Search results for "ethylammonium"
showing 10 items of 335 documents
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.
Thermodynamics of transfer of some nitroalkanes from aqueous to dodecyltrimethylammonium bromide micellar phases
1988
Abstract The enthalpies of mixing of some aqueous n-nitroalkane solutions with dodecyltrimethylammonium bromide micellar solutions were determined. The experimental data were treated by using a previously reported approach giving the enthalpies of transfer of solute from the aqueous to the micellar phases and the distribution constant of solute between the two phases at the same time. From these, the standard thermodynamic quantities of transfer (ΔtrfG°, ΔtrfH° and ΔtrfS°) are derived. In order to study the effect of the nature of both the solvent and the head group of solute, these properties are compared with those from water to octane and with those of alcohols and nitriles from aqueous …
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…
Non-adrenergic non-cholinergic nerve-mediated inhibitory control of pigeon oesophageal muscle.
1996
Pigeon oesophageal smooth muscle in vitro has spontaneous electromechanical activity. In the presence of atropine and guanethidine, electrical field stimulation evokes a transient TTX-sensitive response comprising inhibition of electric bursting activity and muscular relaxation. This NANC inhibitory response was analysed using the K+ channel blockers TEA and apamin, TEA perfusion (0.1-5 mM) induced a concentration-dependent reduction in amplitude of EFS-evoked relaxation. Responses to higher stimulation frequencies were more sensitive to TEA than those to lower ones. The maximum reduction in amplitude (29% of control) was obtained on 30 Hz EFS evoked responses during 5 mM TEA perfusion. In …
Mechanisms involved in the relaxant action of testosterone in the renal artery from male normoglycemic and diabetic rabbits.
2009
Kidney disease is a frequent complication in diabetes, and significant differences have been reported between male and female patients. Our working hypothesis was that diabetes might modify the vascular actions of testosterone in isolated rabbit renal arteries and the mechanisms involved in these actions. Testosterone (10(-8) to 10(-4)M) induced relaxation of precontracted arteries, without significant differences between control and diabetic rabbits. Both in control and diabetic rabbits endothelium removal inhibited testosterone relaxant action. In arteries with endothelium, incubation with indomethacin (10(-5)M), N(G)-nitro-l-arginine (10(-5)M) or tetraethylammonium (10(-5)M) did not modi…
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…
The relaxant effects of cromakalim (BRL 34915) on human isolated airway smooth muscle
1992
Cromakalim (BRL 34915) is a potassium channel opener with therapeutic potential as a bronchodilator in asthma. Cromakalim (0.1–30 μmol/l) inhibited the spontaneous tone of human isolated bronchi n a concentration-related manner being nearly as effective as isoprenaline or theophylline. The order of relaxant potencies (expressed as -log10 IC50 mol/l; mean ±SEM) was isoprenaline (7.29 ± 0.27; n = 8) > cromakalim (5.89 ± 0.12; n = 7) > theophylline (4.07 ±0.13; n = 10). In human bronchi where tone had been raised by addition of histamine (0.1 mmol/l), acetylcholine (0.1 mmol/l) or leukotriene D4 (LTD4, 0.1 μmol/l), the relaxant effect of cromakalim was substantially reduced. Cromakalim suppres…
The essential identity of the framework structures of ZSM-8 and ZSM-5
1994
The crystal structures of TEA-ZSM-8 and its calcined template-free form have been studied by Rietveld analyses based on X-ray powder diffraction data. The results show that the aluminosilicate framework structure of ZSM-8 is essentially identical to that of ZSM-5. The tetraethylammonium molecule could be located in the difference Fourier analysis yielding positions similar to its TPA counterpart in ZSM-5. Lattice constants of ZSM-8 are in the same range as for ZSM-5. Contrary results are related to incorrectly indexed powder patterns. Optical investigations of ZSM-5 and ZSM-8 crystals showed that the zeolites studied here are both twinned exhibiting differently shaped twin individuals.