<b>Boron Hydrides. V. Methanolysis of Sodium Borohydride</b>

Davis, Robert Earl; Gottbrath, Judith Ann

doi:10.1021/ja00865a003

Cited by 89 publications

(74 citation statements)

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“…In this case, the THB-reduced Cu could be able to adsorb stibane but not to decompose it, and the additive can act through a mechanism based on the competitive adsorption for the active sites on the surface of THB-reduced Cu deposited in the CHG apparatus. electron release from the oxygen group increases the hydridic character of the hydrogen [170]. A similar conclusion, supported by experimental evidence, has already been made for a similar species, [BH 3 OH] -(Section 4.2).…”

confidence: 79%

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Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

D’Ulivo

Dědina

Mester

et al. 2011

Pure and Applied Chemistry

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Aqueous-phase chemical generation of volatile hydrides (CHG) by derivatization with borane complexes is one of the most powerful and widely employed methods for determination and speciation analysis of trace and ultratrace elements (viz. Ge, Sn, Pb, As, Sb, Bi, Se, Te, Hg, Cd, and, more recently, several transition and noble metals) when coupled with atomic and mass spectrometric detection techniques. Analytical CHG is still dominated by erroneous concepts, which have been disseminated and consolidated within the analytical scientific community over the course of many years. The overall approach to CHG has thus remained completely empirical, which hinders possibilities for further development. This report is focused on the rationalization and clarification of fundamental aspects related to CHG: (i) mechanism of hydrolysis of borane complexes; (ii) mechanism of hydrogen transfer from the borane complex to the analytical substrate; (iii) mechanisms through which the different chemical reaction conditions control the CHG process; and (iv) mechanism of action of chemical additives and foreign species. Enhanced comprehension of these different mechanisms and their mutual influence can be achieved in light of the present state of knowledge. This provides the tools to explain the reactivity of a CHG system and contributes to the clarification of several controversial aspects and the elimination of erroneous concepts in CHG.

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confidence: 79%

“…The kinetics of decomposition THB in methanol have been investigated by Davis and Gottbrath [170]. At 25 °C, the rate of decomposition of THB in methanol was found to be about one order of magnitude faster than in water, with a rate constant of (1.6 ± 0.3) × 10 7 L mol -1 s -1 .…”

Section: Effect Of Alcoholsmentioning

confidence: 99%

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

D’Ulivo

Dědina

Mester

et al. 2011

Pure and Applied Chemistry

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“…This feature is not surprising since hydrolysis of sodium borohydride (27), hydrolysis of pyridine alkylboranes (28), and the methanolysis of lithium borohydride (29) all have inverse isotope effects. In the reduction of ketones by borohydride, it has been shown (30,46) that the rate determining step is transfer of the first hydrogen (Fig. 4).…”

Section: The Terms Steric Approach Control Andmentioning

confidence: 99%

Deuterium Isotope Effects in the Reduction of Cyclohexanones. The Concepts of Steric Approach Control and Product Development Control

Wigfield¹,

Phelps²

1972

Can. J. Chem.

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Definitions for the terms steric approach control and product deuelopment control in relation to the degree of bonding in the transition state are put forward. Kinetic deuterium isotope effects in the reduction of a graded series of ketones by NaBH, and NaBD, have been measured. These effects are inverse, and show no systematic dependence on the degree of steric hindrance of the ketone. This evidence appears to invalidate the steric approach control-product development control explanation of the axial to equatorial product ratios (1). The primary isotope effect is very small, which is consistent with an early transition state in these reductions, as demanded by other explanations of product ratios, but since several other factors causing small isotope effects may be applicable, the evidence does not constitute proof of an early transition state.The main conclusions of this work have already been published in preliminary form (2).Les notions de "steric approach control" et 'kroduct deuelopment control" en relation avec le degri. de liaison dans I'ttat de transition, sont precisees. Les effets isotopiques du deuterium sur la cinbtique de reduction d'une serie de cetones par NaBH, et NaBD,, ont Ct C mesurts. Ces effets sont inverses et ne montrent aucune dependance systematique avec le degrt d'empschement sttrique de la cCtone. Cette mise en evidence montre que I'explication des rapports du produit axial et equatorial par le "steric approach control" et "product development control", n'est pas valable (1). L'effet isotopique primaire, trts faible, est compatible avec un debut d'6tat de transition dans ces rbductions. Ce rbsultat, deji mentionnt dans d'autres etudes, ne constitue pas une preuve puisque de nombreux autres facteurs peuvent Etre la cause de ces faibles effets isotopiques. Les conclusions principales de ce travail ont deja Ct C publikes dans une note preliminaire (2).

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“…In accord with literature reports, MeOH and EtOH directly reacted with BH 4 -, and performed methanolysis and ethanolysis, respectively, of BH 4 -to H 2 . 12,13 These alcohols therefore supplant BH 4 -hydrolysis with equally deleterious reactions. Though NaBH 4 is "soluble" in multiple glymes, 14 we found that it made a cloudy suspension, and we concluded BH 4 -would have greatly diminished activity if not fully dissolved.…”

Section: Bmentioning

confidence: 99%

Transport Phenomena and Interfacial Kinetics in Planar Microfluidic Membraneless Fuel Cells

Abruña

2013

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Abstract:Our work is focused on membraneless laminar flow fuel cells, an unconventional fuel cell technology, intended to create a system that not only avoids most typical fuel cell drawbacks, but also achieves the highest power density yet recorded for a non-H 2 fuel cell. We have employed rigorous electrochemistry to characterize the high-energydensity fuel BH 4 -, providing important mechanistic insight for anode catalyst choice and avoiding deleterious side reactions. Numerous fuel cell oxidants, used in place of O 2 , are compared in a detailed, uniform manner, and a powerful new oxidant, cerium ammonium nitrate (CAN), is described. The high-voltage BH 4 -/CAN fuel/oxidant combination is employed in a membraneless, room temperature, laminar-flow fuel cell, with herringbone micromixers which provide chaotic-convective flow which, in turn, enhances both the power output and efficiency of the device. We have also been involved in the design of a scaled-up version of the membraneless laminar flow fuel cell intended to provide a 10W output. Research FindingsA.Electroanalytical investigation of borohydride (BH 4 -): Oxidation mechanism, best catalysts, and performance optimization.Our search for a highly soluble fuel for microfluidic fuel cell applications quickly focused on BH 4 -, most commonly used as its sodium salt, NaBH 4 . This compound has considerable solubility in aqueous solutions (>14 M), a high electron recovery per molecule (8e -, Reaction 1), a very low potential for oxidation in base (-1.44 V vs. Ag/AgCl), and extremely fast kinetics at room temperature:Thus, it has approximately the same low onset potential for oxidation as H 2 , allowing for high voltage systems. However, because of its very high solubility, about 14,000 times that of H 2 , it can have a theoretical maximum current density that is multiple orders of Reaction E°' (V vs. Ag/AgCl, 1M NaOH)

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Boron Hydrides. V. Methanolysis of Sodium Borohydride

Cited by 89 publications

References 0 publications

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

Deuterium Isotope Effects in the Reduction of Cyclohexanones. The Concepts of Steric Approach Control and Product Development Control

Transport Phenomena and Interfacial Kinetics in Planar Microfluidic Membraneless Fuel Cells

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