Search results for "Alkali metal"

Para-Localization Energy (Free-Electron Molecular-Orbital Method) and Polarographic Half-Wave Potentials of some Polynuclear Hydrocarbons

1957

POLYNUCLEAR aromatic hydrocarbons in 75 per cent dioxane solution which contains 0.175 M tetrabutyl ammonium iodide are reducible in the dropping mercury electrode1. As shown by the corresponding polarograms, it is a two-electron addition step process, and it is similar to the reduction of these compounds by alkali metals or their amalgams and alcohol2, a fact which can be easily explained.

Catalytic effect of Ca and K on CO2 gasification of spruce wood char

2015

Abstract Gasification is one route to produce chemicals and liquid fuels from biomass. The gasification of the char is catalyzed by alkali and alkaline earth metals in the biomass. In this work the catalytic effect of calcium (Ca) and potassium (K) on CO2 gasification of spruce wood was studied using a thermo gravimetric analyzer (TGA). The ash-forming elements were first removed from the wood using an acid leaching method. Then, various concentrations of K and Ca were absorbed to the wood by ion-exchange to carboxylic and phenolic groups, impregnation of K2CO3 or physically mixing of CaC2O4. The prepared spruce samples were placed in a mesh holder and gasified in the TGA at 850 °C in 100% …

Interaction of metal ions with N-glycosylamines: isolation and characterization of the products of 4,6-O-benzylidene-N-(o-carboxyphenyl)-β-D-glucopyr…

2001

Metal-ion complexes of Li+, Na+, K+, Mg2+, Ca2+, Ba2+, Pb2+, Cd2+, Hg2+ with 4,6–O–benzylidene–N–(o–carboxyphenyl)–β–D–glucopyranosylamine were synthesized and isolated as solid products and characterized by analytical means as well as by spectral techniques, such as, 1H and 13C NMR, FTIR, absorption, FAB mass spectrometry, optical rotation and CD. While the alkali metal ions formed ML type of complexes, the other metal ions formed ML2 type complexes. Molecular weights of the complexes of Li+, Na+ and K+ were established based on the molecular-ion peaks in the FAB mass spectra. The saccharide portion remians in the β-anomeric form even after the complexation. The spectral data, as well as t…

Laser synthesis of ultracold alkali metal dimers: optimization and control

2015

High-contrast dark resonances on the D1 line in cesium nanocell: the advantages compared with the other alkali D lines

2015

Electromagnetically induced transparency (EIT) effect in a -system formed by Cs atoms line, enclosed in nanometric-thin cells, is studied both experimentally and theoretically for the first time. T...

Effect of the Alkaline Cations on the Stability of the Model Polynucleotide Poly(dG-dC)·Poly(dG-dC)

2011

When the model polynucleotide poly(dG-dC)∙poly(dG-dC) [polyGC] is titrated with a strong acid (HCl) in unbuffered aqueous solutions containing the chlorides of the alkali metals in the concentration range 0.010 M-0.600 M, two transitions in the absorbance vs. pH plots are evidenced, characterized by the constants pK(a(₁)) and pK(a(₂)). The limiting values at infinite saline concentrations of these two constants, namely pK(∞)(a(₁)) and pK(∞)(a(₂)) obtained making use of the "one site saturation constant" equation or, in turn, of the double logarithmic plot: pK(a) vs. log([salt]⁻¹), exhibit a clear dependence on the nature of the cations. The effects of the different alkali cations on the pK(…

Optimal hydrogen storage in sodium substituted lithium fullerides

2017

Through the substitution of Li with Na in Li6C60, we synthesized a series of mixed alkali cluster intercalated fullerides, NaxLi6−xC60. These compounds share lattices of Na6C60 and Li6C60 with a cubic parameter linearly dependent on x. H2 absorption and desorption were studied by means of charge/discharge kinetic measurements and coupled calorimetric–manometric evaluation. By varying the stoichiometry, we found the best compromise among the absorption rate, temperature and amount of hydrogen for x = 0.5 and 1. Small concentrations of Na substituted to Li significantly lower the absorption temperature of Li6C60, improving the hydrogenation capacity, the kinetics, and the dehydrogenation enth…

Pyrogallarenes as alkali metal receptors: the role of cation-pi interactions in complexation.

2006

Crystallization studies of C-methyl pyrogallarene with potassium, rubidium and caesium bromides or chlorides resulted in a hydrogen bonded molecular cage in which the alkali metal cations are eta6 coordinated to aromatic rings via strong cation-pi interactions.

Electrochemical Monitoring of Compartmentalization Effects in the Stability of Meisenheimer Anions Supported in Hydrotalcite and X and Y Zeolites

2005

Meisenheimer anions (MS - ) derived from 2,4-dinitroaniline are stabilized into Li + - and Na + -exchanged zeolites X and Y forming alkali ion-MS ion pairs. Upon attachment of the zeolites to polymer film electrodes immersedinto Et 4 N + /MeCN and Li + /MeCN electrolytes, boundary-associated MS - ions display two oxidation processes at +0.40 and +0.65 V vs. AgCl/Ag. This response sharply contrasts with that recorded for MS - in solution and incorporated within hydrotalcite, for which a unique oxidation peak at +0.35 V is recorded. The electrochemistry of zeolite-associated MS - can be described in terms of an unusual electron-transfer/ chemical reaction/electron-transfer/comproportionation …

The Reductive σ Bond Cleavage of Barbaralane and 2,6‐Diphenylbarbaralane

1987

Barbaralane (2) and 2,6-diphenylbarbaralane (8) are synthesized in a straightforward way. The reductive cleavage of the strained hydrocarbons is achieved with alkali metals. The structure of the metallation products, in particular the bonding in the resulting allyl moieties, is elucidated by 1H- and 13C-NMR spectroscopy. The chemical behavior (oxidation, protonation, alkylation) sheds light on the modes of stabilization of the alkali metal derivatives. Die reduktive σ-Bindungsspaltung von Barbaralan und 2,6-Diphenylbarbaralan Barbaralan (2) und 2,6-Diphenylbarbaralan (8) werden auf rationelle Weise synthetisiert und die gespannten Kohlenwasserstoffe durch Reaktion mit Alkalimetallen redukti…