Water-methanol-benzene ternary system. Thermochemical experiment and computer simulation

Solution heats have been measured for benzene dissolved in mixtures of water with methanol at 25°C. The resulting values are compared with data for water-methanol-aniline, water-acetonitrile-benzene, and water-acetonitrile-aniline systems. Computer simulations have been performed for binary mixtures of water with methanol and dilute solutions of benzene in these mixtures. Thermodynamic and structural characteristics of solutions were obtained by calculations. The enthalpy of benzene transfer from water into a mixed solvent correlates with the relative deviation of the local composition from the mean composition of the mixture.     

Electrophilic fluorinating reagent mediated synthesis of fluorinated alpha-keto Ethers,benzil, and 6,6'-dialkoxy-2,2'-bipyridines

Interactions of various fluorinated and nonfluorinated alcohols with trans-stilbene in the presence of electrophilic reagents were studied. Under neat conditions, reactions of trans-stilbene (1) with fluorinated alcohols, R(f)OH (R(f) = CF3CH2-, CFH2CH2-, CF3CF2CH2-, CF2H(CF2)3CH2-, (CF3)2CH-, (CF3)3C- (2a-f) in the presence of an electrophilic reagent, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) or N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31), gave alpha-keto ethers (3a-f) and benzil (4) in good to moderate yields. alpha-Keto ether and benzil formation was very much dependent on the reaction time, the degree of fluorination of the alcohols, and whether a solvent such as CH3CN, DMF or DMA was utilized. In solution, alpha-keto ethers and benzil did not form. Interestingly, under neat conditions, nonfluorinated alcohols, ROH (R = CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, CH3CH2CH2CH2CH2CH2-) (5g-k) did not react with trans-stilbene in the presence of MEC-31 but gave 6,6'-dialkoxy-2,2'-bipyridines (6g-k), regioselectively, in excellent isolated yields. On the other hand, fluorinated alcohols did not react with MEC-31. Reaction of MEC-31 with an excess of diethylene glycol (7) gave the bipyridine derivative (8) in 88% isolated yield. Reaction of 8 either with diethylaminosulfur trifluoride (DAST) or bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor) readily produced the corresponding difluoro derivative (9) in 85% isolated yield. All new compounds have been characterized by spectroscopic and elemental analysis.     

Study of the mechanism of recyclization of furans into thiophenes and selenophenes in conditions of acid catalysis. 5. Direction of protonation of furans

2,5-Dimethyl-3-D-furan was prepared for the first time. Its recyclization into the corresponding thiophene and selenophene was investigated. The possibility of -C-protonation of the furan ring was confirmed by experimental and quantum chemical data.See [1] for Communication 4.Scientific-Research Institute of Chemistry, N. G. Chernyshevskii Saratov State University, Saratov 410026. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1030–1034, August, 1997.     

Research on heterocyclic compounds. XXIII. Phenyl derivatives of fused imidazole systems

The reaction of various heteroarylamines with ethyl 2-benzoyl-2-bromoacetate was used to obtain some imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, imidazo[2,1-b]thiazoles and imidazo[2,1-b]benzothiazoles characterized by the presence of a phenyl moiety on the imidazole ring. In the case of thiazole and benzothiazole derivatives, unexpected by-products were isolated and their structures elucidated.     

Some applications of supercritical fluid extraction

Supercritical fluid extraction (SFE) exploits the solvation power of fluids at temperatures and pressures close to their critical point. Use of SFE with supercritical CO₂ is reported for the extraction of caffeine and quinine from various plant materials and of morphine from serum. Results are compared with those obtained by extractions with subcritical methanol and tetrahydrofuran, normal organic Soxhlet extractions and solid-phase extraction.     

The separation of the alkaloids of Anabasis aphylla

Summary 1. The optimum conditions for the extraction of the high-boiling alkaloids from technical anabasine sulfate by dilution with water and at various pH values of the medium have been established.2. A method for removing anabasine and lupinine from a mixture of the high-boiling alkaloids ofAnabasis aphylla has been developed which is based on the formation of the carbonates of the strong bases.V. I. Lenin Tashkent State University. Dzerzhinskii Chimkent Pharmaceutical Chemicals Factory. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 468–472, July–August, 1974.     

On incorporation of atomic correlation in transition-metal molecular calculations: NiH

The atomic correlation terms necessary to lead to anaccurate 4s²3d⁸-4s^t 3d⁹ separation for the Ni atom have been incorporated into all-electron MC SCF/Cl calculations for the X² Δ state of NiH. The calculated potential curve properties are significantly improved compared to calculations which dissociate to Hartree-Fock atoms.     

Effect of conformational constraints on gated electron-transfer kinetics. 3. Copper(II/I) complexes with cis- and trans-cyclopentanediyl-1,4,8,11-tetrathiacyclotetradecane

Previous kinetic and electrochemical studies of copper complexes with macrocyclic tetrathiaethers-such as 1,4,8,11-tetrathiacyclotetradecane ([14]aneS4)-have indicated that electron transfer and the accompanying conformational change occur sequentially to give rise to a dual-pathway mechanism. Under appropriate conditions, the conformational change itself may become rate-limiting, a condition known as "gated" electron transfer. We have recently hypothesized that the controlling conformational change involves inversion of two donor atoms, which suggests that "gated" behavior should be affected by appropriate steric constraints. In the current work, two derivatives of [14]aneS4 have been synthesized in which one of the ethylene bridges has been replaced by either cis- or trans-1,2-cyclopentane. The resulting copper systems have been characterized in terms of their Cu(II/I)L potentials, the stabilities of their oxidized and reduced complexes, and their crystal structures. The electron self-exchange rate constants have been determined both by NMR line-broadening and by kinetic measurements of their rates of reduction and oxidation with six or seven counter reagents. All studies have been carried out at 25 degrees C, mu = 0.10 M (NaClO4 and/or Cu(ClO4)2), in aqueous solution. Both Cu(II/I) systems show evidence of a dual-pathway mechanism, and the electron self-exchange rate constants representative of both mechanistic pathways have been determined. The first-order rate constant for gated behavior has also been resolved for the Cu(I)(trans-cyclopentane-[14]aneS4) complex, but only a limiting value can be established for the corresponding cis-cyclopentane system. The rate constants for both systems investigated in this work are compared to values previously determined for the Cu(II/I) systems with the parent [14]aneS4 macrocycle and its derivatives involving phenylene and cis- or trans-cyclohexane substituents. The results are discussed in terms of the influence of the fused rings on the probable conformational changes accompanying the electron-transfer process.     

The multiconfiguration time-dependent Hartree-Fock method for quantum chemical calculations

We apply the multiconfiguration time-dependent Hartree-Fock method to electronic structure calculations and show that quantum chemical information can be obtained with this explicitly time-dependent approach. Different equations of motion are discussed, as well as the numerical cost. The two-electron integrals are calculated using a natural potential expansion, of which we describe the convergence behavior in detail.     

Reaction of alkali-metal hypohalites with stereoisomeric 2-methyl-1-alkyl-2-methyl-4-ethynyldecahydro-4-quinolols

Isomeric 1-alkyl-2-methyl-4- (haloethynyl) decahydro-4-quinolols were synthesized by reaction of the individual stereoisomers of 1-alkyl-2-methyl-4-ethynyl-decahydro-4-quinolols with alkali solutions of potassium hypochlorite and hypobromite. 1-Chloro-2-methyl-4-ethynyl decahydro-4-quinolols are formed by the action of an alkaline solution of potassium hypochlorite on isomeric 2-methyl-4-ethynyldecahydro-4-quinolols. Hydrogenolysis of the carbon-halogen bond accompanied by hydrogenation of the CC bond was observed under conditions of catalytic hydrogenation of 1,2-dimethy1-4-(haloethynyl) decahydro-4-quinolols. Primarily hydrogenolysis of the nitrogen-halogen bond and subsequent reduction of the acetylenic bond occur in the hydrogenation of 1-chloro-2-methyl-4-ethynyldecahydro-4-quinolols. Replacement of chlorine by hydrogen and subsequent alkylation of the resulting secondary amine and formation of the hydrochlorides of the corresponding N-methyl-substituted acetylenic alcohols occur in the reaction of the chloramines with a mixture of formaldehyde and formic acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 98–103, January, 1976.