Activation of reducing agents. Sodium hydride containing complex reducing agents 28. Stereochemistry of reduction of ketones by complex reducing agents

The stereochemistry of reduction of selected ketones by a variety of Complex Reducing Agents (MCRA) has been investigated. The selectivity depends on the nature of the CRA constituents and principally on that of the metal salt.     

Activation of reducing agents. Sodium hydride containing complex reducing agents 29. Epimerization of alcohols by nickel-containing complex reducing agents (NiCRA)

Epimerization of selected alcohols has been easily achieved by nickel-containing Complex Reducing Agents (termed NiCRA) prepared from 2,5-dimethyl-2,5-hexanediol. It is shown that these reactions are under thermodynamic control.     

Back titration with mercuric nitrate in alkaline : medium volumetric analysis of binary mixtures of the alkaline earths,magnesium, zinc and cadmium

Mercuric nitiate has proved to be suitable for the back titration of the excess amount of EDTA remaining in solution when this compound has reacted quantitatively either with zinc or cadmium in the presence of one of the three elements barium, strontium and magnesium at pH 8 or 9, or with both cations at pH 11. Advantage is taken of this behaviour for analysing binary mixtures of the above mentioned cations by back titration at lower and higher pH's The end-points are detected potentiometrically, reasonable jumps being obtained; the agreement with the theoretical end-points is satisfactory.     

Activation of reducing agents. Sodium hydride containing complex reducing agents 21. Regioselective reduction of alkene oxides

It is shown that epoxides are reduced by ZnCRA and NiCRA. Interestingly, the simple change in the nature of the metal included in the reagent, changes the regiochemistry of the reduction.     

Determination of nitrate and nitrite in mixtures with a nitrate ion electrode

A rapid method for the determination of nitrate and nitrite ions is described. The potential of a mixture of nitrate and nitrite was measured with a nitrate ion selective electrode. The nitrite in the mixture is then oxidized to nitrate with permanganate in acid solution, and the potential of the oxidized solution is also measured with the electrode. The fundamental equations for the response of the nitrate ion electrode to nitrate ion in the presence of interfering ions were used, and a new equation was developed for calculating the original nitrate concentration of the mixture. The absolute errors for solutions of known concentrations (2.5–100 p.p.m. each) were 1.8 p.p.m. nitrate and 2 p.p.m. nitrite. When the results are calculated by computer, five determinations can be performed in 30 min. The method was applied to the determination of the oxides of nitrogen in cigarette smoke as nitrite and nitrate after dissolution in basic solution.     

Activation of reducing agents. Sodium hydride containing complex reducing agents 24. Beneficial effect of Me3SiCl on the reducing properties of NiCRA

Reduction of carbon-carbon double bonds can be achieved with either NiCRA or NiCRASi (nickel containing Complex Reducing Agent activated by Me₃SiCl). Selective reduction of polyunsaturated hydrocarbons or unsaturated ketones are easily performed with both reagents.     

BackTitration with mercuric nitrate in alkaline medium

Summary Potentiometric back titration of excess EDTA than required to chelate with lanthanum using mercuric nitrate as the back titrant provides an excellent method for the estimation of this metal. By aid of the method amounts of lanthanum in the order of 50 g up to 60 mg were determined with high accuracy in most cases. The method is further successfully applied for analysis of pairs of La with Th, Ba, Hg^II, Mn^II, Cu, Zn, Cd, Ni, Co or Bi using a suitable precipitant or masking agent or selective P_H. NH₄F has proved to be a suitable masking agent for small amounts of lanthanum.See also Z. analyt. Chem. 169, 109 (1959).     

Back titration with mercuric nitrate in alkaline medium

Summary Potentiometric back titration of excess EDTA than required to chelate with gallium or indium using mercuric nitrate as the back titrant provides an excellent method for the determination of amounts of both metal ions in the order of 0.07 to 11 and 0.05 to 18 mg, respectively. The method is further successfully applied for analysis of binary and ternary mixtures of gallium or indium with some other cations using simple procedures.

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Zusammenfassung Gallium oder Indium können in Mengen von 0,07–11 bzw. 0,05 bis 18 mg bestimmt werden, wenn man mit einem überschuß an äDTA versetzt und mit Quecksilber(II)-nitratlösung potentiometrisch zurücktitriert. Auf einfache Weise können auch binäre und ternäre Mischungen von Ga oder In mit einigen anderen Kationen erfolgreich analysiert werden.

     

Back titration with mercuric nitrate in alkaline medium

Summary A rapid, reliable and accurate method for the determination of trivalent chromium, based on back titrating excess EDTA solutions in the presence of chromium versenate, with mercuric nitrate in alkaline media is given. By its aid amounts of chromium in the order of 50 micro- to 15 milligrams can be determined with fair accuracy. The method is applied for analysis of binary mixtures of chromium with thorium, copper(II), bismuth or mercury(II).     

Back titration with mercuric nitrate in alkaline medium

Summary The back titration procedure making use of mercuric nitrate as back titrant for excess EDTA in alkaline media, has been successfully applied for the determination of small amounts of scandium or palladium in the order of 0.045 to 7 or 0.1 to 4mg, respectively. Simple procedures are given for the analysis of binary or ternary mixtures of scandium or palladium with some other metals, yielding results of quite reasonable accuracy.

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Zusammenfassung Scandium oder Palladium können in Mengen von 0,045–7 bzw. 0,1–4 mg bestimmt werden, wenn man mit einem Überschuß an ÄDTA versetzt und in alkalischem Medium mit Quecksilber(II)-nitratlösung zurücktitriert. Auf einfache Weise können auch binäre und ternäre Gemische von Scandium oder Palladium mit anderen Metallen mit befriedigender Genauigkeit analysiert werden.

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See also: Z. analyt. Chemie 184, 92 (1961).     

Back titration with mercuric nitrate in alkaline medium

Summary Small amounts of bismuth in the order of 100 g up to 25 mg were potentiometrically determined by back titration with mercuric nitrate in alkaline media. The method gives highly accurate results and is further successfully applied for analysis of pairs of bismuth together with one of the cations of calcium, copper, cadmium, zinc, manganese, nickel, lead, aluminium and lanthanum.See also Z. analyt. Chem. 161, 401 (1958); 163, 81 (1958).     

Activation of reducing agents. Sodium hydride containing complex reducing agents 25. A one pot one reagent cross-coupling reaction of aryl halides

The preparation of NiCRA [NaH-AtmONa-Ni(OAc)₂] in the presence of 2,2′-bipyridyl and KI leads to a reagent (termed NiCRA-bpy-KI) which is shown to be one of the most efficient Ni containing reagents reported so far for the cross-coupling of aryl halides.     

Back titration with mercuric nitrate in alkaline medium analysis of tertiary mixtures of mercury(II) with some other metals

Summary Tertiary mixtures each containing mercury(II) were analysed by simple procedures involving combination between the recent method of back titration with mercuric nitrate in alkaline medium, and the volumetric methods which make use of masking agents as cyanide. The content of mercury(II) in most mixtures is determined potentiometrically with potassium iodide using the silver amalgam as indicator electrode. End points are attended with fair accuracy within 0.02 ml titrant and with reasonable jumps from 60 to 90 mv per 0.1 ml of mercuric nitrate solution or from 170 to 200 mv per 0.1 ml of potassium iodide solution.