Experimental studies of the hydrolysis kinetics of aqueous-alkaline solutions of sodium borohydride

Experimental data were used to study the hydrolysis kinetics and construct an approximating expression for calculation of quasistationary hydrolysis constants for sodium borohydride in a wide range of alkali concentrations and temperatures.     

Reactivity of 4-hydroxy-2-methyl-7,8,9,10-tetrahydrobenzo[h] quinoline towards base-catalyzed cyclization,mannich and turpin reactions

Mannich reaction upon 4-hydroxy-2-methyl-7,8,9,10-tetrahydrobenzo[h]quinoline ( 1 ) as well as its nitration were studied. Condensation of the chloroquinoline 6b with sodium azide, benzylamine and ethanolamine gave the quinoline derivatives 6c, 6f and 6g , respectively. Phenylhydrazine and sodium borohydride effected reduction of the azidoquinoline 6c to the corresponding amino- and hydroxyamino derivatives 6d and 6e , respectively. Also, Turpin's reaction gave the benzoquinobenzoxazines 7a-d when applied to 6b . Treatment of 6f, 6g with alkali and the condensation of 6b with glycine in alcoholic sodium carbonate solution afforded the imidazo[4,5-c]quinoline derivatives 9a-c , respectively.     

以硼氢化钠为还原剂化学镀镍的电化学研究

采用线性电位扫描伏安法研究了以硼氢化钠为还原剂的化学镀镍体系, 考查了镀液组成及工艺条件对化学镀镍硼阴、阳极过程的影响, 结果表明: 乙酸镍和硼氢化钠含量的提高分别促进了Ni²⁺的还原反应和BH₄^-的氧化反应; 乙二胺、氢氧化钠以及添加剂硫脲、糖精钠对阴、阳极反应均有不同程度的抑制作用, 同时添加剂中的硫元素加速了镍的氧化; 升高温度有利于阴、阳极反应的进行.     

Reinvestigation of the Reaction of Sodium Borohydrate with Benzhydryl Halides under Solvolytic Conditions

Solvolysis of benzhydryl halides in aqueous diglyme containing sodium borohydride was studied. Contrary to the literature, sodium borohydride was found not to be a convenient trap for benzhydryl carbocations, especially for those containing electron-withdrawing substituent, and it decomposed appreciably in 80% aqueous diglyme at 45 °C. In addition, significant acceleration of reactions due to the presence of sodium borohydride was realized in the solvolysis of 3-chloro- and 3-trifluoromethyl-benzhydryl chlorides.     

Solid-State Hydrogen-Generating Composites Based on Sodium Borohydride: Effect of the Heat Treatment of Boron–Cobalt Catalysts on the Hydrogen Generation Rate

Calcined boron–cobalt catalysts prepared by reduction of cobalt chloride in an aqueous sodium borohydride solution can be successfully used as components of pelletized solid-state hydrogen-generating composites based on sodium borohydride. Morphological changes and phase and chemical transformations occurring in the catalysts with an increase in the calcination temperature were studied. The catalyst performance in hydrolysis of sodium borohydride was determined. The hydrogen generation rate depends on the specific surface area of the calcined sample.     

三角形银纳米片的合成及其影响因素

报道了一种在不需光照的条件下制备三角形银纳米片的新方法.在表面活性剂BRIJ35存在下,将硝酸银用硼氢化钠和柠檬酸钠还原,在不同温度范围内反应形成各种尺度的三角形银纳米片,探讨了硼氢化钠浓度、BRIJ35浓度和表面活性剂的种类和溶液pH值等因素对银纳米颗粒形貌和尺寸的影响.     

Borohydride reduction of Ag<Superscript>+</Superscript> in aqueous poly(acrylic acid-<Emphasis Type="Italic">co</Emphasis>-acrylamide) solutions

Silver clusters stabilized with poly(acrylic acid-co-acrylamide) are chemically synthesized via reduction of silver cations with sodium borohydride. Metallopolymer systems obtained at different concentrations of sodium borohydride in reaction mixtures are studied spectrophotometrically, and the effect of reductant content on the composition of the products is investigated.     

Stereoelective Conversion of Ethyl Pipecolinate into (±)-α- and (±)-β-Conhydrins

Reaction of ethyl N-benzhydrylpipecolinate with ethylmagnesium bromide in the presence of catalytic amount of titanium(IV) isopropoxide furnished in a high yield the corresponding hydroxypropyl-substituted piperidine that by treating with alcoholic alkali was quantitatively converted into 1-benzhydryl-2-propionylpiperidine. The reduction in the latter of carbonyl group with lithium aluminum hydride or sodium borohydride in methanol gave rise prevailingly to threo-aminoalcohol. With sodium borohydride in the presence of cerium chloride an erythro-aminoalcohol was the main product. Deprotection of the nitrogen atom from the benzhydryl group of the aminoalcohols obtained provided racemic - and -conhydrines.     

Structure and some reactions of coriose

Coriose was obtained in a higher yield from the root of Coriaria japonica. The structure, -altro-3-heptulose (I) was determined by the sodium borohydride reduction which yielded volemitol (II) and -glycero- -altro-hepitol (IV). Other reactions in agreement with this structure (I) were also carried out: The oxidative degradation of coriose in cold alkali produced a pentanolactone syrup which was reduced to ribose, while the degradation at elevated temperature gave a hexanolactone syrup which yielded ribose on treatment with ferric acetate-hydrogen peroxide. The rearrangement of coriose in alkali at room temperature to 2-heptuloses was investigated. Lead tetraacetate oxidation of coriose produced -glyceraldehyde and -glyceric acid.     

Sulfurated borohydride used as bleaching chemical on a softwood TMP

We studied the bleaching potential of a highly reductive chemical: sulfurated borohydride, also known as the Lalancette’s reagent, on a spruce/fir softwood TMP. The influences of reaction time, temperature, pulp consistency and reactant concentration on pulp brightness were studied. A very fast reaction was observed, along with an adverse effect of high temperature on brightness. High reactant concentration increases brightness gain. Sulfurated borohydride was compared to sodium hydrosulfite and sodium borohydride. The Lalancette’s reagent bleaches pulp to the same level as sodium hydrosulfite, but lowers the yellowness of the pulp to a greater extent.

     

Size-controlled gold nanocolloids on polymer microsphere-stabilizer via interaction between functional groups and gold nanocolloids

Gold nanocolloids with the controlled diameter ranging from 5.2 to 10.7 nm were in situ prepared by reduction of gold chloride trihydrate with sodium borohydride as reductant via the interaction between the gold naocolloids and the functional groups on the surface of polymer microsphere-stabilizer. The nature of such interaction was studied in detail by X-ray photoelectron spectroscopy (XPS). The effect of the functional groups on the catalytic activity of the gold nanocolloids was preliminarily investigated with the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride as reductant.     

Ruthenium(III) acetylacetonate: A homogeneous catalyst in the hydrolysis of sodium borohydride

Ruthenium(III) acetylacetonate was employed for the first time as homogeneous catalyst in the hydrolysis of sodium borohydride. Ruthenium(III) acetylacetonate was not reduced by sodium borohydride under the experimental conditions and remains unchanged after the catalysis. Poisoning experiments with mercury and trimethylphosphite provide compelling evidence for the fact that ruthenium(III) acetylacetonate is indeed a homogenous catalyst in the hydrolysis of sodium borohydride. Kinetics of the ruthenium(III) acetylacetonate catalyzed hydrolysis of sodium borohydride was studied depending on the catalyst concentration, substrate concentration, and temperature. The hydrogen generation was found to be first order with respect to both the substrate concentration and catalyst concentration. The activation parameters of this reaction were also determined from the evaluation of the kinetic data: activation energy; E_a = 58.2 ± 2.6 kJ mol⁻¹, the enthalpy of activation; ΔH^# = 55.7 ± 2.5 kJ mol⁻¹ and the entropy of activation ΔS^# = 118 ± 5 J mol⁻¹ K⁻¹. Ruthenium(III) acetylacetonate was found to be highly active catalyst providing 1200 turnovers over 180 min in hydrogen generation from the hydrolysis of sodium borohydride before deactivation.     

The Reactive Intermediate of Catalytic Borohydride Reduction by Schiff Base–Cobalt Complexes

The key reactive intermediate of borohydride reduction catalyzed by Schiff base–cobalt complexes is proposed to be the dichloromethylcobalt hydride with a sodium cation, based on experimental and theoretical studies. It was revealed that chloroform is not the solvent but the reactant that activates the cobalt catalyst. The substrate carbonyl compounds are fixed and activated by the alkali cation, which is captured by the oxygen atoms of the planar ligand and the chlorine atom of the axial ligand, and attacked by the hydride on the cobalt atom via a six‐membered‐like transition state to afford the corresponding alcohol.     

钌/氮掺杂石墨烯催化硼氢化钠水解制氢的研究

本文采用原位合成法制备了钌/氮掺杂石墨烯(Ru/NGR)催化剂,并采用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)等手段对催化剂的结构形貌进行了表征。将Ru/NGR催化剂应用于硼氢化钠水解制氢体系,考察了钌的负载量、硼氢化钠的浓度、反应温度等对硼氢化钠产氢的催化性能的影响。研究结果表明:当温度为25℃,硼氢化钠浓度为2 wt%,钌负载量为3.9%时,产氢速率可达32.95 L·(gRu·min)^-1。通过对Ru/NGR催化剂催化硼氢化钠水解反应动力学数据研究研究得出该催化剂的活化能为46 kJ·mol^-1。     

High-performance liquid chromatographic evaluation of pyridoxyl 5'-phosphate hemoglobin derivatives produced by different reduction procedures

Pyridoxylated hemoglobin derivatives have been studied by many investigators. In this study hemoglobin A0 rather than stroma-free hemoglobin was used as a starting material in order to reduce the number of proteins to A0 and A1c. Derivatives were characterized using a Synchropak Q300 strong anion-exchange column, a PolyCAT A weak cation-exchange column and a VYDAC reversed-phase high-performance liquid chromatographic column. Resulting peak profiles of these two ion-exchange separations demonstrated enhanced resolution and showed the presence of pyridoxylated hemoglobin products not previously described. We compared products from the reduction of these Schiff base derivatives using either sodium borohydride or sodium cyanoborohydride reduction procedures. The sodium cyanoborohydride reduction method produced a lower percentage of products with multiple-site pyridoxylation modifications than the sodium borohydride reduction process.     

苷类化合物研究(Ⅰ)——天麻苷类似物的合成

本文合成了16种天麻苷类似物,测定了它们的¹³CNMR和¹HNMR。依据NMR数据,这些化合物的端基构型指定为β构型。     

Biomimetic reduction of nimesulide with NaBH4 catalyzed by metalloporphyrins

The biomimetic reduction of anti-inflammatory drug, nimesulide (1) with sodium borohydride catalyzed by 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides [TAPFe(III)Cl] has been studied in organic solvents under anaerobic and aerobic conditions.     

Reduction of (+)-usninic acid and its pyrazole derivative by sodium borohydride

The reaction of (+)-usninic acid and its pyrazole derivative with sodium borohydride was studied. The reduction occurred stereoselectively at the endocyclic carbonyl group. Novel (+)-usninic acid derivatives that were reduction products of the carbonyls were obtained.     

NaBH_4还原二氟乙酸乙酯合成二氟乙醇的研究

采用硼氢化钠(NaBH4)还原二氟乙酸乙酯(CF2HCOOCH2CH3)合成二氟乙醇(HCF2CH2OH)。探讨NaBH4用量、溶剂、反应温度和反应时间等因素对反应的影响。实验结果表明:在投料比n(NaBH4)/n(CF2HCOOCH2CH3)=0.6,乙醇为溶剂,温度0℃反应条件下,二氟乙醇的收率可以达到98.1%。在极性溶剂中,随着反应温度的升高(5℃及以上),NaBH4的分解加剧,低温对反应有利。     

Comparative study of sodium borohydride tablet and tin(II) chloride reducing systems in the determination of mercury by atomic-absorption spectrophotometry

Summary An atomic-absorption spectrophotometric method for the rapid and precise determination of mercury has been studied by using the sodium borohydride tablet reduction and cold-vapour atomicabsorption procedure coupled with amalgamation on gold. The comparison of the sodium borohydride tablet and tin(II) chloride solution reducing systems are described in detail. The use of the sodium borohydride tablet wrapped in a wafer sheet is very simple and gives more precise results. From the comparison of the effect of diverse ions, it is obvious that both reducing systems have their merits and demerits.

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AAS-Bestimmung von Quecksilber. Vergleichende Untersuchung der Reduktion mit Natriumborhydrid oder Zinn(II)-Chlorid

Zusammenfassung Ein atomabsorptions-spektralphotometrisches Kaltdampf-Verfahren zur schnellen Quecksilberbestimmung wird beschrieben, das auf der Reduktion mit Hilfe der Natriumborhydridtablette und der Amalgamierung mit Gold beruht. Der Vergleich mit der Zinn(II)-Chloridmethode wird diskutiert. Genaue Ergebnisse werden durch einfaches Einhüllen der Reduktionstablette in ein Waffelblatt erzielt, wodurch der Reaktionsbeginn verzögert wird. In bezug auf Störelemente ergeben sich für beide Verfahren Vor- und Nachteile.