Search results for "Tetramethylammonium"
showing 10 items of 109 documents
Modeling S-carboxymethyl-L-cysteine protonation and activity coefficients in sodium and tetramethylammonium chloride aqueous solutions by SIT and Pit…
2007
Solubility and acid–base properties of S-carboxymethyl-l-cysteine (carbocysteine, ccys) in NaClaq and tetramethylammonium chloride, (CH3)4NClaq ,a tt =2 5 ◦ C and at different ionic strengths were investigated. Solubility was studied at 1.0 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 1.0 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq, while potentiometric measurements (by ISE-H + , glass electrode) were performed at 0.1 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 0.5 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq. Solubility data allowed us to determine Setschenow constants and activity coefficients of neutral carbocysteine (H2ccys). Dependence on ionic strength and ionic medium of protonation constants and activity coeff…
Synthesis and structure of tetrakis(tetramethylammonium) octacosachlorooctaantimonate(III) [(CH3)4N]4Sb8Cl28
2000
Abstract The reaction between antimony trichloride and tetramethylammonium chloride in nitromethane gives transparent, irregular crystals of tetrakis(tetramethylammonium) octacosachlorooctaantimonate(III) [(CH 3 ) 4 N] 4 Sb 8 Cl 28 . Crystals are triclinic, space group P-1, a =11.846(2), b =12.217(2), c=14.120(3) A , α =95.71(3), β =101.39(3), γ =118.59(3)°, V=1713.7(5) A 3 , Z =1, d c =2.193, d m =2.17(2) Mg m −3 . The structure contains a structurally novel Sb 8 Cl 28 4- anion. It is composed of eight deformed octahedra, connected with each other by faces. In cavities formed by inorganic sublattice are located two crystallographically nonequivalent tetramethylammonium cations. One of them…
Protonation thermodynamics of 2,2'-bipyridyl in aqueous solution. Salt effects and weak complex formation
1993
Abstract Protonation constants of 2,2'-bipyridyl (bipy) have been determined potentiometrically, using (H + )-glass electrode, in different aqueous media (alkali and alkaline earth chlorides, tetramethylammonium chloride and tetramethylammonium iodide) at different temperatures and ionic strengths. The differences in log K H values are explained using a complex formation model. Formation thermodynamic parameters are given.
Protonation of Carbonate in Aqueous Tetraalkylammonium Salts at 25°C.
2006
Protonation constants of carbonate were determined in tetramethylammonium chloride (Me4NClaq 0.1≤I/mol kg−1 ≤4) and tetraethylammonium iodide (Et4NIaq 0.1≤I/mol kg−1 ≤1) by potentiometric ([H+]-glass electrode) measurements. Dependence of protonation constants on ionic strength was taken into account by modified specific ion interaction theory (SIT) and by Pitzer models. Literature data on the protonation of carbonate in NaClaq (0.1≤I/mol kg−1 ≤6) were also critically analysed. Both protonation constants of carbonate follow the trend Et4NI>Me4NCl > NaCl. An ion pair formation model designed to take into account the different protonation behaviours of carbonate in different supporting electr…
Synthesis and fluorescence emission of neutral and anionic di- and tetra-carboranyl compounds
2011
A new family of photoluminescent neutral and anionic di-carboranyl and tetra-carboranyl derivatives have been synthesized and characterized. The reaction of α,α'-bis(3,5-bis(bromomethyl)phenoxy-m-xylene with 4 equiv. of the monolithium salt of 1-Ph-1,2-C(2)B(10)H(11) or 1-Me-1,2-C(2)B(10)H(11) gives the neutral tetracarboranyl-functionalized aryl ether derivatives closo-1 and closo-2, respectively. The addition of the monolithium salt of 1-Ph-1,2-closo-C(2)B(10)H(11) to α,α,'-dibromo-m-xylene or 2,6-dibromomethyl-pyridine gives the corresponding di-carboranyl derivatives closo-3 and closo-4. These compounds, which contain four or two closo clusters, were degraded using the classical method,…
Diffusion in slice preparations bathed in unstirred solutions
1987
A diffusion model is described here, which allows for the estimations of drug concentration changes in porous media, such as in slice tissues of the central nervous system (CNS) bathed in unstirred solutions following abrupt changes of drug concentration. This model may be used for the interpretation of data obtained in neuropharmacological studies if (i) the diffusion coefficient of the molecules under investigation is constant within the excised tissue, (ii) drug molecules are diffusing only in the extracellular space (ECS) and are not bound by the tissue, (iii) drug molecules diffuse mainly within one dimension, (iv) the drug concentration in the bath is changed within 5 s, and (v) the b…
Structure and properties of tris(tetramethylammonium) nonabromodiarsenate(III), [(CH3)4N]3[As2Br9]
2007
The new tetramethylammonium bromoarsenate(III) crystal [(CH3)4N]3 [As2Br9] has been synthesized and its phase behaviour established by differential scanning calorimetry and dilatometry. Three phase transitions are found: at 346/346 K , at 165/171 K and at 157/165 K on cooling/heating. Single-crystal x-ray diffraction studies of phases I (at 370 K) and II (at 298 K) have shown that the structure comprises discrete [As2Br9]3− anions and disordered [(CH3)4N]+ cations. Phase II crystallizes in the polar space group P31c; its polar nature was confirmed by pyroelectric measurements. Phase I has higher symmetry, P63mc or . Dielectric dispersion measurements revealed a relaxation process in the cry…
Tetraalkylammonium Cations Conduction through a Single Nanofluidic Diode: Experimental and Theoretical Studies
2017
[EN] We describe experimentally and theoretically the concentration-dependent conduction of tetraalkylammonium (TAA+) cations through a nanofluidic diode fabricated in a polymer membrane via asymmetric track-etching techniques. This single-pore membrane exhibits current rectification characteristics because of the ionized carboxylate groups on the pore surface. We use aqueous solutions of potassium (K+ ), ammonium (A+ ), tetramethylammonium (TMA+ ), tetraethylammonium (TEA+ ), and tetrabutylammonium (TBA+ ) ions with concentrations ranging from 50 to 500 mM under acidic (pH 3.5) and physiological (pH 6.5) conditions. Compared with the K+ and A+ ions, the TMA+ , TEA+ , and TBA+ ions show rel…
Complexes of organometallic compounds
1974
Abstract Tetraphenylarsonium and tetramethylammonium salts of the complex anions Ph 3 Pb(N 3 ) − 2 , Ph 3 Pb(N 3 )(NCS) − , Ph 2 Pb(N 3 ( 2 − 4 )) and Ph 2 Pb(N 3 )(NCS) − 2 have been prepared and characterized. Infrared spectra and solution conductance data are reported. Possible configurations of the complex anions are discussed.
Synthesis and structure of mono-bridged resorcinarene host: a ditopic receptor for ammonium guests.
2009
The synthesis and structural properties of tetramethoxy resorcinarene mono-crown-5 (1) are described. The binding characteristics of 1 toward acetylcholine and tetramethylammonium salts were investigated by 1H NMR titration. It was observed that the cavity of 1 provides a better fit to acetylcholine compared to the smaller tetramethylammonium cation, as acetylcholine is able to interact with both the crown ether moiety and the free hydroxyl groups of receptor 1 simultaneously.