Search results for "EH"

Selective Formation of 4,4'-Biphenols by Anodic Dehydrogenative Cross- and Homo-Coupling Reaction.

2019

A simple and selective electrochemical synthesis by dehydrogenative coupling of unprotected 2,6- or 2,5-substituted phenols to the desired 4,4'-biphenols is reported. Using electricity as the oxidizing reagent avoids pre-functionalization of the starting materials, since a selective activation of the substrates takes place. Without the necessity for metal-catalysts or the use of stoichiometric reagents it is an economic and environmentally friendly transformation. The elaborated electrochemical protocol leads to a broad variety of the desired 4,4'-biphenols in a very simplified manner compared to classical approaches. This is particular the case for the cross-coupled products.

Hierarchical Beta zeolites as catalysts in a one-pot three-component cascade Prins–Friedel–Crafts reaction

2020

Hierarchical Beta zeolites obtained from concentrated reaction mixtures (H2O/Si = 2.5–7.0) in the presence of CTAB and their conventional and nanosponge analogues were investigated in a one-pot cascade environmentally friendly Prins–Friedel–Crafts reaction of butyraldehyde with 3-buten-1-ol and anisole under mild conditions (60 °C). The highest yields of the desired products with 4-aryltetrahydropyran structure were achieved when using hierarchical zeolites characterised by well-developed mesoporosity (facilitating the formation of bulky intermediates and products) and by an increased fraction of highly accessible (evaluated by TTBPy method) medium-strength Bronsted acid sites. Acid sites w…

R�ntgenkristallographische Daten von Bi(NO3)3�5H2O und BiONO3�1/2H2O

1967

Modulation of the ordering temperature in anilato-based magnets

2019

Abstract Four new 2D honeycomb anilato-based ferrimagnets with Mn(II) and Cr(III) have been prepared and characterized. These compounds, formulated as (NBu4)[MnCr(C6O4X2)3(PhCHO)]·PhY (X/Y = Cl/H (1), Br/H (2), Cl/CHO (3) and Br/CHO (4) show that it is possible to include benzaldehyde as a co-ligand coordinated to the Mn(II) metal atom in these 2D ferrimagnets. This inclusion increases the coordination number of Mn(II) to seven resulting in a change in the ordering temperatures of these 2D ferrimagnets (from ca. 10–11 K to ca. 7 K). Here we show the role played by the additional benzaldehyde ligand and by the crystallization solvent molecules (benzene in 1 and 2 and benzaldehyde in 3 and 4)…

A robust viologen and Mn-based porous coordination polymer with two types of Lewis acid sites providing high affinity for H 2 O, CO 2 and NH 3

2017

A novel porous coordination polymer [Mn(pc3)(H2O)2]·xH2O (3 < x < 4) is synthesized in water at pH = 7 using the anionic viologen-carboxylate ligand 4,4′-bipyridinium,1,1′-bis-(2,4-dicarboxyphenyl) (pc32−). Dehydration of the material results in the formation of open pores containing two types of accessible Lewis acid sites: exposed Mn2+ cations and N+ atoms of viologen units. Due to this property the PCP shows high affinity and capacity in the adsorption of H2O, CO2 and NH3. Despite the presence of strong adsorption sites this material is stable in liquid water and in gaseous NH3.

Annually resolved δ13Cshell chronologies of long-lived bivalve mollusks (Arctica islandica) reveal oceanic carbon dynamics in the temperate North Atl…

2011

Abstract The ability of the ocean to absorb carbon dioxide is likely to be adversely affected by recent climate change. However, relatively little is known about the spatiotemporal variability in the oceanic carbon cycle due to the lack of long-term, high-resolution dissolved inorganic carbon isotope ( δ 13 C DIC ) data, especially for the temperate North Atlantic, which is the major oceanic sink for anthropogenic CO 2 . Here, we report shell carbon isotope values ( δ 13 C shell ), a potential proxy for δ 13 C DIC , of old-grown specimens of the long-lived bivalve mollusk, Arctica islandica . This paper presents the first absolutely dated, annually resolved δ 13 C shell record from surface …

Influence of Wind on Suspended Matter in the Water of the Albufera of Valencia (Spain)

2021

Wind is one of the factors that has a great influence on suspended matter in lakes, especially in shallow lagoons. In order to know how wind affects the water in Albufera of Valencia, a shallow coastal lagoon, the measured variables of turbidity and transparency have been correlated with the estimates by processing Sentinel-2 satellite images with the Sen2Cor processor. Data from four years of study show that most of them are light to gentle easterly breezes and moderate to fresh westerly breezes. The results obtained show significant correlations between the measured variables and those obtained from the satellite images for total suspended matter and water transparency and with the averag…

An Ecohydrological Cellular Automata Model Investigation of Juniper Tree Encroachment in a Western North American Landscape

2016

Woody plant encroachment over the past 140 years has substantially changed grasslands in western North American. We studied encroachment of western juniper (Juniperus occidentalis var. occidentalis) into a previously mixed shrub–grassland site in central Oregon (USA) using a modified version of Cellular Automata Tree–Grass–Shrub Simulator (CATGraSS) ecohydrological model. We developed simple algorithms to simulate three encroachment factors (grazing, fire frequency reduction, and seed dispersal by herbivores) in CATGraSS. Local ecohydrological dynamics represented by the model were first evaluated using satellite-derived leaf area index and measured evapotranspiration data. Reconstruc…

The BepiColombo MORE gravimetry and rotation experiments with the ORBIT14 software

2016

The BepiColombo mission to Mercury is an ESA/JAXA cornerstone mission, consisting of two spacecraft in orbit around Mercury addressing several scientific issues. One spacecraft is the Mercury Planetary Orbiter, with full instrumentation to perform radio science experiments. Very precise radio tracking from Earth, on-board accelerometer and optical measurements will provide large data sets. From these it will be possible to study the global gravity field of Mercury and its tidal variations, its rotation state and the orbit of its centre of mass. With the gravity field and rotation state, it is possible to constrain the internal structure of the planet. With the orbit of Mercury, it is possib…

Inter-annual climate variability in Europe during the Oligocene icehouse

2017

Abstract New sclerochronological data suggest that a variability comparable to the North Atlantic Oscillation (NAO) was already present during the middle Oligocene, about 20 Myr earlier than formerly assumed. Annual increment width data of long-lived marine bivalves of Oligocene (30–25 Ma) strata from Central Europe revealed a distinct quasi-decadal climate variability modulated on 2–12 (mainly 3–7) year cycles. As in many other modern bivalves, these periodic changes in shell growth were most likely related to changes in primary productivity, which in turn, were coupled to atmospheric circulation patterns. Stable carbon isotope values of the shells (δ 13 C shell ) further corroborated the …