The first chemoenzymatic total synthesis of the phytotoxic nonenolide putaminoxin and its (5S,6E,9S)-diastereomer

The limitations of an alcohol dehydrogenase regarding the oxidative kinetic resolution of homoallylic alcohol containing alkyl chains were investigated, leading to a valuable building block for the total synthesis of phytotoxic nonenolide putaminoxin. The enzymatic approach towards the enantioenriched homoallylic alcohol was compared to classical, nonenzymatic approaches using asymmetric reagent controlled allyl additions and the obtained building block was used for the total synthesis of putaminoxin and its (5S,6E,9S)-diastereomer. After the spectroscopic analysis of the synthesized compounds, discrepancies were observed to already published data of isolated and synthesized putaminoxin. Therefore, a systematic comparison of NMR data was carried out. The result underlines the necessity of total synthesis for the absolute assignment of configuration.     

Adiabatic compressibility of critical binary mixtures of nitroethane/isooctane and nitroethane/3-methylpentane

The adiabatic compressibility β_S of nitroethane/isooctane is measured from 18 to 900 Hz at reduced temperatures ? ranging from 5 × 10^-5 to 5 × 10^-2. The zero-frequency compressibility extrapolated from the data is related with the specific heat at constant pressure c_p through the theory of Ferrell and Bhattacharjee (FB). The coupling constant g is evaluated from this relation as 0.38, which agrees with that from the thermodynamic definition of g. β_S at 900 Hz is observed for nitroethane/3-methylpentane at ? 5 × 10^-5-6 × 10^-2. A linear plot of the critical part of β_S against 1n? gives g = 0.34, which agrees with g from the thermodynamic definition and also with that from ultrasonic absorption. Numerical values of the critical and background components of β_S, the isothermal compressibility β_T, c_p, the specific heat at constant volume c_v, and the thermal expansion coefficient α_p are calculated for the two mixtures. The expression of β_S from Anisimov's theory is found to be consistent with that from the FB theory.     

Biocatalytic and chemical routes to all the stereoisomers of methionine and ethionine sulfoxides

Biotransformations of the N-phthaloyl derivatives of d- and l-methionine and of d- and l-ethionine by Beauveria bassiana ATCC 7159 or Beauveria caledonica ATCC 64970 produce the corresponding (S_S) sulfoxides in good yield and diastereomeric excess. Pure (S_SS_C) diastereomers can be obtained from l-series substrates by crystallisation of the biotransformation extract, and the corresponding (S_SR_C) products obtained from d-series substrates by chromatography of the biotransformation extract. Hydrogen peroxide-catalysed oxidation of the N-phthaloyl derivatives of d- and l-methionine and of d- and l-ethionine gives diastereomeric mixtures from which the (S_SS_C) and (R_SR_C) diastereomers can be obtained by crystallisation, and the (S_SR_C) and (R_SS_C) diastereomers obtained by chromatography. N-Cbz- and N-t-Boc methionines are also converted to sulfoxides with predominant (S_S) configuration by both B. bassiana and B. caledonica, but the isolated yields and d.e. of products were generally lower than those obtained from the N-phthaloyl substrates.Removal of the N-phthaloyl group from diastereomerically pure methionine and ethionine sulfoxides gave the corresponding amino acid sulfoxides in high yield; removal of N-Cbz and N-t-Boc groups from protected methionine sulfoxides was also achieved without loss of configuration at sulfur.     

Control of polymorphism by crystallization of N,N-diisopropylcarbamoylisatin

N,N-Diisopropylcarbamoylisatin showed polymorphism and was crystallized into two different space groups, chiral P2₁2₁2₁ and racemic P2₁/c from the solvent; the polymorphism could be controlled by crystallization from the melt using the difference of melting points.     

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group 13. Copolymerization of vinylidene fluoride with 2-benzoyloxypentafluoropropene

The synthesis of 2-benzoyloxypentafluoropropene (BPFP) and its radical copolymerization with vinylidene fluoride (VDF), initiated by tert-butyl peroxypivalate is presented. In a first step, the preparation of two monomers [F₂CC(CF₃)OCOR were R stands for CH₃ or C₆H₅] was attempted. In contrast to the acetoxy derivative that could not be isolated, the benzoyl monomer was purified and then copolymerized with VDF. A series of 11 copolymerization reactions was achieved starting from initial [VDF]₀/([BPFP]₀+[VDF]₀) molar ratios ranging from 19 to 99 mol%. The molar compositions of the obtained copolymers were assessed by means of ¹⁹F nuclear magnetic resonance spectroscopy. From the Tidwell and Mortimer method, this kinetics of copolymerization led to the determination of the reactivity ratios, r_i, of both comonomers (r_VDF=0.77±0.40 and r_BPFP=0.11±0.32). Hence, the Alfrey and Price equation enabled one to assess the Q and e parameters of BPFP as follows: 0.019 (from Q_VDF=0.008), 0.043 (from Q_VDF=0.015) or 0.182 (from Q_VDF=0.036) and 1.97 (vs e_VDF=0.40), 2.07 (vs e_VDF=0.50) or 2.77 (vs e_VDF=1.20), respectively. These Q-e parameters and r_i were compared to those of other fluoroalkenes and are discussed.     

A quantitative interpretation of the magnetic field effect on hyperfine-coupling-induced triplet fromation from radical ion pairs

Experimentally determined B_1/2 values characterizing the magnetic field dependence of molecular triplet production from radical ion pairs originating from photoinduced electron transfer are compared with semi-empirical values obtained according to B_1/2(hfi) = 2(B₁² + B₂²)/(B₁ + B₂) from the root-mean-square values for the hyperfine coupling of the two radicals, B₁ and B₂. The very good agreement is discussed.     

The infrared spectrum of chd2cn and the ground state geometry of methyl cyanide

Analysis of the rovibration spectrum of CHD₂CN enables the rotation parameter (A_o—B?_o) to be determined, from which the value of A_o may be found using the microwave B_o and C_o constants. The use of A_o (CHD₂CN) in conjunction with all other available B_o and C_o constants for isotopes of methyl cyanide enables the ground state geometry to be defined within fairly narrow limits. The CH bond length is in agreement with the value predicted from the CH vibration frequency of CHD₂CN, and with the value calculated from the results of a recent analysis of the infrared spectrum of CD₃CN.     

Molecular weight dependence of crystal pattern transitions of poly(ethylene oxide)

Crystal patterns in ultrathin films of six poly(ethylene oxide) fractions with molecular weights from 25000 to 932000 g/mol were characterized within crystallization temperature range from 20 ℃ to 60 ℃.Labyrinthine,dendritic and faceted crystal patterns were observed in different temperature ranges,and then labyrinthine-to-dendritic and dendritic-tofaceted transition temperatures T L-D and T D-F were quantitatively identified.Their molecular weight dependences are T L-D(M w) = T L-D(∞) K L-D /M w,where T L-D(∞) = 38.2 ℃ and K L-D = 253000 ℃.g/mol and T D-F(M w) = T D-F(∞) K D-F /M w,where T D-F(∞) = 54.7 ℃ and K D-F = 27000 ℃.g/mol.Quasi two-dimensional blob models were proposed to provide empirical explanations of the molecular weight dependences.The labyrinthine-to-dendritic transition is attributed to a molecular diffusion process change from a local-diffusion to diffusion-limited-aggregation(DLA) and a polymer chain with M w ≈ 253000 g/mol within a blob can join crystals independently.The dendritic-to-faceted transition is attributed to a turnover of the pattern formation mechanism from DLA to crystallization control,and a polymer chain with a M w ≈ 27000 g/mol as an independent blob crosses to a depletion zone to join crystals.These molecular weight dependences reveal a macromolecular effect on the crystal pattern formation and selection of crystalline polymers.     

Relative permittivities and refractive indices of binary mixtures of cyclohexanone with dichloromethane,trichloromethane, 1,2-dichloroethane,trichloroethene and cyclohexane at T=303.15 K

Relative permittivities, ϵ_r, and refractive indices, n_D, have been measured for binary liquid mixtures of cyclohexanone (C₆H₁₀O) with dichloromethane (CH₂Cl₂), trichloromethane (CHCl₃), 1,2-dichloroethane (CH₂ClCH₂Cl), trichloroethene (CHClCCl₂), and cyclohexane (c-C₆H₁₂) at T=303.15 K. The values of the deviations of ϵ_r and n_D from values arising from mole fraction average, which are represented respectively by Δϵ_r and Δn_D have been calculated. Values of ϵ_r and Δn_D have been fitted by the method of least squares to smoothing equations. Δϵ_r for the various mixtures has been discussed from the viewpoint of the existence of specific interactions between the components.     

Concentration dependence of critical exponents for gelation in gellan gum aqueous solutions upon cooling

The sol-gel transition in aqueous gellan gum solutions induced upon cooling was investigated by rheology measurements. The gelation temperature was determined from the crossover point of storage and loss moduli, i.e., G′ = G′′ (T_c) and from the Winter’s criterion (T_gel), respectively, which increased with gellan concentration. T_gel was higher than T_c and the difference became larger as the gellan concentration got higher. The relaxation critical exponent n was estimated with the Winter’s method and the self-similarity was observed from the critical gel. The scaling for the zero-shear viscosity η₀ before the gel point and the equilibrium modulus G_e after the gel point was established against the relative distance ε from the gel point over the gellan concentration C_g of 1.0-2.5 wt%, giving the critical exponents k and z. The critical exponent n calculated from k and z agrees well with n from the Winter’s criterion. However, no universal n was found for the gelation in aqueous gellan gum solutions, indicating that this gelation should be classified into the cross-linking category for the physical gelation. The critical exponent n decreased with increasing C_g for the gellan gum solution. The fractal dimension d_f calculated from n with the screened hydrodynamic interaction and the excluded volume effect suggested a denser structure in the critical gel with higher C_g.     

Vibrational energy disposal in reactions of fluorine atoms with hydrides of groups III,IV and V

The HF infrared chemiluminescence from the reactions of F atoms with B₂H₆, CH₄, CH₃F, CH₂F₂, CH₂Cl₂, CH₃ONO. CH₃NO₂, NH₃ (and ND₃). PH₃ and HNCO has been observed from a 300 K flowing-afterglow reactor. Experiments were done for a range of CH₄ and F atom concentrations to identify conditions which were free of vibrational relaxation and secondary reactions, and these conditions were used to assign initial HF(v) vibrational distributions for each reaction. The emission intensity from each reaction also was compared to that from CH₄ in order to obtain the relative HF formation rate constants at 300 K. Since the absolute rate constant for F + CH₄ is well established, the combination of all of these data provides absolute rate constants for HF(v) formation at 300 K. The ND₃ reaction was studied to obtain information on more vibrational levels in order to better estimate the HF(v = 0) and DF(v = 0) components of the ammonia distributions. With NH₃ and ND₃ there is no significant isotope effect on the energy disposal. Except for NHCO, for which an addition-elimination channel is possible, the HF(v) distributions are inverted and <f_v > = 0.60. Differences between the HF(v) distributions reported here and some other reports in the literature are noted: the present data are discussed as representative of direct H atom abstraction for 300 K Boltzmann conditions. The HCl infrared chemiluminescence from the F + CHCl₂ secondary reaction also was observed; the HCl(v) distribution was v₁: v₂: v₃: v₄: v₅ - 0.47: 0.23: 0.18: 0.08: 0.04.     

Quantum chemical calculations of intracell potential profile in superionic transition range in LaF3

The results of quantum chemical calculations of the potential profile in the LaF₃ crystal lattice in the range of superionic phase transition are presented for clusters containing 24 to 1200 ions. It is found that the values of formation energy E _a of vacancy-interstitial fluoride ion defects and potential barriers E _d hindering the movement of fluoride ions and determining the efficiency of charge transport in the lattice grow monotonously from the minimum values E _a = 0.12 eV and E _d = 0.22 eV for a 24-ion cluster to the maximum E _a = 0.16 eV and E _d = 0.26 eV for clusters of 576 and 1200 ions. It is shown that the values of E _a and E _d obtained for the dielectric phase (T < T _c) are several times the values of E _a and E _d for the superionic state (T ≥ T _c) of LaF₃. The values of E _a and E _d obtained by quantum chemical calculations from clusters of 576 and 1200 ions agree well with energies E _a and E _d obtained from the analysis of the data of the Raman and quasielastic light scattering.     

Correlation of SiO x layer thickness and properties of BOPP/SiO x composite films with spin coating process parameters

The effects of the spin coating process parameters on the thickness of the SiOx layer of the BOPP/SiOx composite film were investigated. When the concentration of tetraethoxysilane (TEOS) increased from 12.5 vol% to 55% vol%, the SiOx thickness increased from about 80 nm to 470 nm. In the sol time range of 1.5 h to 5 h the SiOx layer thickness reached a maximum at about 4 h and the change of the thickness roughly matched the change of the silica colloidal sphere sizes in sol. When the spin-coating speed of the dispensing stage increased from 450 r/min to 500 r/min, the SiOx layer thickness drastically decreased from about 1.67 μm to 400 nm. While the spin-coating speed of the thinning and drying stage went up to 1200 r/min, the SiOx layer thickness was in the range of 330 nm to 390 nm. It was also found that the SiOx layer thickness was almost increased linearly from about 500 nm to 1.02 μm with the ratio of the commercial silica colloidal to the TEOS from 0.2 to 1.0. The water contact angles decreased to about 23.0° for the BOPP/Si-Sol composite film with 1.67 μm SiOx layer and about 4.0° for the BOPP/mixing Si-Sol composite film with 1.02 μm SiOx layer. Compared to BOPP, the light transparency of the BOPP/Si-Sol composite films decreased by about 5.5% with the SiOx layer from about 80 nm to 1.67 μm and by 7.0% for the BOPP/mixing Si-Sol composite film with the SiOx layer from about 350 nm to 1.02 μm respectively.     

Biocatalytic and chemical preparation of all four diastereomers of methionine sulfoxide

Biocatalytic or chemical oxidations can be used in a complementary manner for the preparation of all four diastereomers of methionine sulfoxide with high diastereomeric purity in overall isolated yields of 20–55% from methionine. The N-phthaloyl derivatives of L- and D-methionine were selectively oxidised to the (S_SS_C) and (S_SR_C) sulfoxides respectively by biotransformation using the fungus Beauveria bassiana ATCC 7159. Hydrogen peroxide oxidation of the same materials gave mixtures from which the (S_SS_C) and (R_SR_C) isomers can be readily isolated by crystallisation. Chromatography of the residual material then afforded the (R_SS_C) and (S_SR_C) isomers.     

High-temperature heat capacity of YbAl3(BO3)4

The isobaric heat capacity C _p (T) of YbAl₃(BO₃)₄ grown by spontaneous crystallization from solution (100 ? n) wt % (Bi₂Mo₃O₁₂ + 2.5% B₂O₃ + 0.75% Li₂MoO₄) + n wt % YbAl₃(BO₃)₄ is studied experimentally in the region of 344–1016 K. It is established that there are no extrema on the C _p (T) dependence, and the obtained data can be described using the Berman-Brown polynomial. The temperature variations of enthalpy and entropy are calculated from the C _p (T) dependence.     

Estimation of the heat capacity of some uranium-rare earth mixed oxides from thermal expansion and vice versa

Estimation of the high temperature heat capacity (C _p) data from experimental high temperature thermal expansion (α _v) data and vice versa from the known values of the ratio (α_v/C _p) at low temperatures were carried out by assuming linear relationship of the ratio α _v /C _p with temperature (at T > θ _D). The assumption was examined using the known α _v and C _p values of single phase fluorite systems such as UO₂, ThO₂ and PuO₂. It was also examined using the known α _v and C _p of the mixed oxides (U_1?y La_y) O_2±x (y = 0.2, 0.4, 0.6 and 0.8). The estimated values of α _v and C _p are in good agreement with the experimental values within ±3%. Using the assumption the high temperature heat capacity data of (U_1?y Ce _y ) O₂ (y = 0.2, 0.8) and (U_1?y Gd _y ) O_2±x (y = 0.2, 0.5) were computed from the experimental high temperature α _v data.     

Energetics of formation of alkali and ammonium cobalt and zinc phosphate frameworks

Alkali and ammonium cobalt and zinc phosphates show extensive polymorphism. Thermal behavior, relative stabilities, and enthalpies of formation of KCoPO₄, RbCoPO₄, NH₄CoPO₄, and NH₄ZnPO₄ polymorphs are studied by differential scanning calorimetry, high-temperature oxide melt solution calorimetry, and acid solution calorimetry.α-KCoPO₄ and γ-KCoPO₄ are very similar in enthalpy. γ-KCoPO₄ slowly transforms to α-KCoPO₄ near 673 K. The high-temperature phase, β-KCoPO₄, is 5-7 kJ mol⁻¹ higher in enthalpy than α-KCoPO₄ and γ-KCoPO₄. HEX phases of NH₄CoPO₄ and NH₄ZnPO₄ are about 3 kJ mol⁻¹ lower in enthalpy than the corresponding ABW phases. There is a strong relationship between enthalpy of formation from oxides and acid-base interaction for cobalt and zinc phosphates and also for aluminosilicates with related frameworks. Cobalt and zinc phosphates exhibit similar trends in enthalpies of formation from oxides as aluminosilicates, but their enthalpies of formation from oxides are more exothermic because of their stronger acid-base interactions. Enthalpies of formation from ammonia and oxides of NH₄CoPO₄ and NH₄ZnPO₄ are similar, reflecting the similar basicity of CoO and ZnO.     

Spectroscopy and dynamics of 9,10-dichloroanthracene-Arn van der Waals complexes

In this paper we report on the measurements of the absorption spectra of large van der Waals complexes in planar supersonic jets. The absorption spectra and the fluorescence excitation spectra of the complexes of 9,10-dichloroanthracene (DCA) with Ar atoms are reported for the S₀ → S₁(0) vibrationless transition of DCA·Ar_n (n = 1?6), and from the S₀ → S₁ (1390 cm^?1) transition of DCA·Ar_n (n = 1?4). Information on the structure of these complexes was inferred from the additivity of the spectral shifts per added rare-gas atom (ASSRA) for DCA·AR_n (n = 1.2) and from deviations from the ASSRA for CDA-Ar_n (n = 3?6). The vibrational predissociation (VP) dynamics of DCA-Ar_n (n = 1?3) complexes was interrogated by fluorescence quantum yield, Y, measurements. The value of the S₁ (1390 cm^?1) state of DCA·Ar_n (n = 1?3) exhibits a dramatic enhancement relative to that of DCA. Utilizing the dependence of Y on the excess vibrational energy of bare DCA, we were able to estimate the internal energy of the fragments resulting from VP of DCA·Ar_n of DCA·Ar_n (n = 1?3). An upper limit of ? 100 ps was estimated for the VP (and/or vibrational energy redistribution) lifetime from the S₁ (1390 cm^?1) state of DCA·Ar₃.     

Studies of the system TaS2−xSex

Single crystal and powder samples of the system TaS_2?xSe_x have been prepared and studied. The range of solubility was found to extend from x = 0 to x = 2.0. X-Ray analysis has shown that mixed anion samples exhibit a series of hexagonal layered polymorphs similar to those found in TaS₂ and TaSe₂, with the a and c lattice parameters increasing monotonically from TaS₂ to TaSe₂. Electrical transport properties were measured on single crystals and found to be similar to the end compositions. Organic molecules such as pyridine and collidine were found to intercalate TaS_2?xSe_x for x ≦ 1.4, and superconducting transition temperatures were measured for both intercalated and unintercalated samples. The highest T_c obtained was 4.1 K in the 4H(c) phase of the sample TaS_1.6Se_0.4.     

Complexes of the selected transition metal ions with 4-methoxycinnamic acid

In this study, 4-methoxycinnamates of Mn(II), Co(II), Ni(II), Cu(II), Cd(II), Nd(III) and Gd(III) were synthesised. From the infrared (IR) spectra analysis of complexes, sodium salt and according to the spectroscopic criteria the carboxylate groups seem to be bidentate chelating. The complexes of 4-methoxycinnamates lose the water molecules in one or two steps. The final products of their decomposition are oxides of the respective metals. The enthalpy values of dehydration process were determined. The FTIR spectra of the gas phase products indicate that the decomposition of the complexes is connected mainly with the release of molecules of water (H₂O), carbon dioxide (CO₂), carbon monoxide (CO), methane (CH₄) and other hydrocarbons. The analysed compounds follow the Curie?CWeiss law. The magnetic moment values experimentally determined change as follows: from 5.90??? _B to 6.27??? _B for Mn(II) complex, from 4.57??? _B to 4.99??? _B for Co(II) complex, from 3.68??? _B to 3.30??? _B for Ni(II) complex, from 1.87 ?? _B to 1.96 ?? _B for Cu(II) complex, from 3.06??? _B to 3.51??? _B for Nd(III) complex, and from 6.91??? _B to 6.90??? _B for Gd(III) complex.