Thermal decomposition of sodium propoxides

Sodium alkoxides, namely, sodium n-propoxide and sodium iso-propoxide were synthesized and characterized by various analytical techniques. Thermal decomposition of these compounds was studied under isothermal and non-isothermal conditions using a thermogravimetric analyzer coupled with mass spectrometer. The onset temperatures of decomposition of sodium n-propoxide and sodium iso-propoxide were found to be 590 and 545 K, respectively. These sodium alkoxides form gaseous products of saturated and unsaturated hydrocarbons and leave sodium carbonate, sodium hydroxide, and free carbon as the decomposition residue. Activation energy, E _a, and pre-exponential factor, A, for the decomposition reactions were deduced from the TG data by model-free (iso-conversion) method. The E _a for the decomposition of sodium n-propoxide and sodium iso-propoxide, derived from isothermal experiments are 162.2 ± 3.1 and 141.7 ± 5.3 kJ mol^?1, respectively. The values obtained from the non-isothermal experiments are 147.7 ± 6.8 and 133.6 ± 4.1 kJ mol^?1, respectively, for the decomposition of sodium n-propoxide and sodium iso-propoxide.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Allosteric coextraction of sodium and metal ions with calix[4]arene derivatives 1

Solvent extraction of three alkali metal ions with p-t-octylcalix[6]arene hexacarboxylic acid, p-t-octylcalix[4]arene tetracarboxylic acid, corresponding linear trimeric and monomeric analogs was investigated. Cyclic tetramer selectively extracts sodium ion among alkali ions at extremely low pH, while the corresponding cyclic hexamer, the trimer, and the monomer exhibited only poor extraction ability for all alkali metals examined. The detailed extractive investigation of sodium ions with the cyclic tetramer was carried out. It was found that two sodium ions are simultaneously extracted by a single molecule of calix[4]arene derivative and that the second sodium extraction is facilitated by the uptake of the first sodium. The self-coextraction mechanism of sodium ions proposed in the present paper also strongly supports allosteric coextraction of sodium and other metal ions. In the competitive extraction of four alkali metal ions, potassium ion was slightly extracted as the second ion at low pH region, whereas it was hardly extracted in the individual extraction system. The result also supports the coextraction mechanism and role of the first-extracted sodium ion as an allosteric trigger. The extraction equilibrium constants of the cyclic tetramer and two sodium ions, K _ex1 and K _ex2, were estimated.     

The nature of the sodium dependence of amino acid transport by system A of the S37 cell

The present study was undertaken to answer a specific question: is the activity of amino acid transport system A entirely abolished in the absence of sodium in the medium, or does some residual activity of system A remain? A biphasic double-reciprocal plot was obtained for histidine uptake from media in which sucrose, potassium ion, or choline replaced sodium ion. The uptake of labeled N-methyl-2-aminoisobutyric acid or labeled histidine from sodium-free media was inhibited by added N-methyl-2-aminoisobutyric acid. N-methyl-2-aminoisobutyric acid also inhibited transport of labeled alanine when system L was already blocked in a choline chloride medium. Concentrative uptake of N-methyl-2-aminoisobutyric acid or alanine occurred in a choline chloride medium. Uptake of N-methyl-2-aminoisobutyric acid was saturable in the absence of sodium ion, but was stimulated by the presence of sodium ion. A non -saturable uptake route was not detectable in the S37 cell. The activity of amino acid transport system A in the S37 cell is clearly enhanced by the presence of sodium ion, but sodium ion is not an obligatory requirement for transfer of amino acids through system A to occur.     

Solubilities of imidazolium-based ionic liquids in aqueous salt solutions at 298.15 K

The solubilities of ionic liquids in the ternary systems (ionic liquid + H₂O + inorganic salt) were reported at 298.15 K and atmospheric pressure. The examined ionic liquids are [C₄mim][PF₆] (1-n-butyl-3-methylimidazolium hexafluorophosphate), [C₈mim][PF₆] (1-n-octyl-3-methylimidazolium hexafluorophosphate), and [C₈mim][BF₄] (1-n-octyl-3-methylimidazolium tetrafluoroborate). The examined inorganic salts are the chloride-based salts (sodium chloride, lithium chloride, potassium chloride, and magnesium chloride) and the sodium-based salts (sodium thiocyanate, sodium nitrate, sodium trifluoroacetate, sodium bromide, sodium iodide, sodium perchlorate, sodium acetate, sodium hydroxide, sodium dihydrogen phosphate, sodium phosphate, sodium tetrafluoroborate, sodium sulfate, and sodium carbonate). The effects of the cations and the anions of the ionic liquids and of the inorganic salts on the solubility of the ionic liquids in the ternary solutions were systematically compared and discussed.     

Synthesis of carborane analogues of γ-aminobutanoic acid

General method for preparation of high yields of novel N-protected carborane amino acid derivatives, 3-acylamino-1-carboxymethyl-2-R-o-carboranes (R = H, Me, Ph), is reported. The synthesis starts from readily available 3-amino-o-carboranes and includes the protection of amino group, introduction of carboxymethyl function to the carbon atom of polyhedron via the metallation of carborane CH bond with sodium amide in liquid ammonia, and treatment of corresponding sodium carboranes with sodium bromoacetate. Deprotection of N-acylated carborane amino acids is studied in acidic media. Depending on the procedure employed, closo- or nido-carborane amino acids were obtained.     

Effect of sodium bicarbonate and sodium chloride on protein conformation and gel properties of pork myofibrillar protein

To explore the potential of using sodium bicarbonate to take the place of sodium chloride, the changes in endogenous fluorescence, ultraviolet absorption spectrum, water holding capacity, gel properties and water distribution of pork myofibrillar protein were investigated. Because of the increase in pH and the exposure of more tryptophan and tyrosine residues with increasing sodium bicarbonate, the cooking yield and gel strength of pork myofibrillar protein significantly increased (P < 0.05), and centrifugal loss significantly decreased (P < 0.05). Meanwhile, the colour of the cooked pork myofibrillar protein was darker with increasing sodium bicarbonate, the bound water and immobile water were bound more tightly to the protein matrix, and the mobility of the water was lower, except for in the sample with 0.4 % sodium bicarbonate. Moreover, free water significantly increased (P < 0.05) when 0.4 % sodium bicarbonate was added, indicating that the mobility of the water was enhanced. Overall, the use of sodium bicarbonate could induce the protein conformation change, and improve the bond water content and texture properties of reduced-salt pork myofibrillar protein.     

Synthesis and extension/contraction motion of spiroborate-based double-stranded helicates consisting of substituted oligophenol strands

A new class of ortho- and meta-substituted tetraphenols at the terminal phenyl residues with a biphenylene unit in the middle were synthesized and the effect of the substitution position on the spiroborate-based double-stranded helicate formation with sodium borohydride was investigated. The ortho-substitution considerably hampered the spiroborate formation between the terminal biphenol units and the boron atoms, whereas the meta-substituted oligomers formed a double-stranded helicate bridged by spiroborate groups accommodating a sodium cation in the center, which displayed an extension and contraction motion triggered by the removal and addition of sodium ions in solution.     

Reaction of 1-bromovinyl and 1-bromo-2-phenylvinyl sulfones with some CH acids

Benzyl, methyl, and phenyl α-bromovinyl sulfones reacted with malononitrile and dimethyl malonate sodium enolates in THF to give sulfonyl-substituted cyclopropanes. Reactions of the same sulfones with methyl acetoacetate sodium enolate afforded the corresponding sulfonyl-substituted cyclopropanes as mixtures of cis and trans isomers with a small impurity of 5-sulfonyl-4,5-dihydrofuran derivative. Phenyl and p-tolyl 1-bromo-2-phenylvinyl sulfones reacted with methyl acetoacetate sodium salt to produce a mixture of trans-isomeric 5-sulfonyl-4,5-dihydrofuran and Michael adduct of the CH acid with activated acetylene generated by concurrent 1,2-dehydrobromination of the initial α-bromovinyl sulfone.     

Vanadametry Estimation of Thiosulphate

1.(a) We have found that sodium thiosulphate is quantitatively oxidized to tetrathionate in five minutes at room temperature (28°) by excess sodium vanadate in a medium containing sulphuric acid at 0.06N to 0.1N concentration and a little copper sulphate as catalyst. (b) Quantitative emulation of sodium thiosulphate to tetrathionate has also been achieved by the action of excess sodium vanadate during five minutes at room temperature in a medium containing 2.0N—8.0N acetic acid and a little copper salt as catalyst. Further oxidation to sulphate does not occur, even if the mixture is heated to boiling. (c) The excess of unreacted vanadate in 1(a) and 1(b) can be titrated with a standard solution of ferrous ammonium sulphate using diphenylbenzidine as indicator, after adding the requisite quantity of syrupy phosphoric acid. 2. On the other hand, sodium thiosulphate is easily and quantitatively oxidized to sulphate at room temperature, when. acted upon by excess sodium vanadate in a medium containing hydrochloric acid at an overall concentration of 5-6N and 1.0 ml of iodine monochloride as catalyst. The time required for reaction is ten minutes. The unreacted vanadate can be estimated by titration with a standard solution of ferrous ammonium sulphate, using N-phenylanthranilic acid as indicator or with diphenylbenzidine as indicator after suitably diluting and adding phosphoric acid.     

Syntheses and reactions of terpene β-hydroxyselenides and β-hydroxydiselenides

A convenient method for the synthesis of optically active trans-hydroxyselenides and trans-hydroxydiselenides from the bicyclic terpene group based on the reactions of sodium selenide or sodium diselenide with cis- and trans-(+)-3-carane, trans-(+)-2-carane and (?)-β-pinane epoxides is described. The corresponding cis-hydroxy and cis-methoxydiselenides were obtained in the reaction of sodium diselenide with β-hydroxy- and β-methoxytosylates. The influence of a hydroxy group at the β-position on the diastereomeric ratio of the products of the asymmetric methoxyselenenylation of styrene has been established by composition of the products, crystal structure analyses, and theoretical calculations using a DFT method on the B3LYP level (6-311G(d)).     

Indirect determination of ampicillin sodium with sodium nitrate-ammonium thiocyanate-water system by extraction-flotation of cuprous thiocyanate

A novel method for indirect determination of ampicillin sodium by the extraction-flotation is proposed in this paper. It is indicated that the degradation of ampicillin sodium took place in the presence of 0.30 M sodium hydroxide in boiling water for 20 min. At pH 4.0, in the presence of ammonium thiocyanate, the thiol group of the degradation product of ampicillin sodium could reduce copper(II) to copper(I) due to the formation of the emulsion cuprous thiocyanate precipitation. By determining the residual amount of copper(II) in the solution and calculating the flotation yield of cuprous thiocyanate, the indirect determination of ampicillin sodium can be performed. When the concentration of cooper(II) was 5.0 μg/mL, a good linear relationship was obtained between the flotation yield of cuprous thiocyanate and the amount of ampicillin sodium in the range of 0.40～9.6 μg/mL. The linear equation is E = 4.1469 + 3.7949c with the correlation coefficient r = 0.9992, and the detection limit (3σ/K) of 0.37 μg/mL. Each parameter has been optimized and the reaction mechanism has been studied. The method has been successfully applied to the determination of ampicillin sodium in pharmaceutical, human plasma and urine samples. Analytical results obtained are satisfactory.     

Cobalt-catalyzed stereoselective iodosulfonylation and diiodination of alkynes via oxidation of potassium iodide in air

Cobalt-catalyzed iodosulfonylation of alkynes can be achieved using sodium sulfinates in the presence of KI. This procedure produces numerous stereoselective (E)-β-iodoalkenyl sulfones with good yields and suppresses the formation of diiodoalkenes. Furthermore, when this reaction is performed in the absence of sodium sulfinates, the expected (E)-diiodoalkenes are obtained.     

Reaction of 2,2,3,3-tetracyanocyclopropyl ketones with sodium and potassium hydroxides

Reaction of 2,2,3,3-tetracyanocyclopropyl ketones with water solution of sodium hydroxide after neutralization with sulfuric acid leads to the formation of 4-amino-1-hydroxy-3,6-dioxo-2,3,5,6-tetrahydro-1Hpyrrolo[3,4-c]pyridine-7-carbonitriles. Pivaloyltetracyanocyclopropane reacts in another way and is converted into sodium 6a-tert-butyl-3,4-dicyano-5-oxo-1,5,6,6a-tetrahydropyrrolo[2,3-b]pyrrol-2-olate. 1-Benzoyl-1-methylcyclopropane-2,2,3,3-tetracarbonitrile reacts with the sodium hydroxide with the retention of the threemembered ring and the formation of 11-methyl-4-phenyl-3,5,9-triazatetracyclo[5.3.1.01,7.0^4,11]undecane-2,6,8,10-tetraone.     

Vibrational analysis of alkyl xanthates

Rotational isomers are indicated in the Raman spectra of sodium ethyl and other xanthates. Vibrational bands useful for characterizing xanthate solids and aqueous solutions are given. Vibrational analyses are reported for sodium ethyl xanthate, trans and gauche forms, and the methyl and isopropyl analogs using a Cartesian coordinate force field derived from ab initio molecular orbital calculations.     

Determination of semimicro amounts of tellurium by electrodeposition

Electrodeposition of tellurium in micro or semimicro amounts can be achieved using copper or copper-plated platinum cathodes. Best results are obtained from electrolytic baths of approximately 2 M sulfuric acid, 0.4 M ammonium sulfate, 0.1 M sodium tartrate and 0.06 M sodium nitrate. Electrodeposition of tellurium can be carried out with an accuracy better than 1% at the 90% confidence level.     

Studies on epoxides—VI : Opening reactions of α-substituted epoxysteroids

Treatment of 1,2-epoxy-3-ketosteroids with tosylhydrazine and sodium borohydride in methanol lead to mixtures consisting of (i) ring A seco-acetylenic alcohols, (ii) methoxyhydrins formed by opening of the epoxide ring following the carbonyl reduction, and (iii) an epoxy-3,3-di- methylketal. For the corresponding 4-methylene derivative, the ring A fragmentation product was found to be the conjugated en-yne 8a. Reduction of these epoxyketones with sodium borohydride alone affords mixtures of cis- and trans epoxyalcohols; the cis derivatives were unaffected by heating with sodium borohydride in methanol, whereas the trans were converted into the corresponding diaxial methoxyhydrins.     

Esr and electronic absorption spectra of the products of deprotonation of iron arene-cyclopentadienyl complexes

Paramagnetic d⁷ complexes have been obtained by reducing deprotonated arenecyclopentadienyliron borofluorides (arene  diphenylmethane, fluorene, hexamethylbenzene) with sodium. The interaction of deprotonated d⁷ complexes with ethanol leads to neutral d⁷ complexes which are formed by direct reduction of the initial cations with sodium. Hexamethylbenzenecyclopentadienyliron was shown to undergo deprotonation under the action of sodium.The electronic absorption spectra of the deprotonated complexes have been studied. Analysis of the positions and intensifies of the absorption bands made it possible to draw some structural conclusions about deprotonated arene ligands.     

Per-O-methylation of neutral carbohydrates directly from aqueous samples for gas chromatography and mass spectrometry analysis

Per-O-methylation of neutral carbohydrates in one step by adding dimethyl sulfoxide, powdered sodium hydroxide, and methyl iodide directly to aqueous sample is described. The influence of the water on the methylation reaction is investigated. Solid powdered sodium hydroxide is very hygroscopic and can scavenge the water from sample if an additional excess of sodium hydroxide is added. The degree of per-O-methylation of carbohydrates is checked by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Gas chromatography-mass spectrometry analysis of mono- and disaccharides from grape juice is presented.