Substituent effect on the formation of organically-modified silicate-phosphate alternating copolymer through nonaqueous acid–base reaction

Organically-modified silicate-phosphate and silicate-phosphite copolymers were prepared through nonaqueous acid–base reaction. The inductive effect of the organic substituent of the starting materials such as organically-modified chlorosilane and phosphorous acid on the acid–base reaction was investigated by ³¹P NMR measurement and ab initio molecular orbital calculation. The condensation reaction takes place by nucleophilic addition of phosphate ion (or phosphite ion) to chlorosilane through S_N2 mechanism to form silicate-phosphate (or phosphite) network. The reactivity of the acid–base pair can be controlled by changing the inductive effect of the organic substituents on the starting materials.     

Simultaneous uptake of Ni2+, NH4+ and PO4(3-) by amorphous CaO-Al2O3-SiO2 compounds

Simultaneous uptake of Ni2+, NH4+, and PO4(3-) by amorphous CaO-Al2O3-SiO2 (C-A-S) compounds was investigated using batch and column methods. Fifteen different C-A-S samples with systematically varied chemical compositions were prepared by coprecipitation from ethanol-water solutions containing Ca(NO3)2.4H2O, Al(NO3)3.9H2O, and Si(OC2H5)4, using NH4OH as the precipitating agent. The resulting precipitates were dried and heated at various temperatures to produce the C-A-S samples, which were then characterized by XRD, FTIR, solid state MAS NMR, DTA-TG, and N2 adsorption. All the C-A-S samples prepared at 600-900 degrees C were amorphous, apart from the CaO-rich samples. Simultaneous uptake of Ni2+, NH4+, and PO4(3-) was determined by a batch method using a solution with an initial concentration of 2 mM. In these experiments, the uptake abilities of the C-A-S samples for Ni2+ and PO4(3-) were high, but were relatively low for NH4+. The uptake abilities for Ni2+ and PO4(3-) increased but that for NH4+ decreased as the silica content in the C-A-S decreased, suggesting that similar uptake mechanisms (ion substitution and/or precipitation) are operating for Ni2+ and PO4(3-), but the uptake mechanism for NH4+ is different (physical adsorption). The column experiments indicate that the order of uptake ability of C-A-S for the three ions is NH4+ < PO4(3-) < Ni2+. Although the silica content of the C-A-S does not have the expected influence on the uptake of these three ions, for NH4+ it plays an important role in the formation of the amorphous phase and also in the suppression of Ca2+ and/or Al3+ release from the C-A-S during the uptake experiments. The optimum uptake properties of the C-A-S can thus be controlled by adjusting the chemical compositions and heating conditions under which the samples are prepared.     

The vibrational structure of the X 1A1 - A 1B1 and A 1B1 - B 1A1 band systems of GeH2/GeD2 based on global potential energy surfaces

Transition probabilities were evaluated for the X (1)A(1)-A (1)B(1) and A (1)B(1)-B (1)A(1) systems of GeH(2) and GeD(2) to analyze the X-->A-->B photoexcitation. Franck-Condon factors (FCFs) and Einstein's B coefficients were computed by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of the X (1)A(1), A (1)B(1), and B (1)A(1) electronic states and the transition dipole moments for the X-A and A-B systems. The global PESs were determined by the multireference configuration interaction calculations with the Davidson correction and the interpolant moving least squares method combined with the Shepard [Proceedings of the 1968 23rd ACM National Conference (ACM, New York, 1968)] interpolation. The barriers to linearity correcting the spin-orbit interaction are evaluated to be 22,000 cm(-1) for the X state, 6300 cm(-1) for the A state, and 560 cm(-1) for the B state. The obtained FCFs for the X-A and A-B systems indicate that the bending mode is strongly enhanced in the excitation since the equilibrium bond angle greatly varies within the three states. The photoexcitation and fluorescence spectra calculated for the X-A system agree well with the observed spectra. The theoretical lifetimes for lower vibrational levels of the A and B states were calculated from the fluorescence decay rates for the A-X, B-A, and B-X emissions, and the lifetimes for the A state are in good agreement with the observed values except those affected by predissociation.     

Tandem five membered-ring selective Prins reaction and Friedel–Crafts reaction

A tandem reaction consisting of five membered-ring selective Prins cyclization and subsequent Friedel–Crafts cyclization was developed. The reactions of phenyl homoallylic alcohol 3 and benzaldehyde derivatives 6 afforded tetrahydroindenofurans 7 or pentacyclic products 8, depending upon the quantity of 6. Also homoallylic alcohol 12 having an alkyne–cobalt moiety reacted with 6 to give rise to tetrahydroindenofurans 13 in good yields.     

Total synthesis and absolute stereochemistry of plakortone E

The absolute stereochemistry of plakortone E, a cytotoxic metabolite of the Caribbean sponge, was established to be 1, by the synthesis of the racemic C-8 epimer (±)-2 and then of (−)-1 itself, which was identical with the natural compound.     

Measurement of a genotoxic hydrazine, agaritine, and its derivatives by HPLC with fluorescence derivatization in the agaricus mushroom and its products

Agaricus blazei MURRILL mushroom products are sold as so-called health foods in Japan. However, a part of Agaricus is known to contain hydrazines. A sensitive and specific method for analyzing a genotoxic hydrazine, agaritine, and its derivatives was developed to assess the safety of Agaricus products. beta-N-(gamma-L(+)-Glutamyl)-4-(hydroxymethyl)phenylhydrazine (agaritine, AGT), 4-hydrazinylbenzylalcohol (HMPH), 4-hydrazinylbenzoic acid (CPH), 4-methylphenylhydrazine (MPH) and phenylhydrazine (PH) were converted to their correspond-ing fluorescent derivatives with 3,4-dihydro-6,7 dimethoxy-4-methyl-3-oxoquinoxaline-2-carbonyl chloride (DMEQ-COCl) as the fluorescence derivatization reagent. The detection limits (S/N=3) for CPH, AGT, PH and MPH were 422, 45.3, 16.5 and 138 fmol, respectively, in a 20 mul injection volume. Recoveries, achieved by adding known AGT amounts to the Agaricus sample and Agaricus products, ranged from 92.8 to 102%. By using this method which does not require partial purification of the Agaricus sample, the amounts of AGT in several types of foods were found to be 112-1836 mug/g dry weight.     

Rate of homogeneous nucleation in alkali disilicate glasses

Rates of crystal nucleation in alkali disilicate glasses were measured by counting the number of crystals under an optical microscope. The viscosities of these glasses were measured by the method of beam-bending and penetration. Using the data of rate of nucleation and viscosity obtained in the present study and the data of free energy measured by Takahashi and Yoshio, crystal-glass interfacial energies for alkali disilicate systems were estimated on the basis of homogeneous nucleation theory as follows: 196 erg/cm² for Li₂O·2SiO₂, 126–144 erg/cm² for Na₂O·2SiO₂ and 88–104 erg/cm² for K₂O·2SiO₂. The effects of the viscosity of glass, the free energy difference between crystal and glass and crystal-glass interfacial energy on the rate of nucleation were discussed, and the remarkably higher rate of crystal nucleation in the Li₂O·2SiO₂ glass was attributed to the larger free energy difference.