PHOTOCHEMICAL REARRANGEMENT OF 3-PHENYLATED 2(3H)-OXEPINONES IN ACIDIC MEDIA. FORMATION OF 5-STYRYL-2(5H)-FURANONES

Mn-Mo-O catalysts with a different Mo/Mn ratio have been prepared by precipitation. The precipitate composition as a function of solution concentration and pH was studied by X-ray, IR, thermal and chemical methods. Formation of manganese molybdates with MnMoO4.1.5H2O, Mn3Mo3O12.2.5H2O, and Mn3Mo4O15.4H2O composition has been supposed. It is concluded that pure MnMoO4 may be obtained in both acid and alkaline media, the pH values depending on the concentration of the initial solutions. The maximum Mo/Mn ratio in the precipitates is 1.33. The formation of pure Mn3Mo4O15.4H2O is possible in weakly acidic media. This process is favoured by increasing the concentration of initial solutions.

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Sorption of Cadmium and Lead by Chelating Ion Exchangers Ostsorb OXIN, Ostsorb DETA, and Ostsorb DTTA

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19941311 ◽

1994 ◽

Vol 59 (6) ◽

pp. 1311-1318 ◽

Cited By ~ 5

Author(s):

Ladislav Svoboda ◽

Petr Vořechovský

Keyword(s):

Ionic Strength ◽

Aqueous Solutions ◽

Sodium Perchlorate ◽

Exchange Capacity ◽

Chloride Ions ◽

Point Of View ◽

Alkaline Media ◽

Ion Exchangers ◽

Acidic Media ◽

Cadmium And Lead

The properties of cellulose chelating ion exchangers Ostsorb have been studied in the sorption of cadmium and lead from aqueous solutions. The Cd(II) and Pb(II) ions are trapped by the Ostsorb OXIN and Ostsorb DETA ion exchangers most effectively in neutral and alkaline media but at these conditions formation of stable hydrolytic products of both metals competes with the exchange equilibria. From this point of view, Ostsorb DTTA appears to be a more suitable sorbent since it traps the Pb(II) and Cd(II) ions in acidic media already. Chloride ions interfere with the sorption of the two metals by Ostsorb DTTA whereas the ionic strength adjusted by the addition of sodium perchlorate does not affect the exchange capacity of this ion exchanger.

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Some Aspects of the Electroreduction of Niazid to Nicotinamide on Mercury Electrodes in Acidic Media

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19921836 ◽

1992 ◽

Vol 57 (9) ◽

pp. 1836-1842 ◽

Cited By ~ 9

Author(s):

Rafael Marín Galvín ◽

José Miguel Rodríguez Mellado

Keyword(s):

Electron Transfer ◽

Essential Role ◽

Uv Spectroscopy ◽

Acidic Media ◽

Polarographic Wave ◽

Rate Determining Step ◽

Tafel Slopes ◽

Reaction Orders ◽

Mercury Electrodes ◽

The Waves

The electroreduction of niazid on mercury electrodes has been studied in acidic media (pH < 6). Tafel slopes and reaction orders were obtained at potentials corresponding to the foot of the first polarographic wave. On the basis of both polarographic and voltammetric results it has been shown that the waves appearing at more negative potentials correspond to the reduction of nicotinamide. Protonation of niazid plays an essential role in its reduction and pK values of 1.4, 3.2 and 11.5 were obtained by UV spectroscopy. The process corresponding to the first wave is irreversible, being the second one-electron transfer the rate determining step. Above pH 4 the process is complex due to the overlapping of the waves caused by the occurrence of protonation reactions.

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