A study on the solvent extraction of Ag/I/ with 1,2,3-benzotriazole in chloroform

A rapid and selective method has been developed for the substoichiometric extraction of Ag/I/with 1,2,3-benzotriazole /1,2,3-BT/ in chloroform in the presence of versenate. The effect of various parameters such as pH, time of equilibration, solvent, anions, cations, etc., on the extraction coefficient value has been studied. The stoichiometry of the extracted species of 11 /Ag:1,2, 3-BT/ was obtained by the slope ratio method and substoichiometric extraction. Decontamination factors for most elements in the substoichiometric extraction of Ag/I/ were found to be higher than 10⁴.     

A study on the solvent extraction of Pd/II/ with 1,2,3-benzotriazole into methyl iso-butyl ketone

A novel method has been developed for the extraction of Pd/II/ with 1,2,3-benzotriazole /1,2,3-BT/ into methyl isobutyl ketone /MIBK/ at a pH of 4.0. The effects of pH, time of equilibration, solvent, anions and cations on the extraction coefficient have been evaluated. The stoichiometry of the extracted species of 12 was obtained by the slope ratio method and by the method of substoichiometric extraction. Separation factors and decontamination factors for a number of elements in the extraction of Pd/II/ were also obtained.     

A theoretical study of substituted allyl anions

CNDO/2 calculations have been used to optimise the geometry of the allyl anion. Electron-withdrawing substituents are found to decrease the proton affinities of allylic anion, with the trans-substituted anion being the more stable. However when the only substituent on the anion is an alkyl group then the cis anion is the more stable. The calculated proton affinities of several monosubstituted allyl anions and the electron densities of the methyl hydrogens in the hydrocarbons are both found to correlate with the Hammett substituent constants.     

On the complexation of the sodium cation with beauvericin: experimental and theoretical study

Abstract  

From extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements, the stability constant of the beauvericin·Na⁺ complex species dissolved in nitrobenzene saturated with water was determined. By using quantum mechanical density functional level of theory (DFT) calculations, the most probable structure of this complex species was derived.     

A theoretical study of the structure and vibrational spectrum of trifluoromethanol

Ab initio molecular orbital calculations have been applied to trifluoromethanol. The potential barrier for rotation has been computed. The internal coordinate valence force field is presented and harmonic vibrational frequencies of all the normal modes are reported. Theoretical results are in good agreement with the few observed frequencies.     

Synthesis of Dihydro- and Tetrahydro-1,2,4,5-tetrazines from the Reaction of Nitrilimines with 1-Substituted-1-methylhydrazine

Abstract

The reaction of nitrilimines (2) with 1-substituted-1-methylhydrazines (3–6) led to the formation of the respective amidrazones (7) when R = CH₃, Ph, and to the acyclic adducts (8,9) when R = CHO and COCH₃. The acyclic adducts underwent thermal oxidative cyclization at CH₃ to give the unexpected 1,2,4,5-tetrazines (10,11). Dihydro-l,2,4,5-tetrazines (12) were also seperated when R = CHO.     

Extraction and theoretical study on complexation of the strontium cation with antamanide

By using extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Sr²⁺(aq) + 2A^?(aq) + 1(nb) ? 1·Sr²⁺(nb) + 2A^?(nb) occurring in the two-phase water–nitrobenzene system (A^? = picrate, 1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) was determined as log K _ex (1·Sr²⁺, 2A^?) = ?0.3 ± 0.1. Further, the stability constant of the 1·Sr²⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β _nb (1·Sr²⁺) = 8.8 ± 0.1. Finally, applying quantum mechanical density functional level of theory calculations, the most probable structure of the cationic complex species 1·Sr²⁺ was derived. In the resulting complex, the “central” cation Sr²⁺ is bound by six bond interactions to the corresponding six oxygen atoms of the parent ligand 1. The interaction energy of the considered 1·Sr²⁺ complex was found to be ?1,114.9 kJ/mol, confirming the formation of this cationic species as well.     

Extraction and theoretical study on the complexation of the strontium cation with beauvericin

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Sr²⁺(aq) + 2A^?(aq) +1(nb) ? 1·Sr²⁺(nb) + 2A^?(nb) taking place in the two-phase water–nitrobenzene system (A^? = picrate, 1 = beauvericin; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex(1·Sr²⁺,2A^?) = ?0.6 ± 0.1. Further, the stability constant of the 1·Sr²⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β _nb(1·Sr²⁺) = 8.5 ± 0.1. Finally, by using quantum-mechanical DFT calculations, the most probable structure of the resulting cationic complex 1·Sr²⁺ was derived.     

SN(ANRORC) mechanism XX. Degenerate ring transformations in reactions of 1,2,4,5-tetrazines with hydrazine

Evidence is presented that the hydrazinolysis of 3-amino- (5) and 3-bromo-6-methyl-1,2,4,5-tetrazine ( 7 ) into the 3-hydrazino-6-methyl-1,2,4,5-tetrazine ( 6* ) with ¹⁵N-labelled hydrazine leads to incorporation of ¹⁵N in the 1,2,4,5-tetrazine ring. Thus in the hydrazino-deamination and hydrazino-debromination a S_N(ANRORC) mechanism is operative. Based on quantitative mass spectrometry it was found that 20-25% of both 5 and 7 reacts according to this S_N-(ANRORC) mechanism. The mechanism of these degenerate ring transformations is discussed.     

A theoretical and experimental study of vibrational properties of alkyl xanthates

Geometrical structure and vibrational modes of potassium and sodium ethyl/heptyl xanthates were studied, using both theoretical and experimental methods. Both Hartree-Fock and density functional theory were used. The experimental method used was infrared absorption spectroscopy (FTIR). Our work showed that vibrational frequencies calculated with density functional theory, using the local density approximation, are in very good agreement with experiments. The results were not improved by using the more sophisticated and computationally demanding B3LYP functional.     

Experimental and theoretical study on the complexation of Ca2+ with beauvericin

From extraction experiments and γ-activity measurements, the exchange extraction constant corresponding to the equilibrium Ca²⁺(aq) + 1·Sr²⁺(nb) ? 1·Ca²⁺(nb) + Sr²⁺(aq) taking place in the two-phase water–nitrobenzene system (1 = beauvericin; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex(Ca²⁺, 1·Sr²⁺) = 1.1 ± 0.1. Further, the stability constant of the 1·Ca²⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β _nb(1·Ca²⁺) = 10.1 ± 0.2. Finally, by using quantum mechanical density functional level of theory calculations, the most probable structures of the non-hydrated 1·Ca²⁺ and hydrated 1·Ca²⁺·H₂O complex species were predicted.     

A theoretical study of rate coefficients for the O + NO vibrational relaxation

Quasi-classical trajectories have been integrated to study the vibrational relaxation of the O + NO(v) process as a function of the initial vibrational quantum number for T = 298 K, 1500 K, and 3000 K. Two reliable potential energy surfaces have been employed for the A' and A' doublet states of NO2. The calculated vibrational relaxation rate constants show a nearly v-independent behavior at room temperature and a moderate increase with v for higher temperatures. Although deviating significantly from the recommended values, good agreement with recent experimental results has been obtained. The importance of multi-quantum transitions is also analyzed.     

A theoretical study on the ionization of tetrafluoroethylene with analysis of vibrational structure of the photoelectron spectra

Ab initio calculations have been performed to study on the molecular structures and the vibrational levels of the low-lying ionic states (²B_2u,²A_g,²B_2g,²B_3u,²A_u,²B_1g,²B_1u, and²B_3g) of tetrafluoroethylene. The equilibrium molecular structures and vibrational modes of these states are presented. The theoretical ionization intensity curves including the vibrational structures of the low-lying eight ionic states are also presented and compared with the photoelectron spectrum. Some new assignments of the photoelectron spectra are proposed.     

A theoretical study on the ionization of furan with analysis of vibrational structure of the photoelectron spectra

Summary Ab initio calculations have been performed to study on the molecular structures and the vibrational levels of the low-lying ionic states (²A₂ and²B₁) of furan. The equilibrium molecular structures and vibrational modes of these states are presented. The theoretical ionization intensity curves including the vibrational structures of the low-lying two ionic states are also presented and compared with the photoelectron spectrum. A number of new assignments of the photoelectron spectra are proposed.     

A combined experimental and theoretical study on the complexation of Li+ with valinomycin

Abstract  

From extraction experiments in the two-phase water–nitrobenzene system and γ-activity measurements, the stability constant of the valinomycin–lithium complex in nitrobenzene saturated with water was determined. Further, the structure of the resulting complex was indicated by means of the density functional level of theory (DFT) calculations.     

Experimental and theoretical study of Zn(II) complexation with ceftriaxone

Complexation of Zn²⁺ cations with antibiotic ceftriaxone anions (Ctx^2–) has been studies by pH-metric titration at 25°С and a ionic strength of 0.1 (KNO₃). The formation of the ZnCtx complex has been revealed, and logβ(ZnCtx) = 4.45 ± 0.09 has been calculated. The computer model of the complex has been calculated by the DFT method with the use of the B3LYP hybrid functional and the LACV3P**+ basis set. According to these calculations, Zn(II) in the complex has the coordination number 4 and a nearly tetrahedral coordination sphere and is coordinated to Ctx^2– through carboxylate, β-lactam, and hydroxytriazinone oxygen atoms and the thiazole nitrogen atom. Formation of the chelate structure accounts for the high stability of the complex.