Oxidation of organic substances with compounds of trivalent manganese: XIII. Oxidation of pyruvic acid with manganese(III) sulfate in a medium of sulfuric acid and with hexaquomanganese(III) ions in noncomplexing medium of perchloric acid

The oxidation of pyruvic acid with manganese(III) sulfate in a medium of sulfuric acid and with hexaquomanganese(III) ions in noncomplexing perchloric acid medium was studied. It was found that pyruvic acid is oxidized by both reagents to give acetic acid and carbon dioxide and the optimal conditions for the analytical application of this reaction on both a semimicro and micro level were found.     

The oxidation of organic substances by compounds of trivalent manganese: XIV. Oxidation of malonic acid by manganese(III) sulfate in sulfuric acid medium and with hexaquomanganese(III) ions in noncomplexing perchloric acid medium

The oxidation of malonic acid by manganese(III) sulfate in a medium of sulfuric acid and by hexaquomanganese(III) ions in a noncomplexing perchloric acid medium was studied.The reaction stoichiometry was found and the effect of the concentrations of H⁺, Mn²⁺, and HSO₄^? ions and of the initial reactant concentrations on the course and rate of the reaction was studied.The optimum conditions have been found for analytical use of the reaction, procedures have been proposed for the determination of malonic acid using the two reagents, and the accuracy and reproducibility of the determinations have been found.     

The oxidation of organic substances with compounds of trivalent manganese: XXI. The oxidation of glycoaldehyde with hexaquomanganese(III) ions in a noncomplexing perchloric acid medium

The oxidation of glycolaldehyde with hexaquomanganese(III) ions in a noncomplexing perchloric acid medium was studied. The optimum conditions have been found for analytical use of the reaction. The recommended procedure is based on the oxidation of the test substance with the oxidant in the absence of atmospheric oxygen and back-titration of the unconsumed reagent with ferrous sulfate.

2. Accuracy and Reproducibility of the Determination of Glycolaldehyde with Hexaquomanganese(III) Ions in a Noncomplexing Perchloric Acid Medium

Taken (μg)	Found (μg)a	Standard deviation (μg)
751	748	12
1501	1485	15
2252	2192	7

a

The values are the average of seven determinations, from which the standard deviation value was calculated.

     

The oxidation of organic substances with compounds of trivalent manganese: XVIII. A contribution to the coulometric generation of manganese(III) acetate in an acetic acid medium

Conditions were found under which manganese(III) acetate can be electrochemically generated at a platinum anode with 100% current efficiency. It was found that even traces of

5. Time Dependence of the Consumption of the Oxidizing Reagent in the Indirect Determination of Hydroquinone with Coulometric Generated Manganese(III) Acetate

     

5.

The oxidation of organic substances with compounds of trivalent manganese: XXVII. The oxidation of 4,4′-dihydroxyazobenzene with the diphosphate complex of trivalent manganese     

J. Barek  A. Berka  V. Borek 《Microchemical Journal》1985,32(1):76-78

The oxidation of 4,4′-dihydroxyazobenzene with the diphosphate complex of trivalent manganese was studied. The reaction stoichiometry was found and a procedure for a direct potentiometric titration of the test substance has been proposed.     

6.

The oxidation of organic substances with compounds of trivalent manganese: XXII. The oxidation of glyceraldehyde with manganese(III) sulfate     

J. Barek  A. Berka  A. Hladíková 《Microchemical Journal》1982,27(1):66-70

The oxidation of glyceraldehyde with manganese(III) sulfate was studied. The reaction stoichiometry was found and a procedure for an indirect determination of 5–17 mg of the test substance has been proposed. The recommended procedure is based on the oxidation of glyceraldehyde with the reagent, the excess of which is back-titrated with standard solution of ferrous sulfate.     

7.

Oxidation of organic compounds by tervalent manganese compounds: IX. Determination of the titer of hexaquomanganese(III) ion standard solutions in perchloric acid     

J. Barek  A. Berka  A. Pokorná 《Microchemical Journal》1978,23(1):104-109

Optimum conditions have been found for the determination of the titer of 0.005 N solutions of hexaquomanganese(III) ion by potentiometric titration of ferrous chloride. The accuracy and reproducibility of this method were studied. A new method of determining the titer of dilute solutions of hexaquomanganese(III) ion has been proposed, using potassium iodide as a primary standard. The optimum conditions for this titration have been found and its applicability to the determination of the titer of 0.005, 0.001, and 0.0005 N solutions has been verified.     

8.

Oxidation of organic substances by tervalent manganese compounds : VIII. Determination of benzene polyhydroxy and aminohydroxy derivatives with a standard solution of hexaquomanganese(III) ion in perchloric acid     

J. Barek  A. Berka  J. Korečková 《Microchemical Journal》1977,22(4):484-488

The reaction of hexaquomanganese(III) ion with hydroquinone, p-aminophenol, metol, pyrocatechol, resorcinol, and phloroglucinol was studied. It has been found that the first three substances are oxidized quantitatively with the exchange of two electrons to the corresponding quinone compounds and that this reaction can be employed for direct or indirect titrimetric determination of these substances. On the other hand, pyrocatechol, resorcinol, and phloroglucinol are oxidized nonstoichiometrically with a deeper destruction of the aromatic system, which prevents analytical use of these reactions.     

9.

Oxidation of organic substances with compounds of trivalent manganese: XXIII. Preparation,stability, and determination of the titer of standard solutions of the fluoride complex of trivalent manganese     

J. Barek  A. Berka  H. Skokánková 《Microchemical Journal》1982,27(3):393-400

A method of preparation of 10^?2 ?10^?3M standard solutions of the fluoride complex of manganese(III) by the reaction of manganese(II) with permanganate in a medium of potassium fluoride acidified with sulfuric acid has been developed. It has been found that in a medium of 1 M sulfuric acid, 0.5 M manganese(II) sulfate, and 0.1 M potassium fluoride these solutions are sufficiently stable for both direct and indirect titrimetric determinations. The titer was determined using potassium iodide as a primary standard and potentiometric, bipotentiometric, or biamperometric titration.     

10.

Oxidation of organic substances by compounds of trivalent manganese : XXV. Determination of benzene polyhydroxy and aminohydroxy derivatives with a standard solution of the fluoride complex of trivalent manganese     

J. Barek  A. Berka  H. Skoknkov 《Microchemical Journal》1983,28(3):308-313

The redox potential of the Mn(III)/Mn(II) system in a medium of potassium fluoride and sulfuric acid was measured and its dependence on the concentration of both substances was found. Furthermore, the influence of the concentration of potassium fluoride and sulfuric acid on the visible absorption spectrum of trivalent manganese was studied.     

11.

Oxidation of organic substances by compounds of trivalent manganese: XXIV. A study of electrochemical and spectrophotometric properties of the Mn(III)Mn(II) system in a medium of potassium fluoride and sulfuric acid     

J. Barek  A. Berka  H. Skokánková 《Microchemical Journal》1983,28(3):301-307

The redox potential of the $\text{Mn(III)}\text{Mn(II)}$ system in a medium of potassium fluoride and sulfuric acid was measured and its dependence on the concentration of both substances was found. Furthermore, the influence of the concentration of potassium fluoride and sulfuric acid on the visible absorption spectrum of trivalent manganese was studied.     

12.

Ruthenium(III) catalysis in the reaction of hexacyanoferrate(III) and iodide ions in perchloric acid medium     

Praveen K. Tandon  Alka Mehrotra  Manish Srivastava  Mamta Dhusia  Santosh B. Singh 《Transition Metal Chemistry》2007,32(1):74-80

RuCl₃ can further catalyze the reaction between hexacyanoferrate(III) and iodide ions, which is already catalyzed by the hydrogen ions obtained from perchloric acid. Rate, when the reaction is catalyzed only by the hydrogen ions, was separated graphically from the rate when ruthenium(III) and H⁺ ions both catalyze the reaction. Reactions studied separately in the presence as well as in the absence of RuCl₃ under similar conditions were found to follow second order kinetics w.r.t. [I⁻]. While the rate showed direct proportionality w.r.t. [Fe(CN)₆]³⁻ and [RuCl₃]. At low concentrations the reaction shows direct proportionality with respect to [H⁺] which tends to become proportional to the square of hydrogen ion concentrations. External addition of [Fe(CN)₆]⁴⁻ ions retards the reaction velocity while change in ionic strength of the medium has no effect on the rate. With the help of the intercept of the catalyst graph, extent of the reaction, which takes place without adding ruthenium(III) was calculated and it was in accordance with the values obtained from the separately studied reaction in which only H⁺ ions catalyze the reaction. It is proposed that ruthenium forms a complex, which slowly disproportionates into the rate-determining step. Arrhenius parameters at four different temperatures were also calculated.      

13.

The oxidation of organic substances with compounds of trivalent manganese : XXVI. An indirect spectrophotometric determination of polyhydroxy and aminohydroxy derivatives of benzene with the fluoride complex of trivalent manganese     

J. Barek  A. Berka  H. Skoknkov 《Microchemical Journal》1985,31(2):227-232

An indirect spectrophotometric determination of 10–50 μg of hydroquinone, p-amino-phenol, and Metol has been developed. The determination is based on the oxidation of these substances with the fluoride complex of trivalent manganese, the unreacted reagent being determined by the color reaction with o-tolidine.     

14.

The oxidation of organic substances by compounds of tervalent manganese-I Oxidation of mandelic acid, ethylene glycol, glycerol and d-mannitol by the pyrophosphate complex of manganese(III) and by manganese(III) sulphate     

Barek J  Berka A  Procházková I 《Talanta》1974,21(2):157-161

The oxidation of mandelic acid, ethylene glycol, glycerol and d-mannitol by the pyrophosphate complex of manganese(III) and with manganese(III) sulphate was studied. It was shown that benzaldehyde is formed by oxidation of mandelic acid, which undergoes no further oxidation. In the case of ethylene glycol, glycerol and d-mannitol the reactions do not follow a simple course and therefore are not of analytical utility. The effect of acidity and time on the course of the reactions was found and a procedure for the indirect titrimetric determination of mandelic acid with both reagents proposed.     

15.

The oxidation of organic compounds by tervalent manganese compounds-II The determination of mandelic acid with a tervalent manganese standard solution in perchloric acid medium     

Barek J  Berka A 《Talanta》1974,21(8):887-888

An indirect titrimetric determination of mandelic acid, based on its oxidation by a standard solution of hexa-aquomanganese(III) in perchloric acid medium, is described.     

16.

Oxidation of L-aspartic acid and L-glutamic acid by manganese(III) ions in aqueous sulphuric acid,acetic acid,and pyrophosphate media: A kinetic study     

B. S. Sherigara  K. Ishwar Bhat  Ivan Pinto  N. M. Made Gowda 《国际化学动力学杂志》1995,27(7):675-690

Kinetics of oxidation of L-aspartic acid and L-glutamic acid by manganese(III) ions have been studied in aqueous sulphuric acid, acetic acid, and pyrophosphate media. Manganese(III) solutions were prepared by known electrolytic/chemical methods in the three media. The nature of the oxidizing species present in manganese(III) solutions was determined by spectrophotometric and redox potential measurements. The reaction shows a variable order in [manganese(III)]_o: the order changes from two to one as the reactive oxidizing species changes from an aquo ionic form to a complex form. There is a first-order dependence of the rate on [amino acid]_o in all the three media while the other common features include an inverse dependence each on [H⁺] and on [manganese(II)]. Effects of varying ionic strength and solvent composition were studied. Added anions such as pyrophosphate, fluoride, or chloride alter the reaction rate and mechanism by changing the formal redox potential of Mn(III)-Mn(II) couple. Activation parameters have been evaluated using the Arrhenius and Eyring plots. Mechanisms consistent with the kinetic data have been proposed and discussed. © 1995 John Wiley & Sons, Inc.     

17.

Coulometric titration of organic and pharmaceutical compounds with electrogenerated gold(III)     

Marianne Chateau-Gosselin  Gary D. Christian  Gaston J. Patriarche 《Mikrochimica acta》1979,71(5-6):415-421

Summary Electrogenerated AuCl₄– in 0.02M HCl is used to titrate hydroquinone, ascorbic acid, phenylhydrazine, phenelzine sulphate and phenylsemicarbazide, with biamperometric end-point detection. Titration recoveries are reported and compared with results of coulometry with ceric sulphate oxidation. With less than 1 mg of sample, successive titrations can be performed in the same solution, in contrast to coulometry with ceric sulphate. Phenelzine sulphate reacts stoichiometrically, as opposed to its reactions with stronger oxidizing agents.

---

Zusammenfassung An der Elektrode entwickeltes AuCl₄– in 0,02M HCl wurde für die Titration von Hydrochinon, Ascorbinsäure, Phenylhydrazin, Phenelzinsulfat und Phenylsemicarbazid mit biamperometrischer Endpunktanzeige verwendet. Die Ergebnisse wurden mitgeteilt und mit den Resultaten der Coulometrie mit Cersulfatoxydation verglichen. Im Gegensatz dazu können mit weniger als 1 mg Probe in derselben Lösung Folgetitrationen durchgeführt werden. Abweichend von seinem Verhalten gegenüber stärkeren Oxydationsmitteln reagiert Phenelzinsulfat stöchiometrisch.

     

18.

Anodically generated manganese(III) sulphate for the oxidation of dipeptides in aqueous sulphuric acid medium: A kinetic study     

M. N. Kumara  D. Channe Gowda  A. Thimme Gowda  K. S. Rangappa 《Journal of Chemical Sciences》2004,116(1):49-53

The kinetic of oxidation of dipeptides (DP) namely valyl-glycine (Val-Gly), alanyl-glycine (Ala-Gly) and glycyl-glycine (Gly-Gly), by Mn(III) have been studied in the presence of sulphate ions in acid medium at 26°C. The reaction was followed spectrophotometrically at λ_max = 500 nm. A first-order dependence of the rate on both [Mn(III)]_o and [DP]_o was observed. The rate is independent of the concentration of reduction product, Mn(II) and hydrogen ions. The effects of varying the dielectric constant of the medium and addition of anions such as sulphate, chloride and perchlorate were studied. The activation parameters have been evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of DP with Mn(III) in the rate-limiting step is suggested. An apparent correlation was noted between the rate of oxidation and the hydrophobicity of these dimers, where increased hyphobicity results in increased rate of oxidation     

19.

The use of copper(III) complex compounds for the thermochemical analysis (DIE) of different organic substances     

N. Malingerová  M. Malinger 《Journal of Thermal Analysis and Calorimetry》1986,31(5):1161-1169

Potassium diperiodatocuprate(III), K₇[Cu(IO₆)₂], was tested as a reagent for the determination of mono- and disaccharides by means of direct injection enthalpimetry. The reagent reacted readily with acyclic polyhydroxy compounds, the reaction proceeding the better, the more hydroxy groups there were in the substance and the closer the hydroxy groups were one to the other. It also reacted readily with phenols, the polyhydric ones in particular. Carbonyl and amino compounds mostly didn't react or did so slowly, but reacted readily in the presence of some other reactive group such as hydroxy, sulphhydryl or thioxo group. Semicarbazide reacted readily, presumably due to the presence of the reactive-CO-NH-group. It is concluded that carboxy groups in the proximity of hydroxy groups exercise a positive effect on the reaction. The presence of a nitro or sulphonic acid group has a negative effect on the course of the reaction with the copper(III) compound.

---

Zusammenfassung Kalium-diperiodatocuprat(III), K₇[Cu(JO₆)₂], wird als Reagenz für die Bestimmung von Mono- und Disacchariden durch direkte Injektionsenthalpimetrie vorgeschlagen. Es wurde festgestellt, daß das Reagenz leicht mit azyklischen Polyhydroxy-Verbindungen reagiert, und zwar umso besser, je mehr Hydroxylgruppen die Substanz enthält und je näher diese beieinander liegen. Das Reagenz reagiert leicht mit Phenolen, insbesondere wenn diese mehrere Hydroxylgruppen enthalten. Carbonyl- und Aminoverbindungen reagieren meistens nicht oder nur langsam, aber leicht in Gegenwart einiger anderer reaktiver Gruppen, wie Hydroxy-, Sulfhydryl- oder Thioxogruppen. Semicarbazid reagiert leicht, wahrscheinlich wegen der reaktiven Gruppe-CO-NH₂-. Es wird der Schluß gezogen, daß Carboxylgruppen in der Nachbarschaft von Hydroxylgruppen eine positive Wirkung auf die Reaktion ausüben. Die Anwesenheit der Nitro- oder Sulfonsäuregruppe wirkt sich negativ auf den Verlauf der Reaktion mit Kupfer(III)-Verbindungen aus.

---

- K₇[u(IO₆)₂] — - . , . , . , , . . , -, - , . , , , -NH-. , , , , - .

     

20.

Organothallium compounds : XVII. Halogenobis(polyfluorophenyl)thallium(III) complexes     

G.B. Deacon  R.J. Phillips 《Journal of organometallic chemistry》1980,199(1):15-32

The preparations, stabilities and structures of the complexes R₂TlX and R₂ LTlX (R = C₆F₅, p-HC₆F₄, or o-HC₆F₄; X = Br or Cl; L = Ph₃PO, 2,2′-bipyridyl (bpy) or Ph₃P) have been examined or (R = C₆ F₅) reinvestigated. The derivatives R₂TlX are monomeric in acetone, from which the complex (p-HC₆F₄)₂ Me₂COTIBr has been isolated. In this solvent, the complexes R₂LTlX (L = Ph₃PO, bpy, or Ph₃P) undergo partial dissociation by loss of L. When L = bpy, there is also slight ionization into R₂LTl⁺ and R₂TlX^?₂. The acceptor properties of R₂TlX compounds towards uncharged ligands decrease R = C₆F₅ ? p-HC₆F₄ > o-HC₆F₄ > Ph. Dimeric behaviour is observed for R₂TIX compounds in benzene, whilst R₂LTlX (L = Ph₃PO or bpy) derivatives show slight but significant association. In the solid state, R₂TlX compounds are considered to be polymeric with five coordinate thallium, and R₂LTlX derivatives to be dimeric with five (L = Ph₃PO) or six (L = bpy) coordinate thallium by contrast with four coordinate dimeric and four or five coordinate monomeric structures previously proposed for the respective pentafluorophenyl derivatives. Halogen bridging is unsymmetrical for R = C₆F₅ or p-HC₆F₄, but may be more symmetrical for R = o-HC₆F₄ when L = Ph₃PO or bpy. Reported structural data for the complexes (C₆F₅)LTlX (L = Ph₃AsO, Ph₃P, Ph₃As, or 1,10-phenanthroline; X = Br or Cl) and (C₆F₅)₂TlCl^?₂ are reinterpreted and the proposed structures revised.     

Time (min)	0	5	10	30	60
Consumption of Mn(III) (mol/mol)	2.00	1.99	2.00	2.01	2.00

The oxidation of organic substances with compounds of trivalent manganese: XXVII. The oxidation of 4,4′-dihydroxyazobenzene with the diphosphate complex of trivalent manganese

The oxidation of 4,4′-dihydroxyazobenzene with the diphosphate complex of trivalent manganese was studied. The reaction stoichiometry was found and a procedure for a direct potentiometric titration of the test substance has been proposed.     

The oxidation of organic substances with compounds of trivalent manganese: XXII. The oxidation of glyceraldehyde with manganese(III) sulfate

The oxidation of glyceraldehyde with manganese(III) sulfate was studied. The reaction stoichiometry was found and a procedure for an indirect determination of 5–17 mg of the test substance has been proposed. The recommended procedure is based on the oxidation of glyceraldehyde with the reagent, the excess of which is back-titrated with standard solution of ferrous sulfate.     

Oxidation of organic compounds by tervalent manganese compounds: IX. Determination of the titer of hexaquomanganese(III) ion standard solutions in perchloric acid

Optimum conditions have been found for the determination of the titer of 0.005 N solutions of hexaquomanganese(III) ion by potentiometric titration of ferrous chloride. The accuracy and reproducibility of this method were studied. A new method of determining the titer of dilute solutions of hexaquomanganese(III) ion has been proposed, using potassium iodide as a primary standard. The optimum conditions for this titration have been found and its applicability to the determination of the titer of 0.005, 0.001, and 0.0005 N solutions has been verified.     

Oxidation of organic substances by tervalent manganese compounds : VIII. Determination of benzene polyhydroxy and aminohydroxy derivatives with a standard solution of hexaquomanganese(III) ion in perchloric acid

The reaction of hexaquomanganese(III) ion with hydroquinone, p-aminophenol, metol, pyrocatechol, resorcinol, and phloroglucinol was studied. It has been found that the first three substances are oxidized quantitatively with the exchange of two electrons to the corresponding quinone compounds and that this reaction can be employed for direct or indirect titrimetric determination of these substances. On the other hand, pyrocatechol, resorcinol, and phloroglucinol are oxidized nonstoichiometrically with a deeper destruction of the aromatic system, which prevents analytical use of these reactions.     

Oxidation of organic substances with compounds of trivalent manganese: XXIII. Preparation,stability, and determination of the titer of standard solutions of the fluoride complex of trivalent manganese

A method of preparation of 10^?2 ?10^?3M standard solutions of the fluoride complex of manganese(III) by the reaction of manganese(II) with permanganate in a medium of potassium fluoride acidified with sulfuric acid has been developed. It has been found that in a medium of 1 M sulfuric acid, 0.5 M manganese(II) sulfate, and 0.1 M potassium fluoride these solutions are sufficiently stable for both direct and indirect titrimetric determinations. The titer was determined using potassium iodide as a primary standard and potentiometric, bipotentiometric, or biamperometric titration.     

Oxidation of organic substances by compounds of trivalent manganese : XXV. Determination of benzene polyhydroxy and aminohydroxy derivatives with a standard solution of the fluoride complex of trivalent manganese

The redox potential of the Mn(III)/Mn(II) system in a medium of potassium fluoride and sulfuric acid was measured and its dependence on the concentration of both substances was found. Furthermore, the influence of the concentration of potassium fluoride and sulfuric acid on the visible absorption spectrum of trivalent manganese was studied.     

Oxidation of organic substances by compounds of trivalent manganese: XXIV. A study of electrochemical and spectrophotometric properties of the Mn(III)Mn(II) system in a medium of potassium fluoride and sulfuric acid

The redox potential of the $\text{Mn(III)}\text{Mn(II)}$ system in a medium of potassium fluoride and sulfuric acid was measured and its dependence on the concentration of both substances was found. Furthermore, the influence of the concentration of potassium fluoride and sulfuric acid on the visible absorption spectrum of trivalent manganese was studied.     

Ruthenium(III) catalysis in the reaction of hexacyanoferrate(III) and iodide ions in perchloric acid medium

RuCl₃ can further catalyze the reaction between hexacyanoferrate(III) and iodide ions, which is already catalyzed by the hydrogen ions obtained from perchloric acid. Rate, when the reaction is catalyzed only by the hydrogen ions, was separated graphically from the rate when ruthenium(III) and H⁺ ions both catalyze the reaction. Reactions studied separately in the presence as well as in the absence of RuCl₃ under similar conditions were found to follow second order kinetics w.r.t. [I⁻]. While the rate showed direct proportionality w.r.t. [Fe(CN)₆]³⁻ and [RuCl₃]. At low concentrations the reaction shows direct proportionality with respect to [H⁺] which tends to become proportional to the square of hydrogen ion concentrations. External addition of [Fe(CN)₆]⁴⁻ ions retards the reaction velocity while change in ionic strength of the medium has no effect on the rate. With the help of the intercept of the catalyst graph, extent of the reaction, which takes place without adding ruthenium(III) was calculated and it was in accordance with the values obtained from the separately studied reaction in which only H⁺ ions catalyze the reaction. It is proposed that ruthenium forms a complex, which slowly disproportionates into the rate-determining step. Arrhenius parameters at four different temperatures were also calculated.      

The oxidation of organic substances with compounds of trivalent manganese : XXVI. An indirect spectrophotometric determination of polyhydroxy and aminohydroxy derivatives of benzene with the fluoride complex of trivalent manganese

An indirect spectrophotometric determination of 10–50 μg of hydroquinone, p-amino-phenol, and Metol has been developed. The determination is based on the oxidation of these substances with the fluoride complex of trivalent manganese, the unreacted reagent being determined by the color reaction with o-tolidine.     

The oxidation of organic substances by compounds of tervalent manganese-I Oxidation of mandelic acid, ethylene glycol, glycerol and d-mannitol by the pyrophosphate complex of manganese(III) and by manganese(III) sulphate

The oxidation of mandelic acid, ethylene glycol, glycerol and d-mannitol by the pyrophosphate complex of manganese(III) and with manganese(III) sulphate was studied. It was shown that benzaldehyde is formed by oxidation of mandelic acid, which undergoes no further oxidation. In the case of ethylene glycol, glycerol and d-mannitol the reactions do not follow a simple course and therefore are not of analytical utility. The effect of acidity and time on the course of the reactions was found and a procedure for the indirect titrimetric determination of mandelic acid with both reagents proposed.     

The oxidation of organic compounds by tervalent manganese compounds-II The determination of mandelic acid with a tervalent manganese standard solution in perchloric acid medium

An indirect titrimetric determination of mandelic acid, based on its oxidation by a standard solution of hexa-aquomanganese(III) in perchloric acid medium, is described.     

Oxidation of L-aspartic acid and L-glutamic acid by manganese(III) ions in aqueous sulphuric acid,acetic acid,and pyrophosphate media: A kinetic study

Kinetics of oxidation of L-aspartic acid and L-glutamic acid by manganese(III) ions have been studied in aqueous sulphuric acid, acetic acid, and pyrophosphate media. Manganese(III) solutions were prepared by known electrolytic/chemical methods in the three media. The nature of the oxidizing species present in manganese(III) solutions was determined by spectrophotometric and redox potential measurements. The reaction shows a variable order in [manganese(III)]_o: the order changes from two to one as the reactive oxidizing species changes from an aquo ionic form to a complex form. There is a first-order dependence of the rate on [amino acid]_o in all the three media while the other common features include an inverse dependence each on [H⁺] and on [manganese(II)]. Effects of varying ionic strength and solvent composition were studied. Added anions such as pyrophosphate, fluoride, or chloride alter the reaction rate and mechanism by changing the formal redox potential of Mn(III)-Mn(II) couple. Activation parameters have been evaluated using the Arrhenius and Eyring plots. Mechanisms consistent with the kinetic data have been proposed and discussed. © 1995 John Wiley & Sons, Inc.     

Coulometric titration of organic and pharmaceutical compounds with electrogenerated gold(III)

Summary Electrogenerated AuCl₄– in 0.02M HCl is used to titrate hydroquinone, ascorbic acid, phenylhydrazine, phenelzine sulphate and phenylsemicarbazide, with biamperometric end-point detection. Titration recoveries are reported and compared with results of coulometry with ceric sulphate oxidation. With less than 1 mg of sample, successive titrations can be performed in the same solution, in contrast to coulometry with ceric sulphate. Phenelzine sulphate reacts stoichiometrically, as opposed to its reactions with stronger oxidizing agents.

---

Zusammenfassung An der Elektrode entwickeltes AuCl₄– in 0,02M HCl wurde für die Titration von Hydrochinon, Ascorbinsäure, Phenylhydrazin, Phenelzinsulfat und Phenylsemicarbazid mit biamperometrischer Endpunktanzeige verwendet. Die Ergebnisse wurden mitgeteilt und mit den Resultaten der Coulometrie mit Cersulfatoxydation verglichen. Im Gegensatz dazu können mit weniger als 1 mg Probe in derselben Lösung Folgetitrationen durchgeführt werden. Abweichend von seinem Verhalten gegenüber stärkeren Oxydationsmitteln reagiert Phenelzinsulfat stöchiometrisch.

     

Anodically generated manganese(III) sulphate for the oxidation of dipeptides in aqueous sulphuric acid medium: A kinetic study

The kinetic of oxidation of dipeptides (DP) namely valyl-glycine (Val-Gly), alanyl-glycine (Ala-Gly) and glycyl-glycine (Gly-Gly), by Mn(III) have been studied in the presence of sulphate ions in acid medium at 26°C. The reaction was followed spectrophotometrically at λ_max = 500 nm. A first-order dependence of the rate on both [Mn(III)]_o and [DP]_o was observed. The rate is independent of the concentration of reduction product, Mn(II) and hydrogen ions. The effects of varying the dielectric constant of the medium and addition of anions such as sulphate, chloride and perchlorate were studied. The activation parameters have been evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of DP with Mn(III) in the rate-limiting step is suggested. An apparent correlation was noted between the rate of oxidation and the hydrophobicity of these dimers, where increased hyphobicity results in increased rate of oxidation     

The use of copper(III) complex compounds for the thermochemical analysis (DIE) of different organic substances

Potassium diperiodatocuprate(III), K₇[Cu(IO₆)₂], was tested as a reagent for the determination of mono- and disaccharides by means of direct injection enthalpimetry. The reagent reacted readily with acyclic polyhydroxy compounds, the reaction proceeding the better, the more hydroxy groups there were in the substance and the closer the hydroxy groups were one to the other. It also reacted readily with phenols, the polyhydric ones in particular. Carbonyl and amino compounds mostly didn't react or did so slowly, but reacted readily in the presence of some other reactive group such as hydroxy, sulphhydryl or thioxo group. Semicarbazide reacted readily, presumably due to the presence of the reactive-CO-NH-group. It is concluded that carboxy groups in the proximity of hydroxy groups exercise a positive effect on the reaction. The presence of a nitro or sulphonic acid group has a negative effect on the course of the reaction with the copper(III) compound.

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Zusammenfassung Kalium-diperiodatocuprat(III), K₇[Cu(JO₆)₂], wird als Reagenz für die Bestimmung von Mono- und Disacchariden durch direkte Injektionsenthalpimetrie vorgeschlagen. Es wurde festgestellt, daß das Reagenz leicht mit azyklischen Polyhydroxy-Verbindungen reagiert, und zwar umso besser, je mehr Hydroxylgruppen die Substanz enthält und je näher diese beieinander liegen. Das Reagenz reagiert leicht mit Phenolen, insbesondere wenn diese mehrere Hydroxylgruppen enthalten. Carbonyl- und Aminoverbindungen reagieren meistens nicht oder nur langsam, aber leicht in Gegenwart einiger anderer reaktiver Gruppen, wie Hydroxy-, Sulfhydryl- oder Thioxogruppen. Semicarbazid reagiert leicht, wahrscheinlich wegen der reaktiven Gruppe-CO-NH₂-. Es wird der Schluß gezogen, daß Carboxylgruppen in der Nachbarschaft von Hydroxylgruppen eine positive Wirkung auf die Reaktion ausüben. Die Anwesenheit der Nitro- oder Sulfonsäuregruppe wirkt sich negativ auf den Verlauf der Reaktion mit Kupfer(III)-Verbindungen aus.

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- K₇[u(IO₆)₂] — - . , . , . , , . . , -, - , . , , , -NH-. , , , , - .

     

Organothallium compounds : XVII. Halogenobis(polyfluorophenyl)thallium(III) complexes

The preparations, stabilities and structures of the complexes R₂TlX and R₂ LTlX (R = C₆F₅, p-HC₆F₄, or o-HC₆F₄; X = Br or Cl; L = Ph₃PO, 2,2′-bipyridyl (bpy) or Ph₃P) have been examined or (R = C₆ F₅) reinvestigated. The derivatives R₂TlX are monomeric in acetone, from which the complex (p-HC₆F₄)₂ Me₂COTIBr has been isolated. In this solvent, the complexes R₂LTlX (L = Ph₃PO, bpy, or Ph₃P) undergo partial dissociation by loss of L. When L = bpy, there is also slight ionization into R₂LTl⁺ and R₂TlX^?₂. The acceptor properties of R₂TlX compounds towards uncharged ligands decrease R = C₆F₅ ? p-HC₆F₄ > o-HC₆F₄ > Ph. Dimeric behaviour is observed for R₂TIX compounds in benzene, whilst R₂LTlX (L = Ph₃PO or bpy) derivatives show slight but significant association. In the solid state, R₂TlX compounds are considered to be polymeric with five coordinate thallium, and R₂LTlX derivatives to be dimeric with five (L = Ph₃PO) or six (L = bpy) coordinate thallium by contrast with four coordinate dimeric and four or five coordinate monomeric structures previously proposed for the respective pentafluorophenyl derivatives. Halogen bridging is unsymmetrical for R = C₆F₅ or p-HC₆F₄, but may be more symmetrical for R = o-HC₆F₄ when L = Ph₃PO or bpy. Reported structural data for the complexes (C₆F₅)LTlX (L = Ph₃AsO, Ph₃P, Ph₃As, or 1,10-phenanthroline; X = Br or Cl) and (C₆F₅)₂TlCl^?₂ are reinterpreted and the proposed structures revised.