Structural characterization of moganite-type AlPO4 by NMR and powder X-ray diffraction

Structural characterization of a new high-pressure AlPO(4) phase synthesized at 5 GPa and 1500 °C is reported. The phase is monoclinic (P2/a) with a = 8.7437(1) ?, b = 4.8584(1) ?, c = 10.8600(2) ?, β = 90.124(1)° (Z = 6). (31)P MAS NMR and two-dimensional (2D) (27)Al triple-quantum (3Q) MAS NMR revealed that it contains two tetrahedral P sites of 1:2 abundance ratio, and two tetrahedral Al sites with 1:2 ratio. 2D (31)P dipolar-recoupled double-quantum (DQ) MAS NMR and (27)Al → (31)P dipolar-based (through-space) and J coupling-based (through-bond) 3Q-heteronuclear correlation (HETCOR) experiments provided direct information on the linkages of these sites. The crystal structure was solved and refined from synchrotron powder X-ray diffraction data utilizing the information from NMR. The phase is isostructural to moganite, a rare SiO(2) polymorph, and its structure can be derived from the latter via an ordered replacement of tetrahedral Si sites by Al and P. The NMR parameters of the phase were also calculated by first-principles method, which are consistent with those observed. Contrary to the other moganite phases known to date (i.e., SiO(2) and PON), moganite-AlPO(4) has a higher-pressure stability field than the corresponding quartz phase. This is the first moganite-type phase found in the ABX(4) system.     

Environmental analysis of chlorinated and brominated polycyclic aromatic hydrocarbons by comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry

A method for the analysis of chlorinated and brominated polycyclic aromatic hydrocarbon (Cl-/Br-PAHs) congeners in environmental samples, such as a soil extract, by comprehensive two-dimensional gas chromatography coupled to a high resolution time-of-flight mass spectrometry (GC×GC-HRTOF-MS) is described. The GC×GC-HRTOF-MS method allowed highly selective group type analysis in the two-dimensional (2D) mass chromatograms with a very narrow mass window (e.g. 0.02Da), accurate mass measurements for the full mass range (m/z 35-600) in GC×GC mode, and the calculation of the elemental composition for the detected Cl-/Br-PAH congeners in the real-world sample. Thirty Cl-/Br-PAHs including higher chlorinated 10 PAHs (e.g. penta, hexa and hepta substitution) and ClBr-PAHs (without analytical standards) were identified with high probability in the soil extract. To our knowledge, highly chlorinated PAHs, such as C(14)H(3)Cl(7) and C(16)H(3)Cl(7), and ClBr-PAHs, such as C(14)H(7)Cl(2)Br and C(16)H(8)ClBr, were found in the environmental samples for the first time. Other organohalogen compounds; e.g. polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzofurans (PCDFs) were also detected. This technique provides exhaustive analysis and powerful identification for the unknown and unconfirmed Cl-/Br-PAH congeners in environmental samples.     

Al coordination and water speciation in hydrous aluminosilicate glasses: direct evidence from high-resolution heteronuclear 1H-27Al correlation NMR

In order to shed light on the dissolution mechanisms of water in depolymerized aluminosilicate melts/glasses, a comprehensive one- (1D) and two-dimensional (2D) NMR study has been carried out on hydrous Ca- and Mg-aluminosilicate glasses of a haplobasaltic composition. The applied techniques include 1D 1H MAS NMR and 27Al-->1H cross-polarization (CP) MAS NMR, and 2D 1H NOESY and double-quantum (DQ) MAS NMR, 27Al triple-quantum (3Q) MAS NMR and 27Al-->1H heteronuclear correlation (HETCOR) and 3QMAS/HETCOR NMR. Ab initio calculations were also performed to place additional constraints on the 1H NMR characteristics of AlOH and Si(OH)Al groups. This study has revealed, for the first time, the presence of free OH (i.e. (Ca, Mg)OH), SiOH and AlOH species, in addition to molecular H2O, in hydrous glasses of a depolymerized aluminosilicate composition. The AlOH groups are mostly associated with four-coordinate Al, but some are associated with five- and six-coordinate Al.     

A coordinatively unsaturated,polymer-bound palladium(0) complex. Synthesis and catalytic activities

A coordinatively unsaturated palladium(0) complex was prepared by the reduction of a polymer-bound palladium(II) chloride complex, which was prepared by the reaction of poly-4-diphenylphosphinomethylstyrene with palladium chloride, with hydrazine in ethanol in the presence of triphenylphosphine. Catalytic activities of the polymerbound palladium(0) complex were examined for three representative types of palladium(0)-induced reactions involving oxidative addition of halides to the metal: (i) vinylic hydrogen substitutions with aryl halides, (ii) acetylenic hydrogen substitutions with aryl halides, (iii) vinylic halogen substitutions with Grignard reagents. Use of the catalyst resulted in formation of corresponding products in good yields. The catalytic activity is comparable to that of analogous homogeneous catalysts, yet is not remarkably lowered on being recycled.     

Synthesis and biodegradation of poly(ester amide)s containing amino acid residues: The effect of the stereoisomeric composition of L‐ and D‐phenylalanines on the enzymatic degradation of the polymers

Biodegradable poly(ester amide)s that contained phenylalanine residues in the main chains were synthesized by the polycondensation of di‐p‐nitrophenyl sebacate and phenylalanine 2‐aminoethyl ester. The stereoisomeric composition (L /D ratio) of the phenylalanine residue in the monomer did not affect the yield and molecular weight of the polymer much. From the optical rotations of the polymers, it was found that the L /D ratio of the phenylalanine residue in the polymer was almost equal to the L /D ratio of the phenylalanine residue in the monomer. The biodegradability of the poly(ester amide)s was studied in aqueous solutions with proteases as catalysts. The polymer with 100% L ‐phenylalanine residue was effectively degraded by α‐chymotrypsin or subtilisins. However, the replacement of 10% L ‐phenylalanine with D ‐isomer resulted in a dramatic decrease in degradability. The polymers with less than 30% L ‐isomer were hardly degraded by the enzymes. Gel permeation chromatography studies suggested that the solubility of the degradation products in water greatly affected the rate and extent of biodegradation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 385–392, 2002     

Rapid and controlled deswelling of porous poly(N‐isopropylacrylamide) hydrogels prepared by the templating of interpenetrated nanoporous silica particles

Free radical polymerization of N‐isopropylacrylamide (NIPAAm) and crosslinker solutions, which were fulfilled in silica particles with an interpenetrated and nanometer‐sized porous structure (a diameter of 3 mm and mean pore sizes of 15, 30, and 50 nm), fabricated hybrids of organic hydrogels and inorganic silica. Differential scanning calorimetric analyses of the hybrids revealed that silica components affected the thermoresponsive properties of polyNIPAAm hydrogels. Porous polyNIPAAm hydrogels were prepared by the subsequent acid treatment of the hybrids to remove silica. Transmission Fourier transformed infrared spectra indicated the selective extraction of silica. Scanning electron microscopic observation of the hydrogels confirmed the porous structure. The deswelling rate of porous hydrogels was 7 times larger than that of conventional hydrogels and increased with increasing the pore size of silica used. However, the swelling was not affected by the pore formation. The thermoresponsiveness of porous polyNIPAAm hydrogels could be regulated by the pore size. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3542–3547, 2002     

A new route for generation of alpha-lambda3-iodanyl ketones via ester exchange of (Z)-(beta-acetoxyvinyl)-lambda3-iodanes: their nucleophilic substitutions with halides and sulfur and phosphorus nucleophiles

An efficient method for generation of alpha-lambda3-iodanyl ketones from (Z)-(2-acetoxyvinyl)(phenyl)-lambda3-iodanes was developed. The method involves ester exchange of (Z)-2-acetoxyvinyl-lambda3-iodanes with methanol in the presence of triethylamine. alpha-lambda3-Iodanyl ketones react with a variety of nucleophiles such as halides, thiols, phosphines, phosphinic acids, and phosphates, under the conditions which produce alpha-functionalized carbonyl compounds probably via an S(N)2 pathway.     

Chemoselective Catalytic Asymmetric Synthesis of Functionalized Aminals Through the Umpolung Organocascade Reaction of α‐Imino Amides

Chiral functionalized aminals are important core structures of natural products and pharmaceuticals. Their chemo‐ and regioselective catalytic, asymmetric synthesis has been realized through the umpolung reaction of α‐imino amides using a catalyst we originally developed. Functionalized aminals were prepared with high chemoselectivity by treating a hemiaminal intermediate with pyridine in butanol. Evaluation of substrate scope revealed that this transformation could be achieved with a wide range of α‐imino amides to produce the desired products in high yields with up to 97 % ee. A mechanistic study suggested that aminal formation proceeded through the ring opening/ring closing equilibrium of the hemiaminal skeleton.     

Stationary and time-resolved spectra of 2,2′:5′,2″-terthiophene

By analyzing the stationary absorption spectrum of 2,2′:5′,2″-terthiophene in dichloromethane at room temperature, the zero–zero S₁←S₀ transition energy is determined. Time-resolved fluorescence measurements show that the S₁→S₀ radiative relaxation in various solvents decays exponentially with a common time constant of 170±10 ps. The fluorescence anisotropy of 2,2′:5′,2″-terthiophene in dichloromethane is also studied and the transient dichroism is interpreted in terms of the revolution of a hydrodynamic prolate ellipsoid with the emission dipole aligned parallel to the long molecular axis.     

Reaction of unstabilized iodonium ylides with organoboranes

[reaction: see text] Exposure of monocarbonyl iodonium ylides, generated by the ester exchange of (Z)-(2-acetoxyvinyl)-lambda(3)-iodanes with EtOLi, to organoboranes results in a 1,2-shift of a carbon ligand from boron to the ylide carbons, which probably generates hitherto uncharacterized alpha-boryl ketones.