has been successfully applied to the determination of vanadium in standard materials such as pond sediment.

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Spurenbestimmung von Vanadium mit Hilfe der katalytischen Maximumsstufe in der Differential-Puls-Polarographie

Zusammenfassung Ein gut definierter differentialpuls-polarographischer Peak wurde für Vanadium(V) in 10 mmol/l NaCl-Lösung, die 10 mmol/l Essigsäure, 40 mmol/l Brenzcatechin und 2,5 mmol/l KBrO₃ enthielt, beobachtet (Potentialbereich –0,2 bis –0,7 V gegen SCE). Der Peakstrom ist sehr groß und die Vanadiumkonzentration im Bereich von 1×10^–7 bis 1×10^–6 mol/l proportional. Die relative Standardabweichung betrug 2,06% (n=7) bei 0,5 mol/l Vanadium(V). Das Verfahren wurde mit gutem Erfolg zur Vanadiumbestimmung in Standardproben (z.B. Teichsediment) eingesetzt.