Synthesis of 1,3-dihydrobenzo[c]furans from ortho-lithiated aryloxiranes

A general method for the synthesis of hydroxyalkyl 1,3-dihydrobenzo[c]furans from ortho-lithiated aryloxiranes and carbonyl compounds is described.     

Synthesis of Ni-Ru alloy nanoparticles and their high catalytic activity in dehydrogenation of ammonia borane

We report the synthesis and characterization of new Ni(x)Ru(1-x) (x = 0.56-0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet-chemistry method using a rapid lithium triethylborohydride reduction of Ni(2+) and Ru(3+) precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We found that the as-prepared Ni-Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni-Ru alloy NPs, and in particular the Ni(0.74)Ru(0.26) sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core-shell NPs. The hydrolysis activation energy for the Ni(0.74)Ru(0.26) alloy catalyst was measured to be approximately 37?kJ?mol(-1). This value is considerably lower than the values measured for monometallic Ni (≈70?kJ?mol(-1)) and Ru NPs (≈49?kJ?mol(-1)), and for Ni@Ru (≈44?kJ?mol(-1)), and is also lower than the values of most noble-metal-containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.     

Metal-catalyzed reduction of HCONR'2, R' = Me (DMF), Et (DEF), by silanes to produce R'2NMe and disiloxanes: a mechanism unraveled

We demonstrate that using Mo(CO)(6), Mo(CO)(5)NMe(3), and (η(5)-C(5)H(5))Mn(CO)(3) as catalysts for the silane, R(3)SiH, reduction of N,N-dimethylformamide (DMF), and N,N-diethylformamide (DEF), we can observe, intercept, and isolate, the important siloxymethylamine intermediates, R(3)SiOCH(2)NR'(2), R' = Me, Et, for the first time. In the presence of excess DMF such intermediates thermally react with a variety of silanes to form the corresponding disiloxanes in the absence of a metal catalyst. We also show that the germanium hydrides, Et(3)GeH and Bu(3)GeH, also reduce DMF to form trimethylamine and the corresponding digermoxane but observe no intermediates R(3)GeOCH(2)NMe(2). Bu(3)SnH reduces DMF, but along with the low yields of Bu(3)SnOSnBu(3) (but no Bu(3)SnOCH(2)NMe(2)) significant side products are obtained including (Bu(3)Sn)(2) and Bu(4)Sn. In the absence of DMF the siloxymethylamines can undergo metal-catalyzed reactions with silanes, germanes and stannanes to form disiloxanes, and R(3)SiOER(3) E = Ge, Sn, respectively. To date, the most efficient catalyst for this latter process is (η(5)-C(5)H(5))Mo(CO)(3)CH(3) via a photochemical reaction.     

Nonlinear modeling of equilibrium sorption of selected anionic adsorbates from aqueous solutions on cellulosic substrates: part 2: experimental validation

The equilibrium sorption of CI Direct Blue 1, as a model anionic adsorbate, from aqueous solution on cotton fabric was experimentally studied. The equilibrium sorption data were employed to test the performance of a proposed nonlinear sorption model in describing the sorption behavior of anionic adsorbates on cellulosic substrates. The analysis of data based on the nonlinear least-squares curve fitting showed excellent correlation against experimental values as indicated by a high coefficient of determination (R ²). The V and −Δμ° parameters were determined based on the nonlinear model and employed to represent the internal accessible volume of cotton to CI Direct Blue 1 and the standard affinity of sorption. It was shown that variations in temperature and concentration of electrolyte (e.g. NaCl) in the sorption system result in slight variations in V. The findings extend the scope of the previous study and indicate that the nonlinear sorption model can be used to accurately determine the thermodynamic properties of a sorption system, such as the affinity (−Δμ°), enthalpy (ΔH°), and entropy (ΔS°), for anionic adsorbates on cellulosic substrates.     

Thermoresponsive Poly(2‐oxazine)s

The monomers 2‐methyl‐2‐oxazine (MeOZI), 2‐ethyl‐2‐oxazine (EtOZI), and 2‐n‐propyl‐2‐oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring‐opening polymerization (CROP) under microwave‐assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting LCST behavior in water and their cloud point temperatures (T_CP) are lower than for poly(2‐oxazoline)s with similar side chains. However, comparison of poly(2‐oxazine) and poly(2‐oxazoline)s isomers reveals that poly(2‐oxazine)s are more water soluble, indicating that the side chain has a stronger impact on polymer solubility than the main chain. In conclusion, variations of both the side chains and the main chains of the poly(cyclic imino ether)s resulted in a series of distinct homopolymers with tunable T_CP.     

Multireference perturbation CI IV. Selection procedure for one-electron properties

We present in this paper a modification of the selection procedure, within the CIPSI algorithm, specifically intended for the calculation of one-electron properties. In this new procedure the determinants are selected following their contribution to a certain one-electron property. As test cases we report the calculation of the electric dipole of carbon monoxide and of the hyperfine coupling constants of the CH₃ radical. Received: 20 August 2000 / Accepted: 2 October 2000 / Published online: 21 December 2000     

[N,N′-(4-Methyl-4-azaheptane-1,7-diyl-κN)bis(4-methoxysalicylideniminato-κ4O,N,N′,O′)]cobalt(II) ethanol hemisolvate

The title compound, [Co(C₂₃H₂₉N₃O₄)]·0.5C₂H₆O or [Co^II{(4-MeO-sal)₂Medpt}]·0.5CH₃CH₂OH [(4-MeO-sal)₂Medpt is N,N′-(4-methyl-4-aza­heptane-1,7-diyl)­bis(4-methoxysalicyl­iden­iminate)], obtained through the reaction of H₂[(4-MeO-sal)₂Medpt] and Co(CH₃COO)₂ in refluxing ethanol under an atmosphere of ultrapure nitro­gen, has the usual pseudo-trigonal-bipyramidal coordination arrangement previously found for this class of (sal)₂Rdpt compounds. The O—Co—O bond angle [120.4 (1)°] is significantly smaller than the corresponding values previously found for most non-O₂-bound [Co^II{(sal)₂Medpt}]-type mol­ecules (observed range 126.9–138.6°), whereas the equatorial Co—N bond [2.185 (3) Å] is relatively long.     

High-loop perturbative renormalization constants for Lattice QCD (II): three-loop quark currents for tree-level Symanzik improved gauge action and n f =2 Wilson fermions

The European Physical Journal C - Numerical Stochastic Perturbation Theory was able to get three- (and even four-) loop results for finite Lattice QCD renormalization constants. More recently, a...     

Studies on crude oil‐water biphasic mixtures by low‐field NMR

Low‐field ¹H NMR was used in this work for the analysis of mixtures involving crude oils and water. CPMG experiments were performed to determine the transverse relaxation time (T₂) distribution curves, which were computed by the inverse Laplace transform of the echo decay data. The instrument's ability of quantifying water and petroleum in biphasic mixtures following different methodologies was tested. For mixtures between deionized water and petroleum, one achieved excellent results, with root mean squared error of cross‐validation (RMSECV) of 0.8% for a regression between the water content (wt %) and the relative area of the water peak in the T₂ distribution curve, or a standard deviation of 0.9% for the relationship between the water content and the relative water peak area, corrected by the relative hydrogen index of the crude. In the case of biphasic mixtures of Mn²⁺‐doped water and crude oils, the best result of RMSECV = 1.6% was achieved by using the raw magnetization decay data for a partial least squares regression. Copyright © 2012 John Wiley & Sons, Ltd.